Optimized four-qubit quantum error correcting code for amplitude damping channel Authors Xuanhui Mao, Qian Xu, Liang Jiang Published: 11.20.2024 Updated: 11.20.2024 Summary Quantum error correction (QEC) is essential for reliable quantum information processing. Targeting a particular error channel, both the encoding and the recovery channel can be optimized through a biconvex optimization to give a high-performance, noise-adapted QEC scheme. We solve the biconvex optimization by the technique of alternating semi-definite programming and identify a new four-qubit code for amplitude damping channel, one major noise in superconducting circuits and a good model for spontaneous emission and energy dissipation. We also construct analytical encoding and recovery channels that are close to the numerically optimized ones. We show that the new code notably outperforms the Leung-Nielsen-Chuang-Yamamoto four-qubit code in terms of the entanglement fidelity over an amplitude damping channel. Source arXiv: 2411.12952v1
SANDWICH: Towards an Offline, Differentiable, Fully-Trainable Wireless Neural Ray-Tracing Surrogate Authors Yifei Jin, Ali Maatouk, Sarunas Girdzijauskas, Shugong Xu, Leandros Tassiulas, Rex Ying Published: 11.13.2024 Updated: 11.13.2024 Summary Wireless ray-tracing (RT) is emerging as a key tool for three-dimensional (3D) wireless channel modeling, driven by advances in graphical rendering. Current approaches struggle to accurately model beyond 5G (B5G) network signaling, which often operates at higher frequencies and is more susceptible to environmental conditions and changes. Existing online learning solutions require real-time environmental supervision during training, which is both costly and incompatible with GPU-based processing. In response, we propose a novel approach that redefines ray trajectory generation as a sequential decision-making problem, leveraging generative models to jointly learn the optical, physical, and signal properties within each designated environment. Our work introduces the Scene-Aware Neural Decision Wireless Channel Raytracing Hierarchy (SANDWICH), an innovative offline, fully differentiable approach that can be trained entirely on GPUs. SANDWICH offers superior performance compared to existing online learning methods, outperforms the baseline by 4e^-2 radian in RT accuracy, and only fades 0.5 dB away from toplined channel gain estimation. Source arXiv: 2411.08767v1
Multiplexed bi-layered realization of fault-tolerant quantum computation over optically networked trapped-ion modules Authors Nitish K. Chandra, Saikat Guha, Kaushik P. Seshadreesan Published: 11.13.2024 Updated: 11.13.2024 Summary We study an architecture for fault-tolerant measurement-based quantum computation (FT-MBQC) over optically-networked trapped-ion modules. The architecture is implemented with a finite number of modules and ions per module, and leverages photonic interactions for generating remote entanglement between modules and local Coulomb interactions for intra-modular entangling gates. We focus on generating the topologically protected Raussendorf-Harrington-Goyal (RHG) lattice cluster state, which is known to be robust against lattice bond failures and qubit noise, with the modules acting as lattice sites. To ensure that the remote entanglement generation rates surpass the bond-failure tolerance threshold of the RHG lattice, we employ spatial and temporal multiplexing. For realistic system timing parameters, we estimate the code cycle time of the RHG lattice and the ion resources required in a bi-layered implementation, where the number of modules matches the number of sites in two lattice layers, and qubits are reinitialized after measurement. For large distances between modules, we incorporate quantum repeaters between sites and analyze the benefits in terms of cumulative resource requirements. Finally, we derive and analyze a qubit noise-tolerance threshold inequality for the RHG lattice generation in the proposed architecture that accounts for noise from various sources. This includes the depolarizing noise arising from the photonically-mediated remote entanglement generation between modules due to finite optical detection efficiency, limited visibility, and the presence of dark clicks, in addition to the noise from imperfect gates and measurements, and memory decoherence with time. Our work thus underscores the hardware and channel threshold requirements to realize distributed FT-MBQC in a leading qubit platform today — trapped ions. Source arXiv: 2411.08616v1
Quantum limited imaging of a nanomechanical resonator with a spatial mode sorter Authors Morgan Choi, Christian Pluchar, Wenhua He, Saikat Guha, Dalziel Wilson Published: 11.07.2024 Updated: 11.07.2024 Summary We explore the use of a spatial mode sorter to image a nanomechanical resonator, with the goal of studying the quantum limits of active imaging and extending the toolbox for optomechanical force sensing. In our experiment, we reflect a Gaussian laser beam from a vibrating nanoribbon and pass the reflected beam through a commercial spatial mode demultiplexer (Cailabs Proteus). The intensity in each demultiplexed channel depends on the mechanical mode shapes and encodes information about their displacement amplitudes. As a concrete demonstration, we monitor the angular displacement of the ribbon’s fundamental torsion mode by illuminating in the fundamental Hermite-Gauss mode (HG$_{00}$) and reading out in the HG$_{01}$ mode. We show that this technique permits readout of the ribbon’s torsional vibration with a precision near the quantum limit. Our results highlight new opportunities at the interface of quantum imaging and quantum optomechanics. Source arXiv: 2411.04980v1
Integrated electro-optic digital-to-analog link for efficient computing and arbitrary waveform generation Authors Yunxiang Song, Yaowen Hu, Xinrui Zhu, Keith Powell, Letícia Magalhães, Fan Ye, Hana Warner, Shengyuan Lu, Xudong Li, Dylan Renaud, Norman Lippok, Di Zhu, Benjamin Vakoc, Mian Zhang, Neil Sinclair, Marko Lončar Published: 11.07.2024 Updated: 11.07.2024 Summary The rapid growth in artificial intelligence and modern communication systems demands innovative solutions for increased computational power and advanced signaling capabilities. Integrated photonics, leveraging the analog nature of electromagnetic waves at the chip scale, offers a promising complement to approaches based on digital electronics. To fully unlock their potential as analog processors, establishing a common technological base between conventional digital electronic systems and analog photonics is imperative to building next-generation computing and communications hardware. However, the absence of an efficient interface has critically challenged comprehensive demonstrations of analog advantage thus far, with the scalability, speed, and energy consumption as primary bottlenecks. Here, we address this challenge and demonstrate a general electro-optic digital-to-analog link (EO-DiAL) enabled by foundry-based lithium niobate nanophotonics. Using purely digital inputs, we achieve on-demand generation of (i) optical and (ii) electronic waveforms at information rates up to 186 Gbit/s. The former addresses the digital-to-analog electro-optic conversion challenge in photonic computing, showcasing high-fidelity MNIST encoding while consuming 0.058 pJ/bit. The latter enables a pulse-shaping-free microwave arbitrary waveform generation method with ultrabroadband tunable delay and gain. Our results pave the way for efficient and compact digital-to-analog conversion paradigms enabled by integrated photonics and underscore the transformative impact analog photonic hardware may have on various applications, such as computing, optical interconnects, and high-speed ranging. Source arXiv: 2411.04395v1
Holographic deep thermalization Authors Bingzhi Zhang, Peng Xu, Xiaohui Chen, Quntao Zhuang Published: 11.06.2024 Updated: 11.06.2024 Summary Random quantum states play a critical role in quantum information processing. While random quantum circuits typically provide pseudo-random states, deep thermalization introduces quantum measurement to generate genuinely random states. However, the requirement of large ancillae in conventional deep thermalization poses a challenge to scale up the system size. We introduce holographic deep thermalization to substantially reduce the required ancillae to a system-size independent constant. Our circuit design trades space with time, via adopting a sequential application of an scrambling-measure-reset process on a small number of ancillae. Via tuning the ancilla size and number of time steps, holographic deep thermalization allows a continuous trade-off between the total quantum circuit size and the ancilla size. In the case of finite-size systems, we further enhance the performance of holographic deep thermalization via generative quantum machine learning, which leads to constant-factor advantages in the convergence towards Haar random. The theoretical predictions are verified with IBM Quantum noisy simulations. Source arXiv: 2411.03587v1
Integrated lithium niobate photonic computing circuit based on efficient and high-speed electro-optic conversion Authors Yaowen Hu, Yunxiang Song, Xinrui Zhu, Xiangwen Guo, Shengyuan Lu, Qihang Zhang, Lingyan He, C. A. A. Franken, Keith Powell, Hana Warner, Daniel Assumpcao, Dylan Renaud, Ying Wang, Letícia Magalhães, Victoria Rosborough, Amirhassan Shams-Ansari, Xudong Li, Rebecca Cheng, Kevin Luke, Kiyoul Yang, George Barbastathis, Mian Zhang, Di Zhu, Leif Johansson, Andreas Beling, Neil Sinclair, Marko Loncar Published: 11.05.2024 Updated: 11.05.2024 Summary Here we show a photonic computing accelerator utilizing a system-level thin-film lithium niobate circuit which overcomes this limitation. Leveraging the strong electro-optic (Pockels) effect and the scalability of this platform, we demonstrate photonic computation at speeds up to 1.36 TOPS while consuming 0.057 pJ/OP. Our system features more than 100 thin-film lithium niobate high-performance components working synergistically, surpassing state-of-the-art systems on this platform. We further demonstrate binary-classification, handwritten-digit classification, and image classification with remarkable accuracy, showcasing our system’s capability of executing real algorithms. Finally, we investigate the opportunities offered by combining our system with a hybrid-integrated distributed feedback laser source and a heterogeneous-integrated modified uni-traveling carrier photodiode. Our results illustrate the promise of thin-film lithium niobate as a computational platform, addressing current bottlenecks in both electronic and photonic computation. Its unique properties of high-performance electro-optic weight encoding and conversion, wafer-scale scalability, and compatibility with integrated lasers and detectors, position thin-film lithium niobate photonics as a valuable complement to silicon photonics, with extensions to applications in ultrafast and power-efficient signal processing and ranging. Source arXiv: 2411.02734v1
Genuine non-Gaussian entanglement: quantum correlations beyond Hong-Ou-Mandel Authors Xiaobin Zhao, Pengcheng Liao, Quntao Zhuang Published: 11.03.2024 Updated: 11.03.2024 Summary Hong-Ou-Mandel effect is an important demonstration of particle indistinguishability, when identical single photons interfere at a beamsplitter to generate the two-photon entangled NOON state. On the other hand, NOON states with $Nge3$ photons have long been conjectured beyond the deterministic generation of photon interference. To characterize the separation, we introduce the notion of genuine non-Gaussian entanglement (NGE), which cannot be generated via a generalized Hong-Ou-Mandel experiment, with Gaussian protocols extending the beamsplitter and separable input states replacing the single photons. We establish a resource theory to characterize such quantum correlations beyond Hong-Ou-Mandel and prove that NOON states with $Nge 3$ are indeed among the NGE class. With the generalized Hong-Ou-Mandel protocol as free operations, we introduce two monotones to characterize genuine non-Gaussian entanglement: one derived from the entanglement entropy and the other from the minimal extension size required to convert a state into a free state. Finally, we demonstrate that the tomography process of pure free states can be performed efficiently, while all learning protocols of states with genuine non-Gaussian entanglement require exponential overheads connected to the monotone. This implies that states generated in Boson sampling are efficiently learnable despite its measurement statistics being hard to sample from. Source arXiv: 2411.01609v1
Practical hybrid PQC-QKD protocols with enhanced security and performance Authors Pei Zeng, Debayan Bandyopadhyay, José A. Méndez Méndez, Nolan Bitner, Alexander Kolar, Michael T. Solomon, Ziyu Ye, Filip Rozpȩdek, Tian Zhong, F. Joseph Heremans, David D. Awschalom, Liang Jiang, Junyu Liu Published: 11.02.2024 Updated: 11.05.2024 Summary Quantum resistance is vital for emerging cryptographic systems as quantum technologies continue to advance towards large-scale, fault-tolerant quantum computers. Resistance may be offered by quantum key distribution (QKD), which provides information-theoretic security using quantum states of photons, but may be limited by transmission loss at long distances. An alternative approach uses classical means and is conjectured to be resistant to quantum attacks, so-called post-quantum cryptography (PQC), but it is yet to be rigorously proven, and its current implementations are computationally expensive. To overcome the security and performance challenges present in each, here we develop hybrid protocols by which QKD and PQC inter-operate within a joint quantum-classical network. In particular, we consider different hybrid designs that may offer enhanced speed and/or security over the individual performance of either approach. Furthermore, we present a method for analyzing the security of hybrid protocols in key distribution networks. Our hybrid approach paves the way for joint quantum-classical communication networks, which leverage the advantages of both QKD and PQC and can be tailored to the requirements of various practical networks. Source arXiv: 2411.01086v2
Practical hybrid PQC-QKD protocols with enhanced security and performance Authors Pei Zeng, Debayan Bandyopadhyay, José A. Méndez Méndez, Nolan Bitner, Alexander Kolar, Michael T. Solomon, Ziyu Ye, Filip Rozpędek, Tian Zhong, F. Joseph Heremans, David D. Awschalom, Liang Jiang, Junyu Liu Published: 11.02.2024 Updated: 11.07.2024 Summary Quantum resistance is vital for emerging cryptographic systems as quantum technologies continue to advance towards large-scale, fault-tolerant quantum computers. Resistance may be offered by quantum key distribution (QKD), which provides information-theoretic security using quantum states of photons, but may be limited by transmission loss at long distances. An alternative approach uses classical means and is conjectured to be resistant to quantum attacks, so-called post-quantum cryptography (PQC), but it is yet to be rigorously proven, and its current implementations are computationally expensive. To overcome the security and performance challenges present in each, here we develop hybrid protocols by which QKD and PQC inter-operate within a joint quantum-classical network. In particular, we consider different hybrid designs that may offer enhanced speed and/or security over the individual performance of either approach. Furthermore, we present a method for analyzing the security of hybrid protocols in key distribution networks. Our hybrid approach paves the way for joint quantum-classical communication networks, which leverage the advantages of both QKD and PQC and can be tailored to the requirements of various practical networks. Source arXiv: 2411.01086v3
Practical hybrid PQC-QKD protocols with enhanced security and performance Authors Pei Zeng, Debayan Bandyopadhyay, José A. Méndez Méndez, Nolan Bitner, Alexander Kolar, Michael T. Solomon, Filip Rozpedek, Tian Zhong, F. Joseph Heremans, David D. Awschalom, Liang Jiang, Junyu Liu Published: 11.02.2024 Updated: 11.02.2024 Summary Quantum resistance is vital for emerging cryptographic systems as quantum technologies continue to advance towards large-scale, fault-tolerant quantum computers. Resistance may be offered by quantum key distribution (QKD), which provides information-theoretic security using quantum states of photons, but may be limited by transmission loss at long distances. An alternative approach uses classical means and is conjectured to be resistant to quantum attacks, so-called post-quantum cryptography (PQC), but it is yet to be rigorously proven, and its current implementations are computationally expensive. To overcome the security and performance challenges present in each, here we develop hybrid protocols by which QKD and PQC inter-operate within a joint quantum-classical network. In particular, we consider different hybrid designs that may offer enhanced speed and/or security over the individual performance of either approach. Furthermore, we present a method for analyzing the security of hybrid protocols in key distribution networks. Our hybrid approach paves the way for joint quantum-classical communication networks, which leverage the advantages of both QKD and PQC and can be tailored to the requirements of various practical networks. Source arXiv: 2411.01086v1
Towards efficient and secure quantum-classical communication networks Authors Pei Zeng, Debayan Bandyopadhyay, Jose A. Mendez, Nolan Bitner, Alexander Kolar, Michael T. Solomon, F. Joseph Heremans, David D. Awschalom, Liang Jiang, Junyu Liu Published: 11.01.2024 Updated: 11.01.2024 Summary The rapid advancement of quantum technologies calls for the design and deployment of quantum-safe cryptographic protocols and communication networks. There are two primary approaches to achieving quantum-resistant security: quantum key distribution (QKD) and post-quantum cryptography (PQC). While each offers unique advantages, both have drawbacks in practical implementation. In this work, we introduce the pros and cons of these protocols and explore how they can be combined to achieve a higher level of security and/or improved performance in key distribution. We hope our discussion inspires further research into the design of hybrid cryptographic protocols for quantum-classical communication networks. Source arXiv: 2411.01081v1
Towards efficient and secure quantum-classical communication networks Authors Pei Zeng, Debayan Bandyopadhyay, José A. Méndez Méndez, Nolan Bitner, Alexander Kolar, Michael T. Solomon, F. Joseph Heremans, David D. Awschalom, Liang Jiang, Junyu Liu Published: 11.01.2024 Updated: 11.05.2024 Summary The rapid advancement of quantum technologies calls for the design and deployment of quantum-safe cryptographic protocols and communication networks. There are two primary approaches to achieving quantum-resistant security: quantum key distribution (QKD) and post-quantum cryptography (PQC). While each offers unique advantages, both have drawbacks in practical implementation. In this work, we introduce the pros and cons of these protocols and explore how they can be combined to achieve a higher level of security and/or improved performance in key distribution. We hope our discussion inspires further research into the design of hybrid cryptographic protocols for quantum-classical communication networks. Source arXiv: 2411.01081v2
Quantum random access memory with transmon-controlled phonon routing Authors Zhaoyou Wang, Hong Qiao, Andrew N. Cleland, Liang Jiang Published: 11.01.2024 Updated: 11.01.2024 Summary Quantum random access memory (QRAM) promises simultaneous data queries at multiple memory locations, with data retrieved in coherent superpositions, essential for achieving quantum speedup in many quantum algorithms. We introduce a transmon-controlled phonon router and propose a QRAM implementation by connecting these routers in a tree-like architecture. The router controls the motion of itinerant surface acoustic wave phonons based on the state of the control transmon, implementing the core functionality of conditional routing for QRAM. Our QRAM design is compact, supports fast routing operations, and avoids frequency crowding. Additionally, we propose a hybrid dual-rail encoding method to detect dominant loss errors without additional hardware, a versatile approach applicable to other QRAM platforms. Our estimates indicate that the proposed QRAM platform can achieve high heralding rates using current device parameters, with heralding fidelity primarily limited by transmon dephasing. Source arXiv: 2411.00719v1
Optimality Condition for the Transpose Channel Authors Bikun Li, Zhaoyou Wang, Guo Zheng, Liang Jiang Published: 10.31.2024 Updated: 11.04.2024 Summary In quantum error correction, the Petz transpose channel serves as a perfect recovery map when the Knill-Laflamme conditions are satisfied. Notably, while perfect recovery is generally infeasible for most quantum channels of finite dimension, the transpose channel remains a versatile tool with near-optimal performance in recovering quantum states. This work introduces and proves, for the first time, the necessary and sufficient conditions for the strict optimality of the transpose channel in terms of channel fidelity. The violation of this condition can be easily characterized by a simple commutator that can be efficiently computed. We provide multiple examples that substantiate our new findings. Source arXiv: 2410.23622v2
Optimality Condition for the Transpose Channel Authors Bikun Li, Zhaoyou Wang, Guo Zheng, Liang Jiang Published: 10.31.2024 Updated: 10.31.2024 Summary In quantum error correction, the Petz transpose channel serves as a perfect recovery map when the Knill-Laflamme conditions are satisfied. Notably, while perfect recovery is generally infeasible for most quantum channels of finite dimension, the transpose channel remains a versatile tool with near-optimal performance in recovering quantum states. This work introduces and proves, for the first time, the necessary and sufficient conditions for the strict optimality of the transpose channel in terms of channel fidelity. The violation of this condition can be easily characterized by a simple commutator that can be efficiently computed. We provide multiple examples that substantiate our new findings. Source arXiv: 2410.23622v1
Outcomes from a Workshop on a National Center for Quantum Education Authors Edwin Barnes, Michael B. Bennett, Alexandra Boltasseva, Victoria Borish, Bennett Brown, Lincoln D. Carr, Russell R. Ceballos, Faith Dukes, Emily W. Easton, Sophia E. Economou, E. E. Edwards, Noah D. Finkelstein, C. Fracchiolla, Diana Franklin, J. K. Freericks, Valerie Goss, Mark Hannum, Nancy Holincheck, Angela M. Kelly, Olivia Lanes, H. J. Lewandowski, Karen Jo Matsler, Emily Mercurio, Inès Montaño, Maajida Murdock, Kiera Peltz, Justin K. Perron, Christopher J. K. Richardson, Jessica L. Rosenberg, Richard S. Ross, Minjung Ryu, Raymond E. Samuel, Nicole Schrode, Susan Schwamberger, Thomas A. Searles, Chandralekha Singh, Alexandra Tingle, Benjamin M. Zwickl Published: 10.30.2024 Updated: 10.30.2024 Summary In response to numerous programs seeking to advance quantum education and workforce development in the United States, experts from academia, industry, government, and professional societies convened for a National Science Foundation-sponsored workshop in February 2024 to explore the benefits and challenges of establishing a national center for quantum education. Broadly, such a center would foster collaboration and build the infrastructure required to develop a diverse and quantum-ready workforce. The workshop discussions centered around how a center could uniquely address gaps in public, K-12, and undergraduate quantum information science and engineering (QISE) education. Specifically, the community identified activities that, through a center, could lead to an increase in student awareness of quantum careers, boost the number of educators trained in quantum-related subjects, strengthen pathways into quantum careers, enhance the understanding of the U.S. quantum workforce, and elevate public engagement with QISE. Core proposed activities for the center include professional development for educators, coordinated curriculum development and curation, expanded access to educational laboratory equipment, robust evaluation and assessment practices, network building, and enhanced public engagement with quantum science. Source arXiv: 2410.23460v1
Graphene calorimetric single-photon detector Authors Bevin Huang, Ethan G. Arnault, Woochan Jung, Caleb Fried, B. Jordan Russell, Kenji Watanabe, Takashi Taniguchi, Erik A. Henriksen, Dirk Englund, Gil-Ho Lee, Kin Chun Fong Published: 10.29.2024 Updated: 10.29.2024 Summary Single photon detectors (SPDs) are essential technology in quantum science, quantum network, biology, and advanced imaging. To detect the small quantum of energy carried in a photon, conventional SPDs rely on energy excitation across either a semiconductor bandgap or superconducting gap. While the energy gap suppresses the false-positive error, it also sets an energy scale that can limit the detection efficiency of lower energy photons and spectral bandwidth of the SPD. Here, we demonstrate an orthogonal approach to detect single near-infrared photons using graphene calorimeters. By exploiting the extremely low heat capacity of the pseudo-relativistic electrons in graphene near its charge neutrality point, we observe an electron temperature rise up to ~2 K using a hybrid Josephson junction. In this proof-of-principle experiment, we achieve an intrinsic quantum efficiency of 87% (75%) with dark count < 1 per second (per hour) at operation temperatures as high as 1.2 K. Our results highlight the potential of electron calorimetric SPDs for detecting lower-energy photons from the mid-IR to microwave regimes, opening pathways to study space science in far-infrared regime, to search for dark matter axions, and to advance quantum technologies across a broader electromagnetic spectrum. Source arXiv: 2410.22433v1
Low-Dimensional Solid-State Single-Photon Emitters Authors Jinli Chen, Chaohan Cui, Ben Lawrie, Yongzhou Xue, Saikat Guha, Matt Eichenfield, Huan Zhao, Xiaodong Yan Published: 10.29.2024 Updated: 10.29.2024 Summary Solid-state single-photon emitters (SPEs) are attracting significant attention as fundamental components in quantum computing, communication, and sensing. Low-dimensional materials-based SPEs (LD-SPEs) have drawn particular interest due to their high photon extraction efficiency, ease of integration with photonic circuits, and strong coupling with external fields. The accessible surfaces of LD materials allow for deterministic control over quantum light emission, while enhanced quantum confinement and light-matter interactions improve photon emissive properties. This review examines recent progress in LDSPEs across four key materials: zero-dimensional (0D) semiconductor quantum dots, one-dimensional (1D) nanotubes, two-dimensional (2D) materials, including hexagonal boron nitride (hBN) and transition metal dichalcogenides (TMDCs). We explore their structural and photophysical properties, along with techniques such as spectral tuning and cavity coupling that enhance SPE performance. Finally, we address future challenges and suggest strategies for optimizing LD-SPEs for practical quantum applications. Source arXiv: 2410.22106v1
Long Sequence Modeling with Attention Tensorization: From Sequence to Tensor Learning Authors Aosong Feng, Rex Ying, Leandros Tassiulas Published: 10.28.2024 Updated: 10.28.2024 Summary As the demand for processing extended textual data grows, the ability to handle long-range dependencies and maintain computational efficiency is more critical than ever. One of the key issues for long-sequence modeling using attention-based model is the mismatch between the limited-range modeling power of full attention and the long-range token dependency in the input sequence. In this work, we propose to scale up the attention receptive field by tensorizing long input sequences into compact tensor representations followed by attention on each transformed dimension. The resulting Tensorized Attention can be adopted as efficient transformer backbones to extend input context length with improved memory and time efficiency. We show that the proposed attention tensorization encodes token dependencies as a multi-hop attention process, and is equivalent to Kronecker decomposition of full attention. Extensive experiments show that tensorized attention can be used to adapt pretrained LLMs with improved efficiency. Notably, Llama-8B with tensorization is trained under 32,768 context length and can steadily extrapolate to 128k length during inference with $11times$ speedup, compared to full attention with FlashAttention-2. Source arXiv: 2410.20926v1
Piezoelectrically actuated high-speed spatial light modulator for visible to near-infrared wavelengths Authors Tom Vanackere, Artur Hermans, Ian Christen, Christopher Panuski, Mark Dong, Matthew Zimmermann, Hamza Raniwala, Andrew J. Leenheer, Matt Eichenfield, Gerald Gilbert, Dirk Englund Published: 10.24.2024 Updated: 10.24.2024 Summary Advancements in light modulator technology have been driving discoveries and progress across various fields. The problem of large-scale coherent optical control of atomic quantum systems-including cold atoms, ions, and solid-state color centers-presents among the most stringent requirements. This motivates a new generation of high-speed large-scale modulator technology with the following requirements: (R1) operation at a design wavelength of choice in the visible (VIS) to near-infrared (NIR) spectrum, (R2) a scalable technology with a high channel density (> 100mm-2 ), (R3) a high modulation speed (> 100MHz), and (R4) a high extinction ratio (> 20 dB). To fulfill these requirements, we introduce a modulator technology based on piezoelectrically actuated silicon nitride resonant waveguide gratings fabricated on 200mm diameter silicon wafers with CMOS compatible processes. We present a proof-of-concept device with 4 x 4 individually addressable 50 {mu}m x 50 {mu}m pixels or channels, each containing a resonant waveguide grating with a ~ 780 nm design wavelength, supporting > 100MHz modulation speeds, and a spectral response with > 20 dB extinction. Source arXiv: 2410.19058v1
SplitLLM: Collaborative Inference of LLMs for Model Placement and Throughput Optimization Authors Akrit Mudvari, Yuang Jiang, Leandros Tassiulas Published: 10.14.2024 Updated: 10.14.2024 Summary Large language models (LLMs) have been a disruptive innovation in recent years, and they play a crucial role in our daily lives due to their ability to understand and generate human-like text. Their capabilities include natural language understanding, information retrieval and search, translation, chatbots, virtual assistance, and many more. However, it is well known that LLMs are massive in terms of the number of parameters. Additionally, the self-attention mechanism in the underlying architecture of LLMs, Transformers, has quadratic complexity in terms of both computation and memory with respect to the input sequence length. For these reasons, LLM inference is resource-intensive, and thus, the throughput of LLM inference is limited, especially for the longer sequences. In this report, we design a collaborative inference architecture between a server and its clients to alleviate the throughput limit. In this design, we consider the available resources on both sides, i.e., the computation and communication costs. We develop a dynamic programming-based algorithm to optimally allocate computation between the server and the client device to increase the server throughput, while not violating the service level agreement (SLA). We show in the experiments that we are able to efficiently distribute the workload allowing for roughly 1/3 reduction in the server workload, while achieving 19 percent improvement over a greedy method. As a result, we are able to demonstrate that, in an environment with different types of LLM inference requests, the throughput of the server is improved. Source arXiv: 2410.10759v1
SplitLLM: Collaborative Inference of LLMs for Model Placement and Throughput Optimization Authors Akrit Mudvari, Yuang Jiang, Leandros Tassiulas Published: 10.14.2024 Updated: 10.16.2024 Summary Large language models (LLMs) have been a disruptive innovation in recent years, and they play a crucial role in our daily lives due to their ability to understand and generate human-like text. Their capabilities include natural language understanding, information retrieval and search, translation, chatbots, virtual assistance, and many more. However, it is well known that LLMs are massive in terms of the number of parameters. Additionally, the self-attention mechanism in the underlying architecture of LLMs, Transformers, has quadratic complexity in terms of both computation and memory with respect to the input sequence length. For these reasons, LLM inference is resource-intensive, and thus, the throughput of LLM inference is limited, especially for the longer sequences. In this report, we design a collaborative inference architecture between a server and its clients to alleviate the throughput limit. In this design, we consider the available resources on both sides, i.e., the computation and communication costs. We develop a dynamic programming-based algorithm to optimally allocate computation between the server and the client device to increase the server throughput, while not violating the service level agreement (SLA). We show in the experiments that we are able to efficiently distribute the workload allowing for roughly 1/3 reduction in the server workload, while achieving 19 percent improvement over a greedy method. As a result, we are able to demonstrate that, in an environment with different types of LLM inference requests, the throughput of the server is improved. Source arXiv: 2410.10759v2
Leveraging Internet Principles to Build a Quantum Network Authors Leonardo Bacciottini, Aparimit Chandra, Matheus Guedes De Andrade, Nitish K. Panigrahy, Shahrooz Pouryousef, Nageswara S. V. Rao, Emily Van Milligen, Gayane Vardoyan, Don Towsley Published: 10.11.2024 Updated: 10.11.2024 Summary Designing an operational architecture for the Quantum Internet is a challenging task in light of both fundamental limitations imposed by the laws of physics and technological constraints. Here, we propose a method to abstract away most of the quantum-specific elements and formulate a best-effort quantum network architecture based on packet-switching, akin to that of the classical Internet. Such reframing provides an opportunity to exploit the many tools and protocols available and well-understood within the Internet. As an illustration, we tailor and adapt classical congestion control and active queue management protocols to quantum networks, comprising an architecture wherein quantum end- and intermediate nodes effectively regulate demand and resource utilization, respectively. Results show that these classical networking tools can be effectively used to combat quantum memory decoherence and keep end-to-end fidelity around a target value. Source arXiv: 2410.08980v1
Efficient self-consistent learning of gate set Pauli noise Authors Senrui Chen, Zhihan Zhang, Liang Jiang, Steven T. Flammia Published: 10.04.2024 Updated: 10.04.2024 Summary Understanding quantum noise is an essential step towards building practical quantum information processing systems. Pauli noise is a useful model that has been widely applied in quantum benchmarking, error mitigation, and error correction. Despite intensive study, most existing works focus on learning Pauli noise channels associated with some specific gates rather than treating the gate set as a whole. A learning algorithm that is self-consistent, complete, and efficient at the same time is yet to be established. In this work, we study the task of gate set Pauli noise learning, where a set of quantum gates, state preparation, and measurements all suffer from unknown Pauli noise channels with a customized noise ansatz. Using tools from algebraic graph theory, we analytically characterize the self-consistently learnable degrees of freedom for Pauli noise models with arbitrary linear ansatz, and design experiments to efficiently learn all the learnable information. Specifically, we show that all learnable information about the gate noise can be learned to relative precision, under mild assumptions on the noise ansatz. We then demonstrate the flexibility of our theory by applying it to concrete physically motivated ansatzs (such as spatially local or quasi-local noise) and experimentally relevant gate sets (such as parallel CZ gates). These results not only enhance the theoretical understanding of quantum noise learning, but also provide a feasible recipe for characterizing existing and near-future quantum information processing devices. Source arXiv: 2410.03906v1
Scalable construction of hybrid quantum photonic cavities Authors Andrew S. Greenspon, Mark Dong, Ian Christen, Gerald Gilbert, Matt Eichenfield, Dirk Englund Published: 10.04.2024 Updated: 10.04.2024 Summary Nanophotonic resonators are central to numerous applications, from efficient spin-photon interfaces to laser oscillators and precision sensing. A leading approach consists of photonic crystal (PhC) cavities, which have been realized in a wide range of dielectric materials. However, translating proof-of-concept devices into a functional system entails a number of additional challenges, inspiring new approaches that combine: resonators with wavelength-scale confinement and high quality factors; scalable integration with integrated circuits and photonic circuits; electrical or mechanical cavity tuning; and, in many cases, a need for heterogeneous integration with functional materials such as III-V semiconductors or diamond color centers for spin-photon interfaces. Here we introduce a concept that generates a finely tunable PhC cavity at a select wavelength between two heterogeneous optical materials whose properties satisfy the above requirements. The cavity is formed by stamping a hard-to-process material with simple waveguide geometries on top of an easy-to-process material consisting of dielectric grating mirrors and active tuning capability. We simulate our concept for the particularly challenging design problem of multiplexed quantum repeaters based on arrays of cavity-coupled diamond color centers, achieving theoretically calculated unloaded quality factors of $10^6$, mode volumes as small as $1.2(lambda/n_{eff})^3$, and maintaining >60 percent total on-chip collection efficiency of fluorescent photons. We further introduce a method of low-power piezoelectric tuning of these hybrid diamond cavities, simulating optical resonance shifts up to ~760 GHz and color center fluorescence tuning of 5 GHz independent of cavity tuning. These results will motivate integrated photonic cavities toward larger scale systems-compatible designs. Source arXiv: 2410.03851v1
Quantum-data-driven dynamical transition in quantum learning Authors Bingzhi Zhang, Junyu Liu, Liang Jiang, Quntao Zhuang Published: 10.02.2024 Updated: 10.02.2024 Summary Quantum circuits are an essential ingredient of quantum information processing. Parameterized quantum circuits optimized under a specific cost function — quantum neural networks (QNNs) — provide a paradigm for achieving quantum advantage in the near term. Understanding QNN training dynamics is crucial for optimizing their performance. In terms of supervised learning tasks such as classification and regression for large datasets, the role of quantum data in QNN training dynamics remains unclear. We reveal a quantum-data-driven dynamical transition, where the target value and data determine the polynomial or exponential convergence of the training. We analytically derive the complete classification of fixed points from the dynamical equation and reveal a comprehensive `phase diagram’ featuring seven distinct dynamics. These dynamics originate from a bifurcation transition with multiple codimensions induced by training data, extending the transcritical bifurcation in simple optimization tasks. Furthermore, perturbative analyses identify an exponential convergence class and a polynomial convergence class among the seven dynamics. We provide a non-perturbative theory to explain the transition via generalized restricted Haar ensemble. The analytical results are confirmed with numerical simulations of QNN training and experimental verification on IBM quantum devices. As the QNN training dynamics is determined by the choice of the target value, our findings provide guidance on constructing the cost function to optimize the speed of convergence. Source arXiv: 2410.01955v1
Optimizing the Optical Properties of Tin Oxide Aerogels through Defect Passivation Authors John F. Hardy II, Madison King, Stephanie Hurst, Carlo R. daCunha Published: 10.01.2024 Updated: 10.01.2024 Summary Tin oxide aerogels were synthesized using an epoxide-assisted technique and characterized with Fourier transform infrared, X-ray diffraction, and UV-Vis to study the effects of post-synthesis annealing and peroxide treatment. While bulk tin oxide exhibits an optical bandgap of $3.6$ eV, its aerogel form often displays a larger apparent bandgap around $4.6$ eV due to defects. Our study reveals that annealing induces a partial phase change from SnO$_2$ to SnO, but is ineffective in removing defects. Conversely, peroxide passivation effectively lowers the bandgap and disorder levels, suggesting that dangling bonds are the primary cause of the increased bandgap in tin oxide aerogels. These findings offer insights for optimizing the optical properties of tin oxide aerogels for applications like solar cells. Source arXiv: 2410.00883v1
Hardware-efficient quantum error correction using concatenated bosonic qubits Authors Harald Putterman, Kyungjoo Noh, Connor T. Hann, Gregory S. MacCabe, Shahriar Aghaeimeibodi, Rishi N. Patel, Menyoung Lee, William M. Jones, Hesam Moradinejad, Roberto Rodriguez, Neha Mahuli, Jefferson Rose, John Clai Owens, Harry Levine, Emma Rosenfeld, Philip Reinhold, Lorenzo Moncelsi, Joshua Ari Alcid, Nasser Alidoust, Patricio Arrangoiz-Arriola, James Barnett, Przemyslaw Bienias, Hugh A. Carson, Cliff Chen, Li Chen, Harutiun Chinkezian, Eric M. Chisholm, Ming-Han Chou, Aashish Clerk, Andrew Clifford, R. Cosmic, Ana Valdes Curiel, Erik Davis, Laura DeLorenzo, J. Mitchell D'Ewart, Art Diky, Nathan D'Souza, Philipp T. Dumitrescu, Shmuel Eisenmann, Essam Elkhouly, Glen Evenbly, Michael T. Fang, Yawen Fang, Matthew J. Fling, Warren Fon, Gabriel Garcia, Alexey V. Gorshkov, Julia A. Grant, Mason J. Gray, Sebastian Grimberg, Arne L. Grimsmo, Arbel Haim, Justin Hand, Yuan He, Mike Hernandez, David Hover, Jimmy S. C. Hung, Matthew Hunt, Joe Iverson, Ignace Jarrige, Jean-Christophe Jaskula, Liang Jiang, Mahmoud Kalaee, Rassul Karabalin, Peter J. Karalekas, Andrew J. Keller, Amirhossein Khalajhedayati, Aleksander Kubica, Hanho Lee, Catherine Leroux, Simon Lieu, Victor Ly, Keven Villegas Madrigal, Guillaume Marcaud, Gavin McCabe, Cody Miles, Ashley Milsted, Joaquin Minguzzi, Anurag Mishra, Biswaroop Mukherjee, Mahdi Naghiloo, Eric Oblepias, Gerson Ortuno, Jason Pagdilao, Nicola Pancotti, Ashley Panduro, JP Paquette, Minje Park, Gregory A. Peairs, David Perello, Eric C. Peterson, Sophia Ponte, John Preskill, Johnson Qiao, Gil Refael, Rachel Resnick, Alex Retzker, Omar A. Reyna, Marc Runyan, Colm A. Ryan, Abdulrahman Sahmoud, Ernesto Sanchez, Rohan Sanil, Krishanu Sankar, Yuki Sato, Thomas Scaffidi, Salome Siavoshi, Prasahnt Sivarajah, Trenton Skogland, Chun-Ju Su, Loren J. Swenson, Stephanie M. Teo, Astrid Tomada, Giacomo Torlai, E. Alex Wollack, Yufeng Ye, Jessica A. Zerrudo, Kailing Zhang, Fernando G. S. L. Brandão, Matthew H. Matheny, Oskar Painter Published: 09.19.2024 Updated: 09.19.2024 Summary In order to solve problems of practical importance, quantum computers will likely need to incorporate quantum error correction, where a logical qubit is redundantly encoded in many noisy physical qubits. The large physical-qubit overhead typically associated with error correction motivates the search for more hardware-efficient approaches. Here, using a microfabricated superconducting quantum circuit, we realize a logical qubit memory formed from the concatenation of encoded bosonic cat qubits with an outer repetition code of distance $d=5$. The bosonic cat qubits are passively protected against bit flips using a stabilizing circuit. Cat-qubit phase-flip errors are corrected by the repetition code which uses ancilla transmons for syndrome measurement. We realize a noise-biased CX gate which ensures bit-flip error suppression is maintained during error correction. We study the performance and scaling of the logical qubit memory, finding that the phase-flip correcting repetition code operates below threshold, with logical phase-flip error decreasing with code distance from $d=3$ to $d=5$. Concurrently, the logical bit-flip error is suppressed with increasing cat-qubit mean photon number. The minimum measured logical error per cycle is on average $1.75(2)%$ for the distance-3 code sections, and $1.65(3)%$ for the longer distance-5 code, demonstrating the effectiveness of bit-flip error suppression throughout the error correction cycle. These results, where the intrinsic error suppression of the bosonic encodings allows us to use a hardware-efficient outer error correcting code, indicate that concatenated bosonic codes are a compelling paradigm for reaching fault-tolerant quantum computation. Source arXiv: 2409.13025v1
Quantum Margulis Codes Authors Michele Pacenti, Bane Vasic Published: 09.15.2024 Updated: 09.15.2024 Summary Recently, Lin and Pryadko presented the quantum two-block group algebra codes, a generalization of bicycle codes obtained from Cayley graphs of non-Abelian groups. We notice that their construction is naturally suitable to obtain a quantum equivalent of the well-known classical Margulis code. In this paper, we first present an alternative description of the two-block group algebra codes using the left-right Cayley complex; then, we show how to modify the construction of Margulis to get a two-block algebra code. Finally, we construct several quantum Margulis codes and evaluate their performance with numerical simulations. Source arXiv: 2409.09830v1
Throughput-Optimal Scheduling via Rate Learning Authors Panagiotis Promponas, Víctor Valls, Konstantinos Nikolakakis, Dionysis Kalogerias, Leandros Tassiulas Published: 09.13.2024 Updated: 09.13.2024 Summary We study the problem of designing scheduling policies for communication networks. This problem is often addressed with max-weight-type approaches since they are throughput-optimal. However, max-weight policies make scheduling decisions based on the network congestion, which can be sometimes unnecessarily restrictive. In this paper, we present a “schedule as you learn” (SYL) approach, where we learn an average rate, and then select schedules that generate such a rate in expectation. This approach is interesting because scheduling decisions do not depend on the size of the queue backlogs, and so it provides increased flexibility to select schedules based on other criteria or rules, such as serving high-priority queues. We illustrate the results with numerical experiments for a cross-bar switch and show that, compared to max-weight, SYL can achieve lower latency to certain flows without compromising throughput optimality. Source arXiv: 2409.09198v1
Single-photon detectors on arbitrary photonic substrates Authors Max Tao, Hugo Larocque, Samuel Gyger, Marco Colangelo, Owen Medeiros, Ian Christen, Hamed Sattari, Gregory Choong, Yves Petremand, Ivan Prieto, Yang Yu, Stephan Steinhauer, Gerald L. Leake, Daniel J. Coleman, Amir H. Ghadimi, Michael L. Fanto, Val Zwiller, Dirk Englund, Carlos Errando-Herranz Published: 09.12.2024 Updated: 09.12.2024 Summary Detecting non-classical light is a central requirement for photonics-based quantum technologies. Unrivaled high efficiencies and low dark counts have positioned superconducting nanowire single photon detectors (SNSPDs) as the leading detector technology for fiber and integrated photonic applications. However, a central challenge lies in their integration within photonic integrated circuits regardless of material platform or surface topography. Here, we introduce a method based on transfer printing that overcomes these constraints and allows for the integration of SNSPDs onto arbitrary photonic substrates. We prove this by integrating SNSPDs and showing through-waveguide single-photon detection in commercially manufactured silicon and lithium niobate on insulator integrated photonic circuits. Our method eliminates bottlenecks to the integration of high-quality single-photon detectors, turning them into a versatile and accessible building block for scalable quantum information processing. Source arXiv: 2409.08412v1
Over-the-Air Federated Learning via Weighted Aggregation Authors Seyed Mohammad Azimi-Abarghouyi, Leandros Tassiulas Published: 09.12.2024 Updated: 09.12.2024 Summary This paper introduces a new federated learning scheme that leverages over-the-air computation. A novel feature of this scheme is the proposal to employ adaptive weights during aggregation, a facet treated as predefined in other over-the-air schemes. This can mitigate the impact of wireless channel conditions on learning performance, without needing channel state information at transmitter side (CSIT). We provide a mathematical methodology to derive the convergence bound for the proposed scheme in the context of computational heterogeneity and general loss functions, supplemented with design insights. Accordingly, we propose aggregation cost metrics and efficient algorithms to find optimized weights for the aggregation. Finally, through numerical experiments, we validate the effectiveness of the proposed scheme. Even with the challenges posed by channel conditions and device heterogeneity, the proposed scheme surpasses other over-the-air strategies by an accuracy improvement of 15% over the scheme using CSIT and 30% compared to the one without CSIT. Source arXiv: 2409.07822v1
Uncovering Quantum Many-body Scars with Quantum Machine Learning Authors Jiajin Feng, Bingzhi Zhang, Zhi-Cheng Yang, Quntao Zhuang Published: 09.11.2024 Updated: 09.11.2024 Summary Quantum many-body scars are rare eigenstates hidden within the chaotic spectra of many-body systems, representing a weak violation of the eigenstate thermalization hypothesis (ETH). Identifying these scars, as well as other non-thermal states in complex quantum systems, remains a significant challenge. Besides exact scar states, the nature of other non-thermal states lacking simple analytical characterization remains an open question. In this study, we employ tools from quantum machine learning — specifically, quantum convolutional neural networks (QCNNs), to explore hidden non-thermal states in chaotic many-body systems. Our simulations demonstrate that QCNNs achieve over 99% single-shot measurement accuracy in identifying all known scars. Furthermore, we successfully identify new non-thermal states in models such as the xorX model, the PXP model, and the far-coupling Su-Schrieffer-Heeger model. In the xorX model, some of these non-thermal states can be approximately described as spin-wave modes of specific quasiparticles. We further develop effective tight-binding Hamiltonians within the quasiparticle subspace to capture key features of these many-body eigenstates. Finally, we validate the performance of QCNNs on IBM quantum devices, achieving single-shot measurement accuracy exceeding 63% under real-world noise and errors, with the aid of error mitigation techniques. Our results underscore the potential of QCNNs to uncover hidden non-thermal states in quantum many-body systems. Source arXiv: 2409.07405v1
Comparing One- and Two-way Quantum Repeater Architectures Authors Prateek Mantri, Kenneth Goodenough, Don Towsley Published: 09.10.2024 Updated: 09.10.2024 Summary Quantum repeaters are an essential building block for realizing long-distance quantum communications. However, due to the fragile nature of quantum information, these repeaters suffer from loss and operational errors. Prior works have classified repeaters into three broad categories based on their use of probabilistic or near-deterministic methods to mitigate these errors. Besides differences in classical communication times, these approaches also vary in technological complexity, with near-deterministic methods requiring more advanced technology. Recent increases in the number of available memories, and introduction of entanglement generation through multiplexing motivate a re-comparison of one-way and two-way repeater architectures. In this work, we propose a novel protocol that optimizes multiplexed elementary link generation and distillation in memory-unconstrained ‘connection-oriented’ two-way repeaters to boost the entanglement generation rates. We introduce a recursive formulation to derive the probability distribution of the number of Bell pairs in multiplexed two-way repeater architectures, compatible with probabilistic $n$-to-$k$ distillation protocols. We then compare the performance of this new protocol with one-way schemes in the parameter regime where one-way schemes have previously been shown to be advantageous, and find that the multiplexed two-way protocol provides better performance with lower resource and technology requirements. Source arXiv: 2409.06152v1
Tele-LLMs: A Series of Specialized Large Language Models for Telecommunications Authors Ali Maatouk, Kenny Chirino Ampudia, Rex Ying, Leandros Tassiulas Published: 09.09.2024 Updated: 09.09.2024 Summary The emergence of large language models (LLMs) has significantly impacted various fields, from natural language processing to sectors like medicine and finance. However, despite their rapid proliferation, the applications of LLMs in telecommunications remain limited, often relying on general-purpose models that lack domain-specific specialization. This lack of specialization results in underperformance, particularly when dealing with telecommunications-specific technical terminology and their associated mathematical representations. This paper addresses this gap by first creating and disseminating Tele-Data, a comprehensive dataset of telecommunications material curated from relevant sources, and Tele-Eval, a large-scale question-and-answer dataset tailored to the domain. Through extensive experiments, we explore the most effective training techniques for adapting LLMs to the telecommunications domain, ranging from examining the division of expertise across various telecommunications aspects to employing parameter-efficient techniques. We also investigate how models of different sizes behave during adaptation and analyze the impact of their training data on this behavior. Leveraging these findings, we develop and open-source Tele-LLMs, the first series of language models ranging from 1B to 8B parameters, specifically tailored for telecommunications. Our evaluations demonstrate that these models outperform their general-purpose counterparts on Tele-Eval while retaining their previously acquired capabilities, thus avoiding the catastrophic forgetting phenomenon. Source arXiv: 2409.05314v1
Tele-LLMs: A Series of Specialized Large Language Models for Telecommunications Authors Ali Maatouk, Kenny Chirino Ampudia, Rex Ying, Leandros Tassiulas Published: 09.09.2024 Updated: 09.13.2024 Summary The emergence of large language models (LLMs) has significantly impacted various fields, from natural language processing to sectors like medicine and finance. However, despite their rapid proliferation, the applications of LLMs in telecommunications remain limited, often relying on general-purpose models that lack domain-specific specialization. This lack of specialization results in underperformance, particularly when dealing with telecommunications-specific technical terminology and their associated mathematical representations. This paper addresses this gap by first creating and disseminating Tele-Data, a comprehensive dataset of telecommunications material curated from relevant sources, and Tele-Eval, a large-scale question-and-answer dataset tailored to the domain. Through extensive experiments, we explore the most effective training techniques for adapting LLMs to the telecommunications domain, ranging from examining the division of expertise across various telecommunications aspects to employing parameter-efficient techniques. We also investigate how models of different sizes behave during adaptation and analyze the impact of their training data on this behavior. Leveraging these findings, we develop and open-source Tele-LLMs, the first series of language models ranging from 1B to 8B parameters, specifically tailored for telecommunications. Our evaluations demonstrate that these models outperform their general-purpose counterparts on Tele-Eval while retaining their previously acquired capabilities, thus avoiding the catastrophic forgetting phenomenon. Source arXiv: 2409.05314v2
Quantum-enhanced dark matter detection with in-cavity control: mitigating the Rayleigh curse Authors Haowei Shi, Anthony J. Brady, Wojciech Górecki, Lorenzo Maccone, Roberto Di Candia, Quntao Zhuang Published: 09.06.2024 Updated: 09.06.2024 Summary The nature of dark matter is a fundamental puzzle in modern physics. A major approach of searching for dark matter relies on detecting feeble noise in microwave cavities. However, the quantum advantages of common quantum resources such as squeezing are intrinsically limited by the Rayleigh curse — a constant loss places a sensitivity upper bound on these quantum resources. In this paper, we propose an in-situ protocol to mitigate such Rayleigh limit. The protocol consists of three steps: in-cavity quantum state preparation, axion accumulation with tunable time duration, and measurement. For the quantum source, we focus on the single-mode squeezed state (SMSS), and the entanglement-assisted case using signal-ancilla pairs in two-mode squeezed state (TMSS), where the ancilla does not interact with the axion. From quantum Fisher information rate evaluation, we derive the requirement of cavity quality factor, thermal noise level and squeezing gain for quantum advantage. When the squeezing gain becomes larger, the optimal axion accumulation time decreases to reduce loss and mitigate the Rayleigh curse — the quantum advantage keeps increasing with the squeezing gain. Overall, we find that TMSS is more sensitive in the low temperature limit. In the case of SMSS, as large gain is required for advantage over vacuum, homodyne is sufficient to achieve optimality. For TMSS, anti-squeezing and photon counting is necessary to be optimal. Thanks to the recent advance in magnetic-field-resilient in-cavity squeezing and rapidly coupling out for photon counting, the proposed protocol is compatible with axion detection scenario. Source arXiv: 2409.04656v1
Adaptive Super-Resolution Imaging Without Prior Knowledge Using a Programmable Spatial-Mode Sorter Authors Itay Ozer, Michael. R. Grace, Pierre-Alexandre Blanche, Saikat Guha Published: 09.06.2024 Updated: 09.06.2024 Summary We consider an imaging system tasked with estimating the angular distance between two incoherently-emitting sub-Rayleigh-separated point sources, without any prior knowledge of the centroid or the constellation and with a fixed collected-photon budget. It was shown theoretically that splitting the optical recording time into two stages — focal-plane direct imaging to obtain a pre-estimate of the centroid, and using that estimate to center a spatial-mode sorter followed by photon detection of the sorted modes — can achieve 10 to 100 times lower mean squared error in estimating the separation. In this paper, we demonstrate this in proof-of-concept, using a programmable mode sorter we have built using multi-plane light conversion (MPLC) using a reflective spatial-light modulator (SLM) in an emulated experiment where we use a single coherent source to characterize the MPLC to electronically piece together the signature from two closely-separated quasi-monochromatic incoherent emitters. Source arXiv: 2409.04323v1
LitFM: A Retrieval Augmented Structure-aware Foundation Model For Citation Graphs Authors Jiasheng Zhang, Jialin Chen, Ali Maatouk, Ngoc Bui, Qianqian Xie, Leandros Tassiulas, Jie Shao, Hua Xu, Rex Ying Published: 09.05.2024 Updated: 09.05.2024 Summary With the advent of large language models (LLMs), managing scientific literature via LLMs has become a promising direction of research. However, existing approaches often overlook the rich structural and semantic relevance among scientific literature, limiting their ability to discern the relationships between pieces of scientific knowledge, and suffer from various types of hallucinations. These methods also focus narrowly on individual downstream tasks, limiting their applicability across use cases. Here we propose LitFM, the first literature foundation model designed for a wide variety of practical downstream tasks on domain-specific literature, with a focus on citation information. At its core, LitFM contains a novel graph retriever to integrate graph structure by navigating citation graphs and extracting relevant literature, thereby enhancing model reliability. LitFM also leverages a knowledge-infused LLM, fine-tuned through a well-developed instruction paradigm. It enables LitFM to extract domain-specific knowledge from literature and reason relationships among them. By integrating citation graphs during both training and inference, LitFM can generalize to unseen papers and accurately assess their relevance within existing literature. Additionally, we introduce new large-scale literature citation benchmark datasets on three academic fields, featuring sentence-level citation information and local context. Extensive experiments validate the superiority of LitFM, achieving 28.1% improvement on retrieval task in precision, and an average improvement of 7.52% over state-of-the-art across six downstream literature-related tasks Source arXiv: 2409.12177v1
Quantum Illumination Advantage for Classification Among an Arbitrary Library of Targets Authors Ali Cox, Quntao Zhuang, Jeffrey H. Shapiro, Saikat Guha Published: 08.24.2024 Updated: 08.24.2024 Summary Quantum illumination (QI) is the task of querying a scene using a transmitter probe whose quantum state is entangled with a reference beam retained in ideal storage, followed by optimally detecting the target-returned light together with the stored reference, to make decisions on characteristics of targets at stand-off range, at precision that exceeds what is achievable with a classical transmitter of the same brightness and otherwise identical conditions. Using tools from perturbation theory, we show that in the limit of low transmitter brightness, high loss, and high thermal background, there is a factor of four improvement in the Chernoff exponent of the error probability in discriminating any number of apriori-known reflective targets when using a Gaussian-state entangled QI probe, over using classical coherent-state illumination (CI). While this advantage was known for detecting the presence or absence of a target, it had not been proven for the generalized task of discriminating between arbitrary target libraries. In proving our result, we derive simple general analytic expressions for the lowest-order asymptotic expansions of the quantum Chernoff exponents for QI and CI in terms of the signal brightness, loss, thermal noise, and the modal expansion coefficients of the target-reflected light’s radiant exitance profiles when separated by a spatial mode sorter after entering the entrance pupil of the receiver’s aperture. Source arXiv: 2408.13489v1
A Practical Introduction to Benchmarking and Characterization of Quantum Computers Authors Akel Hashim, Long B. Nguyen, Noah Goss, Brian Marinelli, Ravi K. Naik, Trevor Chistolini, Jordan Hines, J. P. Marceaux, Yosep Kim, Pranav Gokhale, Teague Tomesh, Senrui Chen, Liang Jiang, Samuele Ferracin, Kenneth Rudinger, Timothy Proctor, Kevin C. Young, Robin Blume-Kohout, Irfan Siddiqi Published: 08.22.2024 Updated: 08.22.2024 Summary Rapid progress in quantum technology has transformed quantum computing and quantum information science from theoretical possibilities into tangible engineering challenges. Breakthroughs in quantum algorithms, quantum simulations, and quantum error correction are bringing useful quantum computation closer to fruition. These remarkable achievements have been facilitated by advances in quantum characterization, verification, and validation (QCVV). QCVV methods and protocols enable scientists and engineers to scrutinize, understand, and enhance the performance of quantum information-processing devices. In this Tutorial, we review the fundamental principles underpinning QCVV, and introduce a diverse array of QCVV tools used by quantum researchers. We define and explain QCVV’s core models and concepts — quantum states, measurements, and processes — and illustrate how these building blocks are leveraged to examine a target system or operation. We survey and introduce protocols ranging from simple qubit characterization to advanced benchmarking methods. Along the way, we provide illustrated examples and detailed descriptions of the protocols, highlight the advantages and disadvantages of each, and discuss their potential scalability to future large-scale quantum computers. This Tutorial serves as a guidebook for researchers unfamiliar with the benchmarking and characterization of quantum computers, and also as a detailed reference for experienced practitioners. Source arXiv: 2408.12064v1
Is the Lecture Engaging for Learning? Lecture Voice Sentiment Analysis for Knowledge Graph-Supported Intelligent Lecturing Assistant (ILA) System Authors Yuan An, Samarth Kolanupaka, Jacob An, Matthew Ma, Unnat Chhatwal, Alex Kalinowski, Michelle Rogers, Brian Smith Published: 08.20.2024 Updated: 08.20.2024 Summary This paper introduces an intelligent lecturing assistant (ILA) system that utilizes a knowledge graph to represent course content and optimal pedagogical strategies. The system is designed to support instructors in enhancing student learning through real-time analysis of voice, content, and teaching methods. As an initial investigation, we present a case study on lecture voice sentiment analysis, in which we developed a training set comprising over 3,000 one-minute lecture voice clips. Each clip was manually labeled as either engaging or non-engaging. Utilizing this dataset, we constructed and evaluated several classification models based on a variety of features extracted from the voice clips. The results demonstrate promising performance, achieving an F1-score of 90% for boring lectures on an independent set of over 800 test voice clips. This case study lays the groundwork for the development of a more sophisticated model that will integrate content analysis and pedagogical practices. Our ultimate goal is to aid instructors in teaching more engagingly and effectively by leveraging modern artificial intelligence techniques. Source arXiv: 2408.10492v1
Is the Lecture Engaging for Learning? Lecture Voice Sentiment Analysis for Knowledge Graph-Supported Intelligent Lecturing Assistant (ILA) System Authors Yuan An, Samarth Kolanupaka, Jacob An, Matthew Ma, Unnat Chhatwal, Alex Kalinowski, Michelle Rogers, Brian Smith Published: 08.20.2024 Updated: 10.29.2024 Summary This paper introduces an intelligent lecturing assistant (ILA) system that utilizes a knowledge graph to represent course content and optimal pedagogical strategies. The system is designed to support instructors in enhancing student learning through real-time analysis of voice, content, and teaching methods. As an initial investigation, we present a case study on lecture voice sentiment analysis, in which we developed a training set comprising over 3,000 one-minute lecture voice clips. Each clip was manually labeled as either engaging or non-engaging. Utilizing this dataset, we constructed and evaluated several classification models based on a variety of features extracted from the voice clips. The results demonstrate promising performance, achieving an F1-score of 90% for boring lectures on an independent set of over 800 test voice clips. This case study lays the groundwork for the development of a more sophisticated model that will integrate content analysis and pedagogical practices. Our ultimate goal is to aid instructors in teaching more engagingly and effectively by leveraging modern artificial intelligence techniques. Source arXiv: 2408.10492v2
The curse of random quantum data Authors Kaining Zhang, Junyu Liu, Liu Liu, Liang Jiang, Min-Hsiu Hsieh, Dacheng Tao Published: 08.19.2024 Updated: 08.19.2024 Summary Quantum machine learning, which involves running machine learning algorithms on quantum devices, may be one of the most significant flagship applications for these devices. Unlike its classical counterparts, the role of data in quantum machine learning has not been fully understood. In this work, we quantify the performances of quantum machine learning in the landscape of quantum data. Provided that the encoding of quantum data is sufficiently random, the performance, we find that the training efficiency and generalization capabilities in quantum machine learning will be exponentially suppressed with the increase in the number of qubits, which we call “the curse of random quantum data”. Our findings apply to both the quantum kernel method and the large-width limit of quantum neural networks. Conversely, we highlight that through meticulous design of quantum datasets, it is possible to avoid these curses, thereby achieving efficient convergence and robust generalization. Our conclusions are corroborated by extensive numerical simulations. Source arXiv: 2408.09937v1
Towards the Information-Theoretic Limit of Programmable Photonics Authors Ryan Hamerly, Jasvith Raj Basani, Alexander Sludds, Sri Krishna Vadlamani, Dirk Englund Published: 08.19.2024 Updated: 08.19.2024 Summary The scalability of many programmable photonic circuits is limited by the $2pi$ tuning range needed for the constituent phase shifters. To address this problem, we introduce the concept of a phase-efficient circuit architecture, where the average phase shift is $ll 2pi$. We derive a universal information-theoretic limit to the phase-shift efficiency of universal multiport interferometers, and propose a “3-MZI” architecture that approaches this limit to within a factor of $2times$, approximately a $10times$ reduction in average phase shift over the prior art, where the average phase shift scales inversely with system size as $O(1/sqrt{N})$. For non-unitary circuits, we show that the 3-MZI saturates the theoretical bound for Gaussian-distributed target matrices. Using this architecture, we show optical neural network training with all phase shifters constrained to $lesssim 0.2$ radians without loss of accuracy. Source arXiv: 2408.09673v1
Fault-tolerant optical interconnects for neutral-atom arrays Authors Josiah Sinclair, Joshua Ramette, Brandon Grinkemeyer, Dolev Bluvstein, Mikhail Lukin, Vladan Vuletić Published: 08.16.2024 Updated: 08.16.2024 Summary We analyze the use of photonic links to enable large-scale fault-tolerant connectivity of locally error-corrected modules based on neutral atom arrays. Our approach makes use of recent theoretical results showing the robustness of surface codes to boundary noise and combines recent experimental advances in atom array quantum computing with logical qubits with optical quantum networking techniques. We find the conditions for fault-tolerance can be achieved with local two-qubit Rydberg gate and non-local Bell pair errors below 1% and 10%, respectively, without requiring distillation or space-time overheads. Realizing the interconnects with a lens, a single optical cavity, or an array of cavities enables a Bell pair generation rate in the 1-50 MHz range. When directly interfacing logical qubits, this rate translates to error-correction cycles in the 25-2000 kHz range, satisfying all requirements for fault tolerance and in the upper range fast enough for 100 kHz logical clock cycles. Source arXiv: 2408.08955v1
Stabilizer Entanglement Distillation and Efficient Fault-Tolerant Encoder Authors Yu Shi, Ashlesha Patil, Saikat Guha Published: 08.12.2024 Updated: 08.12.2024 Summary Entanglement is essential for quantum information processing but is limited by noise. We address this by developing high-yield entanglement distillation protocols with several advancements. (1) We extend the 2-to-1 recurrence entanglement distillation protocol to higher-rate n-to-(n-1) protocols that can correct any single-qubit errors. These protocols are evaluated through numerical simulations focusing on fidelity and yield. We also outline a method to adapt any classical error-correcting code for entanglement distillation, where the code can correct both bit-flip and phase-flip errors by incorporating Hadamard gates. (2) We propose a constant-depth decoder for stabilizer codes that transforms logical states into physical ones using single-qubit measurements. This decoder is applied to entanglement distillation protocols, reducing circuit depth and enabling protocols derived from advanced quantum error-correcting codes. We demonstrate this by evaluating the circuit complexity for entanglement distillation protocols based on surface codes and quantum convolutional codes. (3) Our stabilizer entanglement distillation techniques advance quantum computing. We propose a fault-tolerant protocol for constant-depth encoding and decoding of arbitrary quantum states, applicable to quantum low-density parity-check (qLDPC) codes and surface codes. This protocol is feasible with state-of-the-art reconfigurable atom arrays and surpasses the limits of conventional logarithmic depth encoders. Overall, our study integrates stabilizer formalism, measurement-based quantum computing, and entanglement distillation, advancing both quantum communication and computing. Source arXiv: 2408.06299v1
Quantum-secure multiparty deep learning Authors Kfir Sulimany, Sri Krishna Vadlamani, Ryan Hamerly, Prahlad Iyengar, Dirk Englund Published: 08.10.2024 Updated: 09.13.2024 Summary Secure multiparty computation enables the joint evaluation of multivariate functions across distributed users while ensuring the privacy of their local inputs. This field has become increasingly urgent due to the exploding demand for computationally intensive deep learning inference. These computations are typically offloaded to cloud computing servers, leading to vulnerabilities that can compromise the security of the clients’ data. To solve this problem, we introduce a linear algebra engine that leverages the quantum nature of light for information-theoretically secure multiparty computation using only conventional telecommunication components. We apply this linear algebra engine to deep learning and derive rigorous upper bounds on the information leakage of both the deep neural network weights and the client’s data via the Holevo and the Cram’er-Rao bounds, respectively. Applied to the MNIST classification task, we obtain test accuracies exceeding $96%$ while leaking less than $0.1$ bits per weight symbol and $0.01$ bits per data symbol. This weight leakage is an order of magnitude below the minimum bit precision required for accurate deep learning using state-of-the-art quantization techniques. Our work lays the foundation for practical quantum-secure computation and unlocks secure cloud deep learning as a field. Source arXiv: 2408.05629v2
Quantum-secure multiparty deep learning Authors Kfir Sulimany, Sri Krishna Vadlamani, Ryan Hamerly, Prahlad Iyengar, Dirk Englund Published: 08.10.2024 Updated: 08.10.2024 Summary Secure multiparty computation enables the joint evaluation of multivariate functions across distributed users while ensuring the privacy of their local inputs. This field has become increasingly urgent due to the exploding demand for computationally intensive deep learning inference. These computations are typically offloaded to cloud computing servers, leading to vulnerabilities that can compromise the security of the clients’ data. To solve this problem, we introduce a linear algebra engine that leverages the quantum nature of light for information-theoretically secure multiparty computation using only conventional telecommunication components. We apply this linear algebra engine to deep learning and derive rigorous upper bounds on the information leakage of both the deep neural network weights and the client’s data via the Holevo and the Cram’er-Rao bounds, respectively. Applied to the MNIST classification task, we obtain test accuracies exceeding $96%$ while leaking less than $0.1$ bits per weight symbol and $0.01$ bits per data symbol. This weight leakage is an order of magnitude below the minimum bit precision required for accurate deep learning using state-of-the-art quantization techniques. Our work lays the foundation for practical quantum-secure computation and unlocks secure cloud deep learning as a field. Source arXiv: 2408.05629v1
Role of Error Syndromes in Teleportation Scheduling Authors Aparimit Chandra, Filip Rozpędek, Don Towsley Published: 08.08.2024 Updated: 08.08.2024 Summary Quantum teleportation enables quantum information transmission, but requires distribution of entangled resource states. Unfortunately, decoherence, caused by environmental interference during quantum state storage, can degrade quantum states, leading to entanglement loss in the resource state and reduction of the fidelity of the teleported information. In this work, we investigate the use of error correction and error syndrome information in scheduling teleportation at a quantum network node in the presence of multiple teleportation requests and a finite rate of remote entanglement distribution. Specifically, we focus on the scenario where stored qubits undergo decoherence over time due to imperfect memories. To protect the qubits from the resulting errors, we employ quantum encodings, and the stored qubits undergo repeated error correction, generating error syndromes in each round. These error syndromes can provide additional benefits, as they can be used to calculate qubit-specific error likelihoods, which can then be utilized to make better scheduling decisions. By integrating error correction techniques into the scheduling process, our goal is to minimize errors and decoherence effects, thereby enhancing the fidelity and efficiency of teleportation in a quantum network setting. Source arXiv: 2408.04536v1
Dark spin-cats as biased qubits Authors Andreas Kruckenhauser, Ming Yuan, Han Zheng, Mikhail Mamaev, Pei Zeng, Xuanhui Mao, Qian Xu, Torsten V. Zache, Liang Jiang, Rick van Bijnen, Peter Zoller Published: 08.08.2024 Updated: 08.08.2024 Summary We present a biased atomic qubit, universally implementable across all atomic platforms, encoded as a `spin-cat’ within ground state Zeeman levels. The key characteristic of our configuration is the coupling of the ground state spin manifold of size $F_g gg 1$ to an excited Zeeman spin manifold of size $F_e = F_g – 1$ using light. This coupling results in eigenstates of the driven atom that include exactly two dark states in the ground state manifold, which are decoupled from light and immune to spontaneous emission from the excited states. These dark states constitute the `spin-cat’, leading to the designation `dark spin-cat’. We demonstrate that under strong Rabi drive and for large $F_g$, the `dark spin-cat’ is autonomously stabilized against common noise sources and encodes a qubit with significantly biased noise. Specifically, the bit-flip error rate decreases exponentially with $F_g$ relative to the dephasing rate. We provide an analysis of dark spin-cats, their robustness to noise, and discuss bias-preserving single qubit and entangling gates, exemplified on a Rydberg tweezer platform. Source arXiv: 2408.04421v1
Entanglement-enhanced learning of quantum processes at scale Authors Alireza Seif, Senrui Chen, Swarnadeep Majumder, Haoran Liao, Derek S. Wang, Moein Malekakhlagh, Ali Javadi-Abhari, Liang Jiang, Zlatko K. Minev Published: 08.06.2024 Updated: 08.06.2024 Summary Learning unknown processes affecting a quantum system reveals underlying physical mechanisms and enables suppression, mitigation, and correction of unwanted effects. Describing a general quantum process requires an exponentially large number of parameters. Measuring these parameters, when they are encoded in incompatible observables, is constrained by the uncertainty principle and requires exponentially many measurements. However, for Pauli channels, having access to an ideal quantum memory and entangling operations allows encoding parameters in commuting observables, thereby exponentially reducing measurement complexity. In practice, though, quantum memory and entangling operations are always noisy and introduce errors, making the advantage of using noisy quantum memory unclear. To address these challenges we introduce error-mitigated entanglement-enhanced learning and show, both theoretically and experimentally, that even with noise, there is a separation in efficiency between learning Pauli channels with and without entanglement with noisy quantum memory. We demonstrate our protocol’s efficacy in examples including hypothesis testing with up to 64 qubits and learning inherent noise processes in a layer of parallel gates using up to 16 qubits on a superconducting quantum processor. Our protocol provides accurate and practical information about the process, with an overhead factor of $1.33 pm 0.05$ per qubit, much smaller than the fundamental lower bound of 2 without entanglement with quantum memory. Our study demonstrates that entanglement with auxiliary noisy quantum memory combined with error mitigation considerably enhances the learning of quantum processes. Source arXiv: 2408.03376v1
Coordinating Decisions via Quantum Telepathy Authors Dawei Ding, Liang Jiang Published: 07.31.2024 Updated: 07.31.2024 Summary Quantum telepathy, or pseudotelepathy, is the phenomenon where two non-communicating parties can exhibit correlated behaviors that are impossible to achieve using classical mechanics. This is also known as Bell inequality violation and is made possible by quantum entanglement. In this work, we present a conceptual framework for applying quantum telepathy to real-world problems. In general, the problems involve coordinating decisions given a set of observations without being able to communicate. We argue this inability is actually quite prevalent in the modern era where the decision-making timescales of computer processors are so short that speed of light delay is actually quite appreciable in comparison. We highlight the example of high-frequency trading (HFT), where trades are made at microsecond timescales, but the speed of light delay between different exchanges can range from the order of 10 microseconds to 10 milliseconds. Due to the maturity of Bell inequality violation experiments, experimental realization of quantum telepathy schemes that can attain a quantum advantage for real-world problems $textit{is already almost immediately possible}$. We demonstrate this by conducting a case study for a concrete HFT scenario that gives rise to a generalization of the CHSH game and evaluate different possible physical implementations for achieving a quantum advantage. It is well known that Bell inequality violation is a rigorous mathematical proof of a quantum advantage over any classical strategy and does not need any complexity-theoretic assumptions such as $text{BQP}neqtext{BPP}$. Moreover, fault tolerance is not necessary to realize a quantum advantage: for example, violating the CHSH inequality only requires single-qubit gates applied on two entangled qubits. Source arXiv: 2407.21723v1
Coordinating Decisions via Quantum Telepathy Authors Dawei Ding, Liang Jiang Published: 07.31.2024 Updated: 09.10.2024 Summary Quantum telepathy is the phenomenon where two non-communicating parties can exhibit correlated behaviors that are impossible to achieve using classical mechanics. This is also known as Bell inequality violation and is made possible by quantum entanglement. In this work, we present a conceptual framework for applying quantum telepathy to real-world problems. In general, the problems involve coordinating decisions given a set of observations without being able to communicate. We argue this inability is actually quite prevalent in the modern era where the decision-making timescales of computer processors are so short that the speed of light delay is actually quite appreciable in comparison. We highlight the example of high-frequency trading (HFT), where trades are made at microsecond timescales, but the speed of light delay between different exchanges can range from the order of 100 microseconds to 10 milliseconds. Due to the maturity of Bell inequality violation experiments, experimental realization of quantum telepathy schemes that can attain a quantum advantage for real-world problems $textit{is already almost immediately possible}$. We demonstrate this by conducting a case study for a concrete HFT scenario that gives rise to a generalization of the CHSH game and evaluate different possible physical implementations for achieving a quantum advantage. It is well known that Bell inequality violation is a rigorous mathematical proof of a quantum advantage over any classical strategy and does not need any complexity-theoretic assumptions such as $text{BQP}neqtext{BPP}$. Moreover, fault tolerance is not necessary to realize a quantum advantage: for example, violating the CHSH inequality only requires single-qubit gates applied on two entangled physical qubits. Source arXiv: 2407.21723v2
On the Capacity of the Quantum Switch with and without Entanglement Decoherence Authors Víctor Valls, Panagiotis Promponas, Leandros Tassiulas Published: 07.29.2024 Updated: 07.29.2024 Summary This paper studies the capacity of the quantum switch for two decoherence models: when link-level entanglements last (i) for a time slot, or (ii) until they are used to serve a request (i.e., there is no decoherence). The two models are important as they set lower and upper bounds on the capacity region for any other decoherence model. The paper’s contributions are to characterize the switch capacity region for both decoherence models and to propose throughput-optimal policies based on gradient descent. Source arXiv: 2407.19903v1
A Brief Introduction to Quantum Network Control Authors Víctor Valls, Panagiotis Promponas, Leandros Tassiulas Published: 07.29.2024 Updated: 07.29.2024 Summary Quantum networking is an emerging area with the potential to transform information processing and communications. In this paper, we present a brief introduction to quantum network control, an area in quantum networking dedicated to designing algorithms for distributing entanglement (i.e., entangled qubits). We start by explaining what qubits and entanglement are and how they furnish quantum network control operations such as entanglement swapping and teleportation. With those operations, we present a model for distributing entanglement in a multi-hop quantum network to enable applications such as quantum key distribution and distributed quantum computing. We conclude the paper by presenting open research problems in the field, including the characterization of the quantum network capacity region and the design of throughput-optimal policies. Source arXiv: 2407.19899v1
Microwave-Optical Entanglement from Pulse-pumped Electro-optomechanics Authors Changchun Zhong, Fangxin Li, Srujan Meesala, Steven Wood, David Lake, Oskar Painter, Liang Jiang Published: 07.26.2024 Updated: 07.26.2024 Summary Entangling microwave and optical photons is one of the promising ways to realize quantum transduction through quantum teleportation. This paper investigates the entanglement of microwave-optical photon pairs generated from an electro-optomechanical system driven by a blue-detuned pulsed Gaussian pump. The photon pairs are obtained through weak parametric-down-conversion, and their temporal correlation is revealed by the second-order correlation function. We then study the discrete variable entanglement encoded in the time bin degree of freedom, where entanglement is identified by Bell inequality violation. Furthermore, we estimate the laser-induced heating and show that the pulse-pumped system features lower heating effects while maintaining a reasonable coincidence photon counting rate. Source arXiv: 2407.19109v1
Fast and Parallelizable Logical Computation with Homological Product Codes Authors Qian Xu, Hengyun Zhou, Guo Zheng, Dolev Bluvstein, J. Pablo Bonilla Ataides, Mikhail D. Lukin, Liang Jiang Published: 07.26.2024 Updated: 07.26.2024 Summary Quantum error correction is necessary to perform large-scale quantum computation, but requires extremely large overheads in both space and time. High-rate quantum low-density-parity-check (qLDPC) codes promise a route to reduce qubit numbers, but performing computation while maintaining low space cost has required serialization of operations and extra time costs. In this work, we design fast and parallelizable logical gates for qLDPC codes, and demonstrate their utility for key algorithmic subroutines such as the quantum adder. Our gate gadgets utilize transversal logical CNOTs between a data qLDPC code and a suitably constructed ancilla code to perform parallel Pauli product measurements (PPMs) on the data logical qubits. For hypergraph product codes, we show that the ancilla can be constructed by simply modifying the base classical codes of the data code, achieving parallel PPMs on a subgrid of the logical qubits with a lower space-time cost than existing schemes for an important class of circuits. Generalizations to 3D and 4D homological product codes further feature fast PPMs in constant depth. While prior work on qLDPC codes has focused on individual logical gates, we initiate the study of fault-tolerant compilation with our expanded set of native qLDPC code operations, constructing algorithmic primitives for preparing $k$-qubit GHZ states and distilling/teleporting $k$ magic states with $O(1)$ space overhead in $O(1)$ and $O(sqrt{k} log k)$ logical cycles, respectively. We further generalize this to key algorithmic subroutines, demonstrating the efficient implementation of quantum adders using parallel operations. Our constructions are naturally compatible with reconfigurable architectures such as neutral atom arrays, paving the way to large-scale quantum computation with low space and time overheads. Source arXiv: 2407.18490v1
Utilizing probabilistic entanglement between sensors in quantum networks Authors Emily A. Van Milligen, Christos N. Gagatsos, Eneet Kaur, Don Towsley, Saikat Guha Published: 07.22.2024 Updated: 07.22.2024 Summary One of the most promising applications of quantum networks is entanglement assisted sensing. The field of quantum metrology exploits quantum correlations to improve the precision bound for applications such as precision timekeeping, field sensing, and biological imaging. When measuring multiple spatially distributed parameters, current literature focuses on quantum entanglement in the discrete variable case, and quantum squeezing in the continuous variable case, distributed amongst all of the sensors in a given network. However, it can be difficult to ensure all sensors pre-share entanglement of sufficiently high fidelity. This work probes the space between fully entangled and fully classical sensing networks by modeling a star network with probabilistic entanglement generation that is attempting to estimate the average of local parameters. The quantum Fisher information is used to determine which protocols best utilize entanglement as a resource for different network conditions. It is shown that without entanglement distillation there is a threshold fidelity below which classical sensing is preferable. For a network with a given number of sensors and links characterized by a certain initial fidelity and probability of success, this work outlines when and how to use entanglement, when to store it, and when it needs to be distilled. Source arXiv: 2407.15652v1
Fundamental Scaling Laws of Covert Communication in the Presence of Block Fading Authors Amir Reza Ramtin, Dennis Goeckel, Don Towsley Published: 07.18.2024 Updated: 07.18.2024 Summary Covert communication is the undetected transmission of sensitive information over a communication channel. In wireless communication systems, channel impairments such as signal fading present challenges in the effective implementation and analysis of covert communication systems. This paper generalizes early work in the covert communication field by considering asymptotic results for the number of bits that can be covertly transmitted in $n$ channel uses on a block fading channel. Critical to the investigation is characterizing the performance of optimal detectors at the adversary. Matching achievable and converse results are presented. Source arXiv: 2407.13898v1
All-optical Loss-tolerant Distributed Quantum Sensing Authors Rajveer Nehra, Changhun Oh, Liang Jiang, Alireza Marandi Published: 07.18.2024 Updated: 07.18.2024 Summary Distributed quantum sensing (DQS) leverages quantum resources to estimate an unknown global property of a networked quantum sensor beyond the classical limit. We propose and analyze an all-optical resource-efficient scheme for the next-generation DQS systems. Our method utilizes phase-sensitive optical parametric amplifiers and linear interferometers and achieves the sensitivity close to the optimal limit, as determined by the quantum Fisher information of the entangled resource state. Furthermore, it utilizes high-gain OPA-assisted detection, offering critical advantages of increased bandwidth and loss tolerance, in contrast to conventional methods employing balanced homodyne detection (BHD). We show the efficacy of our proposal for displacement sensing and show its loss tolerance against high levels of photon loss, thus circumventing the major obstacle in current BHD-based approaches. Our architectural analysis shows that our scheme can be realized with current quantum photonic technology Source arXiv: 2407.13654v1
Experimental Demonstration of a Quantum-Optimal Coronagraph Using Spatial Mode Sorters Authors Nico Deshler, Itay Ozer, Amit Ashok, Saikat Guha Published: 07.17.2024 Updated: 10.31.2024 Summary We present an experimental demonstration of an ideal direct imaging coronagraph design capable of achieving the quantum limits of exoplanet detection and localization by using spatial mode filtering. Our benchtop experimental implementation performs a forward and inverse pass through a free-space programmable spatial mode sorter configured to isolate photons in a point spread function (PSF)-adapted mode basis. During the forward pass, the fundamental mode is rejected, effectively eliminating light from an on-axis point-like star. On the inverse pass, the remaining modes are coherently recombined, enabling direct imaging of a faint companion. Our experimental system is able to localize an artificial exoplanet at sub-diffraction distances from its host star with a 1000:1 star-planet contrast ratio. The ability to resolve faint companions of a host star at sub-diffraction scale is crucial to further the discovery of exoplanets predicted to reside in the sub-diffraction regime. These exoplanets are currently beyond the reach of state-of-the-art coronagraphs, which typically have an inner working angle (IWA) larger than the diffraction scale. Furthermore, our coronagraph architecture is potentially capable of measuring higher-fidelity spectrographs of exoplanets using spatial-spectral mode demultiplexing. Source arXiv: 2407.12776v2
Experimental Demonstration of a Quantum-Optimal Coronagraph Using Spatial Mode Sorters Authors Nico Deshler, Itay Ozer, Amit Ashok, Saikat Guha Published: 07.17.2024 Updated: 07.17.2024 Summary An ideal direct imaging coronagraph, which selectively rejects the fundamental mode of a telescope, has been shown to achieve the quantum information limits for exoplanet detection and localization. In this study, we experimentally implement this quantum-optimal coronagraph using spatial mode (de)multiplexing. Our benchtop system includes a forward and inverse pass through a free-space programmable spatial mode sorter, designed to isolate photons in a point spread function (PSF)-adapted basis. During the forward pass, the fundamental mode is rejected, effectively eliminating light from an on-axis point-like star. On the inverse pass, the remaining modes are coherently recombined, enabling direct imaging of a faint companion. We develop a probabilistic measurement model that accounts for combined effects of fundamental shot noise and experimental noise specific to our benchtop setup, such as modal cross-talk, dark noise, and ambient background illumination. We leverage this measurement model to formulate a maximum-likelihood estimator of the exoplanet position given an image captured with the coronagraph. Using this approach, we successfully localize an artificial exoplanet at sub-diffraction distances $(<sigma)$ from its host star under a 1000:1 star-planet contrast ratio. Our system accurately localizes the exoplanet up to an absolute error $<0.03sigma$ over the separation range $[0,,0.6]sigma$. Finally, we numerically evaluate the precision of our experimental coronagraph against state-of-the-art coronagraphs subject to comparable noise models. Source arXiv: 2407.12776v1
Tutorial on Quantum Error Correction for 2024 Quantum Information Knowledge (QuIK) Workshop Authors Priya J. Nadkarni, Narayanan Rengaswamy, Bane Vasić Published: 07.17.2024 Updated: 07.17.2024 Summary We provide a brief review of the fundamentals of quantum computation and quantum error correction for the participants of the first Quantum Information Knowledge (QuIK) workshop at the 2024 IEEE International Symposium on Information Theory (ISIT 2024). While this is not a comprehensive review, we provide many references for the reader to delve deeper into the concepts and research directions. Source arXiv: 2407.12737v1
A general and modular approach to solid-state integration and readout of zero-dimensional quantum systems Authors Marzieh Kavand, Zoe Phillips, William H. Koll, Morgan Hamilton, Ethel Perez-Hoyos, Rianna Greer, Ferdous Ara, Dan Pharis, Mehdi Maleki Sanukesh, Mingyu Xu, Takashi Taniguchi, Paul Canfield, Michael E. Flatté, Danna E. Freedman, Jay Gupta, Ezekiel Johnston-Halperin Published: 07.15.2024 Updated: 07.15.2024 Summary Electronic spectroscopy of zero-dimensional (0D) quantum systems, including point defects in solids, atomic states, and small molecules, is a critical tool for developing a fundamental understanding of these systems, with applications ranging from solid-state and molecular materials development to emerging technologies rooted in quantum information science. Toward this end, scanning tunneling spectroscopy (STS) has demonstrated atomic-scale sensitivity, but is not easily scalable for applications, while device-based approaches rely on embedding these systems within a solid-state tunnel junction and are not generally applicable. Here we demonstrate an all-electrical readout mechanism for these quasi-0D states that is modular and general, dramatically expanding the phase space of accessible quantum systems and providing an approach that is amenable to scaling and integration with other solid-state quantum technologies. Our approach relies on the creation of high-quality tunnel junctions via the mechanical exfoliation and stacking of multi-layer graphene (MLG) and hexagonal boron nitride (hBN) to encapsulate the target quantum system (QS) in a MLG-hBN-QS-hBN-MLG heterostructure. This structure allows for electronic spectroscopy and readout of candidate quantum systems through a combination of Coulomb and spin-blockade, providing access to entire classes of quantum systems that have previously only been accessible via optical spectroscopy or magnetic resonance measurements of large ensembles, if at all. Source arXiv: 2407.11189v1
A general and modular approach to solid-state integration and readout of zero-dimensional quantum systems Authors Marzieh Kavand, Zoe Phillips, William H. Koll, Morgan Hamilton, Ethel Perez-Hoyos, Rianna Greer, Ferdous Ara, Dan Pharis, Mehdi Maleki Sanukesh, Mingyu Xu, Takashi Taniguchi, Paul Canfield, Michael E. Flatté, Danna E. Freedman, Jay Gupta, Ezekiel Johnston-Halperin Published: 07.15.2024 Updated: 07.31.2024 Summary Electronic spectroscopy of zero-dimensional (0D) quantum systems, including point defects in solids, atomic states, and small molecules, is a critical tool for developing a fundamental understanding of these systems, with applications ranging from solid-state and molecular materials development to emerging technologies rooted in quantum information science. Toward this end, scanning tunneling spectroscopy (STS) has demonstrated atomic-scale sensitivity, but is not easily scalable for applications, whereas device-based approaches rely on embedding these systems within a solid-state tunnel junction (TJ) and are not generally applicable. Here we demonstrate an all-electrical readout mechanism for these quasi-0D states that is modular and general, dramatically expanding the phase space of accessible quantum systems and providing an approach that is amenable to scaling and integration with other solid-state quantum technologies. Our approach relies on the creation of high-quality tunnel junctions via the mechanical exfoliation and stacking of multi-layer graphene (MLG) and hexagonal boron nitride (hBN) to encapsulate the target quantum system (QS) in an MLG/hBN/QS/hBN/MLG heterostructure. This structure allows for electronic spectroscopy and readout of candidate quantum systems through a combination of Coulomb and spin-blockade, providing access to entire classes of quantum systems that have previously only been accessible via optical spectroscopy or magnetic resonance measurements of large ensembles, if at all. Source arXiv: 2407.11189v2
Characterizing Encrypted Application Traffic through Cellular Radio Interface Protocol Authors Md Ruman Islam, Raja Hasnain Anwar, Spyridon Mastorakis, Muhammad Taqi Raza Published: 07.10.2024 Updated: 07.20.2024 Summary Modern applications are end-to-end encrypted to prevent data from being read or secretly modified. 5G tech nology provides ubiquitous access to these applications without compromising the application-specific performance and latency goals. In this paper, we empirically demonstrate that 5G radio communication becomes the side channel to precisely infer the user’s applications in real-time. The key idea lies in observing the 5G physical and MAC layer interactions over time that reveal the application’s behavior. The MAC layer receives the data from the application and requests the network to assign the radio resource blocks. The network assigns the radio resources as per application requirements, such as priority, Quality of Service (QoS) needs, amount of data to be transmitted, and buffer size. The adversary can passively observe the radio resources to fingerprint the applications. We empirically demonstrate this attack by considering four different categories of applications: online shopping, voice/video conferencing, video streaming, and Over-The-Top (OTT) media platforms. Finally, we have also demonstrated that an attacker can differentiate various types of applications in real-time within each category. Source arXiv: 2407.07361v2
Characterizing Encrypted Application Traffic through Cellular Radio Interface Protocol Authors Md Ruman Islam, Raja Hasnain Anwar, Spyridon Mastorakis, Muhammad Taqi Raza Published: 07.10.2024 Updated: 07.10.2024 Summary Modern applications are end-to-end encrypted to prevent data from being read or secretly modified. 5G tech nology provides ubiquitous access to these applications without compromising the application-specific performance and latency goals. In this paper, we empirically demonstrate that 5G radio communication becomes the side channel to precisely infer the user’s applications in real-time. The key idea lies in observing the 5G physical and MAC layer interactions over time that reveal the application’s behavior. The MAC layer receives the data from the application and requests the network to assign the radio resource blocks. The network assigns the radio resources as per application requirements, such as priority, Quality of Service (QoS) needs, amount of data to be transmitted, and buffer size. The adversary can passively observe the radio resources to fingerprint the applications. We empirically demonstrate this attack by considering four different categories of applications: online shopping, voice/video conferencing, video streaming, and Over-The-Top (OTT) media platforms. Finally, we have also demonstrated that an attacker can differentiate various types of applications in real-time within each category. Source arXiv: 2407.07361v1
Imaging-based Quantum Optomechanics Authors Christian M. Pluchar, Wenhua He, Jack Manley, Nicolas Deshler, Saikat Guha, Dalziel J. Wilson Published: 07.09.2024 Updated: 07.09.2024 Summary In active imaging protocols, information about a landscape is encoded into the spatial mode of a scattered photon. A common assumption is that the landscape is rigid; however, in principle it can be altered by radiation pressure, a concept that has found fruitful application in the field of quantum optomechanics. Here we explore active imaging of a mechanical resonator with an eye to generalizing the concept of radiation pressure backaction to spatially multimode light. As a thought experiment, we consider imaging the flexural modes of a membrane by sorting the spatial modes of a laser reflected from its surface. We show that backaction in this setting arises from spatial photon shot noise, an effect that cannot be observed in single-mode optomechanics. We also derive the imprecision-backaction product for coherent illumination in the limit of purely spatial backaction, revealing it to be equivalent to the standard quantum limit for purely dispersive, single-mode optomechanical coupling. Finally, we show that optomechanical correlations due to spatial backaction can give rise to two-mode entangled light. In conjunction with high-$Q$ nanomechanics, our findings point to new opportunities at the interface of quantum imaging and optomechanics, including sensors and networks enhanced by spatial mode entanglement. Source arXiv: 2407.07060v1
Towards quantum-enhanced long-baseline optical/near-IR interferometry Authors Jayadev K. Rajagopal, Ryan M. Lau, Isack Padilla, Stephen T. Ridgway, Chaohan Cui, Brittany McClinton, Aqil Sajjad, Stuartt Corder, Mark Rawlings, Fredrik Rantakyro, J. Gabriel Richardson, Amit Ashok, Saikat Guha Published: 07.08.2024 Updated: 07.08.2024 Summary Microarcsecond resolutions afforded by an optical-NIR array with kilometer-baselines would enable breakthrough science. However significant technology barriers exist in transporting weakly coherent photon states over these distances: primarily photon loss and phase errors. Quantum telescopy, using entangled states to link spatially separated apertures, offers a possible solution to the loss of photons. We report on an initiative launched by NSF NOIRLab in collaboration with the Center for Quantum Networks and Arizona Quantum Initiative at the University of Arizona, Tucson, to explore these concepts further. A brief description of the quantum concepts and a possible technology roadmap towards a quantum-enhanced very long baseline optical-NIR interferometric array is presented. An on-sky demonstration of measuring spatial coherence of photons with apertures linked through the simplest Gottesman protocol over short baselines and with limited phase fluctuations is envisaged as the first step. Source arXiv: 2407.06302v1
Generalized quantum repeater graph states Authors Bikun Li, Kenneth Goodenough, Filip Rozpędek, Liang Jiang Published: 07.01.2024 Updated: 07.01.2024 Summary All-photonic quantum repeaters are essential for establishing long-range quantum entanglement. Within repeater nodes, reliably performing entanglement swapping is a key component of scalable quantum communication. To tackle the challenge of probabilistic Bell state measurement in linear optics, which often leads to information loss, various approaches have been proposed to ensure the loss tolerance of distributing a single ebit. We have generalized previous work regarding repeater graph states with elaborate connectivity, enabling the efficient establishment of exploitable ebits at a finite rate with high probability. We demonstrate that our new scheme significantly outperforms the previous work with much flexibility and discuss the generation overhead of such resource states. These findings offer new insights into the scalability and reliability of loss-tolerant quantum networks. Source arXiv: 2407.01429v1
Deterministic fast and stable phase retrieval in multiple dimensions Authors Cole Brabec, Sivan Trajtenberg-Mills, Luca Daniel, Dirk Englund Published: 07.01.2024 Updated: 07.01.2024 Summary We present the first phase retrieval algorithm guaranteed to solve the multidimensional phase retrieval problem in polynomial arithmetic complexity without prior information. The method successfully terminates in O(N log(N)) operations for Fourier measurements with cardinality N. The algorithm is guaranteed to succeed for a large class of objects, which we term “Schwarz objects”. We further present an easy-to-calculate and well-conditioned diagonal operator that transforms any feasible phase-retrieval instance into one that is solved by our method. We derive our method by combining techniques from classical complex analysis, algebraic topology, and modern numerical analysis. Concretely, we pose the phase retrieval problem as a multiplicative Cousin problem, construct an approximate solution using a modified integral used for the Schwarz problem, and refine the approximate solution to an exact solution via standard optimization methods. We present numerical experimentation demonstrating our algorithm’s performance and its superiority to existing method. Finally, we demonstrate that our method is robust against Gaussian noise. Source arXiv: 2407.01350v1
CMOS-fabricated ultraviolet light modulators using low-loss alumina piezo-optomechanical photonic circuits Authors Roman Shugayev, Daniel Dominguez, Andrew Leenheer, Bethany Little, Matthew N. H. Chow, Nicholas Karl, Matt Koppa, Michael Gehl, Yuan-Yu Jau, Matt Eichenfield Published: 06.29.2024 Updated: 07.02.2024 Summary We demonstrate a CMOS-foundry-fabricated piezo-optomechanical photonic integrated circuit platform for ultraviolet and blue wavelengths, using alumina waveguides that are strongly mechanically coupled to monolithically integrated aluminum nitride piezoelectric actuators. Low waveguide losses are measured down to at least 320 nm, where we achieve 1.6 dB/cm. This allows us to demonstrate broadband amplitude modulators based on piezoelectrically actuated MEMS cantilever phase-shifters down to 320 nm, with a high extinction ratio of 30 dB. We further demonstrate the versatility of the platform by designing and demonstrating a modulator that can work with high extinction and low loss at 320 nm and 420 nm, simultaneously, demonstrating control of multiple, disparate wavelengths in one device. We also demonstrate narrow-band resonant racetrack modulators with quality factors of 4.7E5 and a tuning rate of 27.5 MHz/V. These results should open doors for a range of novel applications in UV photonics, quantum science, sensing and spectroscopy. Source arXiv: 2407.00469v2
High-power and narrow-linewidth laser on thin-film lithium niobate enabled by photonic wire bonding Authors Cornelis A. A. Franken, Rebecca Cheng, Keith Powell, Georgios Kyriazidis, Victoria Rosborough, Juergen Musolf, Maximilian Shah, David R. Barton III, Gage Hills, Leif Johansson, Klaus-J. Boller, Marko Lončar Published: 06.29.2024 Updated: 07.05.2024 Summary Thin-film lithium niobate (TFLN) has emerged as a promising platform for the realization of high performance chip-scale optical systems, spanning a range of applications from optical communications to microwave photonics. Such applications rely on the integration of multiple components onto a single platform. However, while many of these components have already been demonstrated on the TFLN platform, to date, a major bottleneck of the platform is the existence of a tunable, high-power, and narrow-linewidth on-chip laser. Here, we address this problem using photonic wire bonding to integrate optical amplifiers with a thin-film lithium niobate feedback circuit, and demonstrate an extended cavity diode laser yielding high on-chip power of 78 mW, side mode suppression larger than 60 dB and wide wavelength tunability over 43 nm. The laser frequency stability over short timescales shows an ultra-narrow intrinsic linewidth of 550 Hz. Long-term recordings indicate a high passive stability of the photonic wire bonded laser with 58 hours of mode-hop-free operation, with a trend in the frequency drift of only 4.4 MHz/h. This work verifies photonic wire bonding as a viable integration solution for high performance on-chip lasers, opening the path to system level upscaling and Watt-level output powers. Source arXiv: 2407.00269v2
High-power and narrow-linewidth laser on thin-film lithium niobate enabled by photonic wire bonding Authors Cornelis A. A. Franken, Rebecca Cheng, Keith Powell, Georgios Kyriazidis, Victoria Rosborough, Juergen Musolf, Maximilian Shah, David R. Barton III, Gage Hills, Leif Johansson, Klaus-J. Boller, Marko Lončar Published: 06.29.2024 Updated: 06.29.2024 Summary Thin-film lithium niobate (TFLN) has emerged as a promising platform for the realization of high-performance chip-scale optical systems, spanning a range of applications from optical communications to microwave photonics. Such applications rely on the integration of multiple components onto a single platform. However, while many of these components have already been demonstrated on the TFLN platform, to date, a major bottleneck of the platform is the existence of a tunable, high-power, and narrow-linewidth on-chip laser. Here, we address this problem using photonic wire bonding to integrate optical amplifiers with a thin-film lithium niobate feedback circuit, and demonstrate an extended cavity diode laser yielding high on-chip power of 78 mW, side mode suppression larger than 60 dB and wide wavelength tunability over 43 nm. The laser frequency stability over short timescales shows an ultra-narrow intrinsic linewidth of 550 Hz, while long-term recordings indicate a high passive stability of the photonic wire bonded laser with 46 hours of mode-hop-free operation. This work verifies photonic wire bonding as a viable integration solution for high performance on-chip lasers, opening the path to system level upscaling and Watt-level output powers. Source arXiv: 2407.00269v1
Transfer printing micro-assembly of silicon photonic crystal cavity arrays: beating the fabrication tolerance limit Authors Sean P. Bommer, Christopher Panuski, Benoit Guilhabert, Zhongyi Xia, Jack A. Smith, Martin D. Dawson, Dirk Englund, Michael J. Strain Published: 06.28.2024 Updated: 06.28.2024 Summary Photonic crystal cavities (PhCCs) can confine optical fields in ultra-small volumes, enabling efficient light-matter interactions for quantum and non-linear optics, sensing and all-optical signal processing. The inherent nanometric tolerances of micro-fabrication platforms can induce cavity resonant wavelength shifts two-orders of magnitude larger than cavity linewidths, prohibiting fabrication of arrays of nominally identical devices. We address this device variability by fabricating PhCCs as releasable pixels that can be transferred from their native substrate to a receiver where ordered micro-assembly can overcome the inherent fabrication variance. We demonstrate the measurement, binning and transfer of 119 PhCCs in a single session, producing spatially ordered arrays of PhCCs, sorted by resonant wavelength. Furthermore, the rapid in-situ measurement of the devices enables measurements of the PhCCs dynamic response to the print process for the first time, showing plastic and elastic effects in the seconds to hours range. Source arXiv: 2406.20010v1
A piezoelectric ski-jump laser beam scanning chip-to-free space photonic link Authors Matt Saha, Y. Henry Wen, Andrew S. Greenspon, Matthew Zimmermann, Kevin J. Palm, Alex Witte, Mark Dong, Andrew J. Leenheer, Genevieve Clark, Gerald Gilbert, Matt Eichenfield, Dirk Englund Published: 06.25.2024 Updated: 06.25.2024 Summary A seamless interface between integrated photonic processors and targets in free-space enables wide-ranging advancements in telescopy, free-space communication, optical ranging, materials processing, biomedical imaging, near eye display, machine optical intelligence and quantum control. An optimal solution allows for 2D scanning from anywhere on a photonic chip over a large number of diffraction limited spots in the far field. Leading approaches rely on scanners where the numerical aperture and actuator size are linked, resulting in a trade off between resolution, speed and footprint, whereas scanning fibers have been limited to bulk optical and mechanical components. Here, we introduce a CMOS fabricated photonic “ski-jump” composed of a broadband, single mode silicon nitride waveguide monolithically integrated atop a piezo-actuated cantilever. The ski-jump passively curl 90 degrees out-of-plane via mechanical meta-stress engineering in a footprint of less than 0.1 mm squared and emit submicron diffraction-limited optical modes with piezoelectric steering. They also exhibit kHz-rate longitudinal and lateral mechanical resonances with displacement ranges exceeding 400 micron and 180 micron, respectively, and quality factors Q>10,000 under vacuum. These resonances enable 2D beam scanning at footprint-adjusted spot-rates of 68.6 Megaspot/s-mm squared surpassing state-of-the-art MEMS mirrors by more than 50. Using these devices, we demonstrate arbitrary 2D image projection and the repeatable initialization and readout of single photons from silicon vacancies in diamond waveguides. Based on current device performance, we identify pathways for achieving >1 Giga-spots in a square cm area to provide a seamless, scalable optical pipeline between integrated photonic processors and the free-space world. Source arXiv: 2406.17662v1
Nanophotonic waveguide chip-to-free-space beam scanning at 68 Million Spots/(s$cdot$mm$^{2}$) Authors Matt Saha, Y. Henry Wen, Andrew S. Greenspon, Matthew Zimmermann, Kevin J. Palm, Alex Witte, Yin Min Goh, Chao Li, Mark Dong, Andrew J. Leenheer, Genevieve Clark, Gerald Gilbert, Matt Eichenfield, Dirk Englund Published: 06.25.2024 Updated: 10.22.2024 Summary A seamless chip-to-world photonic interface enables wide-ranging advancements in optical ranging, display, communication, computation, imaging, and light-matter interaction. An optimal solution allows for 2D scanning of a diffraction-limited beam from anywhere on a photonic chip over a large number of beam-spots in free-space. Currently, devices with direct PIC integration rely on tiled apertures with poor mode qualities, large footprints, and complex control systems. Micro-mechanical beam scanners have good beam quality but lack direct PIC integration and are inertially-limited due to the use of bulk optical components or structures in which the optical aperture and actuator sizes are inextricably linked, resulting in trade-offs among resolution, speed, and footprint. Here, we overcome these limitations with the photonic “ski-jump”: a nanoscale optical waveguide monolithically integrated atop a piezoelectrically actuated cantilever which passively curls ~90$^{circ}$ out-of-plane in a footprint of 50$times$. Using this device, we demonstrate image projection, video projection, and the initialization and readout of single photons from silicon vacancy centers in diamond waveguides. Based on current performance, we identify pathways for achieving >1 giga-spots at kHz-rates in a ~1 cm$^{2}$ area to provide a seamless, scalable optical pipeline between integrated photonic processors and the free-space world. Source arXiv: 2406.17662v2
Quantum illumination networks Authors Xiaobin Zhao, Zheshen Zhang, Quntao Zhuang Published: 06.24.2024 Updated: 06.24.2024 Summary Quantum illumination is an entanglement-based target detection protocol that provides quantum advantages despite the presence of entanglement-breaking noise. However, the advantage of traditional quantum illumination protocols is limited to impractical scenarios with low transmitted power and simple target configurations. In this work, we propose a quantum illumination network to overcome the limitations, via designing a transmitter array and a single receiver antenna. Thanks to multiple transmitters, quantum advantage is achieved even with a high total transmitted power. Moreover, for single-parameter estimation, the advantage of network over a single transmitter case increases with the number of transmitters before saturation. At the same time, complex target configurations with multiple unknown transmissivity or phase parameters can be resolved. Despite the interference of different returning signals at the single antenna and photon-loss due to multiple-access channel, we provide two types of measurement design, one based on parametric-amplification and one based on the correlation-to-displacement conversion (CtoD) to achieve a quantum advantage in estimating all unknown parameters. We also generalize the parameter estimation scenario to a general hypothesis testing scenario, where the six-decibel quantum illumination advantage is achieved at a much greater total probing power. Source arXiv: 2406.17178v1
Collective Bit Flipping-Based Decoding of Quantum LDPC Codes Authors Dimitris Chytas, Nithin Raveendran, Bane Vasić Published: 06.24.2024 Updated: 06.24.2024 Summary Quantum low-density parity-check (QLDPC) codes have been proven to achieve higher minimum distances at higher code rates than surface codes. However, this family of codes imposes stringent latency requirements and poor performance under iterative decoding, especially when the variable degree is low. In this work, we improve both the error correction performance and decoding latency of variable degree-3 (dv-3) QLDPC codes under iterative decoding. Firstly, we perform a detailed analysis of the structure of a well-known family of QLDPC codes, i.e., hypergraph product-based codes. Then, we propose a decoding approach that stems from the knowledge of harmful configurations apparent in these codes. Our decoding scheme is based on applying a modified version of bit flipping (BF) decoding, namely two-bit bit flipping (TBF) decoding, which adds more degrees of freedom to BF decoding. The granularity offered by TBF decoding helps us design sets of decoders that operate in parallel and can collectively decode error patterns appearing in harmful configurations of the code, thus addressing both the latency and performance requirements. Finally, simulation results demonstrate that the proposed decoding scheme surpasses other iterative decoding approaches for various dv-3 QLDPC codes. Source arXiv: 2406.17070v1
Quantum resolution limit of long-baseline imaging using distributed entanglement Authors Isack Padilla, Aqil Sajjad, Babak N. Saif, Saikat Guha Published: 06.24.2024 Updated: 06.24.2024 Summary It has been shown that shared entanglement between two telescope sites can in principle be used to localize a point source by mimicking the standard phase-scanning interferometer, but without physically bringing the light from the distant telescopes together. In this paper, we show that a receiver that employs spatial-mode sorting at each telescope site, combined with pre-shared entanglement and local quantum operations can be used to mimic the most general multimode interferometer acting on light collected from the telescopes. As an example application to a quantitative passive-imaging problem, we show that the quantum-limited precision of estimating the angular separation between two stars can be attained by an instantiation of the aforesaid entanglement based receiver. We discuss how this entanglement assisted strategy can be used to achieve the quantum-limited precision of any complex quantitative imaging task involving any number of telescopes. We provide a blueprint of this general receiver that involves quantum transduction of starlight into quantum memory banks and spatial mode sorters deployed at each telescope site, and measurements that include optical detection as well as qubit gates and measurements on the quantum memories. We discuss the relative contributions of local mode sorting at telescope sites vis-a-vis distributed entanglement-assisted interferometry, to the overall quantum-limited information about the scene, based on the ratio of the baseline distance to the individual telescope diameter. Source arXiv: 2406.16789v1
Dynamical phase-field model of cavity electromagnonic systems Authors Shihao Zhuang, Yujie Zhu, Changchun Zhong, Liang Jiang, Xufeng Zhang, Jia-Mian Hu Published: 06.19.2024 Updated: 06.19.2024 Summary Cavity electromagnonic system, which simultaneously consists of cavities for photons, magnons (quanta of spin waves), and acoustic phonons, provides an exciting platform to achieve coherent energy transduction among different physical systems down to single quantum level. Here we report a dynamical phase-field model that allows simulating the coupled dynamics of the electromagnetic waves, magnetization, and strain in 3D multiphase systems. As examples of application, we computationally demonstrate the excitation of hybrid magnon-photon modes (magnon polaritons), Floquet-induced magnonic Aulter-Townes splitting, dynamical energy exchange (Rabi oscillation) and relative phase control (Ramsey interference) between the two magnon polariton modes. The simulation results are consistent with analytical calculations based on Floquet Hamiltonian theory. Simulations are also performed to design a cavity electro-magno-mechanical system that enables the triple phonon-magnon-photon resonance, where the resonant excitation of a chiral, fundamental (n=1) transverse acoustic phonon mode by magnon polaritons is demonstrated. With the capability to predict coupling strength, dissipation rates, and temporal evolution of photon/magnon/phonon mode profiles using fundamental materials parameters as the inputs, the present dynamical phase-field model represents a valuable computational tool to guide the fabrication of the cavity electromagnonic system and the design of operating conditions for applications in quantum sensing, transduction, and communication. Source arXiv: 2406.13203v1
Dynamical phase-field model of cavity electromagnonic systems Authors Shihao Zhuang, Yujie Zhu, Changchun Zhong, Liang Jiang, Xufeng Zhang, Jia-Mian Hu Published: 06.19.2024 Updated: 08.25.2024 Summary Cavity electromagnonic system, which simultaneously consists of cavities for photons, magnons (quanta of spin waves), and acoustic phonons, provides an exciting platform to achieve coherent energy transduction among different physical systems down to single quantum level. Here we report a dynamical phase-field model that allows simulating the coupled dynamics of the electromagnetic waves, magnetization, and strain in 3D multiphase systems. As examples of application, we computationally demonstrate the excitation of hybrid magnon-photon modes (magnon polaritons), Floquet-induced magnonic Aulter-Townes splitting, dynamical energy exchange (Rabi oscillation) and relative phase control (Ramsey interference) between the two magnon polariton modes. The simulation results are consistent with analytical calculations based on Floquet Hamiltonian theory. Simulations are also performed to design a cavity electro-magno-mechanical system that enables the triple phonon-magnon-photon resonance, where the resonant excitation of a chiral, fundamental (n=1) transverse acoustic phonon mode by magnon polaritons is demonstrated. With the capability to predict coupling strength, dissipation rates, and temporal evolution of photon/magnon/phonon mode profiles using fundamental materials parameters as the inputs, the present dynamical phase-field model represents a valuable computational tool to guide the fabrication of the cavity electromagnonic system and the design of operating conditions for applications in quantum sensing, transduction, and communication. Source arXiv: 2406.13203v2
Interfacing Gottesman-Kitaev-Preskill Qubits to Quantum Memories Authors Prajit Dhara, Liang Jiang, Saikat Guha Published: 06.06.2024 Updated: 06.06.2024 Summary Gottesman-Kitaev-Preskill (GKP) states have been demonstrated to pose significant advantages when utilized for fault-tolerant all optical continuous-variable quantum computing as well as for quantum communications links for entanglement distribution. However interfacing these systems to long-lived solid-state quantum memories has remained an open problem. Here we propose an interface between quantum memories and GKP qubit states based on a cavity-mediated controlled displacement gate. We characterize the quality of memory-GKP entanglement as a function of cavity parameters suggesting optimal regimes of operation for high-quality state transfer between either qubit states. We further extend this protocol to demonstrate the creation of GKP cluster states by avoiding the requirement of ancillary optical quadrature-squeezed light. Utilizing post-selected entanglement swapping operations for GKP qubits, we demonstrate the utility of our protocol for high-rate entanglement generation between quantum memories. Extensions and derivatives of our proposal could enable a wide variety of applications by utilizing the operational trade-offs for qubits encoded in memory and in the GKP basis. Source arXiv: 2406.04275v1
Interfacing Gottesman-Kitaev-Preskill Qubits to Quantum Memories Authors Prajit Dhara, Liang Jiang, Saikat Guha Published: 06.06.2024 Updated: 10.18.2024 Summary Gottesman-Kitaev-Preskill (GKP) states have been demonstrated to pose significant advantages when utilized for fault-tolerant all optical continuous-variable quantum computing as well as for quantum communications links for entanglement distribution. However interfacing these systems to long-lived solid-state quantum memories has remained an open problem. Here we propose an interface between quantum memories and GKP qubit states based on a cavity-mediated controlled displacement gate. We characterize the quality of memory-GKP entanglement as a function of cavity parameters suggesting optimal regimes of operation for high-quality state transfer between either qubit states. We further extend this protocol to demonstrate the creation of GKP cluster states by avoiding the requirement of ancillary optical quadrature-squeezed light. Utilizing post-selected entanglement swapping operations for GKP qubits, we demonstrate the utility of our protocol for high-rate entanglement generation between quantum memories. Extensions and derivatives of our proposal could enable a wide variety of applications by utilizing the operational trade-offs for qubits encoded in memory and in the GKP basis. Source arXiv: 2406.04275v2
Entangling Quantum Memories at Channel Capacity Authors Prajit Dhara, Liang Jiang, Saikat Guha Published: 06.06.2024 Updated: 10.18.2024 Summary Entangling quantum memories, mediated by optical-frequency or microwave channels, at high rates and fidelities is key for linking qubits across short and long ranges. All well-known protocols encode up to one qubit per optical mode, hence entangling one pair of memory qubits per transmitted mode over the channel, with probability $eta$, the channel’s transmissivity. The rate is proportional to $eta$ ideal Bell states (ebits) per mode. The quantum capacity, $C(eta) = -log_2(1-{eta})$ ebits per mode, which $approx 1.44eta$ for high loss, i.e., $eta ll 1$, thereby making these schemes near rate-optimal. However, $C(eta) to infty$ as $eta to 1$, making the known schemes highly rate-suboptimal for shorter ranges. We show that a cavity-assisted memory-photon interface can be used to entangle matter memories with Gottesman-Kitaev-Preskill (GKP) photonic qudits, which along with dual-homodyne entanglement swaps that retain analog information, enables entangling memories at capacity-approaching rates at low loss. We benefit from loss resilience of GKP qudits, and their ability to encode multiple qubits in one mode. Our memory-photon interface further supports the preparation of needed ancilla GKP qudits. We expect our result to spur research in low-loss high-cooperativity cavity-coupled qubits with high-efficiency optical coupling, and demonstrations of high-rate short-range quantum links. Source arXiv: 2406.04272v2
Entangling Quantum Memories at Channel Capacity Authors Prajit Dhara, Liang Jiang, Saikat Guha Published: 06.06.2024 Updated: 06.06.2024 Summary Entangling quantum memories, mediated by optical-frequency or microwave channels, at high rates and fidelities is key for linking qubits across short and long ranges. All well-known protocols encode up to one qubit per optical mode, hence entangling one pair of memory qubits per transmitted mode over the channel, with probability $eta$, the channel’s transmissivity. The rate is proportional to $eta$ ideal Bell states (ebits) per mode. The quantum capacity, $C(eta) = -log_2(1-{eta})$ ebits per mode, which $approx 1.44eta$ for high loss, i.e., $eta ll 1$, thereby making these schemes near rate-optimal. However, $C(eta) to infty$ as $eta to 1$, making the known schemes highly rate-suboptimal for shorter ranges. We show that a cavity-assisted memory-photon interface can be used to entangle matter memories with Gottesman-Kitaev-Preskill (GKP) photonic qudits, which along with dual-homodyne entanglement swaps that retain analog information, enables entangling memories at capacity-approaching rates at low loss. We benefit from loss resilience of GKP qudits, and their ability to encode multiple qubits in one mode. Our memory-photon interface further supports the preparation of needed ancilla GKP qudits. We expect our result to spur research in low-loss high-cooperativity cavity-coupled qubits with high-efficiency optical coupling, and demonstrations of high-rate short-range quantum links. Source arXiv: 2406.04272v1
A generalized cycle benchmarking algorithm for characterizing mid-circuit measurements Authors Zhihan Zhang, Senrui Chen, Yunchao Liu, Liang Jiang Published: 06.04.2024 Updated: 10.04.2024 Summary Mid-circuit measurements (MCMs) are crucial ingredients in the development of fault-tolerant quantum computation. While there have been rapid experimental progresses in realizing MCMs, a systematic method for characterizing noisy MCMs is still under exploration. In this work we develop a cycle benchmarking (CB)-type algorithm to characterize noisy MCMs. The key idea is to use a joint Fourier transform on the classical and quantum registers and then estimate parameters in the Fourier space, analogous to Pauli fidelities used in CB-type algorithms for characterizing the Pauli noise channel of Clifford gates. Furthermore, we develop a theory of the noise learnability of MCMs, which determines what information can be learned about the noise model (in the presence of state preparation and terminating measurement (SPAM) noise) and what cannot, which shows that all learnable information can be learned using our algorithm. As an application, we show how to use the learned information to test the independence between measurement noise and state preparation noise in an MCM. Finally, we conduct numerical simulations to illustrate the practical applicability of the algorithm. Similar to other CB-type algorithms, we expect the algorithm to provide a useful toolkit that is of experimental interest. Source arXiv: 2406.02669v2
A generalized cycle benchmarking algorithm for characterizing mid-circuit measurements Authors Zhihan Zhang, Senrui Chen, Yunchao Liu, Liang Jiang Published: 06.04.2024 Updated: 06.04.2024 Summary Mid-circuit measurement (MCM) is a crucial ingredient in the development of fault-tolerant quantum computation. While there have been rapid experimental progresses in realizing MCM, a systematic method for characterizing noisy MCM is still under exploration. In this work we develop an algorithm to characterize noisy MCM, via a generalization of cycle benchmarking — a standard approach for characterizing the Pauli noise channel of Clifford gates. The key idea is to use a joint Fourier transform on the classical and quantum registers and then estimate parameters in the Fourier space, analogous to Pauli fidelities used in cycle benchmarking. Furthermore, we develop a theory of the noise learnability of MCM, which determines what information can be learned about the noise model (in the presence of state preparation and measurement noise) and what cannot, which shows that all learnable information can be learned using our algorithm. As an application, we show how to use the learned information to test the independence between measurement noise and state preparation noise in a MCM. Finally, we conduct numerical simulations to illustrate the practical applicability of the algorithm. Similar to cycle benchmarking, we expect the algorithm to provide a useful toolkit that is of experimental interest. Source arXiv: 2406.02669v1
Bipartite entanglement of noisy stabilizer states through the lens of stabilizer codes Authors Kenneth Goodenough, Aqil Sajjad, Eneet Kaur, Saikat Guha, Don Towsley Published: 06.04.2024 Updated: 06.04.2024 Summary Stabilizer states are a prime resource for a number of applications in quantum information science, such as secret-sharing and measurement-based quantum computation. This motivates us to study the entanglement of noisy stabilizer states across a bipartition. We show that the spectra of the corresponding reduced states can be expressed in terms of properties of an associated stabilizer code. In particular, this allows us to show that the coherent information is related to the so-called syndrome entropy of the underlying code. We use this viewpoint to find stabilizer states that are resilient against noise, allowing for more robust entanglement distribution in near-term quantum networks. We specialize our results to the case of graph states, where the found connections with stabilizer codes reduces back to classical linear codes for dephasing noise. On our way we provide an alternative proof of the fact that every qubit stabilizer code is equivalent up to single-qubit Clifford gates to a graph code. Source arXiv: 2406.02427v1
Bipartite entanglement of noisy stabilizer states through the lens of stabilizer codes Authors Kenneth Goodenough, Aqil Sajjad, Eneet Kaur, Saikat Guha, Don Towsley Published: 06.04.2024 Updated: 10.30.2024 Summary Stabilizer states are a prime resource for a number of applications in quantum information science, such as secret-sharing and measurement-based quantum computation. This motivates us to study the entanglement of noisy stabilizer states across a bipartition. We show that the spectra of the corresponding reduced states can be expressed in terms of properties of an associated stabilizer code. In particular, this allows us to show that the coherent information is related to the so-called syndrome entropy of the underlying code. We use this viewpoint to find stabilizer states that are resilient against noise, allowing for more robust entanglement distribution in near-term quantum networks. We specialize our results to the case of graph states, where the found connections with stabilizer codes reduces back to classical linear codes for dephasing noise. On our way we provide an alternative proof of the fact that every qubit stabilizer code is equivalent up to single-qubit Clifford gates to a graph code. Source arXiv: 2406.02427v2
Quantum Circuit Switching with One-Way Repeaters in Star Networks Authors Álvaro G. Iñesta, Hyeongrak Choi, Dirk Englund, Stephanie Wehner Published: 05.29.2024 Updated: 05.29.2024 Summary Distributing quantum states reliably among distant locations is a key challenge in the field of quantum networks. One-way quantum networks address this by using one-way communication and quantum error correction. Here, we analyze quantum circuit switching as a protocol to distribute quantum states in one-way quantum networks. In quantum circuit switching, pairs of users can request the delivery of multiple quantum states from one user to the other. After waiting for approval from the network, the states can be distributed either sequentially, forwarding one at a time along a path of quantum repeaters, or in parallel, sending batches of quantum states from repeater to repeater. Since repeaters can only forward a finite number of quantum states at a time, a pivotal question arises: is it advantageous to send them sequentially (allowing for multiple requests simultaneously) or in parallel (reducing processing time but handling only one request at a time)? We compare both approaches in a quantum network with a star topology. Using tools from queuing theory, we show that requests are met at a higher rate when packets are distributed in parallel, although sequential distribution can generally provide service to a larger number of users simultaneously. We also show that using a large number of quantum repeaters to combat channel losses limits the maximum distance between users, as each repeater introduces additional processing delays. These findings provide insight into the design of protocols for distributing quantum states in one-way quantum networks. Source arXiv: 2405.19049v1
Quantum Circuit Switching with One-Way Repeaters in Star Networks Authors Álvaro G. Iñesta, Hyeongrak Choi, Dirk Englund, Stephanie Wehner Published: 05.29.2024 Updated: 11.01.2024 Summary Distributing quantum states reliably among distant locations is a key challenge in the field of quantum networks. One-way quantum networks address this by using one-way communication and quantum error correction. Here, we analyze quantum circuit switching as a protocol to distribute quantum states in one-way quantum networks. In quantum circuit switching, pairs of users can request the delivery of multiple quantum states from one user to the other. After waiting for approval from the network, the states can be distributed either sequentially, forwarding one at a time along a path of quantum repeaters, or in parallel, sending batches of quantum states from repeater to repeater. Since repeaters can only forward a finite number of quantum states at a time, a pivotal question arises: is it advantageous to send them sequentially (allowing for multiple requests simultaneously) or in parallel (reducing processing time but handling only one request at a time)? We compare both approaches in a quantum network with a star topology. Using tools from queuing theory, we show that requests are met at a higher rate when packets are distributed in parallel, although sequential distribution can generally provide service to a larger number of users simultaneously. We also show that using a large number of quantum repeaters to combat channel losses limits the maximum distance between users, as each repeater introduces additional processing delays. These findings provide insight into the design of protocols for distributing quantum states in one-way quantum networks. Source arXiv: 2405.19049v2
On the Analysis of Quantum Repeater Chains with Sequential Swaps Authors Matheus Guedes de Andrade, Emily A. Van Milligen, Leonardo Bacciottini, Aparimit Chandra, Shahrooz Pouryousef, Nitish K. Panigrahy, Gayane Vardoyan, Don Towsley Published: 05.28.2024 Updated: 05.28.2024 Summary We evaluate the performance of two-way quantum repeater chains with sequential entanglement swapping. Within the analysis we consider memory decoherence, gate imperfections, and imperfect link-level entanglement generation. Our main results include closed-form expressions for the average entanglement fidelity of the generated end-to-end entangled states. We generalize previous findings for the one-shot fidelity analysis and study the case where repeater chains serve end-to-end requests continuously. We provide solutions to the continuous request scenario by combining results from quantum information theory and queuing theory. Finally, we apply the formulas obtained to analyze the impacts of hardware parameters, i.e., coherence times and gate fidelity, and distance on the entanglement fidelity and secret key rate of homogeneous quantum repeater chains. Source arXiv: 2405.18252v1
Dynamic Inhomogeneous Quantum Resource Scheduling with Reinforcement Learning Authors Linsen Li, Pratyush Anand, Kaiming He, Dirk Englund Published: 05.25.2024 Updated: 05.25.2024 Summary A central challenge in quantum information science and technology is achieving real-time estimation and feedforward control of quantum systems. This challenge is compounded by the inherent inhomogeneity of quantum resources, such as qubit properties and controls, and their intrinsically probabilistic nature. This leads to stochastic challenges in error detection and probabilistic outcomes in processes such as heralded remote entanglement. Given these complexities, optimizing the construction of quantum resource states is an NP-hard problem. In this paper, we address the quantum resource scheduling issue by formulating the problem and simulating it within a digitized environment, allowing the exploration and development of agent-based optimization strategies. We employ reinforcement learning agents within this probabilistic setting and introduce a new framework utilizing a Transformer model that emphasizes self-attention mechanisms for pairs of qubits. This approach facilitates dynamic scheduling by providing real-time, next-step guidance. Our method significantly improves the performance of quantum systems, achieving more than a 3$times$ improvement over rule-based agents, and establishes an innovative framework that improves the joint design of physical and control systems for quantum applications in communication, networking, and computing. Source arXiv: 2405.16380v1
Detecting Errors in a Quantum Network with Pauli Checks Authors Alvin Gonzales, Daniel Dilley, Bikun Li, Liang Jiang, Zain Saleem Published: 05.24.2024 Updated: 05.30.2024 Summary We apply the quantum error detection scheme Pauli check sandwiching (PCS) to quantum networks by turning it into a distributed multiparty protocol. PCS is a distance 1 code and requires less resource overhead than standard quantum error correction and detection methods. We provide analytical equations for the final fidelity and postselection rate. We also introduce a recursive version of PCS for entanglement purification that only scales polynomially in the resources required as a function of the number of recursions. The recursive PCS scheme generates a family of distance 2 quantum codes. Our analytical results are benchmarked against BBPSSW in comparable scenarios. We also perform simulations with noisy gates for entanglement swapping and attain substantial fidelity improvements. Lastly, we discuss various setups and graph state properties of PCS. Source arXiv: 2405.15236v2
Detecting Errors in a Quantum Network with Pauli Checks Authors Alvin Gonzales, Daniel Dilley, Bikun Li, Liang Jiang, Zain Saleem Published: 05.24.2024 Updated: 05.24.2024 Summary We apply the quantum error detection scheme Pauli check sandwiching (PCS) to quantum networks by turning it into a distributed multiparty protocol. PCS is a distance 1 code and requires less resource overhead than standard quantum error correction and detection methods. We provide analytical equations for the final fidelity and postselection rate. We also introduce a recursive version of PCS for entanglement purification that only scales polynomially in the resources required as a function of the number of recursions. The recursive PCS scheme generates a family of distance 2 quantum codes. Our analytical results are benchmarked against BBPSSW in comparable scenarios. We also perform simulations with noisy gates for entanglement swapping and attain substantial fidelity improvements. Lastly, we discuss various setups and graph state properties of PCS. Source arXiv: 2405.15236v1
Detecting Errors in a Quantum Network with Pauli Checks Authors Alvin Gonzales, Daniel Dilley, Bikun Li, Liang Jiang, Zain H. Saleem Published: 05.24.2024 Updated: 06.03.2024 Summary We apply the quantum error detection scheme Pauli check sandwiching (PCS) to quantum networks by turning it into a distributed multiparty protocol. PCS is a distance 1 code and requires less resource overhead than standard quantum error correction and detection methods. We provide analytical equations for the final fidelity and postselection rate. We also introduce a recursive version of PCS for entanglement purification that only scales polynomially in the resources required as a function of the number of recursions. The recursive PCS scheme generates a family of distance 2 quantum codes. Our analytical results are benchmarked against BBPSSW in comparable scenarios. We also perform simulations with noisy gates for entanglement swapping and attain substantial fidelity improvements. Lastly, we discuss various setups and graph state properties of PCS. Source arXiv: 2405.15236v3
An Improved Design for All-Photonic Quantum Repeaters Authors Ashlesha Patil, Saikat Guha Published: 05.20.2024 Updated: 05.20.2024 Summary All-photonic quantum repeaters use multi-qubit photonic graph states, called repeater graph states (RGS), instead of matter-based quantum memories, for protection against predominantly loss errors. The RGS comprises tree-graph-encoded logical qubits for error correction at the repeaters and physical {em link} qubits to create entanglement between neighboring repeaters. The two methods to generate the RGS are probabilistic stitching — using linear optical Bell state measurements (fusion) — of small entangled states prepared via multiplexed-probabilistic linear optical circuits fed with single photons, and a direct deterministic preparation using a small number of quantum-logic-capable solid-state emitters. The resource overhead due to fusions and the circuit depth of the quantum emitter system both increase with the size of the RGS. Therefore engineering a resource-efficient RGS is crucial. We propose a new RGS design, which achieves a higher entanglement rate for all-photonic quantum repeaters using fewer qubits than the previously known RGS would. We accomplish this by boosting the probability of entangling neighboring repeaters with tree-encoded link qubits. We also propose a new adaptive scheme to perform logical BSM on the link qubits for loss-only errors. The adaptive BSM outperforms the previous schemes for logical BSM on tree codes when the qubit loss probability is uniform. It reduces the number of optical modes required to perform logical BSM on link qubits to improve the entanglement rate further. Source arXiv: 2405.11768v1
