CQN is developing the entire technology stack to reliably carry quantum data across the globe, serving diverse applications across many user groups simultaneously... spurring new technology industries and a competitive marketplace of quantum service providers and application developers.
Join us for a World Quantum Day panel organized jointly by the Perimeter Institute and Quantum Ethics Project and sponsored by CQN. Our discussion will feature Raymond LaFlamme (Institute for Quantum Computing), Zeki Seskir (Karlsruhe Institute of Technology (KIT)) Jean Olemou (Leap Quantik) Taqi Raza (Center for Quantum Networks) and Joan Arrow (Quantum Ethics Project, Center for Quantum Networks). The panel will discuss how […]
Narayanan Rengaswamy is a an assistant professor in the Electrical and Computer Engineering program at the University of Arizona.He also works at the NSF Engineering Research Center for Quantum Networks (CQN) in the university. He discusses his research focuses on quantum error correction and fault tolerance.
Optica Quantum is a new online-only journal dedicated to high-impact results in quantum information science and technology (QIST), as enabled by optics and photonics. Optica Quantum will publish its first issue in September 2023. Its scope will encompass theoretical and experimental research as well as technological advances in and applications of quantum optics. In addition, the Journal will […]
We are pleased to announce the appointment of Julie Des Jardins as the new Director for Diversity and Culture of Inclusion (DCI) within CQN. Dr. Des Jardins is a cultural historian, educator, and DEI practitioner who examines gender, race, and intersectional identity in American culture, particularly in academia, athletics, politics, and STEM. She has also […]
A short video highlighting CQN’s work in building the quantum Internet was featured at the American Physical Society (APS) meeting in Las Vegas in March 2023. The six-minute video features laboratory footage from multiple CQN campuses and interviews with director Saikat Guha, as well as investigators Linran Fan, Dirk Englund, Jane Bambauer, Don Towsley, and […]
All nine courses can be found on our YouTube channel in the CQN Winter School for Quantum Networks playlist. Slides associated with the courses can be found here.
Leandros Tassiulas has won one of thirteen JP Morgan Chase Faculty Research Awards for his work on artificial intelligence. The awards aim to “empower the best research thinkers across AI today” in order to “advance cutting-edge AI research to solve real-world problems.” Leandros is one of CQN’s primary investigators at Yale, which is one of […]
The team behind the University of Arizona’s $99-million Grand Challenges Research Building (GCRB) is wrapping up a seven-level lab structure. The new building will house around a half-dozen different cutting-edge functions and programs in an extremely tight footprint within just 2.5 years. Among other operations, GCRB will serve as the new headquarters of the Center […]
Check out additional stories and events from the Center for Quantum Networks.
Bell-state measurement (BSM) on entangled states shared between quantum
repeaters is the fundamental operation used to route entanglement in quantum
networks. Performing BSMs on Werner states shared between repeaters leads to
exponential decay in the fidelity of the end-to-end Werner state with the
number of repeaters, necessitating entanglement distillation. Generally,
entanglement routing protocols use emph{probabilistic} distillation techniques
based on local operations and classical communication. In this work, we use
quantum error correcting codes (QECCs) for emph{deterministic} entanglement
distillation to route Werner states on a chain of repeaters. To maximize the
end-to-end distillable entanglement, which depends on the number and fidelity
of end-to-end Bell pairs, we utilize global link-state knowledge to determine
the optimal policy for scheduling distillation and BSMs at the repeaters. We
analyze the effect of the QECC’s properties on the entanglement rate and the
number of quantum memories. We observe that low-rate codes produce
high-fidelity end-to-end states owing to their excellent error-correcting
capability, whereas high-rate codes yield a larger number of end-to-end states
but of lower fidelity. The number of quantum memories used at repeaters
increases with the code rate as well as the classical computation time of the
QECC’s decoder.
In the problem of quickest change detection (QCD), a change occurs at some
unknown time in the distribution of a sequence of independent observations.
This work studies a QCD problem where the change is either a bad change, which
we aim to detect, or a confusing change, which is not of our interest. Our
objective is to detect a bad change as quickly as possible while avoiding
raising a false alarm for pre-change or a confusing change. We identify a
specific set of pre-change, bad change, and confusing change distributions that
pose challenges beyond the capabilities of standard Cumulative Sum (CuSum)
procedures. Proposing novel CuSum-based detection procedures, S-CuSum and
J-CuSum, leveraging two CuSum statistics, we offer solutions applicable across
all kinds of pre-change, bad change, and confusing change distributions. For
both S-CuSum and J-CuSum, we provide analytical performance guarantees and
validate them by numerical results. Furthermore, both procedures are
computationally efficient as they only require simple recursive updates.
Quantum repeaters are necessary to fully realize the capabilities of the
emerging quantum internet, especially applications involving distributing
entanglement across long distances. A more general notion of this can be called
a quantum switch, which connects to many users and can act as a repeater to
create end-to-end entanglement between different subsets of these users. Here
we present a method of calculating the capacity region of both discrete- and
continuous-variable quantum switches that in general support mixed-partite
entanglement generation. The method uses tools from convex analysis to generate
the boundaries of the capacity region. We show example calculations with
illustrative topologies and perform simulations to support the analytical
results.
Quantum subsystem codes have been shown to improve error-correction
performance, ease the implementation of logical operations on codes, and make
stabilizer measurements easier by decomposing stabilizers into smaller-weight
gauge operators. In this paper, we present two algorithms that produce new
subsystem codes from a “seed” CSS code. They replace some stabilizers of a
given CSS code with smaller-weight gauge operators that split the remaining
stabilizers, while being compatible with the logical Pauli operators of the
code. The algorithms recover the well-known Bacon-Shor code computationally as
well as produce a new $left[left[ 9,1,2,2 right]right]$ rotated surface
subsystem code with weight-$3$ gauges and weight-$4$ stabilizers. We illustrate
using a $left[left[ 100,25,3 right]right]$ subsystem hypergraph product
(SHP) code that the algorithms can produce more efficient gauge operators than
the closed-form expressions of the SHP construction. However, we observe that
the stabilizers of the lifted product quantum LDPC codes are more challenging
to split into small-weight gauge operators. Hence, we introduce the subsystem
lifted product (SLP) code construction and develop a new $left[left[ 775,
124, 20 right]right]$ code from Tanner’s classical quasi-cyclic LDPC code.
The code has high-weight stabilizers but all gauge operators that split
stabilizers have weight $5$, except one. In contrast, the LP stabilizer code
from Tanner’s code has parameters $left[left[ 1054, 124, 20 right]right]$.
This serves as a novel example of new subsystem codes that outperform
stabilizer versions of them. Finally, based on our experiments, we share some
general insights about non-locality’s effects on the performance of splitting
stabilizers into small-weight gauges.
See all the latest pre-published papers from our team of collaborators.
