28 research outputs found
The Road From Classical to Quantum Codes: A Hashing Bound Approaching Design Procedure
Powerful Quantum Error Correction Codes (QECCs) are required for stabilizing
and protecting fragile qubits against the undesirable effects of quantum
decoherence. Similar to classical codes, hashing bound approaching QECCs may be
designed by exploiting a concatenated code structure, which invokes iterative
decoding. Therefore, in this paper we provide an extensive step-by-step
tutorial for designing EXtrinsic Information Transfer (EXIT) chart aided
concatenated quantum codes based on the underlying quantum-to-classical
isomorphism. These design lessons are then exemplified in the context of our
proposed Quantum Irregular Convolutional Code (QIRCC), which constitutes the
outer component of a concatenated quantum code. The proposed QIRCC can be
dynamically adapted to match any given inner code using EXIT charts, hence
achieving a performance close to the hashing bound. It is demonstrated that our
QIRCC-based optimized design is capable of operating within 0.4 dB of the noise
limit
Quantum turbo decoding for quantum channels exhibiting memory
Inspired by the success of classical turbo codes, quantum turbo codes (QTCs) have also been conceived for near-hashing-bound transmission of quantum information over memoryless quantum channels. However, in real physical situations, the memoryless channel assumption may not be well justified, since the channel often exhibits memory of previous error events. Here, we investigate the performance of QTCs over depolarizing channels exhibiting memory and we show that they suffer from a performance degradation at low depolarizing probability values. In order to circumvent the performance degradation issue, we conceive a new coding scheme termed quantum turbo coding scheme exploiting error-correlation (QTC-EEC) that is capable of utilizing the error-correlation while performing the iterative decoding at the receiver. The proposed QTC-EEC can achieve convergence threshold at a higher depolarizing probability for channels with a higher value of correlation parameter and achieve performance near to the capacity. Finally, we propose a joint decoding and estimation scheme for our QTC-EEC relying on the correlation estimation (QTC-EEC-E) designed for more realistic quantum systems with unknown correlation parameter. Simulation results reveal that the proposed QTC-EEC-E can achieve the same performance as that of the ideal system of known correlation parameter and hence demonstrate the accurate estimation of the proposed QTC-EEC-E
Model checking quantum protocols
This thesis describes model checking techniques for protocols arising in quantum information
theory and quantum cryptography. We discuss the theory and implementation of a practical
model checker, QMC, for quantum protocols. In our framework, we assume that the quantum
operations performed in a protocol are restricted to those within the stabilizer formalism; while
this particular set of operations is not universal for quantum computation, it allows us to develop
models of several useful protocols as well as of systems involving both classical and quantum
information processing. We detail the syntax, semantics and type system of QMC’s modelling
language, the logic QCTL which is used for verification, and the verification algorithms that have
been implemented in the tool. We demonstrate our techniques with applications to a number of
case studies
How Can Optical Communications Shape the Future of Deep Space Communications? A Survey
With a large number of deep space (DS) missions anticipated by the end of
this decade, reliable and high capacity DS communications systems are needed
more than ever. Nevertheless, existing DS communications technologies are far
from meeting such a goal. Improving current DS communications systems does not
only require system engineering leadership but also, very crucially, an
investigation of potential emerging technologies that overcome the unique
challenges of ultra-long DS communications links. To the best of our knowledge,
there has not been any comprehensive surveys of DS communications technologies
over the last decade. Free space optical (FSO) technology is an emerging DS
technology, proven to acquire lower communications systems size, weight, and
power (SWaP) and achieve a very high capacity compared to its counterpart radio
frequency (RF) technology, the current used DS technology. In this survey, we
discuss the pros and cons of deep space optical communications (DSOC).
Furthermore, we review the modulation, coding, and detection, receiver, and
protocols schemes and technologies for DSOC. We provide, for the very first
time, thoughtful discussions about implementing orbital angular momentum (OAM)
and quantum communications (QC) for DS. We elaborate on how these technologies
among other field advances, including interplanetary network, and RF/FSO
systems improve reliability, capacity, and security and address related
implementation challenges and potential solutions. This paper provides a
holistic survey in DSOC technologies gathering 200+ fragmented literature and
including novel perspectives aiming to setting the stage for more developments
in the field.Comment: 17 pages, 8 Figure
Model checking quantum protocols
This thesis describes model checking techniques for protocols arising in quantum information theory and quantum cryptography. We discuss the theory and implementation of a practical model checker, QMC, for quantum protocols. In our framework, we assume that the quantum operations performed in a protocol are restricted to those within the stabilizer formalism; while this particular set of operations is not universal for quantum computation, it allows us to develop models of several useful protocols as well as of systems involving both classical and quantum information processing. We detail the syntax, semantics and type system of QMC’s modelling language, the logic QCTL which is used for verification, and the verification algorithms that have been implemented in the tool. We demonstrate our techniques with applications to a number of case studies.EThOS - Electronic Theses Online ServiceUniversity of Warwick. Dept. of Computer ScienceEngineering and Physical Sciences Research Council (Great Britain) (EPSRC) (GR/S34090/01, EP/E006833/2, GR/S86037/01)Sixth Framework Programme (European Commission) (SFP)Fundação para a Ciência ea Tecnologia (FCT) (POCI/MAT/55796/2004)Conselho de Reitores das Universidades Portuguesas (CRUP)GBUnited Kingdo