1,817 research outputs found
Entanglement-assisted quantum error-correcting codes over arbitrary finite fields
We prove that the known formulae for computing the optimal number of maximally entangled pairs required for entanglement-assisted quantum error-correcting codes (EAQECCs) over the binary field hold for codes over arbitrary finite fields as well. We also give a Gilbert-Varshamov bound for EAQECCs and constructions of EAQECCs coming from punctured self-orthogonal linear codes which are valid for any finite field.Supported by the Spanish Ministry of Economy/FEDER: grants MTM2015-65764-C3-1-P, MTM2015-65764-C3-2-P, MTM2015-69138-REDT and RYC-2016-20208 (AEI/FSE/UE), the University Jaume I: grant UJI-B2018-10, Spanish Junta de CyL: grant VA166G18, and JSPS Grant No. 17K06419
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
Entanglement-assisted codeword stabilized quantum codes with imperfect ebits
Quantum error correcting codes (QECCs) in quantum communi- cation systems has
been known to exhibit improved performance with the use of error-free
entanglement bits (ebits). In practical situations, ebits inevitably suffer
from errors, and as a result, the error-correcting capability of the code is
diminished. Prior studies have proposed two different schemes as a solu- tion.
One uses only one QECC to correct errors on the receiver's side (i.e., Bob) and
on the sender's side (i.e., Alice). The other uses different QECCs on each
side. In this paper, we present a method to correct errors on both sides by
using single nonadditive Entanglement-assisted codeword stabilized quantum
error correcting code(EACWS QECC). We use the property that the number of
effective error patterns decreases as much as the number of ebits. This
property results in a greater number of logical codewords using the same number
of physical qubits
Entanglement-Assisted Quantum Quasi-Cyclic Low-Density Parity-Check Codes
We investigate the construction of quantum low-density parity-check (LDPC)
codes from classical quasi-cyclic (QC) LDPC codes with girth greater than or
equal to 6. We have shown that the classical codes in the generalized
Calderbank-Shor-Steane (CSS) construction do not need to satisfy the
dual-containing property as long as pre-shared entanglement is available to
both sender and receiver. We can use this to avoid the many 4-cycles which
typically arise in dual-containing LDPC codes. The advantage of such quantum
codes comes from the use of efficient decoding algorithms such as sum-product
algorithm (SPA). It is well known that in the SPA, cycles of length 4 make
successive decoding iterations highly correlated and hence limit the decoding
performance. We show the principle of constructing quantum QC-LDPC codes which
require only small amounts of initial shared entanglement.Comment: 8 pages, 1 figure. Final version that will show up on PRA. Minor
changes in contents and Titl
Entanglement-assisted quantum low-density parity-check codes
This paper develops a general method for constructing entanglement-assisted
quantum low-density parity-check (LDPC) codes, which is based on combinatorial
design theory. Explicit constructions are given for entanglement-assisted
quantum error-correcting codes (EAQECCs) with many desirable properties. These
properties include the requirement of only one initial entanglement bit, high
error correction performance, high rates, and low decoding complexity. The
proposed method produces infinitely many new codes with a wide variety of
parameters and entanglement requirements. Our framework encompasses various
codes including the previously known entanglement-assisted quantum LDPC codes
having the best error correction performance and many new codes with better
block error rates in simulations over the depolarizing channel. We also
determine important parameters of several well-known classes of quantum and
classical LDPC codes for previously unsettled cases.Comment: 20 pages, 5 figures. Final version appearing in Physical Review
Entanglement Increases the Error-Correcting Ability of Quantum Error-Correcting Codes
If entanglement is available, the error-correcting ability of quantum codes
can be increased. We show how to optimize the minimum distance of an
entanglement-assisted quantum error-correcting (EAQEC) code, obtained by adding
ebits to a standard quantum error-correcting code, over different encoding
operators. By this encoding optimization procedure, we found several new EAQEC
codes, including a family of [[n, 1, n; n-1]] EAQEC codes for n odd and code
parameters [[7, 1, 5; 2]], [[7, 1, 5; 3]], [[9, 1, 7; 4]], [[9, 1, 7; 5]],
which saturate the quantum singleton bound for EAQEC codes. A random search
algorithm for the encoding optimization procedure is also proposed.Comment: 39 pages, 10 table
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