Considering the shortcomings of distributed source coding (DSC) in quantum communication, such as the high bit error rate and low compression ratio, an improved distributed source coding is proposed in this paper. In the design of the source encoder, redundancy technology is used to provide error protection, and then the joint design of Low-Density Parity Check code (LDPC) with redundancy is adopted to conduct distributed source coding. Experiment results show that the proposed method can be kept the compression ratio well and be easily implemented when a strong internal correlation of the quantum communication areas. The the reconstructed sequence can reach low bit error rate when the correlation between sources are weak. It is a practical, efficient DSC scheme.
Considering the shortcomings of distributed source coding (DSC) in quantum communication, such as the high bit error rate and low compression ratio, an improved distributed source coding is proposed in this paper. In the design of the source encoder, redundancy technology is used to provide error protection, and then the joint design of Low-Density Parity Check code (LDPC) with redundancy is adopted to conduct distributed source coding. Experiment results show that the proposed method can be kept the compression ratio well and be easily implemented when a strong internal correlation of the quantum communication areas. The the reconstructed sequence can reach low bit error rate when the correlation between sources are weak. It is a practical, efficient DSC scheme.
The focus of this research activity is to work on pragmatic information reconciliation applied to QKD schemes based on single photon or weak pulse laser (WPL) sources, so as to use feed-forward techniques which minimize the interaction between transmitter and receiver. The core ideas of the thesis are employing Forward Error Correction (FEC) coding as opposed to two-way communication for information reconciliation in QKD schemes, exploiting all the available information for data processing at the receiver including information available from the quantum channel, since optimized use of this information can lead to significant performance improvement, and providing a security versus secret-key rate trade-off to the end-user within the context of QKD systems. Moreover, as shown by accurate experimental studies, the communication channel used for quantum key exchange is not able to reach high levels of reliability (the Quantum Bit Error Rate -QBER may have a high value), both because of the inherent characteristics of the system, and of the presence of a possible attacker. In order to obtain acceptable residual error rates, it is necessary to use a parallel classical and public channel, characterized by high transmission rates and low error rates, on which to transmit only the redundancy bits of systematic channel codes with performance possibly close to the capacity limit. Furthermore, since the more redundancy is added by the channel code, the more the corresponding information can be used to decipher the private message itself, it becomes necessary to design high-rate codes obtained by puncturing a low-rate mother code, possibly achieving a redundancy such that elements of the secret message cannot be uniquely determined from the redundancy itself, so for that purpose we designed high rate LDPC codes. Using high rate codes increases the security with trade-off to performance. Other low photon number applications have also been considered, such as weak-laser pulses (WLP) communication. For that purpose, a low-complexity photon-counting receiver has been considered which may be employed in long-distance amplification-free classical optical communication schemes, and which is typically modeled as an equivalent Binary Symmetric Channel (BSC). We have developed a time varying Binary Input-Multiple Output (BIMO) channel model for this low-complexity photon-counting receiver, and analyzed its performance in presence of soft-metric based capacity approaching iteratively decoded error correcting codes, such as soft-metric based Low Density Parity Check (LDPC) codes and polar codes. We show that the classical channel capacity of the suggested BIMO model is higher than the capacity of the BSC model, and that the use of the BIMO model allows to feed the channel decoder with soft information, in the form of Log-Likelihood Ratios (LLRs), achieving a significant reduction in Bit Error Rate (BER) and Frame Error Rate (FER) with respect to classical hard-metric-based schemes which should be used in conjunction with a BSC channel model.
Quantum encryption guarantees the absolute security of key distribution from the physical mechanism. However, in the process of quantum key distribution (QKD), quantum channel noise will reduce the transmission efficiency. Quantum low-density parity check (quantum LDPC) code has become a hot research topic of quantum error correcting code due to its great flexibility in the choice of code length and code rate and its dependence on sparse graphs. In order to improve the transmission reliability, a QKD protocol based on BB84 and quantum LDPC code is designed. First, we construct a quantum LDCP error correcting code. Then we utilize the error correcting code and BB84 to construct our QKD protocol. Finally, we analyze the influence of the quantum LDPC code on the proposed protocol. The results show that the key transmission efficiency of the our protocol is improved, and the validity of the QKD protocol based on BB84 and quantum LDPC codes in noisy quantum channels is verified.
Discrete modulation continuous-variable quantum key distribution protocols are compatible with modern coherent optical communication technologies and devices. As a key part of the protocol, the performance of information reconciliation directly affects the secret key rate and transmission distance. Herein, we propose a reconciliation scheme for hard-decision strategy--based discrete modulation continuous-variable quantum key distribution protocol with eight-phase shift keying by combining slice reconciliation and raptor-like low-density parity-check (RL-LDPC) codes. We design the optimal binary sequence encoding of the discretized values of the receiver and sender, which reduce both the number of levels of error correction and the reconciliation complexity. In order to reduce the frame error rate, both the degree distribution and the size of the base matrix of RL-LDPC code is optimized. Simulation results show that the proposed scheme can reach reconciliation efficiencies of 92.05% and 93% with frame error rates of 6.2% and 11.7% at the signal-to-noise ratio of 0.15, respectively. At these points, the key rates can reach 0.0193 and 0.0195 bits/pulse, respectively.
This paper presents a novel approach to quantum error correction (QEC) utilizing redundancy coding, focusing on enhanced efficiency in quantum information transmission. The core claim revolves around designing multi-particle error-correcting codes to minimize the resource consumption associated with encoding and decoding. The proposed mechanism involves encoding information across multiple qubits, leveraging error detection and correction capabilities inherent in these codes. Crucially, the strategy optimizes the distribution of redundant qubits, significantly reducing unnecessary information redundancy. The research addresses the limitations of existing QEC schemes, which often rely on excessive redundancy, impacting transmission efficiency. This work demonstrates a pathway towards more practical and resource-conscious QEC, representing a key step toward reliable long-distance quantum communication. The primary goal is to reduce the overhead associated with error correction, making quantum information transfer more viable. This is achieved through a refined approach to redundancy, concentrating correction resources where they are most needed.
Quantum error correction (QEC) is crucial for reliable quantum computation, but traditional approaches often suffer from scalability issues. This work introduces a novel distributed information theory protocol for QEC, departing from classical distributed coding paradigms. The core idea is to utilize correlated information sharing across a network of nodes, exploiting quantum entanglement to achieve greater efficiency and resilience to errors. We present a framework where the redundancy is distributed intelligently, minimizing the required resources per qubit while maintaining high correction capabilities. The protocol's performance is analyzed theoretically, demonstrating its potential to significantly improve the practicality of QEC in large-scale quantum systems. We explore the key mathematical concepts underpinning this approach, including the distribution of quantum states, the quantification of information, and the analysis of error propagation within the distributed network. The theoretical analysis focuses on characterizing the rate of information transfer and the fidelity of the corrected state, providing a framework for optimizing the protocol's parameters.