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Quantum key distribution (QKD) provides an unconditional secure key generation method between two distant legitimate parties Alice and Bob based on the fundamental properties of quantum mechanics, in the presence of an eavesdropper Eve. Since key reconciliation cannot always assure that the reconciled keys between Alice and Bob are identical, error verification is an important step in QKD. In this paper, we propose a scheme of delayed error verification using extra keys gained by privacy amplification with an arbitrarily small failure probability. The proposed scheme simplifies the post-processing procedure in QKD, which can be applied in practical QKD systems.

The purpose of reconciliation, one of classical aspects of quantum key distribution (QKD) protocol, is to mitigate errors after the distribution of quantum information over a quantum channel. In this paper, a rate-adaptive method is proposed by means of a channel coding scheme where specific low-density parity-check (LDPC) codes are adapted in the Slepian-Wolf coding system. Puncturing and shortening techniques are adopted to optimize their coding rates with all possible cases of error in QKD. This successful method utilizes the knowledge of the quantum bit error rate (QBER) based on the maximum-likelihood estimator with respect to the syndrome information. Its benefit is that avoids wasting sample keys in the traditional channel estimation and thus increases the size of the final secret key. Evidently, simulation results confirm an improvement in the reconciliation efficiency with minimal interaction that suitable for high QKD throughput applications.

The measurement-device-independent quantum key distribution (MDI-QKD) protocol is proposed to remove the detector side channel attacks, while its security relies on the assumption that the encoding systems are perfectly characterized. In contrast, the MDI-QKD protocol based on the Clauser-Horne-Shimony-Holt inequality (CHSH-MDI-QKD) weakens this assumption, which only requires the quantum state to be prepared in the two-dimensional Hilbert space and the devices are independent. In experimental realizations, the weak coherent state, which is always used in QKD systems due to the lack of an ideal single photon source, may be prepared in the high-dimensional space. In this paper, we investigate the decoy-state CHSH-MDI-QKD protocol with $s(3 \le s \le 5)$ intensities, including one signal state and $s-1$ decoy states, and we also consider the finite-size effect on the decoy-state CHSH-MDI-QKD protocol with five intensities. Simulation results show that this scheme is very practical., Comment: 4 pages, 2 figures

The quantum key reconciliation is an essential step of QKD protocol. Its main objective is to correct the transmission error after the distribution of quantum objects over a quantum channel, where two legitimate parties use a classical interactive communication for agreeing on their common key. This paper presents an alternative quantum key reconciliation method based on the Slepian-Wolf coding scheme with the chosen optimal set of BCH code rates as close to the Slepian-Wolf bound. In the proposed scheme, the BCH decoder is modified by adding one-bit feedback based on syndrome decoding to detect uncorrectable errors whenever the decoding process fails. The performance evaluation of this proposed scheme can achieve the reconciliation efficiency and reduce the cost of interactive communication via an error-free public channel comparable to the well-known reconciliation protocols. It is then suitable to apply for higher-speed discrete-variable QKD applications.

The quantum key reconciliation is an essential step of Quantum Key Distribution (QKD) systems for correcting error in the raw keys which happens after the transmission over a quantum channel, where two legitimate parties make their correlated bits identical by exchanging messages over the public channel. This paper presents an alternative method for error correction of quantum key reconciliation by using ½-rate convolutional code, a class of forward error correcting (FEC) on Winnow for discrete-variable QKD protocol. The convolutional code can be applied to source coding with a side information problem which uses to describe quantum key reconciliation process. In the proposed scheme, it focuses on the performance evaluation of ½-rate convolutional code in quantum key reconciliation. In order to reduce an amount of interactive communication via error-free public channel for high-speed QKD applications, this proposed method is that the suitable solution.

Post-processing is indispensable in quantum key distribution (QKD), which is aimed at sharing secret keys between two distant parties. It mainly consists of key reconciliation and privacy amplification, which is used for sharing the same keys and for distilling unconditional secret keys. In this paper, we focus on speeding up the privacy amplification process by choosing a simple multiplicative universal class of hash functions. By constructing an optimal multiplication algorithm based on four basic multiplication algorithms, we give a fast software implementation of length-adaptive privacy amplification. "Length-adaptive" indicates that the implementation of privacy amplification automatically adapts to different lengths of input blocks. When the lengths of the input blocks are 1 Mbit and 10 Mbit, the speed of privacy amplification can be as fast as 14.86 Mbps and 10.88 Mbps, respectively. Thus, it is practical for GHz or even higher repetition frequency QKD systems.