Finite-size analysis of eight-state continuous-variable quantum key distribution with the linear optics cloning machine

Abstract

We propose a method to improve the secret key rate of an eight-state continuous-variable quantum key distribution (CVQKD) by using a linear optics cloning machine (LOCM). In the proposed scheme, an LOCM is exploited to compensate for the imperfections of Bob's apparatus, so that the generated secret key rate of the eight-state protocol could be well enhanced. We investigate the security of our proposed protocol in a finite-size scenario so as to further approach the practical value of a secret key rate. Numeric simulation shows that the LOCM with reasonable tuning gain λ and transmittance τ can effectively improve the secret key rate of eight-state CVQKD in both an asymptotic limit and a finite-size regime. Furthermore, we obtain the tightest bound of the secure distance by taking the finite-size effect into account, which is more practical than that obtained in the asymptotic limit.

Reference-frame-independent quantum key distribution of wavelength division multiplexing with multiple quantum channels*

“…This assumption usually simplifies the analysis; however, it may also lead to overly optimistic values about the parameter discussed. [28,29] In the finite-key case, [30] the lower bound of single-photon events S Sβ jα,1 is as follows:…”

Improving Eight-State Continuous Variable Quantum Key Distribution by Applying Photon Subtraction

“…It is worth noting that the current four-state CVQKD has been proven secure during an anti-collective attack, which has been experimentally demonstrated [15][16][17]. Recently, another discretely-modulated scheme, called the eight-state CVQKD, has been proposed, which shows better performance compared with the four-state CVQKD [18,19].…”

Reconciliation for CV-QKD using globally-coupled LDPC codes*

“…The post-processing of the CV-QKD system includes the following steps: sifting, [22] parameter estimation, [23,24] information reconciliation, [25] and privacy amplification. [26][27][28][29] The postprocessing procedure is used to extract final secret key from the obtained raw key, [30] and the information reconciliation is used to correct the errors between Alice's and Bob's raw keys by exchanging error correcting messages through an authenticated classical channel. [31] We use LDPC codes to complete information reconciliation in our scheme.…”