Simple security proofs for continuous variable quantum key distribution with intensity fluctuating sources

Chenyang Li,Hoi-Kwong Lo,Li Qian

doi:10.1038/s41534-021-00482-3

Abstract

Despite tremendous theoretical and experimental progress in continuous variable (CV) quantum key distribution (QKD), the security has not been rigorously established for most current continuous variable quantum key distribution systems that have imperfections. Among these imperfections, intensity fluctuation is one of the principal problems affecting security. In this paper, we provide simple security proofs for continuous variable quantum key distribution systems with intensity fluctuating sources. Specifically, depending on device assumptions in the source, the imperfect systems are divided into two general cases for security proofs. In the most conservative case, we prove the security based on the tagging idea, which is a main technique for the security proof of discrete variable quantum key distribution. Our proofs are simple to implement without any hardware adjustment for current continuous variable quantum key distribution systems. Also, we show that our proofs are able to provide secure secret keys in the finite-size scenario.

Highlights

Quantum key distribution (QKD) allows two distant parties to share a common string of secret data[1,2,3]
The implementation of discrete variable (DV) QKD protocols including satellite-to-ground QKD4 and chipbased QKD5–7 have demonstrated the potential for commercial applications in the filed of quantum information
(2) k has a mean value Ek and a variance Vk, where Ek is 1. (3) k is independent of the pulse intensity IA. (4) the probability distribution function of k can be obtained before the experiment by testing the source device. (5) the probability distribution function of k will not change during the QKD transmission

Summary

INTRODUCTION

Quantum key distribution (QKD) allows two distant parties to share a common string of secret data[1,2,3]. Depending on whether the intensity fluctuation information is accessible or not to Alice, our security analysis of a QKD system can be generally divided into two cases: (1) Alice can, and (2) Alice cannot monitor intensity fluctuation values for every pulse. In case (1), because Alice’s information can help modify her data, the security proof is based on the integrating over the distribution of intensity fluctuations. The QKD system users do not need to know whether each signal is tagged or untagged They only need to be able to set a bound for untagged signals, which would lead to the security of their generated key. Our proofs for all cases are simple to implement without any hardware adjustment for the current continuous variable quantum key distribution system. Alice and Bob are free to choose different security proofs to generate the secret key based on their device assumptions

RESULTS AND DISCUSSION

Li et al 4

Discussion