Performance Improvement of Atmospheric Continuous-Variable Quantum Key Distribution with Untrusted Source.

Qin Liao,Shaoliang Peng,Gang Xiao

doi:10.3390/e23060760

Abstract

Atmospheric continuous-variable quantum key distribution (ACVQKD) has been proven to be secure theoretically with the assumption that the signal source is well protected by the sender so that it cannot be compromised. However, this assumption is quite unpractical in realistic quantum communication system. In this work, we investigate a practical situation in which the signal source is no longer protected by the legitimate parts, but is exposed to the untrusted atmospheric channel. We show that the performance of ACVQKD is reduced by removing the assumption, especially when putting the untrusted source at the middle of the channel. To improve the performance of the ACVQKD with the untrusted source, a non-Gaussian operation, called photon subtraction, is subsequently introduced. Numerical analysis shows that the performance of ACVQKD with an untrusted source can be improved by properly adopting the photon subtraction operation. Moreover, a special situation where the untrusted source is located in the middle of the atmospheric channel is also considered. Under direct reconciliation, we find that its performance can be significantly improved when the photon subtraction operation is manipulated by the sender.

Highlights

Continuous-variable quantum key distribution (CVQKD) [1,2,3,4] is a branch of quantum cryptography, it allows two distant legitimate partners (Alice and Bob) to share an identical secret key over an insecure quantum channel, its security is guaranteed by the laws of quantum mechanics [5,6]
This issue can be theoretically fixed by applying plug-and-play measurement-device-independent (PP MDI) configuration in which both the measurement device and signal source are integrated to the third untrusted party, Charlie [23], PP MDI-based DM CVQKD does not work well in a realistic communication system
As the signal source is no longer protected by the sender, the entanglement of EPR may be affected by an untrusted environment, resulting in a performance degeneration of the Atmospheric continuous-variable quantum key distribution (ACVQKD) system

Summary

Introduction

Continuous-variable quantum key distribution (CVQKD) [1,2,3,4] is a branch of quantum cryptography, it allows two distant legitimate partners (Alice and Bob) to share an identical secret key over an insecure quantum channel, its security is guaranteed by the laws of quantum mechanics [5,6]. The author of [21] suggested a tunable CVQKD scheme for the satellite-to-ground free space optical link using orthogonal frequency division multiplexing technology It can theoretically improve the performance of ACVQKD in terms of the secret key rate, the complicated design is hard to implement with current technologies. This is quite unpractical in a real quantum system, since legitimate users may be compromised in a realistic environment, let alone the signal source This issue can be theoretically fixed by applying plug-and-play measurement-device-independent (PP MDI) configuration in which both the measurement device and signal source are integrated to the third untrusted party, Charlie [23], PP MDI-based DM CVQKD does not work well in a realistic communication system.

ACVQKD with Untrusted Source

Photon Subtraction Operation

Calculation of the Secret Key Rate

Findings

Conclusions