Thermal state quantum key distribution

A Walton,A Ghesquiere,D Jennings,B Varcoe,G Brumpton

doi:10.1088/1361-6455/ac2a6e

Abstract

We analyse a central broadcast continuous variable quantum key distribution protocol in which a beam produced by a thermal source is used to create a secret key between two parties, Alice and Bob. A beam splitter divides the initial beam into a pair of output beams, which are sent to Alice and Bob, with Eve intercepting Bob’s beam. We investigate the protocol in detail, calculating mutual informations through a pair of analytic methods and comparing the results to the outputs of a Monte Carlo simulation of the protocol. In a lossless system, we find that a lower bound on the key rate remains positive in the protocol under a beam splitter attack, provided Bob receives a nonzero proportion of the beam initially sent to him. This suggests that the thermal state protocol could be used experimentally to produce secure keys.

Highlights

In quantum key distribution (QKD), two parties, Alice and Bob, want to communicate in a secure fashion despite the presence of Eve, who is eavesdropping on their communication channel
When considering a system without loss and noise, the lower bound placed on the key rate when reverse reconciliation is considered is positive under a beam splitter attack even when Eve has zero loss
This would allow for a secret key to be produced between Alice and Bob, and secure communication could take place in the presence of an eavesdropper performing collective or individual attacks

Summary

Introduction

In quantum key distribution (QKD), two parties, Alice and Bob, want to communicate in a secure fashion despite the presence of Eve, who is eavesdropping on their communication channel. They do this through establishing a cryptographic key that is known only to them and no one else [1, 2]. Alice cannot send Bob a key over their communication channel, as Eve will learn the key by eavesdropping. Protocols are needed which can distribute an identical key to Alice and Bob over an insecure channel, without Eve discovering it. There is no reason to assume that solving these problems within a reasonable timeframe will continue to be difficult in the future as computing power increases and new algorithms are created

Objectives

Results

Conclusion