Wavelength attack on practical continuous-variable quantum-key-distribution system with a heterodyne protocol

TL;DR

This paper introduces a wavelength attack on a practical continuous-variable quantum key distribution system with a heterodyne protocol, emphasizing the importance of shot noise analysis for successful implementation.

Contribution

It provides a rigorous analysis of the wavelength attack equations and accurately calculates shot noise, demonstrating the attack's feasibility under certain parameters.

Findings

Wavelength-dependent beam splitter transmittance enables the attack.

Shot noise is critical for the attack's success.

The attack can be effective within specific parameter regimes.

Abstract

We present the wavelength attack on a practical continuous-variable quantum-key-distribution system with a heterodyne protocol, in which the transmittance of beam splitters at Bob's station is wavelength-dependent. Our strategy is proposed independent of but analogous to that of Huang et al. [arXiv: 1206.6550v1 [quant-ph]], but in that paper the shot noise of the two beams that Eve sends to Bob, transmitting after the homodyne detector, is unconsidered. However, shot noise is the main contribution to the deviation of Bob's measurements from Eve's when implementing the wavelength attack, so it must be considered accurately. In this paper, we firstly analyze the solutions of the equations specifically that must be satisfied in this attack, which is not considered rigorously by Huang et al. Then we calculate the shot noise of the homodyne detector accurately and conclude that the wavelength attack can be implemented successfully in some parameter regime.