Free-space continuous-variable quantum key distribution of unidimensional Gaussian modulation using polarized coherent-states in urban environment

TL;DR

This paper demonstrates a simplified free-space continuous-variable quantum key distribution protocol using unidimensional Gaussian modulation with polarized coherent states, achieving secure communication over 460 meters in urban environments.

Contribution

It introduces a simplified CV QKD scheme with asymmetric modulation in free-space, reducing complexity and maintaining security in urban environments.

Findings

Achieved 460m secure QKD distance in free-space urban environment.

Secure key rate of 0.152 kbps with 95% reconciliation efficiency.

Simplified experimental setup compared to traditional protocols.

Abstract

We use single homodyne detector to accomplish Continuous-Variable quantum key distribution(CV QKD) in a laboratory and urban environment free-space channel. This is based on Gaussian modulation with coherent-states in the polarization degree of freedom. We achieved a QKD distance at 460m, at the repetition rate of 10 kHz. We give the security of this protocol against collective attack in the asymptotic regime. The secure key rate is 0.152 kbps at the typical reconciliation efficiency of 0.95. The experiment setup of this scheme is simplified and the difficulty to realize has been remarkably reduced compared to traditional symmetric modulation ones, for example, GG02 protocol. The influence of security key rate brought by asymmetric modulation is small in a relative low channel loss condition in the free-space environment. This scheme is expected to be significance meaning to the future practically utilize.