Continuous variable quantum key distribution with two-mode squeezed states

TL;DR

This paper proposes and experimentally demonstrates a continuous variable quantum key distribution protocol using squeezed states with large coherent modulation, significantly improving noise tolerance and potentially extending secure communication distances.

Contribution

The authors introduce a CV QKD protocol utilizing fragile squeezed states combined with large coherent modulation, enhancing robustness to channel noise beyond existing coherent state protocols.

Findings

The protocol tolerates more noise than the ideal CV coherent state benchmark.

Experimental demonstration confirms increased noise resilience.

Potential to extend secure communication distances.

Abstract

Quantum key distribution (QKD) enables two remote parties to grow a shared key which they can use for unconditionally secure communication [1]. The applicable distance of a QKD protocol depends on the loss and the excess noise of the connecting quantum channel [2-10]. Several QKD schemes based on coherent states and continuous variable (CV) measurements are resilient to high loss in the channel, but strongly affected by small amounts of channel excess noise [2-6]. Here we propose and experimentally address a CV QKD protocol which uses fragile squeezed states combined with a large coherent modulation to greatly enhance the robustness to channel noise. As a proof of principle we experimentally demonstrate that the resulting QKD protocol can tolerate more noise than the benchmark set by the ideal CV coherent state protocol. Our scheme represents a very promising avenue for extending the distance for which secure communication is possible.