Continuous Variable Quantum Key Distribution with a Noisy Laser

TL;DR

This paper demonstrates that continuous-variable quantum key distribution can be robust against preparation noise from non-ideal lasers, potentially enabling cheaper and integrated quantum communication systems.

Contribution

The authors experimentally show that preparation noise from noisy lasers can be tolerated in CV-QKD using direct reconciliation, challenging the need for shot-noise limited sources.

Findings

Large preparation noise tolerated at small distances with direct reconciliation

Reverse reconciliation is less robust to preparation noise

Quantum key distribution feasible with non-shot-noise limited lasers

Abstract

Existing experimental implementations of continuous-variable quantum key distribution require shot-noise limited operation, achieved with shot-noise limited lasers. However, loosening this requirement on the laser source would allow for cheaper, potentially integrated systems. Here, we implement a theoretically proposed prepare-and-measure continuous-variable protocol and experimentally demonstrate the robustness of it against preparation noise stemming for instance from technical laser noise. Provided that direct reconciliation techniques are used in the post-processing we show that for small distances large amounts of preparation noise can be tolerated in contrast to reverse reconciliation where the key rate quickly drops to zero. Our experiment thereby demonstrates that quantum key distribution with non-shot-noise limited laser diodes might be feasible.