Fully Passive Quantum Key Distribution

We propose a fully passive linear optical quantum key distribution (QKD) source that implements both random decoy-state and encoding choices with postselection only, thus eliminating all side channels in active modulators. Our source is general purpose and can be used in, e.g., BB84, the six-state protocol, and reference-frame-independent QKD. It can even potentially be combined with measurement-deviceindependent QKD to achieve robustness against side channels in both detectors and modulators. We also perform a proof-of-principle experimentalsource characterization to show its feasibility.

Automated summary

We propose a fully passive linear optical quantum key distribution (QKD) source that eliminates all side channels in active modulators by implementing random decoy-state and encoding choices with postselection only. This source is general purpose and can be used in various QKD protocols. It can even potentially achieve robustness against side channels in both detectors and modulators when combined with measurement-device-independent QKD. We also perform a proof-of-principle experimental source characterization to demonstrate its feasibility.