Proof-of-Principle Demonstration of Fully-Passive Quantum Key Distribution

TL;DR

This paper demonstrates a fully passive quantum key distribution system using polarization encoding, eliminating active modulators and addressing security concerns, with experimental results at various channel losses showing its practical feasibility.

Contribution

It provides the first proof-of-principle demonstration of a fully passive polarization-encoded QKD scheme using gain-switching and post-selection techniques.

Findings

Successful demonstration at channel losses of 7.2 dB, 11.6 dB, and 16.7 dB.

Shows feasibility of active-modulation-free QKD in polarization systems.

Addresses security issues related to device imperfections in practical QKD implementations.

Abstract

Quantum key distribution (QKD) offers information-theoretic security based on the fundamental laws of physics. However, device imperfections, such as those in active modulators, may introduce side-channel leakage, thus compromising practical security. Attempts to remove active modulation, including passive decoy intensities preparation and polarization encoding, have faced theoretical constraints and inadequate security verification, thus hindering the achievement of a fully passive QKD scheme. Recent research has systematically analyzed the security of a fully passive modulation protocol. Based on this, we utilize the gain-switching technique in combination with the post-selection scheme and perform a proof-of-principle demonstration of a fully passive quantum key distribution with polarization encoding at channel losses of 7.2 dB, 11.6 dB, and 16.7 dB. Our work demonstrates the feasibility of active-modulation-free QKD in polarization-encoded systems.