Quantum key distribution secure against the efficiency loophole

TL;DR

This paper proposes a modified quantum key distribution scheme that is secure against the efficiency loophole without hardware changes, by adjusting data post-processing to account for detection efficiency correlations.

Contribution

It introduces a post-processing modification enabling loophole-free QKD for generic detection systems, including cases with quantum memory, without hardware alterations.

Findings

Lowest tolerable system transmittance is 50%

Necessary efficiency for loophole-free Bell test is 82.8%

Scheme applies to a broad class of detection systems

Abstract

An efficiency-loophole-free quantum key distribution (QKD) scheme is proposed, which involves no hardware change but a modification in the data post-processing step. The scheme applies to a generic class of detection systems which allow correlations between the detection efficiency and the outcomes. We study the system transmittance and the detection error rate that allow implementing this scheme. We also consider the case that a quantum memory is used to boost the performance and investigate the criteria of the readout probability. The simulation result shows that the lowest tolerable system transmittance (readout probability) is 50%, while the necessary efficiency for an efficiency-loophole-free Bell's inequality test is 82.8%.