Entanglement verification with detection-efficiency mismatch

TL;DR

This paper introduces a method for verifying entanglement in quantum systems with detection-efficiency mismatch, applicable across various degrees of freedom, and highlights how increasing mismatch can compromise quantum security.

Contribution

It provides a novel entanglement verification technique that does not depend on photon number cut-offs and is versatile across different optical modes.

Findings

Verification method works without photon number cut-off

Applicable to multiple degrees of freedom

Efficiency mismatch impacts quantum security

Abstract

The security analysis of quantum key distribution is difficult to perform when there is efficiency mismatch between various threshold detectors involved in an experimental setup. Even the verification that the device actually performs in the quantum domain, referred to as the task of entanglement verification, is hard to perform. In this article we provide such an entanglement-verification method for characterized detection-efficiency mismatch. Our method does not rely on a cut-off of photon numbers in the optical signal. It can be applied independently of the degrees of freedom involved, thus covering, for example, efficiency mismatch in polarization and time-bin modes, but also in spatial modes. The evaluation of typical experimental scenarios suggests that an increase of detection-efficiency mismatch will drive the performance of a given setup out of the quantum domain.