# Quantum Coherence Witness with Untrusted Measurement Devices

## TL;DR

This paper introduces a measurement-device-independent coherence witness scheme that reliably detects quantum coherence without assumptions on measurement devices, using the decoy-state method and experimental validation.

## Contribution

It proposes a novel coherence witness scheme that is immune to measurement device imperfections and demonstrates its effectiveness experimentally.

## Key findings

- Successfully distinguishes coherent states from incoherent ones
- Enhances reliability of quantum coherence detection
- Validates the scheme with optical system experiments

## Abstract

Coherence is a fundamental resource in quantum information processing, which can be certified by a coherence witness. Due to the imperfection of measurement devices, a conventional coherence witness may lead to fallacious results. We show that the conventional witness could mistake an incoherent state as a state with coherence due to the inaccurate settings of measurement bases. In order to make the witness result reliable, we propose a measurement-device-independent coherence witness scheme without any assumptions on the measurement settings. We introduce the decoy-state method to significantly increase the capability of recognizing states with coherence. Furthermore, we experimentally demonstrate the scheme in a time-bin encoding optical system.