# Experimentally reducing the quantum measurement back-action in work distributions by a collective measurement

## TL;DR

This paper demonstrates an experimental implementation of a collective measurement scheme in quantum thermodynamics that reduces measurement back-action, allowing better observation of quantum coherence effects compared to standard projective measurements.

## Contribution

It provides the first experimental realization of a collective measurement scheme to minimize back-action in quantum work distribution estimation.

## Key findings

- Collective measurements reduce measurement back-action compared to standard projective measurements.
- The experiment captures quantum coherence effects that are suppressed by traditional measurements.
- Results show potential for improved quantum thermodynamic measurements using collective schemes.

## Abstract

In quantum thermodynamics, the standard approach to estimate work fluctuations in unitary processes is based on two projective measurements, one performed at the beginning of the process and one at the end. The first measurement destroys any initial coherence in the energy basis, thus preventing later interference effects. In order to decrease this back-action, a scheme based on collective measurements has been proposed in~[PRL 118, 070601 (2017)]. Here, we report its experimental implementation in an optical system. The experiment consists of a deterministic collective measurement on identically prepared two qubits, encoded in the polarisation and path degree of a single photon. The standard two projective measurement approach is also experimentally realized for comparison. Our results show the potential of collective schemes to decrease the back-action of projective measurements, and capture subtle effects arising from quantum coherence.