Quantifying quantum coherence in polariton condensates

TL;DR

This paper combines theoretical and experimental methods to quantify quantum coherence in polariton condensates, demonstrating the transition from thermal to coherent states and highlighting the resourcefulness of such states for quantum technologies.

Contribution

It introduces a novel approach to measure quantum coherence in hybrid light-matter systems, validated through simulations and experiments on polariton condensates.

Findings

Quantum coherence increases across the condensation threshold.

Experimental phase-space distributions confirm the build-up of coherence.

The study links quantum coherence to potential quantum information applications.

Abstract

We theoretically and experimentally investigate quantum features of an interacting light-matter system from a multidisciplinary perspective, unifying approaches from semiconductor physics, quantum optics, and quantum information science. To this end, we quantify the amount of quantum coherence that results from the quantum superposition of Fock states, constituting a measure of the resourcefulness of the produced state for modern quantum protocols. As an archetypal example of a hybrid light-matter interface, we study a polariton condensate and implement a numerical model to predict its properties. Our simulation is confirmed by our proof-of-concept experiment in which we measure and analyze the phase-space distributions of the emitted light. Specifically, we drive a polariton microcavity across the condensation threshold and observe the transition from an incoherent thermal state to a coherent state in the emission, thus confirming the build-up of quantum coherence in the condensate itself.