Postselected Entangled States by Photon Detection

TL;DR

This paper demonstrates how photon detection can entangle highly-excited two-level emitter ensembles, with successive detections acting as a purification process to restore spin squeezing despite decoherence.

Contribution

It introduces a method to generate postselected entanglement in open quantum systems using photon detection and shows how successive detections can mitigate decoherence effects.

Findings

Photon detection entangles highly-excited emitter ensembles.

Successive detections restore spin squeezing degraded by decoherence.

The method enables new avenues for entanglement generation in open systems.

Abstract

Postselection is a non-deterministic mechanism to entangle subsystems, often used in weakly-excited systems. We here show how highly-excited ensembles of two-level emitters can be entangled by photon detection. A collective spin is formed, characterized by a squeezing parameter detected by far-field measurements. While decoherence is detrimental to this conditional entanglement, successive photon detections act as a purification process and restores the spin squeezing. Our work opens up new avenues for the generation of postselected entanglement in open quantum systems.