Generating Entangled Spin States for Quantum Metrology by Single-Photon Detection

TL;DR

This paper presents a probabilistic heralded scheme using single-photon detection to generate pure, entangled spin states in atomic ensembles, enabling quantum metrology beyond the standard quantum limit.

Contribution

It introduces a novel method for creating entangled non-Gaussian spin states with high purity, even with imperfect detection, and discusses making the process quasi-deterministic.

Findings

States include Dicke and Schrödinger cat states.

Method remains effective with finite detection efficiency.

Potential for enhanced quantum metrology beyond classical limits.

Abstract

We propose and analyze a probabilistic but heralded scheme to generate pure, entangled, non-Gaussian states of collective spin in large atomic ensembles by means of single-photon detection. One photon announces the preparation of a Dicke state, while two or more photons announce Schr\"odinger cat states. The method produces pure states even for finite photon detection efficiency and weak atom-photon coupling. The entanglement generation can be made quasi-deterministic by means of repeated trial and feedback, enabling metrology beyond the standard quantum limit.