Hybrid methods for witnessing entanglement in a microscopic-macroscopic system

TL;DR

This paper introduces a hybrid method combining microscopic measurements and phase-space analysis to detect entanglement in systems with both microscopic and macroscopic components, demonstrating feasibility with a photon-based system.

Contribution

It presents a novel hybrid approach for witnessing entanglement in microscopic-macroscopic systems, including a loss-tolerant entanglement witness for practical detection.

Findings

Maximal violation of CHSH inequality achievable under ideal conditions.

Hybrid witness effectively corrects for losses in the few-photon regime.

Feasibility demonstrated with a single-photon and multiphoton entangled state.

Abstract

We propose a hybrid approach to the experimental assessment of the genuine quantum features of a general system consisting of microscopic and macroscopic parts. We infer entanglement by combining dichotomic measurements on a bidimensional system and phase-space inference through the Wigner distribution associated with the macroscopic component of the state. As a benchmark, we investigate the feasibility of our proposal in a bipartite-entangled state composed of a single-photon and a multiphoton field. Our analysis shows that, under ideal conditions, maximal violation of a Clauser-Horne-Shimony-Holt-based inequality is achievable regardless of the number of photons in the macroscopic part of the state. The difficulty in observing entanglement when losses and detection inefficiency are included can be overcome by using a hybrid entanglement witness that allows efficient correction for losses in the few-photon regime.