Bell Inequality Violation with Vacuum-One-Photon Number Superposition States

TL;DR

This paper demonstrates a new method for generating entanglement using vacuum-one-photon superposition states from a quantum dot, leading to Bell inequality violation without multiphoton states, simplifying quantum optics experiments.

Contribution

It introduces a novel entanglement scheme based on RF from a quantum dot that bypasses multiphoton generation, enhancing scalability and experimental simplicity.

Findings

Bell inequality violation observed with vacuum-one-photon superpositions

Time-bin entanglement achieved via a beam splitter

Scheme simplifies entangled photon source development

Abstract

Entanglement is a central resource in quantum technologies, and the realization of photonic entanglement necessarily relies on interaction with matter. Resonance fluorescence (RF), originating from the coherent interaction between a driving field and a two-level system, plays a pivotal role in quantum optics. Here, we demonstrate a novel route to entanglement generation based on RF from a single quantum dot. Rather than relying on generation of multiphoton states, our approach directly exploits vacuum-one-photon number superposition states created under resonant excitation. By delocalizing this superposition via a beam splitter, we realize time-bin entanglement and observe a clear violation of the Clauser-Horn-Shimony-Holt Bell inequality using Franson-type interferometry. Our scheme removes the need for multiphoton generation, simplifies the experimental requirements, and establishes a scalable pathway toward solid-state entangled photon sources.