Engineering energy-time entanglement from resonance fluorescence

TL;DR

This paper demonstrates how to generate energy-time entanglement from resonance fluorescence of a quantum dot using passive linear interferometry, enabling nonlocal quantum correlations with minimal quantum optical fields.

Contribution

It introduces a method to engineer energy-time entanglement from resonance fluorescence with passive optics, advancing quantum information processing capabilities.

Findings

High-visibility nonlocal interference fringes observed.

Violation of Bell inequality confirmed.

Entanglement generated using only passive linear optics.

Abstract

Resonance fluorescence from a coherently driven two-level emitter is a minimal quantum optical field that combines phase coherence with single-photon-level nonlinearity. Here we show that it can be engineered, using only passive linear interferometry, into energy-time entanglement. By injecting resonance fluorescence from a single quantum dot into an asymmetric Mach--Zehnder interferometer operated near destructive interference of the single-photon component, we generate an output field whose coincidence statistics are dominated by the simultaneous two-photon contribution |2> and the temporally separated photon-pair contribution |11>. In a Franson geometry, these two sectors are resolved on the coincidence-delay axis, and both exhibit high-visibility nonlocal interference fringes and violate the Clauser--Horne--Shimony--Holt Bell inequality. Our results reveal a general route for engineering entanglement from resonance fluorescence using passive optics.