Observing optical coherence across Fock layers with weak-field homodyne detectors

TL;DR

This paper demonstrates that weak-field homodyne detectors can observe optical coherence across Fock states in entangled quantum states, bridging wave and particle descriptions and enabling hybrid quantum protocols.

Contribution

It introduces the use of weak-field homodyne detection to observe coherence across Fock layers and explores its application in analyzing entangled states and Bell inequalities.

Findings

Experimental verification of coherence across Fock states using weak-field homodyne detectors

Theoretical analysis of detector response on two-mode squeezed states

Potential for hybrid quantum information protocols

Abstract

Quantum properties of optical modes are typically assessed by observing their photon statistics or the distribution of their quadratures. Both particle- and wave-like behaviours deliver important information, and each may be used as a resource in quantum-enhanced technologies. Weak-field homodyne detection provides a scheme which combines the wave- and particle-like descriptions. Here we show that it is possible to observe a wave-like property such as the optical coherence across Fock basis states in the detection statistics derived from discrete photon counting. We experimentally demonstrate these correlations using two weak-field homodyne detectors on each mode of two classes of two-mode entangled states. Furthermore, we theoretically describe the response of weak-field homodyne detection on a two-mode squeezed state in the context of generalised Bell inequalities. Our work demonstrates the potential of this technique as a tool for hybrid continuous/discrete-variable protocols on a phenomenon that explicitly combines both approaches.