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

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 (WFH) detection provides a scheme that 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 WHF detectors on each mode of two classes of two-mode entangled states. Furthermore, we theoretically describe the response of WHF detection on a two-mode squeezed state in the context of generalized 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.