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.

Quantum tomography of light states by photon-number-resolving detectors

“…We also notice that the scheme adopted in this work is completely different from the so-called weak-homodyne detection ones, in which photon-number-resolving detectors have been employed. Indeed, in those schemes the reconstruction of the states has been achieved by considering only a single output of the interferometer [30][31][32][33][34][35][36][37], whereas here we deal with the difference between the two outputs.…”

Parsing polarization squeezing into Fock layers

“…In contradistinction, in quantum optics (1) implies thatŜ 2 = S When the photon number is fuzzy, we need to consider a three-dimensional Poincaré space (with axes S 1 , S 2 , and S 3 ). This space can be visualized as a set of nested spheres with radii proportional to the diverse photon numbers that contribute to the state and that can be aptly called the Fock layers [19].…”

Tuning between photon-number and quadrature measurements with weak-field homodyne detection

“…In principle, WFHD can be reconfigured to realize both of these measurements simply by controlling the strength of the phase-reference. Moreover, WFHD has the unique ability to perform phasesensitive non-Gaussian measurements since it can access the region between homodyne and photon-counting [18][19][20]. Such measurements provide a powerful state preparation and characterization tool, especially in hybrid discrete-and continuous-variable protocols [21].…”