Abstract
Single-photon states are basic resources for hybrid quantum technology with non-Gaussian states of light. Accelerating quantum technology is already able to produce high-quality single-photon states. These states can be used for hybrid quantum information processing, based on a nonclassical phase-space interference represented by negativity of a Wigner function. Therefore, new quantifiers, capable of evaluating such high-quality single-photon states, are required. We propose and analyze quantifiers which process multiple estimates of single-photon state’s statistics. The quantifiers simulate basic capability of single photons to conditionally bunch into a single mode and form a Fock state. This state exhibits complex nonclassical phase-space interference effects making its Wigner function negative in multiple areas. The quantifiers directly evaluate a presence of the multiple negativities corresponding to the Fock state. We verify applicability of the quantifiers by using them to single-photon states from recent experiments. The quantifiers can be further extended to also test indistinguishability of single-photon states. It allows to verify quantum interference of light from single-photon emitters more sensitively than in the traditional Hong-Ou-Mandel test. Besides quantum optics, the multi-copy quantifiers can be also applied to experiments with atomic memories and mechanical oscillators.
Highlights
Development of single-photon states is crucial for a broad class of applications of quantum technology and experimental tests of principals of quantum physics
The reliable quantifier testing the Fock state |n〉 capability corresponds to a linear optical circuit with detection of no photons in all modes except one
The Fock state |n〉 capability indicates that single-photon statistics is sufficiently good for a broad class of applications of single-photon states in hybrid quantum technology[1, 2] and linear-optical discrete quantum technology[33]
Summary
We derive an expression for the conditional output state density matrix To this end, we apply the virtual physical procedure, depicted, to the estimates ρest,i. The first step of the procedure corresponds to a complex interference of the input modes in a linear optics network represented by the unitary transformationU. It acts on the photon operators of individual modes in the following way. An appearance of its negative values is independent of normalization, which only scales absolute values of Wigner function This measurement conditionally merges all photons from input modes to the remaining output mode labeled by 1.
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