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Kühn B, Vogel W, Thiel V, Merkouche S, Smith BJ. Gaussian versus Non-Gaussian Filtering of Phase-Insensitive Nonclassicality. PHYSICAL REVIEW LETTERS 2021; 126:173603. [PMID: 33988399 DOI: 10.1103/physrevlett.126.173603] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2020] [Accepted: 03/31/2021] [Indexed: 06/12/2023]
Abstract
Measures of quantum properties are essential to understanding the fundamental differences between quantum and classical systems as well as quantifying resources for quantum technologies. Here, two broad classes of bosonic phase-space functions, which are filtered versions of the Glauber-Sudarshan P function, are compared with regard to their ability to uncover nonclassical effects of light through their negativities. Gaussian filtering of the P function yields the family of s-parametrized quasiprobabilities, while more powerful regularized nonclassicality quasiprobabilities are obtained by non-Gaussian filtering. A method is proposed to directly sample such phase-space functions for the restricted case of phase-independent quantum states from balanced homodyne measurements. This overcomes difficulties of previous approaches that manually append uniformly distributed optical phases to the measured quadrature data. We experimentally demonstrate this technique for heralded single- and two-photon states using balanced homodyne detection with varying efficiency. The s-parametrized quasiprobabilities, which can be directly sampled, are non-negative for detection efficiencies below 0.5. By contrast, we show that significant negativities of non-Gaussian filtered quasiprobabilities uncover nonclassical effects for arbitrarily low efficiencies.
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Affiliation(s)
- B Kühn
- Arbeitsgruppe Quantenoptik, Institut für Physik, Universität Rostock, D-18051 Rostock, Germany
| | - W Vogel
- Arbeitsgruppe Quantenoptik, Institut für Physik, Universität Rostock, D-18051 Rostock, Germany
| | - V Thiel
- Clarendon Laboratory, University of Oxford, Parks Road, Oxford, OX1 3PU, United Kingdom
- Department of Physics and Oregon Center for Optical, Molecular, and Quantum Science, University of Oregon, Eugene, Oregon 97403, USA
| | - S Merkouche
- Department of Physics and Oregon Center for Optical, Molecular, and Quantum Science, University of Oregon, Eugene, Oregon 97403, USA
| | - B J Smith
- Department of Physics and Oregon Center for Optical, Molecular, and Quantum Science, University of Oregon, Eugene, Oregon 97403, USA
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Wiseman HM. Defending continuous variable teleportation: why a laser is a clock, not a quantum channel. ACTA ACUST UNITED AC 2004. [DOI: 10.1088/1464-4266/6/8/035] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Hillery M, Zou M, Buzek V. Difference-phase squeezing from amplitude squeezing by means of a beamsplitter. ACTA ACUST UNITED AC 1999. [DOI: 10.1088/1355-5111/8/5/009] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Royer A. Phase states and phase operators for the quantum harmonic oscillator. PHYSICAL REVIEW. A, ATOMIC, MOLECULAR, AND OPTICAL PHYSICS 1996; 53:70-108. [PMID: 9912862 DOI: 10.1103/physreva.53.70] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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