Phase-Space Inequalities Beyond Negativities

We derive a family of inequalities involving different phase-space distributions of a quantum state which have to be fulfilled by any classical state. The violation of these inequalities is a clear signature of nonclassicality. Our approach combines the characterization of nonclassical effects via n...

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Bibliographic Details
Published in:Physical review letters 2020-04, Vol.124 (13), p.133601-133601, Article 133601
Main Authors: Bohmann, Martin, Agudelo, Elizabeth
Format: Article
Language:English
Subjects:
Correlation analysis
Inequalities
Squeezed states (quantum theory)
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Summary:We derive a family of inequalities involving different phase-space distributions of a quantum state which have to be fulfilled by any classical state. The violation of these inequalities is a clear signature of nonclassicality. Our approach combines the characterization of nonclassical effects via negativities in phase-space distributions with inequality conditions usually being formulated for moments of physical observables. Importantly, the obtained criteria certify nonclassicality even when the involved phase-space distributions are non-negative. Moreover, we show how these inequalities are related to correlation measurements. The strength of the derived conditions is demonstrated by different examples, including squeezed states, lossy single-photon states, and even coherent states.
ISSN:0031-9007
1079-7114
DOI:10.1103/PhysRevLett.124.133601