Phase-Space Inequalities Beyond Negativities
Abstract
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.
- Publication:
-
Physical Review Letters
- Pub Date:
- April 2020
- DOI:
- 10.1103/PhysRevLett.124.133601
- arXiv:
- arXiv:1909.10534
- Bibcode:
- 2020PhRvL.124m3601B
- Keywords:
-
- Quantum Physics
- E-Print:
- Published version. Includes supplemental material