title: Testing nonclassicality and non-gaussianity in phase space.
abstract: We theoretically propose and experimentally demonstrate a nonclassicality test of a single-mode field in phase space, which has an analogy with the nonlocality test proposed by Banaszek and Wódkiewicz [Phys. Rev. Lett. 82, 2009 (1999)]. Our approach to deriving the classical bound draws on the fact that the Wigner function of a coherent state is a product of two independent distributions as if the orthogonal quadratures (position and momentum) in phase space behave as local realistic variables. Our method detects every pure nonclassical Gaussian state, which can also be extended to mixed states. Furthermore, it sets a bound for all Gaussian states and their mixtures, thereby providing a criterion to detect a genuine quantum non-Gaussian state. Remarkably, our phase-space approach with invariance under Gaussian unitary operations leads to an optimized test for a given non-Gaussian state. We experimentally show how this enhanced method can manifest quantum non-Gaussianity of a state by simply choosing phase-space points appropriately, which is essentially equivalent to implementing a squeezing operation on a given state.
authors.affiliation: Department of Physics, Texas A&M University at Qatar, Education City, P.O. Box 23874, Doha, Qatar.
authors.forename: Jiyong
authors.initials: J
authors.lastname: Park
authors.affiliation: Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, Beijing 100084, People's Republic of China.
authors.forename: Junhua
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Department of Physics, Texas A&M University at Qatar, Education City, P.O. Box 23874, Doha, Qatar.
authors.forename: Jaehak
authors.initials: J
authors.lastname: Lee
authors.affiliation: Department of Physics, Texas A&M University at Qatar, Education City, P.O. Box 23874, Doha, Qatar.
authors.forename: Se-Wan
authors.initials: SW
authors.lastname: Ji
authors.affiliation: Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, Beijing 100084, People's Republic of China.
authors.forename: Mark
authors.initials: M
authors.lastname: Um
authors.affiliation: Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, Beijing 100084, People's Republic of China.
authors.forename: Dingshun
authors.initials: D
authors.lastname: Lv
authors.affiliation: Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, Beijing 100084, People's Republic of China.
authors.forename: Kihwan
authors.initials: K
authors.lastname: Kim
authors.affiliation: Department of Physics, Texas A&M University at Qatar, Education City, P.O. Box 23874, Doha, Qatar.|School of Computational Sciences, Korea Institute for Advanced Study, Seoul 130-722, Korea.
authors.forename: Hyunchul
authors.initials: H
authors.lastname: Nha