Search

The article describes a formalism to derive quantum entanglement criteria beyond the Gaussian regime that employ the Einstein-Podolsky-Rosen (EPR) correlation and Gaussian measurements. It demonstrates that non-Gaussian entanglement can be more robust than Gaussian entanglement in parameter regime. The authors conclude that non-Gaussian entangled states is relevant to quantum information processing.

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. [ABSTRACT FROM AUTHOR]