Unveiling distinguishable non-Gaussian quantum states

Yue Zhang, Shunlong Luo

Abstract Two prominent classification schemes for Bosonic field states are (i) classical versus nonclassical, and (ii) Gaussian versus non-Gaussian. These two paradigms are closely related yet fundamentally different. In particular, classical states may be Gaussian or non-Gaussian, and Gaussian states may be classical or nonclassical. Both non-Gaussianity and nonclassicality are important resources for quantum information processing. It is desirable to study the interplay between non-Gaussianity and nonclassicality, and seek effective methods of detecting them. In this work, we introduce a quantifier for non-Gaussianity by exploiting and optimizing an information-theoretic quantifier for nonclassicality, and exhibit its basic properties. A criterion for simultaneously detecting non-Gaussianity and nonclassicality follows, and its applications are illustrated through several examples. This unveils some intrinsic relations between non-Gaussianity and nonclassicality.

Priyanka Chowdhury

Shuangshuang Fu, Shunlong Luo, Yue Zhang

While Gaussian states and associated Gaussian operations are basic ingredients and convenient objects for continuous-variable quantum information, it is also realized that non-Gaussianity is an important resource for quantum information processing. The characterization and quantification of non-Gaussianity have been widely studied in the past decade, with several significant measures for non-Gaussianity introduced. In this work, by exploiting an information-theoretic refinement of the conventional Heisenberg uncertainty relation and a physical characterization of Gaussian states as minimum uncertainty states, we introduce an easily computable measure for non-Gaussianity of bosonic field states in terms of the Wigner-Yanase skew information. Fundamental properties, as well as intuitive meaning, of this measure are unveiled. The concept is illustrated by prototypical non-Gaussian states, and compared with various existent measures for non-Gaussianity. Its merit and physical significance are elucidated.

Mikhail S. Podoshvedov, Sergey A. Podoshvedov, S. P. Kulik

Philippe Grangier

Lukáš Lachman, Ivo Straka, Josef Hloušek +2 more

We propose an experimental method of recognizing quantum non-Gaussian multiphoton states.This is a native quantum property of Fock states, the fundamental quantum states with a constant number of particles.Our method allows experimental development and characterization of higher Fock states of light, reaching even beyond the current technical limits of their generation.We experimentally demonstrate that it is capable of distinguishing realistic quantum non-Gaussian light with the mean number of photons up to 5 despite detection efficiency of 50 %.We also provide evidence that our method can help to distinguish the number of single-photon emitters based only on their collective emission.