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Physical Review A

Information-theoretic approach to atomic spin nonclassicality

Hao Dai, Shunlong Luo

Published Dec 12, 2019• 17 citations
Publisher

Abstract

Nonclassicality of light has been studied, both extensively and intensively, in terms of optical coherent states, and various quantifiers for nonclassicality of light have been introduced in recent decades. In contrast, the corresponding quantification issue for atomic spin systems is relatively less studied, though there has been some remarkable progress. In this paper, by virtue of the Wigner-Yanase skew information and working in the framework of atomic coherent states, we introduce a quantifier for nonclassicality of atomic spin states from an information-theoretic perspective and reveal its fundamental properties. This quantifier leads to a simple yet powerful criterion for detecting nonclassicality via convexity of the skew information. This criterion is sufficient, but not necessary. The concept is illustrated through several paradigms. We further elucidate some intrinsic relations between nonclassicality and entanglement and indicate that the nonclassicality quantifier may be transferred to an entanglement quantifier.

DOI
10.1103/physreva.100.062114

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We propose a convenient and easily computable nonclassicality quantifier for bosonic field states based on the Wigner-Yanase skew information. The proposed nonclassicality quantifier is reflected by the quantum interaction between the maximum phase angle of the homodyne rotated quadrature operator and the bosonic field states. If the value of the nonclassical quantifier is greater than one-half, the state is nonclassical, and the quantifier is one-half for the pure classical. It is worth mentioning that an increase in the strength of nonclassicality inducing operations, such as squeezing and photon addition, leads to an enhancement of the nonclassicality in the quantum state. By computing some well-known nonclassical states and summarizing their existence features, we have confirmed the validity of our proposed nonclassicality quantifier. We have shown that in a range of values of the nonclassicality of the Gaussian state, revealing the sufficiency of the quantifier. We also compare it with two common nonclassical quantifiers to illustrate its advantages.