Nonclassicality Of Squeezed Number States

Quantum resource theory is a fundamental tool for studying quantum information.The resource theory is defined by the concepts of free operation(i.e.,it is restricted to be unable to convert a free state into a resource state)and free state(i.e.,excluding resources and is assumed to be used for free).An object or state can be regarded as a resource if it cannot be generated from a non-resource state through a free operation.Quantum resource theory essentially describes that quantum information processing is limited to a limited set of operations.The resource theory framework has been applied to various concepts in quantum information science,such as entanglement,purity,coherence,information balance in quantum thermodynamics,quantum detuning.Quantum nonclassicality means that the behavior of a quantum system cannot be described by classical physics.Nonclassicality is a useful quantum resource in quantum information and has important applications in various quantum tasks such as quantum computing,quantum communication.The robustness of nonclassicality is used to quantify the nonclassicality.Therefore,measuring the quantum non-classicality of quantum states is of great significance to the development,research and utilization of quantum resources.Robust nonclassicity is a direct physical explanation of the nonclassical measurement method under the nonclassical operation resource theory.This paper uses the robust nonclassical measurement method to measure quantum nonclassicity,in which the quantum nonclassicity of the number state,the squeezed state and the cat state has been obtained.In this paper,the squeezed single-photon state and squeezed two-photon state are studied based on the existing research results.The research process and main results are as follows:(1)In the process of verifying the nonclassical properties of squeezed states,it provides certain calculation methods and ideas for the analytical calculation of the nonclassical properties of squeezed single-photon states.The robust nonclassical lower bound of squeezed single-photon states is calculated as a free state.The theoretical upper bound values of the two squeezed single-photon states are obtained by constructing free states by two methods.The theoretical upper and lower bound values of the robust nonclassical properties of the squeezed single-photon state calculated analytically are far from each other.The bound values of the squeezed single-photon state are calculated through modeling analysis and numerical calculation.Except for a small part of the upper and lower limits,the upper and lower limits of the rest are basically coincident.(2)The experience gained in calculating the robust nonclassical limit of squeezed twophoton state is a good reference for calculating the value of squeezed two-photon state.Similarly,the lower bound of the robust nonclassical limit of squeezed two-photon state is calculated as a free state,and the tight lower bound of the robust nonclassical limit of squeezed two-photon state is obtained by numerical calculation.