Experimental demonstration on the quantum coherence evolution of two-mode squeezed state

Yu Juan, Zhang Yan, Wu Yin-Hua, Yang Wen-Hai, Yan Zhi-Hui, Jia Xiao-Jun, 1) (School of Optoelectronic Engineering, Xi'an Technological University, Xi'an 710021, China), 2) (State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan 030006, China), 3) (Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China), 4) (China Academy of Space Technology (Xi'an), Xi'an, 710000, China)
2022 Wuli xuebao  
As one of the most remarkable features of quantum mechanics, quantum coherence is regarded as an important quantum resource in the quantum information processing. The one-mode squeezed state and the two-mode squeezed state (Einstein-Podolsky-Rosen entangled states) as the most representative examples of nonclassical states both have quantum coherence. The squeezing property of the squeezed state is described by the variance of quadrature components and the positive partial transposition (PPT)
more » ... iterion is applied to describe the entanglement of the EPR entangled states. The research of the quantum coherence of Gaussian states is also a bridge between the properties of squeezing and entanglement. It has been shown that the quantum coherence with infinite-dimensional systems can be quantified by relative Entropy. One of the widely used effective methods to obtain the value of quantum coherence experimentally is quantum tomography. The covariance matrices of the quantum states are reconstructed via balanced homodyne detection and then be taken into quantum coherence expression to calculate the corresponding value. The main factors affecting quantum coherence are the classical and uncorrelated noise in the actual experimental generation processing and the decoherence effect caused by the coupling between quantum resources and the surrounding environment. And the quantum coherence evolution in the generation and transmission process of the quantum resources is essential for the practical applications. Therefore, we analyze in detail the influence of the impurity of quantum resource on squeezing, entanglement and quantum coherence. The evolution of quantum coherence of these Gaussian states in the lossy channels is demonstrated experimentally. We show that quantum coherence is robust against loss in the lossy channels, which is similar to the case of squeezing and entanglement. Quantum coherences of the squeezed state and the EPR entangled states are robust against the thermal photons in the actual experimental generation processing, although the squeezing and entanglement of Gaussian states disappear at a certain number of thermal photons. Our research provide a reference for the practical application of quantum coherence of the squeezed state and entangled states in the lossy environment.
doi:10.7498/aps.72.20221923 fatcat:e46t6ynidjf3hamjxqikli57om