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Paper IPM / P / 14941  


Abstract:  
It has been shown that a macroscopic quantum system being in a hightemperature thermal coherent state can, in principle, be driven into nonclassical states by coupling it to a microscopic quantum system. Therefore, thermal coherent states do not truly represent a purely classical system such as a measurement apparatus. Here, we investigate the classical limit of the quantum description of a more relevant macroscopic quantum system, namely a phasepreserving linear amplifier. In particular, we examine to what extent it is possible to find an amplified coherent state, supposedly representing the pointer state of a detector, in a superposition state, by coupling it to a qubit system. We demonstrate quantitatively that the classicalization induced by a realistic amplifier might not be isomorphic to that of a hightemperature thermal coherent state, offering a route to a classical state in a sense of not being able to be projected into a macroscopically distinct superposed state.
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