Nonzero-temperature coherent and squeezed states for the harmonic oscillator: The time-dependent frequency case

Abstract

We present a density-matrix method, based on information theory, which makes it possible to find nonzero-temperature coherent and squeezed states for the harmonic oscillator with time-dependent frequency. We establish a connection between the appearance of squeezed states and the relevant operators included in the density matrix, compare our results with previous ones that were obtained using wave functions, and analyze the particular case of a sudden jump in the oscillator's frequency.