Nonclassicality induced by nonstationary squeezed reservoirs

We study nonclassical effects in the dynamics of an open quantum system. The model involves a harmonic oscillator coupled to a reservoir of noninteracting harmonic oscillators. Different system-bath interaction schemes as well as reservoir states are considered. Particularly, the squeezed reservoirs coupled to the system through single and two quanta exchange processes are put in the spotlight. We investigate the quantumness conveyed to the system through the bath by computing a nonclassicality measure for different bath properties. The measure of nonclassicality is calculated for projective measurements both in the number state basis and in a basis formed by a set of coherent states. Our results show that in both bases the measure exhibits characteristic features for each bath state and the form of its interaction with the system. Some of those features are independent from the measurement scheme (number or coherent) and, thus, emergent from the reservoir. This allows for fingerprinting and identifying the environmental effects by tracking a given probe with appropriate measurements. Hence, it may prove useful for distinguishing different sources of decoherence.