Oscillator coupled to a very small environment (another oscillator)

What is it about?

Quantum oscillator coupled to another oscillator which plays the role of an environment. The system (main oscillator) is in a coherent state and the environment in a thermal state. Two models of coupling system-environment are considered, and the evolution of the system's linear entropy is calculated. A comparison is made with the usual formalism based on the master equation.

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Why is it important?

It is shown that even very small environments may have a significant effect over simple quantum systems. Considering sufficiently short time scales, we discuss similarities and differences compared to the usual master equation approach.