Title: Entropy production in open quantum systems: exactly solvable qubit models
Author(s):

	V.G. Morozov (Moscow State Technical University of Radioengineering, Electronics, and Automation, Vernadsky Prospect 78, 119454 Moscow, Russia) ,
	G. Röpke (University of Rostock, FB Physik, Universit\""atsplatz 3, D--18051 Rostock, Germany)

We present analytical results for the time-dependent information entropy in exactly solvable two-state (qubit) models. The first model describes dephasing (decoherence) in a qubit coupled to a bath of harmonic oscillators. The entropy production for this model in the regimes of "complete" and "incomplete" decoherence is discussed. As another example, we consider the damped Jaynes-Cummings model describing a spontaneous decay of a two-level system into the field vacuum. It is shown that, for all strengths of coupling, the open system passes through the mixed state with the maximum information entropy.

Key words: information entropy, open quantum systems, qubit models, decoherence, quantum entanglement
PACS: 03.65.Ud, 03.65.Yz

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