Condensed Matter Physics, 2012, vol. 15, No. 4, p. 43004:1-9
Entropy production in open quantum systems: exactly solvable qubit models
(Moscow State Technical University of Radioengineering, Electronics, and Automation, Vernadsky Prospect 78, 119454 Moscow, Russia)
(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.
information entropy, open quantum systems, qubit models, decoherence, quantum entanglement