Condensed Matter Physics, 2013, vol. 16, No. 3, p. 34001:1-6
DOI:10.5488/CMP.16.34001           arXiv:1310.1236

Title: Bath dynamics in an exactly solvable qubit model with initial qubit-environment correlations
  V.V. Ignatyuk (Institute for Condensed Matter Physics of the National Academy of Sciences of Ukraine, 1 Svientsitskii St., 79011 Lviv, Ukraine) ,
  V.G. Morozov (Moscow State Technical University of Radioengineering, Electronics, and Automation, 78 Vernadsky Prospect, 119454 Moscow, Russia)

We study the bath dynamics in the dephasing model of a two-state quantum system (qubit) coupled to an environment of harmonic oscillators. This model was shown [Morozov et al., Phys. Rev. A, 2012 85, 022101] to admit the analytic solution for the qubit and environment dynamics. Using this solution, we derive the exact expression for the bath reduced density matrix in the presence of initial qubit-environment correlations. We obtain the non-equilibrium phonon distribution function and discuss in detail the time behavior of the bath energy. It is shown that only the inclusion of dynamic correlations between the qubit and the bath ensures the proper time behavior of the quantity which may be interpreted as the "environment energy".

Key words: open quantum systems, qubit-environment correlations
PACS: 03.65.Yz

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