Low-Temperature Decoherence of Qubit Coupled to Background Charges
  We have found an exact expression for the decoherence rate of a Josephson charge qubit coupled to fluctuating background charges. At low temperatures $T$ the decoherence rate ${\Gamma}$ is linear in $T$ while at high temperatures it saturates in agreement with a known classical solution which, however, reached at surprisingly high $T$. In contrast to the classical picture, impurity states spread in a wide interval of energies ($\gg T$) may essentially contribute to ${\Gamma}$. 
Alex Grishin, Igor V. Yurkevich, and Igor V. Lerner (School of Physics   and Astronomy, University of Birmingham, United Kin...