Low-temperature decoherence of qubit coupled to background charges
A. G. Grishin, I. V. Yurkevich, Igor V. Lerner · Physical Review B · 2005
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 $\ensuremath{\Gamma}$ 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 $(⪢T)$ may essentially contribute to $\ensuremath{\Gamma}$.