Initial Decoherence in Solid State Qubits

We study decoherence due to low frequency noise in Josephson qubits. Non-Markovian classical noise
due to switching impurities determines inhomogeneous broadening of the signal. The theory is extended
to include effects of high-frequency quantum noise, due to impurities or to the electromagnetic environ-
ment. The interplay of slow noise with intrinsically non-Gaussian noise sources may explain the rich
physics observed in the spectroscopy and in the dynamics of charge based devices.