Non-Stationary Dephasing by a Classical Intermittent Noise

We investigate the influence of non-stationary intermittent 1/f noise on a quantum two-level system. Adopting a simple phenomenological model for this (collective) noise, we describe exactly the corresponding dephasing in various regimes. The non-stationarity and pronounced non-Gaussian features of this noise induce new anomalous dephasing scenarii. Beyond a history-dependent crossover coupling strength, the dephasing time exhibits a strong dependence on the age of the noise and the decay of coherence is not exponential.