Quantum Decoherence in Disordered Mesoscopic Systems

We point out that the low temperature saturation of the electron phase decoherence time in a disordered conductor can be explained within the existing theory of weak localization provided the effect of quantum (high frequency) fluctuations is taken into account. Making use of the fluctuation-dissipation theorem we evaluate the quantum decoherence time, the crossover temperature below which thermal effects become unimportant, and the weak localization correction $\delta \sigma$ at T=0. For 1d systems the latter is found to be $\delta \sigma \propto 1/ \sqrt{N}$, where $N$ is the number of conducting channels.