Phase-coherence time saturation in mesoscopic systems: Wave-function collapse

A finite phase-coherence time tau (meas)(phi) emerges from a sequence of id ealized measurements over a quantum system. For a rapid sequence, the phase -coherence time is found explicitly and, for the stationary charge conducti on problem, is bounded. For an arbitrary time interval between measurements , we propose a general expression for tau (meas)(phi) to all orders.