ELECTRON COUNTING STATISTICS AND COHERENT STATES OF ELECTRIC-CURRENT

A theory of electron counting statistics in quantum transport is prese nted. It involves an idealized scheme of current measurement using a s pin 1/2 coupled to the current so that it precesses at the rate propor tional to the current. Within such an approach, counting charge withou t breaking the circuit is possible. As an application, we derive the c ounting statistics in a single channel conductor at finite temperature and bias. For a perfectly transmitting channel the counting distribut ion is Gaussian, both for zero-point fluctuations and at finite temper ature. At constant bias and low temperature the distribution is binomi al, i.e., it arises from Bernoulli statistics. Another application con sidered is the noise due to short current pulses that involve few elec trons. We find the time-dependence of the driving potential that produ ces coherent noise-minimizing current pulses, and display analogies of such current states with quantum-mechanical coherent states. (C) 1996 American Institute of Physics.