Electron counting statistics and coherent states of electric current

Abstract

A theory of electron counting statistics in quantum transport is presented. It involves an idealized scheme of current measurement using a spin 1/2 coupled to the current so that it precesses at the rate proportional to the current.Within such an approach, counting charge without breaking the circuit is possible. As an application, we derive the counting statistics in a single channel conductor at finite temperature and bias. For a perfectly transmitting channel the counting distribution is gaussian, both for zero-point fluctuations and at finite temperature. At constant bias and low temperature the distribution is binomial, i.e., it arises from Bernoulli statistics. Another application considered is the noise due to short current pulses that involve few electrons.We find the time-dependence of the driving potential that produces coherent noise-minimizing current pulses, and display analogies of such current states with quantum-mechanical coherent states.

Theory of excitation of Rydberg polarons in an atomic quantum gas

“…The strength of the FDA is that it allows one to express overlaps of many-body states in terms of single-particle eigenstates [10,[51][52][53][54]. In our case this implies that we must calculate single-particle eigenstates and energies of the free and "interacting" Hamiltonian, i.e.,ĥ 0 |n = n |n andĥ |β = ω β |β , respectively (whereĥ 0 andĥ are the single-particle representatives of the many-body operatorsĤ 0 andĤ , respectively).…”

Model of qubits as devices to detect the third moment of current fluctuations

“…7,28 Moreover, by means of Eq. ͑40͒, it is possible to check the validity of the perturbative hypothesis and give an estimate of the ratio between the third-and the second-order contributions to the qubit dynamics.…”

“…6͒ analyzed the properties of higher moments and of the full counting statistics. 7 In contrast to the large theoretical activity, experiments are very difficult and only few have appeared so far. The first pioneering measurement of the third moment, performed by Reulet et al 8 has been hindered by environmental effects.…”

Double detected spin-dependent quantum dot

“…The latter involves the problem of accuracy. If the current can be detected directly, via its magnetic field [29], then the states of the dot can be monitored with any accuracy.…”