Coherence oscillations in dephasing by non-Gaussian shot noise

TL;DR

This paper develops a non-perturbative approach to understand how non-Gaussian shot noise causes coherence oscillations in quantum systems like charge qubits and interferometers, explaining recent experimental observations.

Contribution

It introduces a novel non-perturbative method to analyze dephasing by non-Gaussian shot noise and explains oscillatory visibility phenomena in quantum interference experiments.

Findings

Visibility oscillations depend on detector voltage and interaction time.

Oscillations occur only in the strong coupling regime with phase > pi.

The formula matches recent experimental results and explains earlier observations.

Abstract

A non-perturbative treatment is developed for the dephasing produced by the shot noise of a one- dimensional electron channel. It is applied to two systems: a charge qubit and the electronic Mach-Zehnder interferometer, both of them interacting with an adjacent partitioned electronic channel acting as a detector. We find that the visibility (interference contrast) can display oscillations as a function of detector voltage and interaction time. This is a unique consequence of the non-Gaussian properties of the shot noise, and only occurs in the strong coupling regime, when the phase contributed by a single electron exceeds pi. The resulting formula reproduces the recent surprising experimental observations reported in [I. Neder et al., cond-mat/0610634], and indicates a general explanation for similar visibility oscillations observed earlier in the Mach-Zehnder interferometer at large bias voltage. We explore in detail the full pattern of oscillations as a function of coupling strength, voltage and time, which might be observable in future experiments.