We consider dephasing in the electronic Mach-Zehnder interferometer strongly coupled to current noise created by a voltage biased quantum point contact (QPC). We find the visibility of Aharonov-Bohm oscillations as a function of voltage bias and express it via the cumulant generating function of noise. In the large-bias regime, high-order cumulants of current add up to cancel the dilution effect of a QPC. This leads to an abrupt change in the dependence of the visibility on voltage bias which occurs at the QPC’s transparency $T=1/2$. Quantum fluctuations in the vicinity of this point smear out the sharp transition.

• Received 19 March 2009

DOI:https://doi.org/10.1103/PhysRevLett.103.036801