How to Measure the Transmission Phase via a Quantum Dot in a Two-Terminal Interferometer

TL;DR

This paper proposes a method to measure the transmission phase of a quantum dot in a two-terminal interferometer by breaking phase symmetry with a biased quantum point contact, enabling phase extraction from AB oscillations.

Contribution

It introduces a novel approach to measure the transmission phase by using a capacitively coupled QPC to break phase symmetry in a two-terminal setup.

Findings

Phase symmetry is broken when a bias is applied to the QPC.

The transmission phase can be deduced from the odd component of AB oscillations.

The method allows phase measurement without direct phase-sensitive detection.

Abstract

Measurement of the transmission phase through a quantum dot (QD) embedded in an arm of a two-terminal Aharonov-Bohm (AB) interferometer is inhibited by phase symmetry, i.e. the property that the linear response conductance of a two-terminal device is an even function of magnetic field. It is demonstrated that in a setup consisting of an interferometer with a QD in each of its arms, with one of the QDs capacitively coupled to a nearby quantum point contact (QPC), phase symmetry is broken when a finite voltage bias is applied to the QPC. The transmission phase via the uncoupled QD can then be deduced from the amplitude of the odd component of the AB oscillations.