Impact of classical forces and decoherence in multi-terminal Aharonov-Bohm networks

TL;DR

This study investigates how classical forces and decoherence affect quantum interference in multi-terminal Aharonov-Bohm networks, combining experiments with a refined scattering-matrix model to understand phase behavior and optimize device performance.

Contribution

The paper introduces an improved scattering-matrix model that accounts for classical forces and decoherence, accurately describing experimental observations in multi-terminal AB devices.

Findings

AB oscillations show abrupt phase jumps at low magnetic fields.

Output currents are symmetric with respect to magnetic field B.

The refined model can predict conditions for minimum oscillation visibility.

Abstract

Multi-terminal Aharonov-Bohm (AB) rings are ideal building blocks for quantum networks (QNs) thanks to their ability to map input states into controlled coherent superpositions of output states. We report on experiments performed on three-terminal GaAs/Al_(x)Ga_(1-x)As AB devices and compare our results with a scattering-matrix model including Lorentz forces and decoherence. Our devices were studied as a function of external magnetic field (B) and gate voltage at temperatures down to 350 mK. The total output current from two terminals while applying a small bias to the third lead was found to be symmetric with respect to B with AB oscillations showing abrupt phase jumps between 0 and pi at different values of gate voltage and at low magnetic fields, reminiscent of the phase-rigidity constraint due to Onsager-Casimir relations. Individual outputs show quasi-linear dependence of the oscillation phase on the external electric field. We emphasize that a simple scattering-matrix approach can not model the observed behavior and propose an improved description that can fully describe the observed phenomena. Furthermore, we shall show that our model can be successfully exploited to determine the range of experimental parameters that guarantee a minimum oscillation visibility, given the geometry and coherence length of a QN.