Interference Effects in a Tunable Quantum Point Contact Integrated with an Electronic Cavity

TL;DR

This paper experimentally demonstrates quantum interference effects, including Fano resonances, in a tunable integrated quantum system combining a quantum point contact and an electronic cavity, revealing potential for quantum circuit applications.

Contribution

It introduces a novel integrated quantum device exhibiting tunable interference and Fano resonances, advancing the understanding of quantum state coupling in open systems.

Findings

Observation of fine oscillations indicating interference between 1D states and cavity states.

Identification of Fano resonance behavior in resistance tuning.

Oscillatory Fano factor confirming coupling between discrete and continuum states.

Abstract

We show experimentally how quantum interference can be produced using an integrated quantum system comprising an arch-shaped short quantum wire (or quantum point contact, QPC) of 1D electrons and a reflector forming an electronic cavity. On tuning the coupling between the QPC and the electronic cavity, fine oscillations are observed when the arch QPC is operated in the quasi-1D regime. These oscillations correspond to interference between the 1D states and a state which is similar to the Fabry-Perot state and suppressed by a small transverse magnetic field of 60mT. Tuning the reflector, we find a peak in resistance which follows the behavior expected for a Fano resonance. We suggest that this is an interesting example of a Fano resonance in an open system which corresponds to interference at or near the Ohmic contacts due to a directly propagating, reflected discrete path and the continuum states of the cavity corresponding to multiple scattering. Remarkably, the Fano factor shows an oscillatory behavior taking peaks for each fine oscillation, thus, confirming coupling between the discrete and continuum states. The results indicate that such a simple quantum device can be used as building blocks to create more complex integrated quantum circuits for possible applications ranging from quantum-information processing to realizing the fundamentals of complex quantum systems.