Threshold resonance and controlled filtering in quantum star graphs

TL;DR

This paper introduces two quantum devices utilizing threshold resonance in star graphs with external potentials, enabling adjustable quantum filtering and flux control by external field manipulation, a novel approach in quantum flow regulation.

Contribution

The paper presents the first example of quantum flow control achieved through external fields applied to lines connected at a vertex, not directly on the channel.

Findings

Quantum devices for spectral filtering and flux control are designed.

External potential strength directly modulates quantum flow.

First demonstration of flow control via external fields on connected lines.

Abstract

We design two simple quantum devices applicable as an adjustable quantum spectral filter and as a flux controller. Their function is based upon the threshold resonance in a F\"ul\"op-Tsutsui type star graph with an external potential added on one of the lines. Adjustment of the potential strength directly controls the quantum flow from the input to the output line. This is the first example to date in which the quantum flow control is achieved by addition of an external field not on the channel itself, but on other lines connected to the channel at a vertex.