Superconducting atomic contacts inductively coupled to a microwave resonator

TL;DR

This paper presents a microwave spectroscopy setup for probing and manipulating Andreev levels in superconducting atomic contacts, enabling coherent control of quantum states in superconducting circuits.

Contribution

It introduces a novel microwave measurement technique to access and control Andreev states in superconducting atomic contacts, advancing quantum circuit research.

Findings

Successful spectroscopy of Andreev level transitions

Demonstration of flux-dependent control of Andreev states

Potential for coherent manipulation of quantum states

Abstract

We describe and characterize a microwave setup to probe the Andreev levels of a superconducting atomic contact. The contact is part of a superconducting loop inductively coupled to a superconducting coplanar resonator. By monitoring the resonator reflection coefficient close to its resonance frequency as a function of both flux through the loop and frequency of a second tone we perform spectroscopy of the transition between two Andreev levels of highly transmitting channels of the contact. The results indicate how to perform coherent manipulation of these states.