Two-tone spectroscopy of high-frequency quantum circuits with a Josephson emitter

TL;DR

This paper introduces a two-tone spectroscopy method using a Josephson junction to generate high-frequency radiation for probing quantum circuits, successfully reaching frequencies above 80 GHz and applicable to highly coherent systems.

Contribution

The study demonstrates a novel two-tone spectroscopy technique with a Josephson emitter capable of operating at millimeter-wave frequencies for quantum circuit analysis.

Findings

Operates well into the millimeter-wave band (>80 GHz)

Effective for probing highly coherent quantum systems

Applicable to different quantum circuit architectures

Abstract

We perform two-tone spectroscopy on quantum circuits, where high-frequency radiation is generated by a voltage-biased superconductor-normal-superconductor Josephson junction and detection is carried out by an ancillary microwave resonator. We implement this protocol on two different systems, a transmon qubit and a $\lambda/4$ resonator. We demonstrate that this two-tone Josephson spectroscopy operates well into the millimeter-wave band, reaching frequencies larger than 80 GHz, and is well-suited for probing highly coherent quantum systems.