Frequency-Tunable Josephson Junction Resonator for Quantum Computing

TL;DR

This paper reports the development of a frequency-tunable high-Q Josephson junction resonator with potential applications in quantum computing, including qubit readout and junction quality assessment.

Contribution

It introduces a tunable Josephson junction resonator with high quality factor and explores its nonlinear behavior at different photon levels for quantum computing applications.

Findings

Resonance frequency tunable by over 10% using magnetic flux.

Achieves a quality factor of approximately 7000 at low photon numbers.

Demonstrates nonlinear stable states at high photon levels.

Abstract

We have fabricated and measured a high-Q Josephson junction resonator with a tunable resonance frequency. A dc magnetic flux allows the resonance frequency to be changed by over 10 %. Weak coupling to the environment allows a quality factor of $\thicksim$7000 when on average less than one photon is stored in the resonator. At large photon numbers, the nonlinearity of the Josephson junction creates two stable oscillation states. This resonator can be used as a tool for investigating the quality of Josephson junctions in qubits below the single photon limit, and can be used as a microwave qubit readout at high photon numbers.