A long-lived capacitively shunted flux qubit embedded in a 3D cavity

TL;DR

This paper reports the development of a 3D capacitively-shunted flux qubit with significantly improved coherence times, demonstrating its potential for quantum sensing applications.

Contribution

The paper presents the first experimental realization of a long-lived 3D capacitively-shunted flux qubit with coherence times exceeding 80 microseconds.

Findings

Energy relaxation times of 60-90 microseconds at optimal bias

Hahn-echo coherence time of about 80 microseconds

Performance improvements over other flux qubit types

Abstract

We report the experimental realization of a 3D capacitively-shunt superconducting flux qubit with long coherence times. At the optimal flux bias point, the qubit demonstrates energy relaxation times in the 60-90 $\mu$s range, and Hahn-echo coherence time of about 80 $\mu$s which can be further improved by dynamical decoupling. Qubit energy relaxation can be attributed to quasiparticle tunneling, while qubit dephasing is caused by flux noise away from the optimal point. Our results show that 3D c-shunt flux qubits demonstrate improved performance over other types of flux qubits which is advantageous for applications such as quantum magnetometry and spin sensing.