Superconducting qubit in waveguide cavity with coherence time approaching 0.1ms

TL;DR

This paper presents a superconducting transmon qubit embedded in a waveguide cavity achieving a coherence time close to 0.1ms, demonstrating significant improvements in quantum coherence for potential quantum computing applications.

Contribution

The study introduces a simplified device design with enhanced coherence times by reducing residual cavity photon effects, advancing superconducting qubit technology.

Findings

Quantum coherence time T2* of 95 microseconds achieved

Energy relaxation time T1 of 70 microseconds observed

Device modifications significantly improved coherence quality

Abstract

We report a superconducting artificial atom with an observed quantum coherence time of T2*=95us and energy relaxation time T1=70us. The system consists of a single Josephson junction transmon qubit embedded in an otherwise empty copper waveguide cavity whose lowest eigenmode is dispersively coupled to the qubit transition. We attribute the factor of four increase in the coherence quality factor relative to previous reports to device modifications aimed at reducing qubit dephasing from residual cavity photons. This simple device holds great promise as a robust and easily produced artificial quantum system whose intrinsic coherence properties are sufficient to allow tests of quantum error correction.