Suppression of photon shot noise dephasing in a tunable coupling superconducting qubit

TL;DR

This paper demonstrates that by tuning the coupling in a superconducting qubit, photon shot noise dephasing can be significantly suppressed, leading to longer coherence times and improved qubit performance.

Contribution

The study introduces a tunable coupling qubit design that independently controls qubit frequency and coupling, effectively reducing photon shot noise dephasing.

Findings

Coherence time nearly doubles the relaxation time.

Dephasing becomes less sensitive to thermal photon noise.

Tunable coupling reduces dispersive coupling to 22 kHz.

Abstract

We demonstrate the suppression of photon shot noise dephasing in a superconducting qubit by eliminating its dispersive coupling to the readout cavity. This is achieved in a tunable coupling qubit, where the qubit frequency and coupling rate can be controlled independently. We observe that the coherence time approaches twice the relaxation time and becomes less sensitive to thermal photon noise when the dispersive coupling rate is tuned from several MHz to 22 kHz. This work provides a promising building block in circuit quantum electrodynamics that can hold high coherence and be integrated into larger systems.