Extending the coherence of a quantum dot hybrid qubit

TL;DR

This paper demonstrates significant improvements in the coherence times of a quantum dot hybrid qubit by tuning parameters to mitigate charge noise, achieving over an order of magnitude enhancement in $T_{2}^{*}$ and Rabi decay times.

Contribution

It introduces a method to extend qubit coherence by operating in a specific regime and tuning parameters to reduce charge noise effects.

Findings

Ramsey decay time $T_{2}^{*}$ reached 177 ns

Rabi decay time exceeded 1 microsecond

Charge noise limits the Rabi frequency fluctuations

Abstract

Identifying and ameliorating dominant sources of decoherence are important steps in understanding and improving quantum systems. Here we show that the free induction decay time ($T_{2}^{*}$) and the Rabi decay rate ($\Gamma_{\mathrm{Rabi}}$) of the quantum dot hybrid qubit can be increased by more than an order of magnitude by appropriate tuning of the qubit parameters and operating points. By operating in the spin-like regime of this qubit, and choosing parameters that increase the qubit's resilience to charge noise (which we show is presently the limiting noise source for this qubit), we achieve a Ramsey decay time $T_{2}^{*}$ of $177~\mathrm{ns}$ and a Rabi decay time, $1/\Gamma_{\mathrm{Rabi}}$, exceeding $1~\mathrm{\mu s}$. We find that the slowest $\Gamma_{\mathrm{Rabi}}$ is limited by fluctuations in the Rabi frequency induced by charge noise and not by fluctuations in the qubit energy itself.