Mitigating the effects of charge noise and improving the coherence of a quantum dot hybrid qubit

Brandur Thorgrimsson, Dohun Kim, Yuan-Chi Yang, C. B. Simmons, Daniel R. Ward, Ryan H. Foote, D. E. Savage, M. G. Lagally, Mark Friesen, S. N. Coppersmith, M. A. Eriksson

Published 2016-11-15Version 1

Identifying dominant sources of decoherence is an important step 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 are limited by charge noise for a large range of detunings. We show that by tuning the parameters of the qubit, and by operating the qubit at larger detunings, the coherence times can be increased by more than an order of magnitude. We achieve a Ramsey decay time $T_{2}^{*}$ of $127~\mathrm{ns}$ and a Rabi decay time, $1/\Gamma_{\mathrm{Rabi}}$, exceeding $1~\mathrm{\mu s}$. We show 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.