Extending the coherence of a quantum dot hybrid qubit

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 ($T_2^{\ast }$) 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 $T_2^{\ast }$ of $177\mathrm{ns}$ and a Rabi decay time, $1/{\Gamma }_{\mathrm{Rabi}}$, exceeding $1\mu \mathrm{s}$. 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.