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 ($T_2^{*}$) and the Rabi decay rate (Γ_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 ns and a Rabi decay time 1/Γ_Rabi exceeding 1 μs. We find that the slowest Γ_Rabi is limited by fluctuations in the Rabi frequency induced by charge noise and not by fluctuations in the qubit energy itself.

Quantum information: improving semiconducting qubit performance

Researchers in the United States demonstrate high tunability of spin qubits in silicon-based quantum dots. Mark Eriksson at the University of Wisconsin-Madison and colleagues have achieved more than a tenfold improvement in the performance of these three-electron double dot qubits by tuning the electric fields used to confine electrons to quantum dots to a regime where the qubit was predicted to be much less susceptible to the effects of charge noise. Since charge noise limits the performance of many such qubits, these findings provide a path toward the fabrication of electrically gated qubits in silicon quantum dots with very high fidelities.