Gate fidelity and coherence of an electron spin in a Si/SiGe quantum dot with micromagnet

摘要

The gate fidelity and the coherence time of a qubit are important benchmarksfor quantum computation. We construct a qubit using a single electron spin in aSi/SiGe quantum dot and control it electrically via an artificial spin-orbitfield from a micromagnet. We measure an average single-qubit gate fidelity of$\approx$ 99$\%$ using randomized benchmarking, which is consistent withdephasing from the slowly evolving nuclear spins in substrate. The coherencetime measured using dynamical decoupling extends up to $\approx$ 400 $\mu$s for128 decoupling pulses, with no sign of saturation. We find evidence that thecoherence time is limited by noise in the 10 kHz $-$ 1 MHz range, possiblybecause charge noise affecting the spin via the micromagnet gradient. This workshows that an electron spin in a Si/SiGe quantum dot is a good candidate forquantum information processing as well as for a quantum memory, even withoutisotopic purification.