Gate fidelity and coherence of an electron spin in an Si/SiGe quantum dot with micromagnet
Erika Kawakami (Kavli institute of nanoscience Delft, TU Delft - QCD/Vandersypen Lab, TU Delft - QuTech Advanced Research Centre, TU Delft - QN/Quantum Transport)
Thibaut Jullien (TU Delft - QuTech Advanced Research Centre, TU Delft - QN/Quantum Transport, Kavli institute of nanoscience Delft)
Pasquale Scarlino (TU Delft - QuTech Advanced Research Centre, TU Delft - QCD/Vandersypen Lab, Kavli institute of nanoscience Delft)
Daniel R. Ward (University of Wisconsin-Madison)
Donald E. Savage (University of Wisconsin-Madison)
Max G. Lagally (University of Wisconsin-Madison)
Viatcheslav V. Dobrovitski (Iowa State University)
Mark Friesen (University of Wisconsin-Madison)
Susan N. Coppersmith (University of Wisconsin-Madison)
Mark A. Eriksson (University of Wisconsin-Madison)
Lieven M.K. Vandersypen (TU Delft - QuTech Advanced Research Centre, Components Research, Kavli institute of nanoscience Delft, TU Delft - QN/Vandersypen Lab, TU Delft - QCD/Vandersypen Lab)
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Abstract
The gate fidelity and the coherence time of a quantum bit (qubit) are important benchmarks for quantum computation. We construct a qubit using a single electron spin in an Si/SiGe quantum dot and control it electrically via an artificial spin-orbit field from a micromagnet. We measure an average single-qubit gate fidelity of ∼99% using randomized benchmarking, which is consistent with dephasing from the slowly evolving nuclear spins in the substrate. The coherence time measured using dynamical decoupling extends up to ∼400 μs for 128 decoupling pulses, with no sign of saturation. We find evidence that the coherence time is limited by noise in the 10-kHz to 1-MHz range, possibly because charge noise affects the spin via the micromagnet gradient. This work shows that an electron spin in an Si/SiGe quantum dot is a good candidate for quantum information processing as well as for a quantum memory, even without isotopic purification.