Nichol, John M.Orona, LucasHarvey, ShannonFallahi, SaeedGardner, GeoffreyManfra, MichaelYacoby, Amir2019-11-042017-01-19Nichol, John M., Lucas A. Orona, Shannon P. Harvey, Saeed Fallahi, Geoffrey C. Gardner, Michael J. Manfra, and Amir Yacoby. 2017. High-Fidelity Entangling Gate for Double-Quantum-Dot Spin Qubits. NPJ Quantum Information 3, 3.2056-6387http://nrs.harvard.edu/urn-3:HUL.InstRepos:41718767Electron spins in semiconductors are promising qubits because their long coherence times enable nearly 109 coherent quantum gate operations. However, developing a scalable high-fidelity two-qubit gate remains challenging. Here, we demonstrate an entangling gate between two double-quantum-dot spin qubits in GaAs by using a magnetic field gradient between the two dots in each qubit to suppress decoherence due to charge noise. When the magnetic gradient dominates the voltage-controlled exchange interaction between electrons, qubit coherence times increase by an order of magnitude. Using randomized benchmarking, we measure single-qubit gate fidelities of ~ 99%, and through self-consistent quantum measurement, state, and process tomography, we measure an entangling gate fidelity of 90%. In the future, operating double quantum dot spin qubits with large gradients in nuclear-spin-free materials, such as Si, should enable a two-qubit gate fidelity surpassing the threshold for fault-tolerant quantum information processing.en-USJournal Article2019-11-0410.1038/s41534-016-0003-1