Resonantly driven singlet-triplet spin qubit in silicon

We report implementation of a resonantly driven singlet-triplet spin qubit in silicon. The qubit is defined by the two-electron anti-parallel spin states and universal quantum control is provided through a resonant drive of the exchange interaction at the qubit frequency. The qubit exhibits long $T_2^*$ exceeding 1 $\mu$s that is limited by dephasing due to the $^{29}$Si nuclei rather than charge noise thanks to the symmetric operation and a large micro-magnet Zeeman field gradient. The randomized benchmarking shows 99.6 % single gate fidelity which is the highest reported for singlet-triplet qubits.