Fast high-fidelity spin readout in the singlet-triplet basis using a resonator and tailored pulses

Abstract

Electron spins in semiconductor quantum dots are a promising platform for qubits. An essential step toward quantum error correction with spin qubits requires the ability to read out states and identify errors in the two-spin logical basis in a fast and high-fidelity way. Here we propose a scheme for spin singlet-triplet readout in a double quantum dot, with a superconducting resonator serving as the detector. Making use of a spin driving pulse sequence, this procedure can read out the spin states with a fidelity of $99.9%$ in a time 100 ns. Interestingly, this method makes use of the spin driving pulse to adjust the resonator signal field, leading to significant improvement of the spin readout. In addition, this method can be directly applied to multiplexed readout of qubits and repeated readout to identify logical errors. These results pave the way for the implementation of quantum error correction and scalable quantum processor with spin qubits.