Measuring and Correcting Nanosecond Pulse Distortions in Quantum-Dot Spin Qubits.

Gate-defined semiconductor quantum dots utilize fast electrical control to manipulate spin and charge states of individual electrons. Electrical pulse distortions can limit control fidelities but are difficult to measure at the device level. Here, we use detuning-axis pulsed spectroscopy to characterize baseband pulse distortions in a silicon double quantum dot. We extract the gate-voltage impulse response and apply a digital predistortion filter to eliminate pulse distortions on timescales longer than 1 ns. With the predistortion, we reduce the frequency chirp of coherent exchange oscillations in a singlet-triplet qubit. Our results suggest a scalable and tuning-efficient method for characterizing pulse distortions in quantum-dot spin qubits.