The siZZle Gate – Using AC Stark tones to modulate ZZ in Superconducting Transmon Qubits*

Fixed frequency superconducting transmon qubits are an attractive technology for scaling due to their high coherence and stability. However, there are a number of challenges associated with always on coupling. In particular, the higher levels cause shifts in the computational levels that leads to unwanted ZZ quantum crosstalk. Here, we will discuss a novel technique to manipulate the energy levels and mitigate this crosstalk via a simultaneous AC Stark effect on coupled qubits. This breaks a fundamental deadlock between qubit-qubit coupling and crosstalk, leading to a 90ns CNOT with a gate error of (0.19 ± 0.02)% and the demonstration of a novel CZ gate with fixed-coupling single-junction transmon qubits. Furthermore, we show a definitive improvement in circuit performance with crosstalk cancellation over seven qubits, demonstrating the scalability of the technique. This talk is based on work published in arXiv:2106.00675 (2021).