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

Abstract

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). *The device bring-up, gate calibration and characterization work was supported by IARPA under LogiQ (contractW911NF-16-1-0114).