Adiabatic Pulse Design for Entangling Gate with Tunable Couplers

The error rate of two-qubit entangling gates is a critical metric for developing robust systems of interacting qubits. To mitigate errors due to qubit decoherence, gate durations must be short. However, rapid modulation of the system can induce non-adiabatic transitions to states outside the computational subspace during gate operations. While non-adiabatic dynamics and optimal pulse shaping to suppress leakage are well understood for simple two-level systems [1], designing pulses for more complex multi-level systems, such as superconducting quantum processors, remains an active area of research [2,3].

Here, we present a method to extend the two-level system theory [1] to a system of two transmons coupled via a tunable coupler [4]. We design baseband control pulses for both the qubits and the coupler to implement an adiabatic CZ gate with suppressed leakage and improved fidelity.

[1] J. Martinis and M. Geller, Phys. Rev. A 90, 022307 (2014).

[2] Y. Sung et al., Phys. Rev. X 11, 021058 (2021).

[3] J. Chu and F. Yan, Phys. Rev. Applied 16, 054020 (2021).

[4] B. Foxen et al., Phys. Rev. Lett. 125, 120504 (2020).