Optimized qubit reset in a multimode superconducting circuit

Having the ability to efficiently reset a qubit in its ground state is essential for performing fast and reliable quantum computation. Recently, a fast and unconditional all-microwave reset of a superconducting qubit via a lossy cavity has been successfully implemented; allowing to perform this operation without the use of active feedback [1]. The reset is also a key element for autonomous stabilization of Gottesman-Kitaev-Preskill (GKP) states with the added complexity of having the qubit coupled to an additional, long-lived, cavity mode. In this setup, the unconditionality of the qubit reset is more challenging and the back-action of the controls further detrimental. Our work explores optimal quantum control in open systems to design feasible and efficient microwave pulse sequences that maximize the gate efficiency and minimize its impact on the logical lifetime of the GKP states. We compare the experimental implementation of the pulse sequence proposed in ref. [1] with optimized protocols and comment on the practical benefits of using optimized pulse sequences.

[1] Fast and Unconditional All-Microwave Reset of a Superconducting Qubit, P. Magnard et al. Phys. Rev. Lett. 121, 060502 (2018)