The Optimization of Flux Trajectories for the Adiabatic Controlled-Z Gate on Split-Tunable Transmons

TL;DR

This paper develops a generalized method to optimize flux trajectories for adiabatic controlled-Z gates in split-tunable transmons, improving qubit control by minimizing leakage and enhancing gate performance.

Contribution

It introduces a novel optimization approach for flux trajectories in transmon qubits, addressing a gap in selecting effective adiabatic paths.

Findings

Optimized flux trajectories reduce leakage in transmon qubits.

The method applies to multiple parameterized trajectory families.

Improved adiabatic control enhances gate fidelity.

Abstract

In a system of two tunable-frequency qubits, it is well-known that adiabatic tuning into strong coupling-interaction regions between the qubit subspace and the rest of the Hilbert space can be used to generate an effective controlled Z rotation. We address the problem of determining a preferable adiabatic trajectory along which to tune the qubit frequency, and apply this to the flux-tunable transmon model. The especially minimally anharmonic nature of these quantum processors makes them good candidates for qubit control using non-computational states, as long as higher-level leakage is properly addressed. While the statement of this method has occurred multiple times in literature, there has been little discussion of which trajectories may be used. We present a generalized method for optimizing parameterized families of possible flux trajectories and provide examples of use on five test families of one and two parameters.