Cross-resonance interactions are a promising way to implement all-microwave two-qubit gates with fixed-frequency qubits. In this work, we study the dependence of the cross-resonance interaction rate on qubit-qubit detuning and compare with a model that includes the higher levels of a transmon system. To carry out this study we employ two transmon qubits--one fixed frequency and the other flux tunable--to allow us to vary the detuning between qubits. We find that the interaction closely follows a three-level model of the transmon, thus confirming the presence of an optimal regime for cross-resonance gates.
@article{arxiv.1905.11480,
title = {Cross-resonance interactions between superconducting qubits with variable detuning},
author = {Matthew Ware and Blake R. Johnson and Jay M. Gambetta and Thomas A. Ohki and Jerry M. Chow and B. L. T. Plourde},
journal= {arXiv preprint arXiv:1905.11480},
year = {2019}
}