Generating high-fidelity, tunable entanglement between qubits is crucial for realizing gate-based quantum computation. In superconducting circuits, tunable interactions are often implemented using flux-tunable qubits or coupling elements, adding control complexity and noise sources. Here, we realize a tunable ZZ interaction between two transmon qubits with fixed frequencies and fixed coupling, induced by driving both transmons off-resonantly. We show tunable coupling over one order of magnitude larger than the static coupling, and change the sign of the interaction, enabling cancellation of the idle coupling. Further, this interaction is amenable to large quantum processors: the drive frequency can be flexibly chosen to avoid spurious transitions, and because both transmons are driven, it is resilient to microwave crosstalk. We apply this interaction to implement a controlled phase (CZ) gate with a gate fidelity of 99.43(1)% as measured by cycle benchmarking, and we find the fidelity is limited by incoherent errors.
@article{arxiv.2105.05384,
title = {Hardware-Efficient Microwave-Activated Tunable Coupling Between Superconducting Qubits},
author = {Bradley K. Mitchell and Ravi K. Naik and Alexis Morvan and Akel Hashim and John Mark Kreikebaum and Brian Marinelli and Wim Lavrijsen and Kasra Nowrouzi and David I. Santiago and Irfan Siddiqi},
journal= {arXiv preprint arXiv:2105.05384},
year = {2021}
}