Developing quantum computers for real-world applications requires understanding theoretical sources of quantum advantage and applying those insights to design more powerful machines. Toward that end, we introduce a high-fidelity gate set inspired by a proposal for near-term quantum advantage in optimization problems. By orchestrating coherent, multi-level control over three transmon qutrits, we synthesize a family of deterministic, continuous-angle quantum phase gates acting in the natural three-qubit computational basis (CCPHASE(θ)). We estimate the process fidelity for this scheme via Cycle Benchmarking of F=87.1±0.8%, higher than reference two-qubit gate decompositions. CCPHASE(θ) is anticipated to have broad experimental implications, and we report a blueprint demonstration for solving a class of binary constraint satisfaction problems whose construction is consistent with a path to quantum advantage.
@article{arxiv.2108.01652,
title = {Realization of arbitrary doubly-controlled quantum phase gates},
author = {Alexander D. Hill and Mark J. Hodson and Nicolas Didier and Matthew J. Reagor},
journal= {arXiv preprint arXiv:2108.01652},
year = {2021}
}