Tunable Coupling Scheme for Implementing High-Fidelity Two-Qubit Gates

The prospect of computational hardware with quantum advantage relies critically on the quality of quantum-gate operations. Imperfect two-qubit gates are a major bottleneck for achieving scalable quantum-information processors. Here, we propose a generalizable and extensible scheme for a two-qubit tunable coupler that controls the qubit-qubit coupling by modulating the coupler frequency. Two-qubit gate operations can be implemented by operating the coupler in the dispersive regime, which is noninvasive to the qubit states. We investigate the performance of the scheme by simulating a universal two-qubit gate on a superconducting quantum circuit, and find that errors from known parasitic effects are strongly suppressed. The scheme is compatible with existing high-coherence hardware, thereby promising a higher gate fidelity with current technologies.United States. Department of Defense. Assistant Secretary of Defense for Research & Engineering (Lincoln Laboratory. Contract FA8721-05-C-0002)United States. Army Research Office (Grant W911NF-14-1-0682)National Science Foundation (U.S.) (Grant PHY-1720311)Korea Foundation for Advanced Studie