Fast, high-fidelity two-qubit entangling gates in superconducting multiqubit systems

Superconducting quantum circuit is a promising technology for building a fault-tolerant quantum computer. However, challenges remain in the development of a two-qubit entangling gate with an ultra-high fidelity and a short gate time compared to qubit relaxation and decoherence times. Especially for a large-scale multiqubit system, the quality of the entangling gate suffers from the unintended excitations of the nearly-degenerate harmful transitions and the leakage outside the qubit computational subspace. Recently, the SWIPHT gate has been shown numerically to be a robust scheme for solving the above problems by incorporating the unwanted dynamics into the designs of the gate [1]. In this talk, we describe our designs of multiqubit systems, where the primitive is a coupled two-qubit device with one of the qubits being magnetic-flux tunable. We also present the experimental progress on demonstration of the SWIFT gate in the multiqubit systems.

[1] X.-H. Deng, E. Barnes, and S. E. Economou, Phys. Rev. B 96, 035441 (2017)