High-Fidelity Two-Qubit Gates between Fluxonium Qubits with a Resonator Coupler
Emma L. Rosenfeld, Connor T. Hann, David Schuster, Matthew H. Matheny, Aashish A. Clerk · PRX Quantum · 2024
We take a bottom-up first-principles approach to designing a two-qubit gate between fluxonium qubits for minimal error, speed, and control simplicity. Our proposed architecture consists of two fluxoniums coupled via a resonator. The use of a simple linear coupler has many practical benefits, including the possibility of material optimization for suppressing loss, reducing fabrication complexity, and increasing yield by circumventing the need for Josephson junctions. Crucially, a resonator-as-coupler approach also suggests a clear path to increased connectivity between fluxonium qubits, by reducing capacitive loading when the coupler has a high impedance. After performing analytic and numerical analyses of the circuit Hamiltonian and gate dynamics, we tune circuit parameters to destructively interfere sources of coherent error, revealing an efficient fourth-order scaling of coherent error with gate duration. For component properties from the literature, we predict an open-system average controlled- Z () gate infidelity of 1.86 × 10 − 4 in 70 ns. Published by the American Physical Society 2024