Optimization of high-fidelity single-qubit gates for fluxonium qubits using single-flux quantum control
Phys. Rev. Applied 26, 014048 – Published 17 July, 2026
DOI: https://doi.org/10.1103/dz26-n1jc
Abstract
We present a gradient-based method to construct memory-efficient, high-fidelity, single-qubit gates for fluxonium qubits. These gates are constructed using a sequence of single-flux quantum (SFQ) pulses that are sent to the qubit through either capacitive or inductive coupling. The schedule of SFQ pulses is constructed with an on-ramp and an off-ramp applied prior to and after a pulse train, where the pulses are spaced at intervals equal to the qubit period. We reduce the optimization problem to the scheduling of a fixed number of SFQ pulses in the on-ramp and solve it by relaxing the discretization constraint of the SFQ clock as an intermediate step, allowing the use of the Broyden-Fletcher-Goldfarb-Shanno optimizer. Using this approach, gate fidelities of 99.99% can be achieved for inductive coupling and 99.9% for capacitive coupling, with leakage being the main source of coherent errors for both approaches.
