Optimising Fluxonium Qubits for High Fidelity SFQ Control

Two major problems with current superconducting quantum computers are: i) the rapid decoherence of transmon qubits and ii) the limited scalability of microwave-based control. In this work, we explore the potential of using digital Single Flux Quantum (SFQ) cryogenic control to manipulate fluxonium qubits as an architecture that mitigates against both these issues.

The use of SFQ driving for transmon control has been previously explored [1,2] and show that complex pulse sequences are necessary for high fidelity operation. Our Hamiltonian simulations show that a well-engineered fluxonium qubit can achieve high fidelity operations (>99.99 %) without such complexity. We demonstrate a 98 % fidelity improvement for the Ry(π) gate in a fluxonium-based system compared to a transmon-based system, with reduced sensitivity to timing errors and slower gates offset by the longer coherence time of fluxonium qubits. These results highlight the potential advantage of SFQ-driven fluxonium qubits for scalable, high fidelity quantum computing, making it a promising architecture for future systems.

[1] - McDermott, Robert, et al. "Quantum–classical interface based on single flux quantum digital logic." Quantum science and technology 3.2 (2018): 024004.

[2] - Shillito, Ross, et al. "Compact Pulse Schedules for High-Fidelity Single-Flux Quantum Qubit Control." arXiv preprint arXiv:2309.04606 (2023).