A Fluxonium Architecture for QEC, Part 1: Fast, High-Fidelity and Quantum Non-Demolition Readout

Fault-tolerant quantum computing remains a central goal of the superconducting qubit community, with fluxonium qubits showing significant promise due to their extended coherence times [1] and recent demonstrations of high-fidelity single-qubit [2] and two-qubit gates [3]. Despite this progress, two major challenges must be addressed before fluxonium qubits can be widely adopted for quantum error correction (QEC) applications: the development of fast, high-fidelity, quantum non-demolition measurement and the demonstration of an extensible two-qubit gate scheme resilient to spectator errors.

In this talk, we present a hardware-efficient scheme for fast, high-fidelity readout of the fluxonium qubit using a single dispersively coupled readout resonator. We mitigate Purcell loss in the computational subspace and second excited state by leveraging the unique level structure of the fluxonium qubit, and we study measurement-induced state transitions [4-5]. Notably, this approach does not require additional components, such as Purcell filters, simplifying the system architecture. Given the stringent requirements for repeated measurements in QEC, we believe these results highlight the potential of the fluxonium qubit for such applications.

[1] A. Somoroff, et al., PRL, 2023

[2] D. Rower, L. Ding, et al., arXiv:2406.08295, 2024

[3] L. Ding, et al., PRX, 2023

[4] M. Khezri, et al., PRA, 2023s

[5] M. F. Dumas, et al., arXiv:2402.06615, 2024