Improving T1 in dielectric-loss-limited fluxonium qubits*

The long coherence times and high anharmonicity of fluxonium qubits make it an attractive candidate for a superconducting quantum computer. However, past generations of high-coherence fluxonium qubits [1,2] have been limited by the dielectric loss associated with lossy capacitors. Recent studies on tantalum-based transmons have shown improvement in dielectric-loss-limited coherence times, realizing new records in device coherence [3]. Utilizing the same approach, we present a study of the coherence properties of fluxonium while being informed by the material surface participation ratio of the electric field in tantalum. As a result of our study, we showcase improvements in the coherence times of current 2D fluxonium qubits.

[1] Nguyen, L. B., Lin, Y. H., Somoroff, A., Mencia, R., Grabon, N., & Manucharyan, V. E. (2019). High-Coherence Fluxonium Qubit. Physical Review X, 9(4). 

[2] Zhang, H., Chakram, S., Roy, T., Earnest, N., Lu, Y., Huang, Z., Weiss, D. K., Koch, J., & Schuster, D. I. (2021). Universal Fast-Flux Control of a Coherent, Low-Frequency Qubit. 

[3] Place, A. P. M., Rodgers, L. V. H., Mundada, P., Smitham, B. M., Fitzpatrick, M., Leng, Z., Premkumar, A., Bryon, J., Vrajitoarea, A., Sussman, S., Cheng, G., Madhavan, T., Babla, H. K., Le, X. H., Gang, Y., Jäck, B., Gyenis, A., Yao, N., Cava, R. J., … Houck, A. A. (2021). New material platform for superconducting transmon qubits with coherence times exceeding 0.3 milliseconds. Nature Communications, 12(1).