Controlling the protected soft zero-pi qubit

The soft zero-pi circuit [1, 2, 3] has shown experimental evidence of protection against relaxation and dephasing, making it a promising candidate for high-fidelity quantum processing. Here, we show improved Ramsey dephasing times resulting from a larger ratio of the charging energies for the two participating modes, pushing the zero-pi further into its protected regime. We review possible gate schemes for the zero-pi, emphasizing the challenges of realizing two-tone Raman gates in protected superconducting qubits.

[1] A. Kitaev. arXiv:cond-mat/0609441 (2006).

[2] P. Brooks, A. Kitaev, J. Preskill. Phys. Rev. A 87, 052306 (2013).

[3] A. Gyenis, P. Mundada, A. Di Paolo et. al. arXiv:1910.07542 (2019).