Protected Symmetrical Superconducting Qubit Based on Quantum Flux Parametron

Abstract

Conventional Quantum Flux Parametrons (QFPs) have historically been used for storing classical bits in Josephson junction-based computers. In this work, we propose a novel QFP-based topology dubbed"Degenerium"qubit, to process and compute quantum information. Degenerium combines principles from the 0-$\pi$ qubit and flux qubit to create ideally degenerate quantum ground states, while significantly simplifying the 0-$\pi$ qubit structure. The symmetrical design of Degenerium enables easier qubit control and fabrication. We demonstrate that due to the inherent symmetry of Degenerium, our designed qubit is insensitive to fabrication-induced variations in critical current ($I_c$) of the Josephson junctions. Our calculations of depolarization and dephasing rates due to charge, flux, and critical current noise sources result in depolarization and dephasing times of 1.25 s and 90 $\mu$s, respectively. Further parameter tuning and optimization is possible to meet specific application demands.