Bifluxon: Fluxon-Parity-Protected Superconducting Qubit

Summary

Introduces and experimentally demonstrates the bifluxon qubit — a fluxon-parity-protected superconducting qubit consisting of a Cooper-pair box shunted by a granular aluminum superinductor. At the charge-parity sweet spot (odd electron number), Aharonov-Casher interference creates a $\cos (\phi /2)$ potential with degenerate double-well minima, providing exponential suppression of both charge-noise-induced energy decay and flux-noise dephasing. Demonstrates tenfold increase in $T_1$ (up to 100 μs) when toggling protection via gate-controlled charge.

Cited In

• bifluxon-qubit