Salamanca team proposes topologically protected edge states in a single flux qubit
Researchers at Universidad de Salamanca, including Manuel Pino and P. Pérez-Fernández, report a design in which a single three-junction superconducting flux qubit hosts topologically protected edge states. The circuit's Josephson potential forms a honeycomb lattice like graphene, and shunting the qubit with parallel Josephson-junction arrays adds a quartic potential that confines its phase dynamics and acts as a boundary. The team mapped the low-energy dynamics to an extended Su-Schrieffer-Heeger chain and says numerical simulations of the full circuit confirm the mapping. Their data are consistent with an exponential suppression of the coupling of the edge-state doublet to charge noise in the topological region -1/2 < k2 < -1/3; flux noise breaks the chiral symmetry and reduces the protection. The work is posted on arXiv and, as a preprint, is not yet peer reviewed.