Charge-parity qubits based on concatenation of \pi-periodic Josephson elements: Part 1

Superconducting qubits with topological protection against local noise hold the promise of significantly enhanced coherence times and higher gate fidelities than are possible with conventional qubits. We are pursuing a design that uses compact, high inductances and conventional Josephson junctions with individual flux control for tuning each plaquette to reach a regime with a \pi-periodic Josephson energy. Concatenating multiple \pi-periodic elements further enhances the degree of protection that can be achieved. Here we describe the design, fabrication, and flux characterization of such a qubit.