Four-junction superconducting circuit

Understand

We develop a theory for the quantum circuit consisting of a superconducting loop interrupted by four Josephson junctions and pierced by a magnetic flux (either static or time-dependent).

• In addition to the similarity with the typical three-junction flux qubit in the double-well regime, we demonstrate the difference of the four-junction circuit from its three-junction analogue, including its advantages over the latter.
• Moreover, the four-junction circuit in the single-well regime is also investigated.
• Our theory provides a tool to explore the physical properties of this four-junction superconducting circuit.