Implementation of pairwise longitudinal coupling in a three-qubit superconducting circuit

Understand

We present the "trimon", a multi-mode superconducting circuit implementing three qubits with all-to-all longitudinal coupling.

• This always-on interaction enables simple implementation of generalized controlled-NOT gates which form a universal set.
• Further, two of the three qubits are protected against Purcell decay while retaining measurability.
• We demonstrate high-fidelity state swapping operations between two qubits and characterize the coupling of all three qubits to a neighbouring transmon qubit.