  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. Our results offer a new paradigm
for multi-qubit architecture with applications in quantum error correction,
quantum simulations and quantum annealing.
