Harnessing Quantum Tunnelling for Gate Acceleration

Abstract: Two-qubit gates remain a central challenge in the realization of large-scale superconducting quantum processors. We propose and analyze a gate mechanism based on Tunneling-Assisted Couplers (TACs), which dynamically mediate an effective exchange interaction between fixed-frequency transmon qubits via a flux-tunable Josephson element. Compared to conventional cross-resonance or flux-pulsed gates, TAC-based gates offer substantial improvements in speed (∼10 ns) and fidelity (>99%) by preserving qubit sweet-spot operation. We derive the effective Hamiltonian, outline implementation techniques, and discuss limitations and extensions of the approach.