Floating tunable coupler for scalable quantum computing architectures

We propose a floating tunable coupler that does not rely on direct qubit-qubit coupling capacitances to achieve the zero-coupling condition. We show that the polarity of the qubit-coupler couplings can be engineered to offset the otherwise constant qubit-qubit coupling and attain the zero-coupling condition when the coupler frequency is above or below the qubit frequencies. We experimentally demonstrate these two operating regimes of the tunable coupler by implementing symmetric and asymmetric configurations of the superconducting pads of the coupler with respect to the qubits.  We demonstrate parametric-resonance iSWAP and CZ gates for both operating regimes of the tunable coupler with two-qubit interleaved randomized benchmarking fidelity exceeding 99%. We show a simple and scalable calibration method for both parametric-resonance and fast DC pulse enabled iSWAP gates.