Parametric entangling gates in a superconducting quantum processor, Part I: Theory

Realizing high-fidelity two-qubit gates is one of the main challenges in building quantum processors. Controllability and selectivity are particularly advantageous to reduce crosstalks in experimental implementations. We present two-qubit gates based on parametrically-activated entangling interactions and fully controlled by a RF flux pulse on the SQUID of a tunable transmon that is capacitively coupled to other transmon qubits. The modulation frequency acts as a pump to enable on-resonance Rabi oscillations between two desired two-qubit states, the gate is switched on and off by the modulation amplitude. We show that several kinds of gates can be realized, selected by the modulation frequency. We discuss the rate and fidelity of iSWAP and controlled-phase gates for experimentally realized superconducting circuits. arXiv:1706.06566