Parametric Entangling Gates in a Superconducting Quantum Processor, Part III: Experiment

A central challenge in building a scalable quantum computer is the execution of high-fidelity entangling gates within an architecture containing many resonant elements. As elements are added, or as the multiplicity of couplings between elements is increased, the frequency space of the design becomes crowded and device performance suffers. By applying flux modulation to tunable transmons, one can drive the resonant exchange of photons directly between energy levels of a statically coupled multi-transmon system. This obviates the need for mediating qubits or resonator modes and allows the full utilization of all qubits in a scalable architecture. The resonance condition is selective in both the frequency and amplitude of modulation and thus alleviates frequency crowding.