Parametric entangling gates in a superconducting quantum processor, Part II: Dephasing due to modulation

Parametric entangling gates can be operated at a flux bias that is first-order insensitive to flux-noise. However, parametric modulation itself induces frequency excursions from these flux sweet spots, which can degrade coherence and ultimately limit two-qubit parametric gate fidelities. In this talk, we analyze the effect of modulation on the dephasing rate, in particular, due to 1/f magnetic flux noise in asymmetric transmons. We show that the flux-bias modulation significantly affects the dephasing rate. It has been shown that the sensitivity to flux-noise can be reduced by increasing the asymmetry of the SQUID junctions. We, therefore, leverage our model to analyze the trade-off between the qubit frequency tunability and the effective qubit-qubit coupling for improving the performance of parametric entangling gates.