Two-qubit operation on gatemons using an AC gate voltage modulation of epitaxial superconductor-semiconductor junctions*

Tunable qubits have been proposed as a way to construct entangling gates that can be controlled by intrinsic parameters of the qubits. By keeping one of the qubit's frequency tunable through AC modulation, we can bring the sidebands of tunable qubit to a resonance with a state of another qubit effectively enhancing  a two-qubit interaction. In particular, the modulation of the external flux for a tunable transmon was used to demonstrate entangling two-qubit gates [Didier et al., Phys. Rev. A 97, 022330 (2018)]. Inspired by this demonstration, we propose to apply a side gate AC voltage to epitaxial superconductor-semiconductor junctions of gatemon qubits. We demonstrate that high-fidelity two-bit operations are possible between pairs of capacitively coupled gatemons, when the side gate AC voltage changes the Josephson energy of the super-semi junction and generates a parametric resonance between the qubits. We also analyze performance of a two-qubit  coupler with a super-semi junction modulated by an AC parametric drive. Our analysis demonstrates that the AC voltage control can be used to generate high-fidelity fast entangling operations with errors below 0.1%.