Fast tunable coupling scheme of Kerr parametric oscillators using shortcuts to adiabaticity

Kerr parametric oscillators (KPOs) implemented with Josephson parametric oscillators can work as qubits and have been attracting much attention in terms of their applications to quantum annealing, universal quantum computation and quantum simulation. It is important for these applications to realize fast and accurate tunable coupling between KPOs in a simple manner. We propose a simple scheme of tunable coupling of KPOs with high tunability in speed and amplitude by using the fast transitionless rotation of a KPO in the phase space based on the counter-diabatic protocol [1]. The scheme of the tunable effective coupling between KPOs can be implemented with always-on linear coupling between KPOs, by modulating the phase of the pump field and the resonance frequency of the KPO. We apply the coupling scheme to a two-qubit gate, and show that our scheme realizes higher gate fidelity than a purely adiabatic one, by decreasing detrimental nonadiabatic transitions.

[1] S. Masuda, et al., Phys. Rev. Applied 18, 034076 (2022).