Ultrafast and deterministic generation of Bell states in the ultrastrong coupling regime

TL;DR

This paper presents a method for ultrafast, deterministic generation of Bell states in the ultrastrong coupling regime of the quantum Rabi model, achieving high fidelity and subnanosecond timescales.

Contribution

It introduces a scheme utilizing dark states and adiabatic evolution to generate Bell states rapidly and reliably in the ultrastrong coupling regime.

Findings

Bell states generated within subnanosecond timescales

Fidelity of generated states reaches 99%

Scheme applicable to multiple Bell state types

Abstract

We have found the special dark state solutions of the anisotropic two-qubit quantum Rabi model (QRM), which has at most one photon, and constant eigenenergy in the whole coupling regime. Accordingly, we propose a scheme to deterministically generate two kinds of the two-qubit Bell states through adiabatic evolution along the dark states. With the assistance of the Stark shift, the generation time can be reduced to subnanosecond scales, proportional to the reverse of the resonator frequency, with fidelity reaching 99%. Furthermore, the other two kinds of Bell states can also be ultrafast generated.