Trapped ions beyond carrier and sideband interactions

TL;DR

This paper explores the behavior of trapped ions under strong driving conditions, extending existing protocols and models to enable faster quantum operations beyond traditional weak-driving regimes.

Contribution

It introduces a new model for analyzing strong ion-radiation interactions and extends motional Wigner function reconstruction protocols to stronger driving fields.

Findings

Extended Wigner function reconstruction to stronger lasers.

Developed an analytical model for non-resonant, strong drivings.

Demonstrated potential for faster quantum gates.

Abstract

Trapped ions driven by electromagnetic radiation constitute one of the most developed quantum technologies to date. The scenarios range from proof-of-principle experiments to on-chip integration for quantum information units. In most cases, these systems have operated in a regime where the magnitude of the ion-radiation coupling constant is much smaller than the trap and electronic transition frequencies. This regime allows the use of simple effective Hamiltonians based on the validity of the rotating wave approximation. However, novel trap and cavity designs now permit regimes in which the trap frequency and the ion-radiation coupling constant are commensurate. This opens up new venues for faster quantum gates and state transfers from the ion to a photon, and other quantum operations. From the theoretical side, however, there is not yet much known in terms of models and applications that go beyond the weak driving scenario. In this work, we will present two main results in the scenario of stronger drivings. First, we revisit a known protocol to reconstruct the motional Wigner function and expand it to stronger driving lasers. This extension is not trivial because the original protocol makes use of effective Hamiltonians valid only for weak drivings. The use of stronger fields or faster operations is desirable since experimental reconstruction methods of that kind are usually hindered by decoherence. We then present a model that allows the analytical treatment of stronger drivings and that works well for non-resonant interactions, which are generally out of the reach of the previous models.