Asymmetric quantum Rabi model, trap-dipole resonance, and quantum gates with optically trapped ultracold polar molecules

TL;DR

This paper explores how the quantized motion of ultracold polar molecules in optical traps can realize an asymmetric quantum Rabi model, leading to novel resonance phenomena and high-fidelity quantum gate protocols.

Contribution

It introduces the realization of an asymmetric quantum Rabi model via molecular quantum motion and proposes high-fidelity quantum gate protocols considering these effects.

Findings

Molecular quantum motion can realize an asymmetric quantum Rabi model.

Identification of an exotic trap-dipole resonance affecting molecular states.

Proposed fast iSWAP and controlled-phase gates with high fidelity.

Abstract

Optically trapped ultracold polar molecules can have multiple long-lived states for coding quantum information, and can exhibit electric dipole-dipole interactions~(DDI) which enables entanglement generation. The general understanding on the quantized motion~(QM) of molecules in the traps is that it causes fluctuation of DDI. Here, we find that the molecular QM can realize an asymmetric quantum Rabi model, which is of specific importance in the study of fundamental physics. The molecular QM can also lead to an exotic trap-dipole resonance, resulting in excess population loss to uncoupled motional states, and, hence, should be avoided in a general quantum control over polar molecules. To examine the impact of QM on quantum computing based on polar molecules, we introduce two gate protocols, a fast iSWAP gate which can be realized by a global microwave pulse of pulse area smaller than $2\pi$, and a controlled-phase gate with an arbitrary controlled phase, and find that both gates can attain a high fidelity.