Sympathetic rotational cooling of large trapped molecular ions

TL;DR

This paper proposes a protocol for sympathetically cooling large molecular ions' rotational states by coupling their electric dipole moments with trapped atomic ions, enabling precise control over molecular rotations for quantum tech and spectroscopy.

Contribution

It introduces a novel method combining sympathetic sideband cooling and microwave excitation to efficiently cool molecular rotational states into a single quantum state.

Findings

Efficient depopulation of rotational subspaces demonstrated.

Ability to cool molecules into a specific rotational quantum state.

Potential applications in quantum information and spectroscopy.

Abstract

We suggest a protocol for the sympathetic cooling of a molecular asymmetric top rotor co-trapped with laser-cooled atomic ions, based on resonant coupling between the molecular ion's electric dipole moment and a common normal mode of the trapped particles. By combining sympathetic sideband laser cooling with coherent microwave excitation, we demonstrate the efficient depopulation of arbitrary rotational subspaces and the ability to cool an incoherent distribution of rotational states into a single, well-defined quantum state. This capability opens the door to exploiting the rotational Hilbert space for applications in quantum information processing and high-precision spectroscopy.