Adiabatically controlled motional states of a ground-state cooled CaO$^{+}$ and Ca$^{+}$ trapped ion chain

TL;DR

This paper demonstrates near ground-state cooling of a CaO$^{+}$ and Ca$^{+}$ ion chain's motional modes and shows that the phonon state can be maintained during adiabatic frequency ramping, enabling future molecular interaction studies.

Contribution

It introduces a method for adiabatically controlling motional states of a ground-state cooled molecular ion chain, advancing quantum control techniques.

Findings

Achieved near ground-state cooling of CaO$^{+}$ ion's axial modes.

Maintained phonon state during adiabatic frequency ramping.

Enabled potential for molecular dipole-phonon interaction studies.

Abstract

Control of the external degree of freedom of trapped molecular ions is a prerequisite for their promising applications to spectroscopy, precision measurements of fundamental constants, and quantum information technology. Here, we demonstrate near ground-state cooling of the axial motional modes of a calcium mono-oxide ion via sympathetic sideband cooling with a co-trapped calcium ion. We also show that the phonon state of the axial out-of-phase mode of the ion chain is maintained while the mode frequency is adiabatically ramped up and down. The adiabatic ramping of the motional mode frequency is a prerequisite for searching for the proposed molecular dipole-phonon interaction.