Parallel-Electromagnetically-Induced-Transparency Near Ground-State Cooling of a Trapped-ion Crystal

TL;DR

This paper introduces a parallel-EIT cooling method for ion crystals that enables simultaneous near-ground-state cooling of multiple motional modes with less restrictive conditions, demonstrated experimentally with 40Ca+ ions.

Contribution

The paper presents a novel parallel-EIT cooling technique that relaxes resonance requirements and achieves broad-range, simultaneous cooling of ion motional modes.

Findings

Successful experimental demonstration with up to 4 ions

Achieved average phonon number of about 0.2 for all modes

Effective broadband cooling comparable to standard EIT cooling

Abstract

We theoretically propose and experimentally demonstrate a parallel-electromagnetically-induced transparency (parallel-EIT) cooling technique for ion crystals in the Paul trap. It has less stringent requirements on the cooling resonance condition than the standard electromagnetically-induced transparency (EIT) cooling, thus allowing, in principle, to simultaneously cool the motional mode spectrum with an arbitrary range. A proof-of-principle validation for this cooling scheme is experimentally demonstrated with up to 4 trapped 40Ca+ ions. We observe simultaneous near-ground-state cooling for all motional modes with best average phonon number about 0.2. By tuning the trap frequency in a large range to imitate a broadband motional mode spectrum, we can still reach almost the same cooling limit for all the modes while standard EIT cooling shows limited cooling range. Our method has a simple experimental configuration, requiring only appropriate modulation of the probe beam of standard EIT cooling, and can be applied to various types of ions (e.g., 171Yb+, 40Ca+). This cooling scheme provides a powerful tool for the initialization of the trapped-ion quantum computers and simulators.