Towards Trapped-Ion Thermometry Using Cavity-Based EIT

TL;DR

This paper introduces a cavity-based EIT technique for measuring ion temperature in trapped-ion systems, enabling efficient thermometry near the motional ground state with simplified measurement procedures.

Contribution

It proposes a novel cavity EIT method for ion thermometry that works in the resolved-sideband regime and can determine motional states even in weak coupling conditions.

Findings

Theoretical model linking thermal state to EIT linewidth.

Numerical simulations demonstrate accurate ion temperature measurement.

Method applicable in weak coupling and sub-Doppler cooling regimes.

Abstract

We present a technique for measuring ion temperature using cavity-based electromagnetically induced transparency (EIT) applicable for cavity QED systems. This method enables efficient extraction of the ion's phonon occupation number following sub-Doppler cooling close to the motional ground state. The proposed method requires operation in the resolved-sideband regime, where individual motional states can be selectively addressed for all relevant transitions either by selecting appropriate energy levels for the three-level system or by employing strong confinement with high secular frequencies ($\sim 10 MHz$). It relies on monitoring the cavity probe transmission while scanning the probe laser frequency to establish cavity-induced EIT using a control beam, thereby significantly simplifying the measurement procedure. We establish a theoretical model that demonstrates the influence of the thermal state of the trapped ion vis-\`a-vis the EIT linewidth measured. We show through numerical simulations how the cavity-induced EIT transmission may be used as a thermometry tool to deduce the ion temperature as well as its motional state in the sub-Doppler cooling regime, even for systems that are in the weak coupling regime.