Optical frequency standard with trapped Al⁺ and Ca⁺

Precision

Quantum Logic Spectroscopy with trapped Al⁺ and Ca⁺

The goal of our experiment is to investigate quantum logic schemes for reliably reading out the quantum state of ion clocks.

Spectrally narrow optical transitions in trapped ions provide highly stable and accurate references for optical frequency standards. Due to the low sensitivity to external perturbations, the ¹S₀ – ³P₀ clock transition in ²⁷Al⁺ ions is well suited for time keeping. The lack of a practical closed transition for cooling and state detection can be overcome by simultaneously trapping a logic ion (here ⁴⁰Ca⁺ ), that can be directly cooled.

Sympathetic cooling of a hot trapped ion with a cold one

We investigate the dynamics of an ion sympathetically cooled by another laser-cooled ion or small ion crystal.  Experimentally, we create a two-ion crystal of Ca⁺ and Al⁺ by photo-ionization of neutral atoms produced by laser ablation. We characterize the velocity distribution of the laser-ablated atoms crossing the trap by time-resolved fluorescence spectroscopy. We observe neutral atom velocities much higher than the ones of thermally heated samples and find as a consequence long sympathethic cooling times before crystallization occurs. Our key result is a new technique for detecting the loading of an initially hot ion with energy in the eV range by monitoring the motional state of a Doppler-cooled ion already present in the trap. This technique not only detects the ion but also provides information about the dynamics of the sympathetic cooling process.

Publications:

Project members

 Milena Guevara-Bertsch,Daniel Heinrich, Mahmood Irtiza Hussain, Christian Roos, and Rainer Blatt

Former project members

 Óscar Andrey Herrera

 Michael Guggemos