Energy distribution and cooling of a single atom in an optical tweezer

TL;DR

This paper experimentally studies the energy distribution of a single rubidium atom in an optical tweezer, demonstrating methods to cool and prepare the atom at microKelvin temperatures near the ground state.

Contribution

It introduces two methods for measuring and reducing the energy of a single atom in an optical trap, achieving low-temperature states close to the ground state.

Findings

Energy distribution is close to thermal under radiative cooling

Adiabatic cooling effectively reduces atom energy

Truncating the Boltzmann distribution prepares lower energy states

Abstract

We investigate experimentally the energy distribution of a single rubidium atom trapped in a strongly focused dipole trap under various cooling regimes. Using two different methods to measure the mean energy of the atom, we show that the energy distribution of the radiatively cooled atom is close to thermal. We then demonstrate how to reduce the energy of the single atom, first by adiabatic cooling, and then by truncating the Boltzmann distribution of the single atom. This provides a non-deterministic way to prepare atoms at low microKelvin temperatures, close to the ground state of the trapping potential.