# Creation of a Bose-condensed gas of rubidium 87 by laser cooling

## TL;DR

This paper reports a rapid, evaporative-cooling-free method to produce a Bose-Einstein condensate of rubidium 87 atoms using laser cooling within an optical lattice, achieving quantum degeneracy efficiently.

## Contribution

It introduces a novel laser cooling technique that bypasses evaporative cooling, enabling fast and low-loss creation of Bose-Einstein condensates in rubidium 87.

## Key findings

- Achieved quantum degeneracy with 1400 atoms in 300 ms.
- Demonstrated a bimodal velocity distribution indicating Bose-Einstein condensation.
- Reduced light-induced atom loss at high densities.

## Abstract

We demonstrate direct laser cooling of a gas of rubidium 87 atoms to quantum degeneracy. The method does not involve evaporative cooling, is fast, and induces little atom loss. The atoms are trapped in a two-dimensional optical lattice that enables cycles of cloud compression to increase the density, followed by degenerate Raman sideband cooling to decrease the temperature. Light-induced loss at high atomic density is substantially reduced by using far red detuned optical pumping light. Starting with 2000 atoms, we prepare 1400 atoms in 300 ms at quantum degeneracy, as confirmed by the appearance of a bimodal velocity distribution as the system crosses over from a classical gas to a Bose-condensed, interacting one-dimensional gas with a macroscopic population of the quantum ground state. The method should be broadly applicable to many bosonic and fermionic species, and to systems where evaporative cooling is not possible.