# Thermal counting statistics in an atomic two-mode squeezed vacuum state

## TL;DR

This study measures the particle number distribution in atomic twin beams generated by four-wave mixing, confirming exponential statistics and validating the source for future quantum tests like Bell inequalities.

## Contribution

It provides the first experimental validation of exponential counting statistics in atomic two-mode squeezed vacuum states generated by four-wave mixing.

## Key findings

- Particle number follows exponential distribution in single-mode selection.
- Distribution explains the contrast in atomic Hong--Ou--Mandel experiments.
- Validates the atomic twin beam source for quantum nonlocality tests.

## Abstract

We measure the population distribution in one of the atomic twin beams generated by four-wave mixing in an optical lattice. Although the produced two-mode squeezed vacuum state is pure, each individual mode is described as a statistical mixture. We confirm the prediction that the particle number follows an exponential distribution when only one spatio-temporal mode is selected. We also show that this distribution accounts well for the contrast of an atomic Hong--Ou--Mandel experiment. These experiments constitute an important validation of our twin beam source in view of a future test of a Bell inequalities.