# Sensing spontaneous collapse and decoherence with interfering Bose-Einstein condensates

## TL;DR

This paper investigates how matter-wave interferometry with Bose-Einstein condensates can detect environmental decoherence and test collapse models, highlighting the effects on coherence and the potential for probing many-body quantum effects.

## Contribution

It provides a detailed analysis of observable signatures of decoherence and collapse models in BEC interferometry, including higher-order correlations and scaling with particle number.

## Key findings

- Interference fringes are most affected by environmental decoherence.
- Quantum signatures of independent condensates are more resistant to collapse.
- Higher-order correlations can reveal many-body decoherence effects.

## Abstract

We study how matter-wave interferometry with Bose-Einstein condensates is affected by hypothetical collapse models and by environmental decoherence processes. Motivated by recent atom fountain experiments with macroscopic arm separations, we focus on the observable signatures of first-order and higher-order coherence for different two-mode superposition states, and on their scaling with particle number. This can be used not only to assess the impact of environmental decoherence on many-body coherence, but also to quantify the extent to which macrorealistic collapse models are ruled out by such experiments. We find that interference fringes of phase-coherently split condensates are most strongly affected by decoherence, whereas the quantum signatures of independent interfering condensates are more immune against macrorealistic collapse. A many-body enhanced decoherence effect beyond the level of a single atom can be probed if higher-order correlations are resolved in the interferogram.