Reduced fluctuations for bosons in a double well

TL;DR

This paper reviews recent findings on how large bosonic systems in a double well potential exhibit reduced particle number fluctuations, indicating a transition from independent particles to a correlated phase driven by interactions.

Contribution

It proves that in large, separated double wells, particle number fluctuations are suppressed compared to standard predictions, revealing a new correlated ground state phase.

Findings

Fluctuations occur at a reduced scale compared to a0a0a0

Breakdown of independent particle picture in Bose-Einstein condensation

Emergence of an interaction-driven correlated phase

Abstract

We review two recent results on the ground state properties of bosonic systems trapped by a double well external potential. In the limit of large population and large separation between the wells we prove that fluctuations in the number of particles occupying each single-well low energy mode occur at a reduced scale with respect to $ \sqrt{N}$, the latter being the typical prediction of the central limit theorem. This signals the breakdown of the independent and uncorrelated particles picture of standard Bose-Einstein condensation and the emergence of an interaction-driven correlated phase in the ground state.