Opposite sign correlations in fermion or boson gases

TL;DR

This paper explores how opposite sign pair correlations in trapped quantum gases reveal non-free quantum states, aiding interpretation of ultracold atomic gas experiments.

Contribution

It demonstrates that opposite sign correlations serve as a signature of non-free quantum many-particle states in fermion and boson gases.

Findings

Positive pair correlations in fermions indicate non-Slater determinant states.

Negative pair correlations in bosons suggest non-Gaussian quantum states.

The analysis aids in interpreting experimental results on ultracold gases.

Abstract

We investigate pair correlations in trapped fermion and boson gases as a means to probe the quantum states producing the density fluctuations. We point out that "opposite sign correlations" (meaning pair correlations that are positive for fermions and negative for bosons) unambiguously indicate that the quantum many-particle state cannot be "free." In particular, a system of fermions that exhibits positive pair correlations cannot be described by any Slater determinant wavefunction. This insight may help one to interpret results of current experiments on ultracold atomic gases.