Spin noise spectroscopy to probe quantum states of ultracold fermionic atomic gases

TL;DR

This paper proposes using optical spin noise spectroscopy as a non-invasive method to identify and distinguish microscopic interaction models in ultracold fermionic gases, aiding the understanding of complex quantum states.

Contribution

It introduces a theoretical framework for using spin noise measurements to probe and differentiate interatomic interaction models in ultracold fermionic gases.

Findings

Different interaction models predict distinct noise resonance patterns.

Spin noise line-shapes can constrain the correct microscopic interaction model.

Feasibility of experimental spin noise measurements in ultracold gases is demonstrated.

Abstract

Ultracold alkali atoms provide experimentally accessible model systems for probing quantum states that manifest themselves at the macroscopic scale. Recent experimental realizations of superfluidity in dilute gases of ultracold fermionic (half-integer spin) atoms offer exciting opportunities to directly test theoretical models of related many-body fermion systems that are inaccessible to experimental manipulation, such as neutron stars and quark-gluon plasmas. However, the microscopic interactions between fermions are potentially quite complex, and experiments in ultracold gases to date cannot clearly distinguish between the qualitatively different microscopic models that have been proposed. Here, we theoretically demonstrate that optical measurements of electron spin noise -- the intrinsic, random fluctuations of spin -- can probe the entangled quantum states of ultracold fermionic atomic gases and unambiguously reveal the detailed nature of the interatomic interactions. We show that different models predict different sets of resonances in the noise spectrum, and once the correct effective interatomic interaction model is identified, the line-shapes of the spin noise can be used to constrain this model. Further, experimental measurements of spin noise in classical (Boltzmann) alkali vapors are used to estimate the expected signal magnitudes for spin noise measurements in ultracold atom systems and to show that these measurements are feasible.