Impurity effects on the quantum coherence of a few-boson system

TL;DR

This paper investigates how impurities affect quantum coherence in a few-boson system modeled by the two-site Hubbard model, revealing conditions for coherence revivals and damping based on impurity interactions.

Contribution

It provides a detailed analysis of impurity effects on coherence revivals, highlighting the role of interaction ratios and impurity polarization, aligning with experimental findings.

Findings

Coherence revivals depend on the ratio U_{BF}/U_{BB} and impurity polarization.

Odd revival peaks are damped at half-integer interaction ratios.

Unpolarized impurities do not influence coherence revivals based on fermion-fermion interactions.

Abstract

The impurity effects on the quantum coherence of a few-boson system are studied within the two-site Hubbard model. Periodical collapses and revivals of coherence occur in the presence of either polarized or unpolarized fermionic impurities. The relative strength $U_{BF}/U_{BB}$ of the boson-fermion versus the boson-boson interactions plays a key role in the coherence revivals. As the average filling of the impurity increases, the coherence revivals remain nearly unaffected for $U_{BF}/U_{BB}=z$ ($z\in Z$ is an integer) while the odd revival peaks are damped for $U_{BF}/U_{BB}=z+1/2$, in agreement with the experimental observations. For unpolarized fermionic impurities, the coherence revivals are irrelevant to the strength of the fermion-fermion interactions.