  We study the correlation between an impurity and a small ensemble of bosonic
particles in one dimension. Our study analyzes the one-body density matrix and
calculates the corresponding von Neumann entanglement entropy as a function of
the interaction strength between the impurity and the bosons when all particles
have the same mass. We show that the entropy grows very fast for small and
moderate interaction strength and then increases slowly toward the strongly
interacting regime. Then we study the effect over the quantum correlations of a
mass imbalance between the impurity and the bosons. In the strongly interacting
case, we discover that when the impurity is much heavier than the bosons, then
we have the least possible correlation. However, the entropy tops its maximum
when the mass ratio is between 3 and 4 in the case where there are four bosonic
particles and then falls off to its minimum for higher mass imbalance.
