Entanglement sharing in one-particle states

Entanglement sharing among sites of one-particle states is considered using the measure of concurrence. These are the simplest in a hierarchy of number-specific states of many qubits and correspond to ``one-magnon'' states of spins. We study the effects of onsite potentials that are both integrable and nonintegrable. In the integrable case, we point to a metal-insulator transition that reflects on the way entanglement is shared. In the nonintegrable case, the average entanglement content increases and saturates along with a transition to classical chaos. Such quantum chaotic states are shown to have universal concurrence distributions that are modified Bessel functions derivable within random matrix theory. Time-reversal breaking and time-evolving states are shown to possess significantly higher entanglement sharing capacity than eigenstates of time-reversal symmetric systems. We use the ordinary Harper and the kicked Harper Hamiltonians as model systems.