Unidirectional quantum walk of two correlated particles: Manipulating bound-pair and unbound wave-packet components

We study the unidirectional transport of two-particle quantum wave-packets in a regular one-dimensional lattice. We show that the bound-pair state component behaves differently from unbound states when subjected to an external pulsed electric field. Thus, strongly entangled particles exhibit a quite distinct dynamics when compared to a single particle system. With respect to centroid motion, our numerical results are corroborated with an analytical expression obtained using a semi-classical approach. The wave function profile reveals that the particle-particle interaction induces the splitting of the initial wave-packet into two branches that propagate with specific directions and drift velocities. With a proper external field tuning, the wave-packet components can perform an unidirectional transport on the same or opposite directions. The amplitude of each mode is related to the degree of entanglement between particles, which presents a non monotonic dependence on the interaction strength.