# Unidirectional quantum walk of two correlated particles: Separating bound-pair and unbound wavepacket components

## TL;DR

This paper investigates how two entangled particles in a one-dimensional lattice behave under an external electric field, revealing distinct dynamics for bound and unbound states and demonstrating controllable unidirectional transport influenced by entanglement.

## Contribution

It provides a combined numerical and analytical study of two-particle quantum walks, highlighting the interaction-induced wavepacket splitting and controllable unidirectional transport.

## Key findings

- Bound-pair states behave differently from unbound states under electric fields.
- Wavepacket splits into two components with specific directions and velocities.
- Transport direction and amplitude depend on entanglement and interaction strength.

## Abstract

We study the unidirectional transport of two-particle quantum wavepackets 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 wavefunction profile reveals that the particle-particle interaction induces the splitting of the initial wavepacket into two branches that propagate with specific directions and drift velocities. With a proper external field tunning, the wavepacket components can perform an unidirectional transport on the same or opposite directions. The amplitude of each mode is related to the degree of entanglement betweem particles, which presents a non-monotonic dependence on the interaction strength.