Distribution of Bell state entanglement in qubit networks via collision models

Abstract

We investigate the selective generation of Bell-pair entanglement in three-qubit networks using a standard quantum collision model. By varying the network geometry, the node contacted by the ancilla, and the interaction Hamiltonians, we identify configurations in which high pairwise concurrence and Bell-state fidelity are generated between different target qubits, including nonadjacent qubits and qubits not directly coupled to the ancilla. For comparison, we also consider the continuous-time unitary evolution of the complete ancilla–network system, sampled at the same discrete time intervals. This reference calculation clarifies how discarding each outgoing ancilla and removing its correlations from subsequent dynamics modifies the attainable entanglement and preparation time. Our results provide a proof-of-principle demonstration of geometry-dependent Bell-pair generation and routing in small qubit networks.