Delayed (sudden) birth of entanglement

TL;DR

This paper investigates the phenomenon of delayed entanglement creation, termed 'sudden birth,' in two qubits due to spontaneous emission, revealing controllable threshold times and potential for on-demand entanglement generation.

Contribution

It introduces the concept of sudden birth of entanglement, showing how it can be controlled by qubit distance and initial excitation direction, contrasting with entanglement death.

Findings

Threshold effect for entanglement creation identified

Threshold time depends on qubit distance and excitation direction

Delayed entanglement can be used for on-demand quantum resources

Abstract

The concept of time delayed creation of entanglement by the dissipative process of spontaneous emission is investigated. A threshold effect for the creation of entanglement is found that the initially unentangled qubits can be entangled after a finite time despite the fact that the coherence between the qubits exists for all times. This delayed creation of entanglement, that we call sudden birth of entanglement, is opposite to the currently extensively discussed sudden death of entanglement and is characteristic for transient dynamics of one-photon entangled states of the system. We determine the threshold time for the creation of entanglement and find that it is related to time at which the antisymmetric state remains the only excited state being populated. It is shown that the threshold time can be controlled by the distance between the qubits and the direction of initial excitation relative to the interatomic axis. This effect suggests a new alternative for the study of entanglement and provides an interesting resource for creation on demand of entanglement between two qubits.