Entanglement of two qubits mediated by a localized surface plasmon

TL;DR

This paper explores how two quantum dipole emitters become entangled through their interaction with a localized surface plasmon on a metal nanoparticle, revealing a stable superposition state formed rapidly and dependent on their relative positions.

Contribution

It demonstrates the formation of a stable entangled superposition state mediated by a localized surface plasmon, with the entanglement degree depending on the emitters' distances from the nanoparticle.

Findings

Maximum concurrence of ~0.65 achieved at specific emitter-nanoparticle distances.

Stable superposition state forms during the transition time, much shorter than spontaneous decay.

Entanglement depends only on the ratio of distances between QDEs and the MNP.

Abstract

We investigate relaxation dynamics in the system of two identical quantum dipole emitters (QDEs) located near a metal nanoparticle (MNP) exhibiting a dipolar localized surface plasmon (LSP) resonance at the frequency of the QDE radiative transition. Considering one QDE to be brought into an optically active excited state and weakly coupled to the resonant LSP, we show that a stable superposition state of two QDEs is formed during the transition time, which is much shorter than the QDE spontaneous decay time and determined by the efficiency of resonant interaction between the QDEs and induced LSP. It is elucidated that the superposition state is established as a result of redistribution of the energy of the initially excited QDE so that the corresponding steady-state QDE fields induced at the MNP site cancel each other. The degree of steady-state entanglement characterized by the concurrence is found dependent only on the ratio of distances between the QDEs and the MNP, reaching its maximum value of ~ 0.65, when the separation between the MNP and the initially excited QDE is larger by ~ 20% than the distance from the other QDE to the MNP.