Abstract
Quantum entanglement provides an essential resource for quantum computation, quantum communication, and quantum network. How to conveniently and efficiently produce entanglement between bright light beams presents a challenging task to build realistic quantum information processing networks. Here, we present an efficient and convenient way to realize a novel quantum phenomenon, named electromagnetically induced entanglement, in the conventional Λ-type three-level atomic system driven by a strong pump field and a relatively weak probe field. Nearly perfect entanglement between the two fields can be achieved with a low coherence decay rate between the two lower levels, high pump-field intensity, and large optical depth of the atomic ensemble. The physical origin is quantum coherence between the lower doublet produced by the pump and probe fields, similar to the well-known electromagnetically induced transparency. This method would greatly facilitate the generation of nondegenerate narrow-band continuous-variable entanglement between bright light beams by using only coherent laser fields, and may find potential and broad applications in realistic quantum information processing.
Highlights
The considered Λ -type three-level atomic system driven by a strong pump field (Ec) and a relatively weak probe field (Ep), as shown in Fig. 1a, is based on the D1 transitions in 85Rb atom used in the experiment30
We take into account the quantum features of both the pump and probe fields by using the Heisenberg-Langevin method, and show how EIE in this Λ -type three-level atomic system can be established via the atomic coherence between the lower doublet created by the two fields
Here we show that the two laser fields for pre-establishing atomic coherence in EIT regime are intrinsically entangled themselves under certain conditions
Summary
Xihua Yang1 & Min Xiao received: 02 June 2015 accepted: 29 July 2015 Published: 28 August 2015. In the traditional EIT regime, nearly perfectly correlated and entangled pump and probe fields can be achieved at high pump-field intensity, high optical depth of the atomic medium, and a relatively low coherence decay rate between the two lower levels (as compared to the spontaneous decay rate of the excited state). This method provides an efficient and convenient way to generate bright nondegenerate narrow-band entangled fields by using only coherent light fields, which may hold great promise for practical applications in quantum communication and quantum networks
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