Entanglement beating in free space through spin–orbit coupling

Otte, E., Rosales-Guzmán, C., Ndagano, B. , Denz, C. and Forbes, A. (2018) Entanglement beating in free space through spin–orbit coupling. Light: Science and Applications, 7, 18009. (doi: 10.1038/lsa.2018.9) (PMID:30839563) (PMCID:PMC6060074)

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Abstract

It is well known that the entanglement of a quantum state is invariant under local unitary transformations. This rule dictates, for example, that the entanglement of internal degrees of freedom of a photon remains invariant during free-space propagation. Here, we outline a scenario in which this paradigm does not hold. Using local Bell states engineered from classical vector vortex beams with non-separable degrees of freedom, the so-called classically entangled states, we demonstrate that the entanglement evolves during propagation, oscillating between maximally entangled (purely vector) and product states (purely scalar). We outline the spin–orbit interaction behind these novel propagation dynamics and confirm the results experimentally, demonstrating spin–orbit coupling in paraxial beams. This demonstration highlights a hitherto unnoticed property of classical entanglement and simultaneously offers a device for the on-demand delivery of vector states to targets, for example, for dynamic laser materials processing, switchable resolution within stimulated emission depletion (STED) systems, and a tractor beam for entanglement.

Item Type:Articles
Additional Information:EO acknowledges financial support from the German Research Foundation DFG (EXC 1003 – CiM, TRR61), CRG from the Claude Leon foundation, and BN from the National Research Foundation of South Africa.
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Ndagano, Mr Bienvenu
Authors: Otte, E., Rosales-Guzmán, C., Ndagano, B., Denz, C., and Forbes, A.
College/School:College of Science and Engineering > School of Physics and Astronomy
Journal Name:Light: Science and Applications
Publisher:Springer Nature
ISSN:2095-5545
ISSN (Online):2047-7538
Published Online:04 May 2018
Copyright Holders:Copyright © 2018 The Authors
First Published:First published in Light: Science and Applications 7:18009
Publisher Policy:Reproduced under a Creative Commons license

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