Entanglement beating in free space through spin–orbit coupling
Date
2018
Journal Title
Journal ISSN
Volume Title
Publisher
Springer Nature
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.
Description
Keywords
Classical entanglement, Complex light fields, Entanglement oscillation, Spin–orbit coupling
Citation
Otte, E., Rosales-Guzmán, C., Ndagano, B. et al. Entanglement beating in free space through spin–orbit coupling. Light Sci Appl 7, 18009 (2018). https://doi.org/10.1038/lsa.2018.9