Hybrid Entangled Entanglement in Vector Vortex Beams

TL;DR

This paper demonstrates a novel form of quantum entanglement between two photons, each in vector-vortex states, combining single-particle and two-particle entanglement properties for advanced quantum applications.

Contribution

It introduces the first demonstration of entanglement between two photons both in vector-vortex states, merging single-particle and two-particle quantum entanglement concepts.

Findings

Successfully generated entangled VV photon pairs.

Potential for quantum-enhanced applications using VV beams.

Advances understanding of complex quantum entanglement structures.

Abstract

Light beams having a vectorial field structure - or polarization - that varies over the transverse profile and a central optical singularity are called vector-vortex (VV) beams and may exhibit specific properties, such as focusing into "light needles" or rotation invariance, with applications ranging from microscopy and light trapping to communication and metrology. Individual photons in such beams exhibit a form of single-particle quantum entanglement between different degrees of freedom. On the other hand, the quantum states of two photons can be also entangled with each other. Here we combine these two concepts and demonstrate the generation of quantum entanglement between two photons that are both in VV states - a new form of quantum "entangled entanglement". This result may lead to quantum-enhanced applications of VV beams as well as to quantum-information protocols fully exploiting the vectorial features of light.