Interface between path and orbital angular momentum entanglement for high-dimensional photonic quantum information

• Published in: Nature communications 2014-07, Vol.5 (1), p.4502-4502, Article 4502
• Main Authors: Fickler, Robert, Lapkiewicz, Radek, Huber, Marcus, Lavery, Martin P.J., Padgett, Miles J., Zeilinger, Anton
• Format: Article
• Language: English
• Subjects: 639/624/1075/1079; 639/624/400; 639/766/483/481; Humanities and Social Sciences; multidisciplinary; Science; Science (multidisciplinary)
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms5502

Photonics has become a mature field of quantum information science, where integrated optical circuits offer a way to scale the complexity of the set-up as well as the dimensionality of the quantum state. On photonic chips, paths are the natural way to encode information. To distribute those high-dimensional quantum states over large distances, transverse spatial modes, like orbital angular momentum possessing Laguerre Gauss modes, are favourable as flying information carriers. Here we demonstrate a quantum interface between these two vibrant photonic fields. We create three-dimensional path entanglement between two photons in a nonlinear crystal and use a mode sorter as the quantum interface to transfer the entanglement to the orbital angular momentum degree of freedom. Thus our results show a flexible way to create high-dimensional spatial mode entanglement. Moreover, they pave the way to implement broad complex quantum networks where high-dimensionally entangled states could be distributed over distant photonic chips. The orbital angular momentum of light is a promising degree of freedom for long-distance information transportation. To create high-dimensional entanglement for pairs of photons, Fickler et al. use an optical mode sorter in reverse to transfer entanglement between the path into the orbital angular momentum.