OAMGHZ · High-dimensional Multipartite Entanglement of Photonic Orbital Angular Momentum

High-dimensional Multipartite Entanglement of Photonic Orbital Angular Momentum

The main objectives of the project OAMGHZ are centered around creating multi-photon entangled states in high dimensions using the photonic orbital angular momentum (OAM) degree of freedom. A series of tools are to be developed that enable the creation of such states. In addition, new applications for such entangled states are to be found. Not only were the project objectives reached, but the results opened up new and interesting directions in research. In particular, the development of methods for generating a more general class of complex entangled states and the creation of one such asymmetrically entangled state bear witness to this. The first objective of developing a device for the manipulation of OAM in a manner akin to polarization devices was met early in the project, with a publication in the journal Nature Communications. However, this device proved too complex for implementation on the scale of a multi-photon experiment, and an alternate device was developed that sorted and mixed the OAM of incoming photons in an elegant and stable manner. Extensive research into the second objective of high-dimensional entanglement swapping found that implementing a Bell-state measurement in high dimensions (which is required for this objective) is nontrivial. An algorithm that was originally developed for finding new quantum experiments is being used to find experimental implementations of such measurements. Focusing on the third and primary objective of creating OAM-GHZ states in high dimensions led to a fruitful research path that has generated many significant results. The OAM sorting device developed in the first objective was stabilized in a double-Sagnac configuration and used to generate various types of multi-photon high-dimensional entangled states. A class of states emerged where different particles can live in different dimensions. One such state was recently realized in the laboratory. Through a close collaboration with a theoretical physicist from the Universitat Autonoma de Barcelona, entanglement in 3 x 3 x 2 dimensions was verified by developing an appropriate entanglement witness. The creation of such states has led to the development of novel applications for multi-party quantum communication. As part of the fourth objective, a layered quantum cryptographic scheme was developed where three parties share secure information asymmetrically. Asymmetric entangled states such as the one we have created constitute a new direction in experimental studies of entanglement, and will allow the development of complex, multi-level quantum networks in the future. During the course of the project, the fellow collaborated with 31 different scientists in 7 different universities in Europe and around the world. The 14 publications (5 of which are currently under preparation) with 279 citations between them bear witness to the wide impact the fellow’s research has had. Two of these publications were published in the journal Nature Communications, while one was published in the journal Reviews of Modern Physics. The fellow delivered talks at 11 different international conferences, 5 of which were invited. He also presented research seminars at 7 different universities and institutes. All in all, he presented his research in 11 different countries including 7 within Europe itself. His frequent visits to different research institutions and universities contributed tremendously to the career development of the fellow as well as to the transfer of knowledge to Europe. To summarize, the project was a thorough success in all of its areas and its results will continue to shape the research endeavors of the fellow for years to come.

Data: CORDIS, © European Union