Review of Progress Using Structured Light in Quantum Protocols

(EurekaAlert) Researchers from the University of Witwatersrand in South Africa review the progress being made in using structured light in quantum protocols to create a larger encoding alphabet, stronger security and better resistance to noise in an article in AVS Quantum Science, from AIP Publishing.
The quantum science community has made many recent noteworthy advances, both in the science and derived technologies. For example, entanglement swapping has now been demonstrated with spatial modes of light, a core ingredient in a quantum repeater, while the means to securely communicate between nodes is now possible through high-dimensional quantum key distribution protocols. Together they bring us a little bit closer to a fast and secure quantum network.
In their publication, the authors review the recent progress in this regard, outlining the core concepts in a tutorial manner before delving into the advances made in creation, manipulation, and detection of such quantum states. The authors cover advances in using orbital angular momentum as well as vectorial states that are hybrid entangled, combining spatial modes with polarization to form an infinite set of two-dimensional spaces: multidimensional entanglement. The authors highlight the exciting work in pushing the boundaries in both the dimension and the photon number, before finally summarizing the open challenges, and the questions that remain unanswered.