A way to make communication and computing devices faster, better, and less noisy is to use more kinds of information and combine them in new ways. Quantum communication uses light particles that can be in many states at the same time. These states are different features of light particles, and they can only show one state when someone looks at them, making them hard to spy on or copy.
Researchers at the University of Pennsylvania have made a microfabricated laser using semiconductor fabrication methods that can control two features of the light particles: their orbit and their spin. This allows them to make light particles with four states simultaneously. These higher-dimensional quantum bits (qudits) can store more information and better avoid noise. They can also make quantum communication more secure and faster and allow more secure communications.
Zhang, Z., Zhao, H., Wu, S., Wu, T., Qiao, X., Gao, Z., Agarwal, R., Longhi, R., Litchinitser, N.M., Ge, L., Feng, L. Nature 612, 246-251 (2022).