A newly developed liquid-crystal-based photonic circuit has overcome a significant challenge in the field of photonic circuits, enabling the manipulation of hundreds of optical modes in a compact, free-space, two-dimensional setup. This breakthrough, reported in Advanced Photonics, advances the scalability of quantum simulations and all-optical AI systems.

Photonic circuits, which manipulate light to perform various computational tasks, have become essential tools for advanced technologies such as quantum simulations and artificial intelligence. These circuits offer a promising way to process information with minimal energy loss, especially in fields like quantum computing where complex systems are simulated to test theories of quantum mechanics. However, the growth in circuit size and complexity has historically led to an increase in optical losses, making it challenging to scale these systems for large-scale applications.

Researchers at the University of Naples Federico II have now developed a new approach to address this problem. Using a liquid-crystal (LC)-based platform, the team designed an optical processor capable of handling hundreds of optical modes in a compact, two-dimensional setup. This system uses a set of three LC metasurfaces, precisely engineered to simulate quantum processes such as the "quantum walk," which is the quantum-mechanical analogue of the classical random walk.

The new system allows for a large number of optical modes to be handled without a significant increase in losses. According to corresponding author Filippo Cardano, professor of physics at the University of Naples, "In theory, this circuit can handle as many modes as needed while maintaining constant optical losses." This represents a significant breakthrough compared to previous implementations.

To overcome challenges such as disruptions in liquid-crystal patterns that would affect light behavior, the researchers developed a new algorithm that creates smooth patterns incorporating isolated vortices that do not significantly impact light propagation. This innovation enabled the system to simulate up to 800 optical modes—much more than could be achieved with one-dimensional approaches.

This technology is versatile and can be easily customized for various computational and simulation tasks. It opens up new possibilities for low-loss circuits that could push the limits of photonic quantum experiments. The original Gold Open Access article by M. G. Ammendola, F. Di Colandrea, et al., titled "Large-scale free-space photonic circuits in two dimensions," was published in Advanced Photonics 7(1), 016006 (2025).