Photonic circuits, which use light instead of electricity to process information, are rapidly transforming modern technology. These circuits are at the heart of cutting-edge advancements in quantum computing, artificial intelligence, and secure communications. Their ability to perform computations with minimal energy loss makes them an attractive alternative to traditional electronic circuits, which struggle with inefficiencies as processing demands grow.
However, as photonic circuits become more complex, they face a fundamental challenge: optical losses increase as the circuit grows. This issue has been a major roadblock in scaling photonic technology for large-scale applications, particularly in quantum simulations and all-optical AI systems.
A groundbreaking solution has now emerged from researchers at the University of Naples Federico II, who have developed a liquid-crystal (LC)-based optical processor that can handle hundreds of optical modes with minimal loss. This breakthrough, reported in Advanced Photonics, is a major step forward in building next-generation photonic systems capable of performing advanced quantum computations efficiently.
The Optical Loss Problem in Photonic Circuits
Photonic circuits rely on light waves traveling through waveguides or other optical structures to perform calculations. Unlike electronic circuits, which use electrons, photonic circuits avoid the resistance and heat generated by electrical currents, making them much more energy-efficient.
Despite these advantages, there is a significant scalability challenge. As the number of optical modes (distinct light paths within the circuit) increases, the optical losses (attenuation or scattering of light) rise. These losses can degrade the circuit’s performance, limiting its ability to handle complex tasks like quantum walks—a key quantum computing operation.
Until now, researchers have struggled to create scalable, low-loss photonic circuits that can support large-scale quantum and AI-driven computations. The challenge lies in designing a system where increasing the number of optical modes does not also increase light losses.
A Breakthrough in Liquid-Crystal Photonics
The research team at the University of Naples Federico II has introduced an innovative approach to overcoming this problem. Instead of relying on traditional photonic architectures, they designed a system based on liquid crystal metasurfaces—ultra-thin optical structures that manipulate light at the nanoscale.
Their new optical processor consists of three liquid-crystal (LC) metasurfaces arranged in a compact two-dimensional (2D) setup. These metasurfaces precisely control light waves, simulating various quantum phenomena while maintaining constant optical losses, even as the number of optical modes increases.
Professor Filippo Cardano, the study’s lead author, explains:
“In theory, this circuit can handle as many modes as needed while maintaining constant optical losses, thus representing a significant breakthrough with respect to previous implementations.”
This innovation enables researchers to build more complex photonic circuits without the usual increase in loss, opening the door to more powerful quantum experiments and AI applications.
Simulating Quantum Walks with Liquid Crystal Metasurfaces
One of the most exciting applications of this new photonic system is its ability to simulate quantum walks.
A quantum walk is the quantum equivalent of a classical random walk, where a particle moves step-by-step in a probabilistic fashion. Unlike classical systems, a quantum walk takes advantage of superposition and entanglement, allowing multiple paths to be explored simultaneously.
Quantum walks are essential for a variety of applications, including:
- Quantum computing algorithms
- Secure cryptographic protocols
- Simulating complex biological and physical systems
In previous research, Cardano’s team demonstrated record-breaking numbers of quantum walk steps in a one-dimensional (1D) photonic circuit. However, expanding this approach to two-dimensional (2D) systems introduced new challenges, such as disruptions in liquid-crystal patterns that affected how light behaved.
Overcoming Optical Disruptions with Algorithmic Precision
To solve this challenge, the researchers developed a new algorithm that generates smooth liquid-crystal patterns while avoiding disruptions that could interfere with light propagation.
This approach incorporates isolated vortices—localized disturbances in the liquid-crystal pattern—that do not significantly impact optical performance. As a result, the system can support up to 800 optical modes, far surpassing previous one-dimensional implementations.
This innovation marks a major leap forward, as higher-mode photonic circuits are essential for simulating more complex quantum systems and enabling more sophisticated AI-driven optical computing.
Expanding the Horizons of Photonic Computing
Beyond quantum simulations, the liquid-crystal photonic processor has potential applications across multiple fields:
1. Artificial Intelligence & Machine Learning
Photonic circuits are emerging as powerful alternatives to traditional AI processors. Light-based computing enables faster data processing with lower energy consumption, making them ideal for AI-driven tasks such as:
- Neural network acceleration
- Image and pattern recognition
- Real-time data analysis
By enabling low-loss, high-mode optical processing, this research could revolutionize AI hardware and make all-optical AI processors a reality.
2. Quantum Computing & Secure Communications
Quantum computing relies on quantum states to perform calculations far beyond the capabilities of classical computers. The ability to scale photonic circuits without excessive loss is critical for:
- Quantum cryptography and secure data transmission
- Quantum simulations of physical and chemical systems
- Scalable quantum networks for distributed quantum computing
This new LC-based system provides a highly adaptable platform for developing next-generation quantum photonic processors.
3. Optical Sensors & Imaging
Advanced photonic circuits play a crucial role in high-resolution optical sensors, which are used in:
- Biomedical imaging
- Remote sensing and environmental monitoring
- Military and defense applications
By reducing optical losses, the new liquid-crystal technology can improve the performance of high-precision optical devices, leading to better medical diagnostics and environmental sensing.
Conclusion: A New Era of Photonic Innovation
The development of low-loss, high-mode photonic circuits using liquid-crystal metasurfaces represents a major milestone in photonic computing. By overcoming the long-standing scalability challenges in optical circuits, researchers at the University of Naples Federico II have paved the way for the next generation of photonic technologies.
Their work not only advances quantum computing and AI but also has broad implications for secure communications, imaging, and sensor technology.
As photonic circuits continue to evolve, this breakthrough brings us closer to a future where light-based processors outperform traditional electronics, driving innovations that will redefine how we process and harness information.
With optical computing poised to revolutionize multiple industries, the future of technology is looking brighter than ever—quite literally.
Reference: Maria Gorizia Ammendola et al, Large-scale free-space photonic circuits in two dimensions, Advanced Photonics (2025). DOI: 10.1117/1.AP.7.1.016006