A practical route to low-loss integrated quantum photonic chips

Light Publishing Center, Changchun Institute of Optics, Fine Mechanics And Physics, CAS

Quantum photonic chips could one day help power quantum networks and quantum computers, but building them has faced a stubborn materials problem. The best materials for hosting quantum emitters are often not the same materials that are best for making large photonic circuits. Bringing those two worlds together without losing light at the interface has been a major challenge for the field.

In a new paper published in Light: Science & Applications, scientists from the United States and Republic of Korea report a way around this problem. They developed a self-aligned heterogeneous photonic integration method that combines diamond, a leading material for solid-state quantum emitters and spin systems, with titanium dioxide photonic circuits in a low-insertion-loss architecture. The result is a practical strategy for bringing solid-state quantum emitters onto scalable photonic circuits.

The key idea is simple in concept but powerful in practice. A tiny diamond nanobeam is guided into a pre-patterned structure where it naturally aligns itself, and the surrounding photonic device is then formed around it. Because the alignment is built directly into the fabrication process, the method avoids many of the positioning errors and excess losses that have limited earlier approaches to heterogeneous quantum photonics.

“We wanted a practical way to combine high-quality quantum emitters with integrated photonics without paying a large price in optical loss,” said Kinfung Ngan, the first author of the study and a graduate student at JILA and the University of Colorado Boulder.

To show the potential of the platform, the researchers demonstrated several important functions on chip. They built a hybrid optical cavity that enhanced light emission from a silicon-vacancy center in diamond. They also showed that light from the emitter could be routed through the photonic circuit, and that the emitter’s spin state could be initialized and read out through the chip itself. Together, these results show that the approach is not just a fabrication concept, but a working route toward integrated quantum devices that can generate, control, and collect quantum light.

The work also points toward future quantum chips with greater complexity and functionality. Because the same platform is compatible with advanced photonic designs for efficient and broadband photon collection, it offers a flexible foundation for building larger quantum photonic circuits. The authors further emphasize that the approach is not limited to diamond or titanium dioxide alone, raising the possibility of extending it to other quantum emitters and photonic materials.

“By showing enhanced emission, on-chip spin control, and efficient photon routing in the same platform, this work points to a realistic path toward scalable quantum photonic chips,” said Dongyeon Daniel Kang, a corresponding author of the study and a senior research scientist at the Korean Institute of Science and Technology.

More broadly, the advance addresses a central bottleneck in quantum photonics: how to connect the best quantum materials to chip-scale photonic technology in a practical way. By reducing optical loss at the interface and demonstrating key device functions on chip, this work opens a promising path toward scalable quantum photonic technologies for future communication and information processing.

“By overcoming a key integration bottleneck, this work opens exciting opportunities for large-scale photonic quantum processors and quantum repeaters,” said Shuo Sun, the corresponding author, a JILA Fellow, and an assistant professor at the University of Colorado Boulder.

This news article was drafted with the assistance of AI tools and reviewed by the author team.