Building a quantum network often comes down to a stubborn materials problem. Diamond can host quantum emitters, tiny systems that produce light signals, while other materials are better suited to building the optical circuits needed to carry them. Joining these materials can mean losing light at the very connection meant to pass it along.
Researchers in the United States and the Republic of Korea have connected diamond with titanium dioxide photonic circuits using a fabrication method that helps the components align themselves. Their study, published in Light: Science & Applications, demonstrates how this connection can keep light loss low while allowing a chip to interact with a diamond emitter and guide its light through a circuit.
“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.
The researchers guided a tiny beam of diamond into a structure patterned in advance, where it naturally settled into alignment. They then formed the surrounding titanium dioxide photonic device around it. Building alignment into fabrication avoids many of the positioning errors that have caused extra light loss in earlier attempts to connect quantum emitters with optical circuits.
With the materials joined, the diamond supplied the light, and the titanium dioxide circuit provided a route for it to travel through the chip. The light source was a silicon-vacancy center, a tiny defect in the diamond’s atomic structure. By confining light around this emitter in a hybrid optical cavity, the team enhanced its emission. They also demonstrated that light from the emitter could be routed through the circuit.
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