Photonic topological insulator could enable quantum computing

Ashley N. Rice, ashley.rice@photonics.com

As computers get faster and chips get denser, there is a need for smaller light-manipulating devices. But as devices get smaller, imperfections in the fabrication processes can make light move irregularly and unpredictably. To tackle this challenge, a new device “topologically protects” light, meaning that light flows uninterrupted despite the presence of defects – which could bring quantum computing a step closer.

Researchers at Technion-Israel Institute of Technology, led by professor Mordechai Segev in collaboration with colleagues at Friedrich-Schiller University in Jena, Germany, have demonstrated the first photonic Floquet topological insulator.

Topological protection was first conceived not for light but for electrons flowing in a solid material. However, Technion’s Dr. Mikael Rechtsman and Yonatan Plotnik discovered a way to bring topological protection into photonics using an array of helical, or spiral-shaped, waveguides that interact with one another.

“The helical nature of the waveguides breaks the symmetry, so that in the forward direction, the waveguides are spinning clockwise, and in the backward direction, counterclockwise,” Rechtsman said. “In our procedure, this is an essential ingredient in preventing unwanted scattering.”

These structures may provide a new platform for understanding and probing the properties of photonic topological insulators, Rechtsman said. “For example, all sorts of experiments that would be difficult or impossible to carry out in solid-state materials can now be accessed using light.”

“This discovery is another step in the progress towards optical and quantum computing,” said Julia Zeuner, a graduate student at Friedrich-Schiller University who fabricated the sophisticated photonic structure and did part of the experiments.

“We have discovered a completely novel phenomenon, and new phenomena are destined to find applications in directions that we can’t even imagine,” Segev said.

The findings appeared in Nature (doi: 10.1038/nature12066).