Ring resonators corner light

Researchers at the Joint Quantum Institute (JQI) have created the first silicon chip that can reliably constrain light to its four corners. The effect, which arises from interfering optical pathways, isn't altered by small defects during fabrication and could eventually enable the creation of robust sources of quantum light. That robustness is due to topological physics, which describes the properties of materials that are insensitive to small changes in geometry. The cornering of light, which was reported June 17 in Nature Photonics, is a realization of a new topological effect, first predicted in 2017.

Pristine quantum light source created at the edge of silicon chip

The smallest amount of light you can have is one photon, so dim that it’s pretty much invisible to humans. While imperceptible, these tiny blips of energy are useful for carrying quantum information around. Ideally, every quantum courier would be the same, but there isn’t a straightforward way to produce a stream of identical photons. This is particularly challenging when individual photons come from fabricated chips. Now, researchers at the Joint Quantum Institute (JQI) have demonstrated a new approach that enables different devices to repeatedly emit nearly identical single photons. The team, led by JQI Fellow Mohammad Hafezi, made a silicon chip that guides light around the device’s edge, where it is inherently protected against disruptions. Previously, Hafezi and colleagues showed that this design can reduce the likelihood of optical signal degradation. In a paper published online on Sept. 10 in Nature, the team explains that the same physics which protects the light along the chip’s edge also ensures reliable photon production.