Now, researchers in China have overcome this limitation by turning almost the entire structure into a four-lane highway for light, allowing four independent microwave signals to travel side by side. This breakthrough could eventually lead to smaller, denser, and more efficient photonic chips for communications, quantum technologies, and optical computing. Our “work exemplifies a design strategy for ultracompact topological photonic circuits, with potential for high-density integrated optics,” the researchers note in their study. Replacing barriers with highways To understand the new design, imagine a conventional topological photonic chip as a road surrounded by wide safety barriers. To test the design, the researchers built the structure for microwave frequencies and sent information-carrying microwave signals through it.