Quantum Circulator on a Chip

Circulators are devices used to route signals in communication and computing systems. They have three or more ports, and allow power to travel in only one direction: a signal entering from port 1, 2, or 3 will exit from port 2, 3, or 1, respectively, with little loss. Integrated on a chip, they could allow quantum-computing schemes to be scaled up. Now, David Reilly at the University of Sydney and colleagues have made a circulator that fits on a chip and has better signal directionality than most available devices.