Making parts like these smaller will help enable quantum computers with millions of qubits.

Above – Lead author of the study, PhD candidate Alice Mahoney, in the quantum science laboratories at the Sydney Nanoscience Hub.

The Sydney team's component, coined a microwave circulator, acts like a traffic roundabout, ensuring that electrical signals only propagate in one direction, clockwise or anti-clockwise, as required. Similar devices are found in mobile phone base-stations and radar systems, and will be required in large quantities in the construction of quantum computers. A major limitation, until now, is that typical circulators are bulky objects the size of your hand.

They used the properties of topological insulators to slow the speed of light in the material. This miniaturization paves the way for many circulators to be integrated on a chip and manufactured in the large quantities that will be needed to build quantum computers.