An optical transistor that uses one laser beam to control another could form the heart of a future generation of ultrafast photonic computers, overcoming the speed limits with wires, say Swiss researchers.

Using a green beam to switch an orange output beam from weak to strong is analogous to the way a transistor’s control electrode switches a current between “on” and “off” voltages, and hence the 0s and 1s of digital data. And doing it with a single molecule means billions could be packed into future photonic chips.