Credit: © 2009 NPG

Electrons carry the information in most transistors, but photons are an attractive alternative because they are less likely to lose quantum information to the environment or decohere. A continued downwards scaling of transistor sizes, however, makes photon manipulation difficult.

Now, Vahid Sandoghdar and colleagues at ETH Zurich in Switzerland have demonstrated an all-photon transistor using a single molecule1. The researchers shone two laser beams onto a single molecule. The first beam excited the molecule to varying degrees, depending on its power. This degree of excitation then controlled whether the second beam was attenuated or amplified. The two beams are analogous to a gate and source signal, and the molecule itself to a transistor.

The work represents the first example of an all-optical single-emitter transistor. Future research directions include extending the range of power that can be handled by the transistor. It may also be possible to simultaneously address a large number of single-emitter transistors, by exploiting the spread in their resonant frequencies.