Electro/photonic 'Excitonic' cryo-computing breakthrough

Boffins in California say they may be on their way to developing new, superfast "excitonic" computers. The latest experiments have seen hybrid electronic/photonic integrated circuits functioning at "around 100" degrees Kelvin, which - while extremely cold - is much more practical to achieve than the previously necessary 1.5°K.

"Our goal is to create efficient devices based on excitons that are operational at room temperature and can replace electronic devices where a high interconnection speed is important," says Leonid Butov, physics prof at UC San Diego.

Excitons are made up of two negatively charged electrons and positively charged "holes". They can be created using light in a semiconducting material such as gallium arsenide, and when the holes and electrons combine the exciton decays into a flash of light once more.

It's already common to connect electronic assemblies using photonic links for greater speed, and some researchers aspire to fully photonic, much faster machines in future. But Butov and his crew suggest that "excitonic" computing could be a better/more feasible method. It would offer the ability to use electrical manipulation for computing as current kit does, and the ability to build compact integrated devices too, but avoid the delay and extra equipment required for photonic comms.

"Our transistors process signals using excitons, which like electrons can be controlled with electrical voltages, but unlike electrons transform into photons at the output of the circuit," says Butov. "This direct coupling of excitons to photons allows us to link computation and communication."

Last year the first excitonic integrated circuit was tested, but it would only work at almost absolute zero - a temperature so cold that it wouldn't be feasible even in the most aggressively chilled data centre. But now Butov and his crew have got prototype excitonic building blocks working at temperatures achievable with nothing fancier than ordinary liquid nitrogen.

Even so, sysadmins probably won't be resting their ice-cube trays on the excitonic cryo-cabinets for a while yet.

"We're still in an early stage of development," cautions Butov. "Our team has only recently demonstrated the proof of principle for a transistor based on excitons and research is in progress."

The latest research can be read online by subscribers to Nature Photonics here. ®