Optical transistor made from a single molecule

Posted by Emma Woollacott

Zurich, Switzerland - Engineers are one step closer to developing an optical computer, following the successful creation of an optical transistor from a single molecule.


A research group at ETH Zurich has achieved something of a breakthrough by making use of the fact that a molecule’s energy is quantized: when laser light strikes a molecule that is in its ground state, the light is absorbed. As a result, the laser beam is quenched.


Conversely, it's possible to release the absorbed energy again in a targeted way with a second light beam. This occurs because the beam changes the molecule’s quantum state, with the result that the light beam is amplified.


The ETH Zurich scientists have now been able to generate stimulated emission using just one molecule. They were helped in this by the fact that, at low temperatures, molecules seem to increase their apparent surface area for interaction with light. The researchers therefore needed to cool the molecule down to minus 272 degrees Celsius - not particularly practical for everyday use, admittedly, but a big step forward nevertheless.


By using one laser beam to prepare the quantum state of a single molecule in a controlled fashion, scientists could significantly attenuate or amplify a second laser beam. This mode of operation is identical to that of a conventional transistor, in which electrical potential can be used to modulate a second signal.


Thus, the new single molecule transistor could also pave the way for a quantum computer. Vahid Sandoghdar, Professor at the Laboratory of Physical Chemistry of ETH Zurich, said, “Many more years of research will still be needed before photons replace electrons in transistors. In the meantime, scientists will learn to manipulate and control quantum systems in a targeted way, moving them closer to the dream of a quantum computer.”


The research is published in Nature.