Controlling Quantum Tunneling with Light

For the first time, light was used to demonstrate quantum tunneling, pushing electrons through a classically impenetrable barrier.

Particles normally cannot pass through walls, but if they are small enough quantum mechanics says that it can happen. This occurs during the production of radioactive decay and in many chemical reactions, as well as in scanning tunneling microscopes.

“The trick to telling electrons how to pass through walls is to now marry them with light,” said professor Jeremy Baumberg of Cavendish Laboratory at the University of Cambridge.

The scientists shot light in the form of cavity photons, or packets of trapped light that bounce back and forth between mirrors, to sandwich the electrons oscillating through their walls.

“The offspring of this marriage are actually new indivisible particles, made of both light and matter, which disappear through the slab-like walls of semiconductor at will,” said research scientist Peter Cristofolini.

The new particles, which the team named dipolaritons, resemble a bar magnet, stretching out in a specific direction. As with magnets, these dipolaritons feel extremely strong forces between each other.

It is the dipolaritons that can tunnel through the barrier. Capable of being in two places at once, these particles could help translate atomic physics into practical devices. Such strongly interacting particles have caught the attention of semiconductor physicists who are attempting to make condensates, the equivalent of superconductors and superfluids that travel without loss in semiconductors.

The work appeared in the April 5 issue of Science.

For more information, visit: www.cam.ac.uk