August 30, 2014 - Like twins separated at birth who are later reunited, two laser
beams revealed invisible objects in a display of their weird quantum connection, researchers reported on Wednesday.
The images, of tiny cats and a trident, are an advance for quantum optics, an emerging physics discipline built on surprising interactions among subatomic particles that Einstein famously called "spooky."
A conventional camera captures light that bounces back from an object. But in the experiment reported in the journal Nature, light particles, or photons, that never strike an object are the ones that produce its picture.
"Even other physicists say 'you can't do that' at first, but that is quantum behavior for you, very strange," says Gabriela Barreto Lemos of the Institute for Quantum
Optics and Quantum Information in Vienna, Austria, who led the study.
A 2009 University of Glasgow experiment with a divided laser beam first demonstrated such "ghost imaging." But experts say the new technique, which uses two laser beams of different colors, offers new visualization advantages.
The two laser beams are "entangled" in quantum physics terms, meaning their photons share characteristics even when far apart. So broadly speaking, altering one alters the other.
"What they've done is a very clever trick. In some ways it is magical," says quantum optics expert Paul Lett of the National Institute of Standards and Technology in Gaithersburg, Maryland, who was not part of the experiment team. "There is not new physics here, though, but a neat demonstration of physics."