A new method has been developed at TU Wien, Austria, to produce entangled atom pairs and not just atoms which are emitted in all directions, but well-defined beams. This was achieved with the help of ultracold atom clouds in electromagnetic traps.
There are different methods of creating quantum entanglement. For example, special crystals can be used to create pairs of entangled photons: a photon with high energy is converted by the crystal into two photons of lower energy—this is called “down conversion.” This allows large numbers of entangled photon pairs to be produced quickly and easily.
Entangling atoms, however, is much more difficult. Individual atoms can be entangled using complicated laser operations—but then you only get a single pair of atoms. Random processes can also be used to create quantum entanglement: if two particles interact with each other in a suitable way, they can turn out to be entangled afterwards. Molecules can be broken up, creating entangled fragments. But these methods cannot be controlled.
The paper has been published in Physical Review Letters.