Entangling Atomic Collisions

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Science  13 Jul 2001:
Vol. 293, Issue 5528, pp. 177
DOI: 10.1126/science.293.5528.177d

We usually think of collisions as destructive processes, but in the quantum world, collisions can be constructive and even desirable events. When quantum systems are brought into close contact and allowed to interact under the right conditions, the wave functions of the systems can become entangled so that the once separate systems effectively become one. Such entanglement could be used for logical operations in quantum computers. However, the entanglement process is rather inefficient for bare atom collisions, and methods are being explored that make the process more efficient. Osnaghi et al. collide two Rydberg atoms—atoms in an electronic excited state that give rise to a large interaction cross section—in a cavity. As the excited rubidium atoms cross the cavity to the point of collision, energy exchange mediated by the virtual emission and absorption of a microwave photon between the two atoms results in entanglement. They find that cavity-assisted entanglement is four orders of magnitude more efficient than free-space collisions, a promising feature for quantum information processing. — ISO

Phys. Rev. Lett. 87, 037902 (2001).

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