Single-atom Laser Built at Caltech

hweimer writes "A research group at Caltech has successfully constructed a laser consisting of only one caesium atom. The emitted light is very weak but highly ordered, so such a device may be used to control a quantum computer. More on this can be found at PhysicsWeb."

Comments

GoogleNews

[Leffe]

Here's a handy link with all the articles on GoogleNews:

http://news.google.com/news?q=single+atom+laser

How does this fit with Quantum computing

[fruey]

(Blatantly stolen from link on the right of the article)

A system with one or more individual atoms at rest and strongly coupled to a single mode of the electromagnetic field is ideal for testing fundamental concepts of quantum computing and quantum information processing (see Physics World 1998 March). Indeed, Scott Parkins, now at the University of Auckland, and collaborators at the JILA Laboratory in Boulder, Colorado, and Caltech first proposed this system as a highly efficient quantum interface in 1993. Using the strong coupling of an atom to a single photon, it should be possible to map a quantum bit at rest from an atomic medium onto a propagating light field, and vice versa. In other words, this scheme could allow quantum information to be sent from one place to another. The first experimental results in this direction were obtained very recently by Markus Hennrich and co-workers at the MPQ. Moreover, two atoms in the cavity should make it possible to realize a "controlled NOT gate", the elementary building block of a quantum computer.

But it does answer the question I was asking myself...

usefulness in quantum computing?

[sluke]

Off the top of my head I can think of two areas where this could be useful for quantum computing. The first would be as a way to comvert flying qubits (photons) in to stationary qubits. If this could be done, than technology such as quantum repeaters would be possible, therefore allowing for long distance quantum cryptography. The second would be as a single photon source, which would have big applications in optical quantum computing.

The article, however, was very light on specifics. It says that the light exhibits antibunching, yet calls it a laser. My understanding of coherent states was that the probability of sending out two photons was high enough that it causes problems with quantum cryptography (Eve can simply observe one of the flying qubits and let the other one go). So do they envision using this as a single photon source? I haven't had a chance to read the journal article yet, so if someone who has a little more info could clarify I would be quite appreciative.