California Institute of Technology researchers
have fashioned a single atom into a light source that generates single
photons on demand.
The light source could eventually be used in quantum cryptography
systems to guarantee perfectly secure cryptographic keys. It could also
be used in quantum computers, which have the potential to solve certain
types of very large problems many orders of magnitude faster than today's
classical computers, including those that would render today's security
A single atom can make a single photon -- the trick is isolating
and controlling the atom. The researchers' system traps a cesium in a
cavity formed by a pair of highly reflective mirrors.
The researchers have showed that it is possible to generate quantum
entanglement between atoms and photons using the system, and then transfer
that entanglement so that atoms in separate cavities can be entangled.
The properties of entangled particles remain in lockstep regardless of
the distance between them. Entanglement promises to make it possible to
build quantum communications networks.
There's a lot to be done before the system can be used practically.
Today the system takes up an entire room. In 10 to 20 years the technology
may exist to integrate large numbers of atoms, each with its own minicavity
onto a chip of some sort, according to the researchers. And the lasers
and electronics would also have to be miniaturized.
It will be least two decades before the system could be used practically,
according to the researchers. The work appeared in the February 26, 2004
issue of Sciencexpress.
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