Tuesday, November 07, 2006

Weird science

Every couple years, there's another one of those quantum teleportation stories in the media. They frequently make it sound as if the latest research breakthrough is the first in this area (which it's not) and they often obscure the fact that it's really "tele-copying" that is being discussed.

Matter and radiation (atoms and photons) are ultimately defined by their quantum state. This state is specified by the list of physical variables. Classically, these would be position, velocity, orbital angular momentum, and spin angular momentum, as well as charge. In quantum mechanics, the state is typically specified by position, radial and orbital quantum numbers, spin quantum numbers, and charges. For photons, it's simpler: a photon is just its frequency, direction, and polarization (spin). The matter quantum state might be familiar to readers of Kavanna from high school or college chemistry.

Quantum copying amounts to "reading" the quantum state of atoms and photons, then impressing this state on another set of atoms and photons elsewhere. The earliest forms of quantum teleportation required destroying the original while making the copy. The more recent forms allow copying-without-destroying, as well as copying quantum numbers from matter to radiation and back. The most important applicaton of quantum teleportation lies in quantum cryptography.

See these articles about quantum teleportation, here, here, and here.



Post a Comment

Links to this post:

Create a Link

<< Home