**Press Release**


(August 21, 2008 - Los Alamos, NM) Two communication channels that
are too noisy to transmit information, such as two cut telephone
lines, would seem to remain useless when used together. Scientists
recently showed this is not the case in the world of the small, where
objects are described by quantum mechanics.

The discovery, that two apparently useless quantum communication links
may be useful together, was made by Dr. Graeme Smith of IBM Research
and Dr. Jon Yard of Los Alamos National Laboratory. It was published
on August 21 in the leading journal Science.

The mathematical study of communication in the presence of noise was
formalized by Claude Shannon in 1948. The cornerstone of Shannon's
theory is a mathematical expression for the capacity of a
communication channel for noiseless communication. This simple
formula places limits on and guides the design of modern communication
schemes used in such varied settings as cellular telephones,
deep-space communication and the internet.

The world is ultimately quantum mechanical, though, and Shannon's
theory is entirely classical. In order to understand the fundamental
limits the universe places on communication, scientists have been
developing a quantum theory of communication and information. However,
researchers have been unable to find an expression for the capacity
for transmitting quantum information in analogy with Shannon's simple
formula. As a result, the quantum capacity of almost any communication
channel is unknown.

This work shows that the quantum capacity of a channel behaves in a
way that is completely different from the classical capacity. It
unveils a rich structure in the theory of quantum communications while
raising a variety of tantalizing questions about the nature of
information in the physical world.

Published Paper


For further information, please contact:

Jon Yard
Los Alamos National Laboratory
Mail Stop B158
Los Alamos, NM 87545