PHYS: Storing information in photons

Max More (
Thu, 03 Jul 1997 09:16:16 -0700

The American Institute of Physics Bulletin of Physics News
Number 328 July 2, 1997 by Phillip F. Schewe and Ben Stein

PHOTON or any other quantum particle is possible even in the
presence of noise, researchers have concluded (B. Schumacher et
al., Physical Review A, July 1997; A.S. Holevo, upcoming in
IEEE Transactions on Information Theory). A photon has many
different quantum states, each of which can be made to represent a
different digit. Furthermore, one can store many digits
simultaneously in a single photon by putting it into a combination
or "superposition" of many states. However, quantum mechanics
prevents a measuring device from perfectly distinguishing between
all these different states. Previously, physicists discovered that the
maximum amount of information that can be read from a photon
can be no greater than the amount of entropy, or disorder, it
acquires when a range of quantum states is created to represent
different digits. Now, the researchers show that this upper limit can
be reached, even in a noisy environment, by utilizing several
strategies, such as employing only those quantum states that are
most distinguishable. These findings provide insights into how little
energy is required to store a message. (For more details, go to; Ben Schumacher, Kenyon
College, 614-427-5832)

Max More, Ph.D.
President, Extropy Institute:,
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