STORING AN OPTIMUM AMOUNT OF INFORMATION IN A
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
www.aip.org/physnews/preview; Ben Schumacher, Kenyon
College, 614-427-5832)
Max More, Ph.D.
more@extropy.org
http://www.primenet.com/~maxmore
President, Extropy Institute: exi-info@extropy.org, http://www.extropy.org
EXTRO 3 CONFERENCE on the future: http://www.extropy.org/extro3.htm