Forward:
PHYSICS NEWS UPDATE
The American Institute of Physics Bulletin of Physics News
Number 293 October 30, 1996
by Phillip F. Schewe and Ben Stein
A QUANTUM COMPUTER COULD TOLERATE ERRORS while carrying out
calculations, researchers at Los Alamos have now shown.
Computers that operated according to the rules of quantum
mechanics have the potential to perform powerful tasks (such as
factoring huge numbers) because of their radically different
approach to logic: unlike a conventional computer's bits, which exist
either as a 0 or a 1, a quantum bit (or "qubit") could not only exist
simultaneously as a 0 and a 1 but could interact with other qubits so
that its properties became "entangled" with those of the other qubits.
Yet some physicists argue quantum computers may be impossible to
achieve on a practical level because the slightest amount of noise
would destroy the entanglement and thus corrupt the state of the
qubits. Up to now, proposed "quantum error correction" schemes
have shown merely how to preserve the state of qubits. Now, Los
Alamos researchers (Raymond Laflamme, 505-665-3394) have
developed an algorithm for carrying out reliable calculations on a
"qubyte" made of 7 entangled qubits while accounting for the
possibility that one of the qubits is corrupt (upcoming paper in Phys
Rev Lett). Experimentally, quantum computing is regarded as a
long-term possibility: although quantum versions of logic gates have
been constructed (see Update #250), researchers are still working to
entangle more than two quantum systems at a time.
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