Number 293 (Story #2), 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.