BY ANNE-MARIE CORLEY // SEPTEMBER 2009
Photo: Jonathan Matthews/University of Bristol
3 September 2009—Modern cryptography relies on the extreme difficulty computers have in factoring huge numbers, but an algorithm that works only on a quantum computer finds factors easily. Today in Science, researchers at the University of Bristol, in England, report the first factoring using this method—called Shor’s algorithm—on a chip-scale quantum computer, bringing the field a tiny step closer to realizing practical quantum computation and code cracking.
Quantum computers are based on the quantum bit, or qubit. A bit in an ordinary computer can be either a 1 or a 0, but a qubit can be 1, 0, or a ”superposition” of both at the same time. That makes solving certain problems—like factoring—exponentially faster, because it lets the computer try many more solutions at once. The race is on to find the ideal quantum computer architecture, with qubit contenders that include ions, electrons, superconducting circuits, and in the University of Bristol’s case, photons.