According to a press release (19 December 2001), researchers at IBM's Almaden Research Center have performed the world's most complicated quantum-computer calculation to date. They used a container full of billions of custom-designed molecules to create a seven-qubit quantum computer that solved a simple version of the numerical factoring problem at the heart of many of today's data-security cryptographic systems. Reporting their work in the 20 December 2001 issue of Nature, the team says they have provided the first demonstration of "Shor's Algorithm" — a method developed in 1994 by AT&T scientist Peter Shor for using a quantum computer to find a number's factors. Today, factoring a large number is so difficult for conventional computers — yet so simple to verify — that it is used by many cryptographic methods to protect data.
The simplest meaningful instance of Shor's Algorithm is finding the factors of the number 15, which requires a seven-qubit quantum computer. IBM chemists designed and made a new molecule that has seven nuclear spins — the nuclei of five fluorine and two carbon atoms — which can interact with each other as qubits, be programmed by radio frequency pulses and be detected by nuclear magnetic resonance (NMR) instruments similar to those commonly used in hospitals and chemistry labs. The IBM scientists controlled a vial of a billion billion (1018) of these molecules so they executed Shor's algorithm and correctly identified 3 and 5 as the factors of 15. "Although the answer may appear to be trivial, the unprecedented control required over the seven spins during the calculation made this the most complex quantum computation performed to date," a member of the research team said.
Additional coverage of the research can be found in the New York Times and an article from the San Francisco Chronicle reprinted on the Small Times website.