# Mathematical Digest

### Short Summaries of Articles about Mathematics

in the Popular Press

"Qubit by Qubit: Building a better quantum computer," by Meher Antia and Peter G. Brown. *The Sciences*, May/June 1997, page 11.

Three years ago, AT&T Labs mathematician Peter Shor developed a "quantum computer" algorithm that could factor in a short period of time numbers 1,000 digits long---numbers far beyond the reach of conventional computers. Shor's work demonstrates the awesome potential of quantum computers, but their physical realization has remained elusive. A computer works by representing numbers and operations as strings of 0s and 1s. The idea of a quantum computer is to exploit the analogy between the "up or down" states in an atom's spin and the 0s and 1s of a computer. Attempts to do quantum computing on a single atom have proven difficult because of the problems associated with insulating the atom from its environment. This article describes the work of physicists Neil A. Gershenfeld and Isaac L. Chuang, who have attempted quantum computing with large collections of molecules, which provide a natural insulation for the atomic nuclei. They were able to exploit the redundancy of using many molecules, rather than a single atom.

*--- Allyn Jackson*