PerspectivePhysics

Quantum Walks Through a Waveguide Maze

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Science  17 Sep 2010:
Vol. 329, Issue 5998, pp. 1477-1478
DOI: 10.1126/science.1195446

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Summary

Two of the major goals of the field of quantum information are to build a quantum computer—one that processes bits of information according to quantum rather than classical rules—and to figure out what to do with one, once you have it. The field that encompasses the latter goal is quantum algorithms. It has not been easy to develop quantum algorithms, but within the past 10 years, a fruitful approach has arisen based on what are known as quantum walks, which in the classical world are the basis for a description of diffusion processes. On page 1500 of this issue, Peruzzo et al. (1) describe a device they have built that substantially improves our ability to perform quantum walks. They used it to follow two photons that are performing a quantum walk along a line.