M. A. Armen, J. K. Au, J. K. Stockton, A. C. Doherty, and H. Mabuchi, “Adaptive homodyne measurement of optical phase,” Phys. Rev. Lett. 89, 133602, (2002); featured in “Editor’s Choice column of Science Magazine, 297, 2171 (2002). PDF quant-ph/0204005 online