[1] Parallel Comp. Research Laboratory, Dept. of Elec. and Electronic Eng., Univ. of Western Australia, Nedlands, WA 6907, Australia
[2] Dept. of Cogn. and Ling. Sciences, Brown Univ., Providence, RI 02912, United States
[3] Natural Selection, 3333 N. Torrey Pines Ct., San Diego, CA 92037, United States
[4] Ctr. for Quantum Computer Technology, Dept. of Physics, Univ. of Queensland, St. Lucia, QLD. 4072, Australia
[5] Department of Computer Science, University of Colorado, Boulder, CO, United States
[6] Inst. of Advanced Computer Science, Leiden Univ., Niels Bohrweg 1, 2333 CA Leiden, Netherlands