1. Infineon technologies AG, Corporate Research CPR ST, Building 10-562, Otto-Hahn-Ring 6, 81730 München, Germany
2. IBM Zürich Research Laboratory, Säumerstrasse 4, CH-8803 Rüschlikon, Switzerland
3. Research Laboratory of Electronics, Massachusetts Institute of Technology, Building 36-865, 77 Massachusetts Avenue, Cambridge, MA 02139, USA