1. School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, United States
2. Hewlett-Packard Laboratories, Palo Alto, California 94304, United States
3. University of Waterloo, Waterloo, ON N2L
3G1, Canada
4. Department of Electrical
and Computer Engineering, University of Wisconsin—Madison, Madison, Wisconsin 53706, United States
5. Singapore Institute of Manufacturing Technology, 71 Nanyang Drive, Singapore 638075, Singapore