1. Université Clermont Auvergne, Clermont Auvergne INP, CNRS, Institut Pascal, F-63000 Clermont-Ferrand, France
2. IBM Research Europe─Zürich, Saumerstrasse 4, 8803 Rüschlikon, Switzerland
3. Department of Electronic and Electrical Engineering, University of Bath, Bath BA2 7AY, United Kingdom
4. Department of Engineering Physics, McMaster University, Hamilton, Ontario L8S4L7 Canada