1. University of California San DiegoUCSD)Physics Department 9500 Gilman Dr. La Jolla, CA 92093-0319 USA
2. Molecular Nano-Optics and Spins (MoNOS)Huygens LaboratoryLeiden University P.O. Box 9504 2300 RA Leiden The Netherlands
3. Institut Lumière MatièreCNRS UMR5306Université Lyon 1Université de Lyon 69622 Villeurbanne CEDEX France