1. Department of Electrical and Systems Engineering University of Pennsylvania Philadelphia PA 19104 USA
2. Department of Physics and Henes Center for Quantum Phenomena Michigan Technological University Houghton MI 49931 USA
3. Department of Physics Lancaster University Lancaster LA1 4YB UK
4. Department of Electrical Engineering The State University of New York at Buffalo Buffalo NY 14260 USA
5. Department of Materials Science and Engineering University of Pennsylvania Philadelphia PA 19104 USA