1. Department of Physics, Brandeis University , 415 South St., Waltham, 02453 MA , USA
2. Department of Physics, University of California , Santa Barbara, 93106 CA , USA
3. Department of Computing and Mathematical Sciences, California Institute of Technology , 1200 E California Blvd. Pasadena, 91125 CA , USA
4. Division of Biology and Biological Engineering, California Institute of Technology , 1200 E California Blvd., Pasadena, 91125 CA , USA