[1] Univ Maryland, Dept Phys, Condensed Matter Theory Ctr, College Pk, MD 20742 USA
[2] Univ Maryland, Joint Quantum Inst, College Pk, MD 20742 USA
[3] CALTECH, Dept Phys, Inst Quantum Informat & Matter, Pasadena, CA 91125 USA
[4] Monash Univ, Sch Phys, Melbourne, Vic 3800, Australia