[1] Nanyang Technol Univ, Sch Phys & Math Sci, Singapore 637371, Singapore
[2] Nanyang Technol Univ, Complex Inst, Singapore 637335, Singapore
[3] Univ Cambridge, Dept Appl Math & Theoret Phys, Cambridge CB3 0WA, England
[4] Univ Maryland, Joint Ctr Quantum Informat & Comp Sci, College Pk, MD 20742 USA
[5] Natl Univ Singapore, Ctr Quantum Technol, 3 Sci Dr 2, Singapore 117543, Singapore