1. School of Physics & Astronomy, University of Birmingham, Birmingham, B15 2TT, United Kingdom
2. State Key Laboratory
of Precision
Measurement Technology and Instruments, Department of Precision Instruments, Tsinghua University, Beijing 100084, China
3. Department of Physics, University of Paderborn, Warburger Straße 100,
D-33098 Paderborn, Germany
4. Department of Physics, Hong Kong Baptist University, Hong Kong