H. T. Ng, C. K. Law and P. T. Leung, Phys. Rev. A 68, 013604 (2003).
 H. T. Ng and Shih-I Chu, Phys. Rev. A 84, 023629 (2011).  H. T. Ng and Shih-I Chu, arXiv:1111.0529.
Dr. Ho-Tsang Ng obtained his PhD in physics at The Chinese University of Hong Kong (CUHK) in 2005. He then was awarded the Croucher Foundation fellowship to support his postdoctoral research at the University of Oxford (2005-2007). He was a researcher at the University College London (UCL) (2007-2009) and RIKEN (2009-2010). Now he is a postdoctoral researcher at the National Taiwan University.