1. Department of Physics, Indian Institute of Science, Education and Research–Bhopal, Bhopal Bypass Road, Bhauri, Bhopal 462066, India
2. Optics & Quantum Information Group, The Institute of Mathematical Sciences, HBNI, C.I.T. Campus, Taramani, Chennai-600113, India
3. Theoretical Statistics and Mathematics Unit, Indian Statistical Institute, 7, S.J.S. Sansanwal Marg, New Delhi, 110 016, India
4. INSA Emeritus Scientist, The Indian National Science Academy, New Delhi, 110 002, India