1. School of Physics, University of Melbourne 1 , Melbourne, Victoria 3010, Australia
2. Centre for Quantum Computing and Communication Technology, University of New South Wales 2 , Kensington, New South Wales 2052, Australia
3. National Institutes for Quantum Science and Technology 3 , 1233 Watanuki, Takasaki 370-1292, Japan
4. Department of Materials Science, Tohoku University 4 , 6-6-02 Aramaki-Aza, Aoba-ku, Sendai 980-8579, Japan
5. School of Science, RMIT University 5 , Melbourne, Victoria 3001, Australia