[1] Univ Porto, Dept Fis & Astron, Fac Ciencias, Rua Campo Alegre s-n, P-4169007 Porto, Portugal
[2] Univ Porto, Ctr Fis Univ Minho & Porto CF UM UP, P-4169007 Porto, Portugal
[3] Univ Porto, Lab Fis Mat & Tecnol Emergentes LaPMET, P-4169007 Porto, Portugal
[4] Univ York, Dept Phys, York YO10 5DD, England
[5] Univ York, York Ctr Quantum Technol, York YO10 5DD, England
[6] Univ Minho, Ctr Fis Univ Minho & Porto CF UM UP, Campus Gualtar 4710-057, Braga, Portugal
[7] Univ Minho, Lab Fis Mat & Tecnol Emergentes LaPMET, Campus Gualtar 4710-057, Braga, Portugal
[8] Imperial Coll London, Dept Mat, London SW7 2AZ, England