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By levitating a tiny, nano-sized diamond using light, physicists in the US and Finland have created a controllable quantum system that has optical, mechanical and spin degrees of freedom. Based on a single nitrogen vacancy (NV) defect in the diamond, the system could be used in devices that measure extremely weak forces – or even to create Schrödinger's cat states.

 

Johnston diamonds

 

NV defects occur in diamond when two adjacent carbon atoms are replaced by a nitrogen atom and an empty lattice site. One type of NV (NV) is of great interest to physicists building quantum devices because its spin state (–1, 0 or +1) can be determined very easily using light. Furthermore, NVs are well isolated from their surroundings, which means that their spin states – unlike those of most other solid-state systems – keep their quantum nature for relatively long times.