In situ single-atom array synthesis by dynamic holographic optical   tweezers
  Cooling and trapping of atoms by light has enabled one to build and manipulate quantum systems at the single atom level. Such a bottom-up approach becomes one of the fascinating challenges toward scalable and highly controllable quantum systems, e.g., a large-scale quantum information machine. Their implementation requires crucial pre-requisites: scalablity, site distinguishability, and reliable single-atom loading into sites. The widely adopted methods satisfies the two former conditions relatively well, but the last condition, filling single atoms onto individual sites, relies mostly on the probabilistic loading, implying that loading a pre-defined set of atoms in given positions will be hampered exponentially. Two approaches are readily thinkable to overcome this issue: increasing the single-atom loading efficiency and relocating abundant atoms into unfilled positions. Realizing the relocation is directly related to how many atoms can be transportable in a designer way. Here, we demonstrate a dynamic holographic single-atom tweezers with unprecedented degrees of freedom of 2N. In a proof-of-principle experiment conducted with cold rubidium atoms, simultaneous rearrangements of N=9 single atoms are successfully performed. This method may be further applicable to deterministic N single-atom loading, coherent transport, and controlled collisions. 
Hyosub Kim, Woojun Lee, Han-gyeol Lee, Hanlae Jo, Yunheung Song and   Jaewook Ahn
physics.atom-ph physics.optics