We demonstrate single-site addressability in a two-dimensional optical lattice with 600 nm lattice spacing. After loading a Bose-Einstein condensate in the lattice potential, we use a focused electron beam to remove atoms from selected sites. The patterned structure is subsequently imaged by means of scanning electron microscopy. This technique allows one to create arbitrary patterns of mesoscopic atomic ensembles. We find that the patterns are remarkably stable against tunneling diffusion. Such microengineered quantum gases are a versatile resource for applications in quantum simulation, quantum optics, and quantum information processing with neutral atoms.

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A stable, continuous wave, single frequency ber ampli er large mode double clad ber cooled to liquid nitrogen temper ampli ed light is frequency quadrupled to 254 nm and used for mode, plane-polarized ytterbium-doped ber master oscillator power ampli er source with 264 W of output Erbium-Doped Fiber Ampli ers: Principles and Applicationoped large-core ber laser with 1.36 kW continuous-

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We demonstrate the first cw two-photon absorption laser-induced stimulated emission. The 7(1)S(0)-6(1)P(1) transition in mercury at a 1014 nm wavelength is used, and selective lasing of different isotopes is observed.