Experimental Demonstration of Single-Site Addressability in a Two-Dimensional Optical Lattice

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.

Figure 1

Electron microscope image of a Bose-Einstein condensate in a 2D optical lattice with 600 nm lattice spacing (sum obtained from 260 individual experimental realizations). Each site has a tubelike shape with an extension of $6\mu \mathrm{m}$ perpendicular to the plane of projection. The central lattice sites contain about 80 atoms.

Figure 2

Patterning a Bose-Einstein condensate in a 2D optical lattice with a spacing of 600 nm. Every emptied site was illuminated with the electron beam (7 nA beam current, 100 nm FWHM beam diameter) for (a),(b) 3, (c),(d) 2, and (e) 1.5 ms, respectively. The imaging time was 45 ms. Between 150 and 250 images from individual experimental realizations have been summed for each pattern.

Figure 3

Single-shot image of the central part of the cloud. Each dot corresponds to a detected ion (800 in total). The integrated data along both lattice axes are shown on the side (black line). A fit to the data (red line) is used to determine the position of the lattice with an uncertainty of $\pm 30\mathrm{nm}$.

Figure 4

Drifts of the optical lattice. (a),(b) Appearance of lattice positions (translated into a phase between 0 and $2\pi$) for 300 experimental runs, corresponding to 1.5 hours of measurement time. The lattice vector is (a) parallel or (b) perpendicular to the condensate axis. (c),(d) Illustration of the drift dynamics for the data in (a) and (b). Each lattice position is converted into a unity vector whose direction is given by the corresponding phase. All 300 vectors are successively plotted. A perfectly stable lattice would result in a straight line. Small long term drifts appear as large circles, while short term fluctuations lead to a pronounced zigzag shape.

Figure 5

Depletion time constant for different positions of the electron beam with respect to the lattice site. At all distances we find an exponential decay. For central hits, the population decays with a time constant of $100\mu \mathrm{s}$. The inset shows the depletion at a distance of 90 nm. The solid line is a fit with an exponential decay. The offset of 10% represents atoms that are refilling the lattice site between the end of the preparation and the instant of imaging.