“Atom Optics” becomes a reality
from the first-assembler-in-vacuum-or-liquid? dept.
Senior Associate Alison Chaiken writes "A recent new message from the ever-wonderful (and free) "Physics News Update" highlights progress in the developing field of "atom optics". When last we left our heroes, Jurg Schmiedmayer and colleagues from the University of Innsbruck had used electromagnetic fields and logic circuits on an IC to guide beams of atoms with high resolution, implying an obvious extension to a computer-controllable high-precision atom placement technique. Now several groups in Europe have come up with new innovations that could lead to the "atomic ink-jet printer" and the "atom-coupled device." Once folks start moving Bose-Einstein condensates this way, all kinds of exciting advanced fabrication techniques may become possible. I'm still betting that the first "assembler" will be an ultra-high vacuum chamber with a bunch of lasers and well-controlled electromagnetic fields. I'd be thrilled if all you organic chemists can prove me wrong!" Read More for the Physics News Update article. PHYSICS NEWS UPDATE
The American Institute of Physics Bulletin of Physics News
Number 516 December 14, 2000 by Phillip F. Schewe and Ben Stein
INTEGRATED ATOM OPTICS. What electrons are for electronics and photons are for photonics, neutral atoms will be for some future "atom-tronics." That is, chilled trapped atoms will be manipulated on or near a planar microchip in such a way as to process information, especially if atoms in their wavelike manifestation can be brought into interference with each other. In recent years there have been many advances in this hot research area: atoms have been guided along wires (Update 416), through waveguides (Update 469), and steered around (and slightly above) a microchip under the influence of patterned currents in the nearby surface (Update 486). And as for atom interferometry, it has been used to measure previously unknown scattering properties of matter waves (Update 209), detect subtle changes in gravitational gradients (Update 384), and used to demonstrate the wave properties of C-60 molecules (Update 453).
Three new innovations come from labs in Germany, Austria, and France. Joerg Schmiedmayer (49-622-154-9325, joerg.schmiedmayer@physl.uni-heidelberg.de) of the University of Heidelberg (recently moved from the University of Innsbruck) and his colleagues have achieved essentially a planar beamsplitter by guiding atoms a few microns above a microstructured surface (an Atom Chip) along a Y-shaped magnetic wave guide (http://www.aip.org/physnews/graphics for figure). Depending on how current is sent through the Y, atoms can be directed either to the left arm, to the right arm, or to both output arms with any desired ratio. By the way, the atoms themselves can be positioned with 100-nm control (the accuracy of the nanofabrication techniques) and can be made to sort of go around bends; as with light in fibers, there is some loss of atoms if their trajectory is bent too sharply (Cassettari et al., Physical Review Letters, 25 December 2000).
Another group, at the Max Planck Institute in Munich, moves atom clouds around and above a lithographic conductor pattern on a wafer, what they call a "magnetic conveyor belt." Unlike a guide, the conveyor belt transports atom clouds (800 nm across) in separate potential wells, keeping them confined in all three dimensions, allowing velocity control and ultra-precise positioning. The conveyer belt would be useful for doing interferometry experiments (especially if Bose-Einstein condensates could be transported), for "atomic ink jet printing," and as part of some future "atom coupled device," which would use atoms for performing measurements much as charge coupled devices (CCD) use electrons for imaging light fields (Hansel et al., upcoming article in Physical Review Letters; Wolfgang Hansel, wolfgang.haensel@mpq.mpg.de, 49-892-180-3937).
Meanwhile at the University of Paris-South, Laurence Pruvost (33-169-35- 2100, laurence.pruvost@lac.u-psud.fr) and her students have generated a beam of guided rubidium atoms from a magneto-optic trap (MOT). The atoms are shepherded by the electric fields of a laser beam. The atoms then meet with a second beam of laser light at an oblique angle. The crossed laser beams generate two collimated atom beams making an angle of 7 degrees. Because the beamsplitter is energy selective, it might be used to help evaporate atoms of higher energy from clouds in an atom trap (Houde et al., Physical Review Letters, 25 Dec.)
December 21st, 2000 at 7:38 PM
caveats
You will not get better than few-nm resolution, and you will get basically incoherent deposition. If the guiding field is optical, the resolution will not be a factor of >1000 finer than the wavelength, which is what you would need in order to achieve atomic specificity. In the case of guidance by wires or IC traces as described in the news item, the resolution will always be poorer than that of the guiding structures. Perhaps a three-dimensional focusing/aperture structure fabricated to atomic specifications (e.g. by an assembler) might be able to deliver atoms with angstrom precision. However, if it were not cold, the atoms would not be, either. In that case, it would be hard to get them to stick in just the right places with 100% yield, and you would need some way of probing to determine when a good bond had been made. This doesn't sound like a way to get around the difficulties of making a first assembler.
Throughput? Resolution? This might be another useful tool for the compleat nanotech lab, but it's not going to be a way of making large-scale products.
Probably intended for quantum computing; however, schemes of this sort have been plagued by heating and decoherence due to fluctuating fields in the electrodes.
For the same reason (heating by the electrodes), it is probably not possible to move BECs around "a few microns above a microstructured surface" as described. BECs are formed and manipulated in optical traps, so again I don't see how you will get angstrom resolution.