Quantum physics ascribes wave-like properties to material objects in order to correctly predict their behavior. Accordingly, atoms and molecules exhibit interference phenomena (diffraction, refraction, etc.) analogous to sound, light, or water waves. In fact, an entire field of "atom optics" has emerged to measure and exploit this wave-like behavior. The characteristic wavelength of an atom/molecule (its "de Broglie" wavelength) is typically under 0.1 nm, about the size of an atom, and some 10,000 times smaller than the wavelength of visible light. Atom optics therefore allows researchers to observe and even influence material interactions on the atomic scale (nano- or sub-nanometer). It often makes use of nanofabricated experimental components. The requested funding will procure an experimental apparatus that employs nanoscale diffraction gratings to split and recombine a beam of atoms/molecules, to make atom wave interference patterns, exactly as would be done using light waves in a conventional optical interferometer. This yields atom optics interference patterns that shift in position when the molecules in one beam path are perturbed relative to those in the other, giving a powerful tool for scientific measurements and technological applications. Atom optics interferometers can be employed as motion sensors (rotation, acceleration) or as scientific tools to measure a broad spectrum of physical and materials properties (gas-gas interactions, gas-surface interactions, precision metrology). Given the minute wavelength of the atom/molecule, atom interferometry offers vastly improved resolution and sensitivity over optical interferometry, in addition to its atomic sensitivity. Matter wave interferometry is a very striking manifestation of quantum physics, providing a superb vehicle for education and public outreach. The apparatus is by far the most advanced of its kind that ever been built, well over a million dollars worth of equipment that would be difficult or impossible to construct in the USA. It is being made available to the P.I's by special arrangement with the German Max-Planck-Society at essentially no cost.
A universal atomic and molecular beam interferometer will enable new measurements in surface science, chemical physics, and quantum optics. By combining a detector that works for every atomic and molecular species with an interferometer based on nanostructure diffraction gratings, the applications of de Broglie wave interferometry will be greatly expanded to address several new scientific goals. Atom interferometers based on nanostructure gratings have recently proven their ability to detect minute perturbations to atomic de Broglie waves. Examples of quantities already measured with this technique include: (1) the polarizability of atoms, (2) the strength of atom-surface van der Waals forces, (3) the rotation rate of a platform, and (4) the rate of quantum decoherence from scattering atoms or photons. In addition, atom optics with supersonic beams and nanostructures have demonstrated (5) coherent quantum reflection of atom waves, (6) generation of atom holograms, (7) focusing with Fresnel zone plates, and (10) the first quantitative detection of 4He2 molecules. The opportunity to generalize these measurement techniques for all gaseous atoms and molecules is now available in the form of a new apparatus. Exploiting the principle of de Broglie wave interferometry for multiple atomic and molecular species will have several benefits. The tensor polarizability of dimer molecules, the atom-surface interaction strength for polar molecules, and the rate of quantum decoherence for complex molecules are all important quantities that merit several series of experiments in the fields of chemical physics, surface science and quantum optics. The advancement of nanotechnology as well as atomic and molecular beam science and education relies on new applications such as molecular beam interferometry. Collaborations between the University of Arizona, and Arizona State University and the German Max-Planck-Society will also be strengthened by this instrumentation for materials research.
