Atomic interferometers implemented to date have employed mechanical gratings or laser beams as the equivalent of an optical beam splitter. An alternative approach1 using diffraction from cleaved crystal surfaces is currently under investigation. The advantages of using crystal diffraction include a large (over 20 deg.) angular separation of the two beams and a simple, stable apparatus. Some design considerations and preliminary results, including diffraction measurements, from an apparatus under construction will be discussed.
Atomic interferometers implemented to date have employed mechanical gratings or laser beams as the equivalent of an optical beam splitter. An alternative approach1 using diffraction from cleaved crystal surfaces is currently under investigation. The advantages of using crystal diffraction include a large (over 20 deg.) angular separation of the two beams and a simple, stable apparatus. Some design considerations and preliminary results, including diffraction measurements, from an apparatus under construction will be discussed.
The key elements for atom interferometers are atomic beam splitters and recombiners. An atomic beam splitter separates a single atomic wave function into a superposition state corresponding to two center of mass wavepackets that propagate in different spatial directions and a recombiner reunites the atomic beams. We report here on the investigation of 1) an atomic beam splitter with large separation angle based on the optical Stern Gerlach effect, 2) an atomic mirror based on the reflection of atoms by different types of evanescent waves (a simple evanescent wave and a surface plasmon wave), 3) an atomic beam splitter realized by the partial spatial reflection of an atom by an evanescent wave and 4) diffraction of atoms by a standing evanescent wave.
Interference with atomic and molecular matter waves is a rich branch of atomic physics and quantum optics. It started with atom diffraction from crystal surfaces and the separated oscillatory fields technique used in atomic clocks. Atom interferometry is now reaching maturity as a powerful art with many applications in modern science. In this review the basic tools for coherent atom optics are described including diffraction by nanostructures and laser light, three-grating interferometers, and double wells on atom chips. Scientific advances in a broad range of fields that have resulted from the application of atom interferometers are reviewed. These are grouped in three categories: (i) fundamental quantum science, (ii) precision metrology, and (iii) atomic and molecular physics. Although some experiments with Bose-Einstein condensates are included, the focus of the review is on linear matter wave optics, i.e., phenomena where each single atom interferes with itself.
Abstract : An atom interferometer is constructed in which the atom waves are physically separated prior to being recombined. Fabricated transmission gratings are used as optical elements for the matter waves. Atom interferometers should be useful in studies of atomic properties, tests of basic quantum physics, for metrology, as rotation sensors, and perhaps ultimately as devices to make ultra- small structures using atom holograms. During the last year our atom interferometer has evolved from a rough plan to an essentially complete device. At present all the major components of the interferometer have been built, and tested at least once. The system will be given its first real try in the next year. Our interferometer consists of three 0.2 microns - period diffraction gratings equally spaced approx. 0.65 m apart in our atomic beam machine. The maximum separation of the beams will be approx. 60 microns. The first two gratings separate and redirect the atomic beam forming a standing wave interference pattern in the atomic flux at the third grating, which acts like a mask to sample this pattern. A principle technical obstacle is the mechanical vibrations of our machine which will blur the interference pattern.
Abstract Among the various areas of neutron optical research, neutron interferometry has provided some of the most challenging and spectacular developments. In most cases, separated coherent beams are used which are produced either by wavefront division (Young’s type) or by amplitude division (Mach− Zehnder type). These beams are subsequently coherently superposed after passing through regions of space where the neutron wavefunction is modified in phase and amplitude by various interactions: nuclear, magnetic, electromagnetic, gravitational, or by geometry and topology (as in Aharonov−Bohm-type experiments). Various types of neutron interferometers that have been tested are shown in Fig. 2.1. The first neutron interferometer was based upon wavefront division and biprism deflection, but it had several constraints for interferometric applications mainly due to the small beam separation (100 μm) (Maier-Leibnitz and Springer 1962). Nevertheless, this method gained further interest for diffraction experiments from macroscopic objects and for the detection of weak interaction effects where the long flight paths (10 m) enhance the sensitivity for the measurements of these effects (Gähler et al. 1980; Klein et al. 1981a). The perfect-crystal interferometer (Rauch et al. 1974) provides widely separated coherent beams and has become a standard method for advanced neutron optical investigations. The development of diffraction and phase grating interferometers extended the Mach-Zehnder interferometer method to very slow neutrons (loffe et al. 1985; Gruber et al. 1989). The superposition of spin-up and spin-down states in the longitudinal direction provides the basis for Larmor and Ramsey interferometry, where no lateral beam splitting is necessary. The well-known spin-echo systems (Mezei 1972) and zero-field spin-echo systems (Gähler and Golub 1987; Dubbers et al. 1989) are examples of such interferometers, which also play an important role in atom interferometry (Bord é 1989; Kasevich and Chu 1991; Riehle et al. 1991).
Atom and, more recently, molecule interferometers are used in fundamental research and industrial applications. Most atom interferometers rely on gratings made from laser beams, which can provide high precision, but cannot reach very short wavelengths and require complex laser systems to function. Contrary to this, simple monolithic interferometers cut from single crystals offer (sub) nanometer wavelengths with an extreme level of stability and robustness. Such devices were conceived and demonstrated several decades ago for neutrons and electrons. Here, we propose a monolithic design for a thermal-beam molecule interferometer based on (quantum) reflection. We show, as an example, how a reflective, monolithic interferometer (Mach-Zehnder type) can be realized for a helium beam using $\mathrm{Si}(111)\text{\ensuremath{-}}\mathrm{H}(1\ifmmode\times\else\texttimes\fi{}1)$ surfaces, which have previously been demonstrated to act as very robust and stable diffractive mirrors for neutral helium atoms.
Atom interferometry, in which atomic waves are coherently split and later recombined, has been called the Swiss Army knife of atomic physics because of its numerous applications [1]. Atom interferometers can be used to study gravity, observe quantum effects, and measure fundamental constants. However, the spitting of atomic beams has always been a challenging task. Several beam splitters for atoms have been developed over the years, many of which rely on complex, high-powered lasers whose photons collide with atoms to steer them along separate beam paths. Paul Hamilton and colleagues at the University of California, Berkeley, have built a more versatile beam splitter by using, for the first time, an optical cavity [2]. Laser pulses bounce back and forth inside the cavity, increasing the effective power in standing waves of light and reducing imperfections in the wave fronts. The light concentration within the cavity allows the use of common low-powered lasers for the initial pulses. The new design may lead to a universal atom interferometer with optical gratings that works with a wide range of atomic species.