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.
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.
We propose and demonstrate a new scheme for atom interferometry, using light pulses inside an optical cavity as matter wave beam splitters. The cavity provides power enhancement, spatial filtering, and a precise beam geometry, enabling new techniques such as low power beam splitters (<100 μW), large momentum transfer beam splitters with modest power, or new self-aligned interferometer geometries utilizing the transverse modes of the optical cavity. As a first demonstration, we obtain Ramsey-Raman fringes with >75% contrast and measure the acceleration due to gravity, g, to 60 μg/sqrt[Hz] resolution in a Mach-Zehnder geometry. We use >10(7) cesium atoms in the compact mode volume (600 μm 1/e(2) waist) of the cavity and show trapping of atoms in higher transverse modes. This work paves the way toward compact, high sensitivity, multiaxis interferometry.
Sometimes you have to think outside the box. Faced with some of the universe’s most stubborn mysteries, such as the identity of dark matter, physicists are turning to a technique that employs the weird laws of quantum mechanics: atom interferometry.
Atom interferometers allow the study of various physical phenomena by splitting atom waves using a nanograting, such as this one. Composed of silicon nitride, this grating, imaged with a scanning electron microscope, has a period of 100 nm. Image courtesy of Alex Cronin (University of Arizona, Tucson, AZ).
This method, which takes advantage of the fact that quantum particles behave like waves, crashes these waves together to study gravity and atoms, and to pinpoint the value of fundamental physical constants. The hope is that the relatively new technique can be developed into a measurement tool of unprecedented sensitivity to test these phenomena, as well as to reveal potentially unseen particles and forces.
“It has a lot of untapped potential,” says Holger Muller of the University of California, Berkeley. But he admits, “Honestly, what drew me mostly was that it’s extremely challenging experimentally ... and I love an experimental challenge.”
The idea that particles can behave as waves that can be sloshed together dates back to the birth of quantum mechanics about a century ago. But it took decades to test because atoms have much shorter inherent wavelengths—about a …
The development of atom interferometry in the last few decades has led to high precision measurements of inertial effects and tests of fundamental physics. New methods for higher sensitivity atom interferometers (AIs) are being explored, particularly the interrogation of atoms with optical cavities [1]. Its benefits would be higher optical power allowing large momentum transfer beam splitters, and possibly cleaner and controlled phase profiles. However high sensitivity AIs require long interrogation times, which combined with cold atom expansion, bring the challenges of large waists in cavities.
The Optics and Interferometry with Atoms symposium provided an opportunity for a general audience to learn about develop ments of this new field.The goal of atom optics is to do with atoms what usual optics does with photons, e.g., reflection, refraction, focusing, interference.Two techniques have been used up to now in order to act on atomic trajectories: interaction with quasiresonant laser light and interaction with diffracting fabricated microstructures.In his introduction, J. Mlynek (Constance) explained that several basic elements of atom optics have already been demonstrated (mirrors, lenses, beam splitters, interferome ters) but many improvements are still expec ted.He also anticipated exciting applications.For instance, atomic microprobes will use particles much less energetic that electronic microscopes (meV instead of KeV) and ato mic interferometers will permit highly sensi tive measurements of gravitational or Inertial effects, both for detection purposes and for fundamental tests of relativity.An example of an atomic interferometer, based on a idea by C. Borde using Ramsey fringes, was described F. Riehle (PTB, Braunschweig).Sensitivity to rotations has been demonstrated, light-shifts measured, and a new experiment based on cold, trap ped atoms instead of an atomic beam is in progress.J. Robert (Paris-Nord) reviewed the basic principles of Stern-Gerlach inter ferometry for application to the so-called "scalar Bohm-Aharonov effect"; a new scheme involving four interaction zones should yield new results.Finally J. Dalibard (Paris) described the atomic cavity based on a concave mirror for bouncing atoms (Fig. 1).It opens the path to the observation of multiple atomic multiple interferences, i.e., observing the modes of an atomic cavity.The ultimate goal would be to accumulate many bosonic atoms in the same mode to realise the atomic equivalent of a laser mode filled with many photons.
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.
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.