David A. Kokorowski

From Single- to Multiple-Photon Decoherence in an Atom Interferometer

We measure the decoherence of a spatially separated atomic superposition due to spontaneous photon scattering. We observe a qualitative change in decoherence versus separation as the number of scattered photons increases, and verify quantitatively the decoherence rate constant in the many-photon limit. Our results illustrate an evolution of decoherence consistent with general models developed for a broad class of decoherence phenomena.

Glory oscillations in the index of refraction for matter waves.

We have measured the index of refraction for sodium de Broglie waves in gases of Ar, Kr, Xe, and N2 over a wide range of sodium velocities. We observe glory oscillations--a velocity-dependent oscillation in the forward scattering amplitude. An atom interferometer was used to observe glory oscillations in the phase shift caused by the collision, which are larger than glory oscillations observed in the cross section. The glory oscillations depend sensitively on the shape of the interatomic potential, allowing us to discriminate among various predictions for these potentials, none of which completely agrees with our measurements.

Atom optics: Old ideas, current technology, and new results

Atom optics is the coherent manipulation of the atomic matter waves originally postulated by the developers of quantum mechanics. These pioneers also proposed the use of stimulated light forces to manipulate particles. These ideas have been combined with current technology to produce the field of atom optics. This, in turn, has shed new light on old quantum problems like the which way problem and the origins of quantum decoherence. Bose Einstein condensates combine naturally with atom optics to produce new results such as the coherent amplification of matter waves. This review of atom optics traces these connections.

Determining the density matrix of a molecular beam using a longitudinal matter wave interferometer

Two separated oscillatory fields, if tuned to different frequencies, can generate or interrogate longitudinal momentum coherences in a beam of two-state particles. We demonstrate that use of differentially detuned separated oscillatory fields is an efficient method to determine the longitudinal density matrix of a particle beam.

Optics and Interferometry with Atoms and Molecules

Publisher Summary This chapter discusses recent accomplishments in the atom and molecular optics and interferometry at MIT. The chapter begins with a discussion of the details of an experimental apparatus and gives an overview of recent accomplishments in atom and molecular optics. It then describes the atom and molecule interferometer, which is unique in that the two interfering components of the atom wave are spatially separated and can be physically isolated by a metal foil. The interferometer is especially well suited for the study of atomic and molecular properties as it enables one to apply different interactions to each of the two components of the wave function, which in turn permits spectroscopic precision in the study of interactions that shift the energy or phase of a single state of the atom. The chapter also describes an experiment in which this capability is used to determine the ground state polarizability of sodium to 0.3%—an order of magnitude improvement—by measuring the energy shift due to a uniform electric field applied to one component of the wave function. The chapter also provides an overview of the relativistic effects in electromagnetic interactions, and differential force interferometry.

Longitudinal quantum beam tomography

We propose an experiment to determine the density operator for the longitudinal quantum state of an atomic beam. The method is based on tomographic reconstruction of the Wigner function via a set of measured probability distributions for the phase-space rotated position operator. The time evolution of the Wigner function in free space effectively performs the required phase-space rotation. We propose a state-selective time-dependent technique for measuring longitudinal probability distributions.

Atom Interferometers and Atomic Coherence

Atom interferometers are powerful tools for the study of fundamental issues in quantum mechanics. This paper describes the use of our atom interferometer [1] for an experimental realization of Feynmans gedanken experiment in which the observation of photons scattered off of particles emerging from a double slit is used to obtain which path information. This determination, in principal, of the particles path, destroys any interference effects downstream. The interference can be regained by observing only those particles which scatter a photon into a small range of final directions.

Longitudinal Atom Interferometry

A detuned, radiofrequency field interacting with atoms in an atomic beam constitutes a beamsplitter in longitudinal momentum space. Using such beamsplitters, we have constructed a longitudinal atom interferometer in a generalization of Ramseys classic SOF configuration. This interferometer is well-suited to studying the longitudinal coherence properties of matter-wave beams. We report on two such experiments, including a deconvolution of the longitudinal density matrix of an atomic beam, and a search for longitudinal coherences coming from our supersonic beam source.

Atomic beam propagation effects: index of refraction and longitudinal tomography

We present initial measurements of the dispersive index of refraction for sodium matter waves passing through argon. In addition, we describe a novel scheme for performing tomography on the longitudinal quantum state of particles in an atomic beam.

Interferometry with atoms and molecules: a tutorial

Since the first interferometers for atoms and molecules were demonstrated in 1991, they have already been applied to measure atomic and molecular properties, to investigate fundamental aspects of quantum mechanics, and to measure inertial motion. This tutorial is designed to introduce those with a vague understanding of optical interferometers to atom interferometry. We outline the basic theory needed to calculate the observed phase shift, indicate how this phase shift is experimentally determined, and then describe how the phase shift is found in two particular cases: phase shifts caused by application of a uniform electric field to atoms on one side of the interferometer, and phase shift arising from the presence of a gaseous medium through which the atom wave on one side of the interferometer must propagate. We illustrate this presentation with a description of our three grating interferometer, including data taken with it.