Showing papers on "Atom interferometer published in 1997"

Precision Rotation Measurements with an Atom Interferometer Gyroscope

Abstract: We report the demonstration of a Sagnac-effect atom interferometer gyroscope which uses stimulated Raman transitions to coherently manipulate atomic wave packets. We have measured the Earth's rotation rate, and demonstrated a short-term sensitivity to rotations of $2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}(\mathrm{rad}/\mathrm{s})/\sqrt{\mathrm{Hz}}$.

Rotation Sensing with an Atom Interferometer

Abstract: We have measured the phase shift induced by rotation of an atom interferometer at rates of $\ensuremath{-}2$ to $+2$ earth rates and obtained $1%$ agreement with the predicted Sagnac phase shift for atomic matter waves. The rotational rms noise of our interferometer was $42$ milliearth rates for $1$ sec of integration time, within $9%$ of shot noise. The high sensitivity and agreement of predicted and measured behavior suggest useful future scientific applications of atom interferometers as inertial sensors.

Optics and Interferometry with Atoms and Molecules

Abstract: 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.

Time-Domain de Broglie Wave Interferometry

Abstract: We report the development of an atom interferometer that uses optical standing waves as phase gratings and operates in the time domain. The observed signal is entirely caused by the wave nature of the atomic center-of-mass motion. The opportunities to measure recoil frequency and gravity acceleration are demonstrated.

Precision atom interferometry

Abstract: The basic physical principles behind atom interferometers based on optical pulses of light are summarized. This method of atom interferometry is based on measurements in the time and frequency domain and is an inherently precise measurement technique. After a brief discussion of some of the important technical requirements for good fringe accuracy and visibility, we describe an interferometer that has measured the acceleration of an atom due to gravity with a resolution better than one part in 10 10 . We project that the absolute accuracy of our measurement will be of the order of a few parts in 10 9 . We also describe an interferometer experiment that measures the recoil energy shift of an atom when it absorbs a photon. When combined with the value of the Rydberg constant and the mass ratios M Cs /m p and m p /m e , one can obtain a value for α, the fine structure constant. Currently, we have an experimental resolution Δα/α ∼ 10 -8 after two hours of integration time and are studying the systematic effects that affect the measurement.

The implications of microwave background anisotropies for laser-interferometer-tested gravitational waves

Abstract: The observed microwave background anisotropies in combination with the theory of quantum mechanically generated cosmological perturbations predict a measurable amount of relic gravitational waves in the frequency intervals tested by LISA and ground-based laser interferometers.

Precision Atom Interferometry with Light Pulses

Abstract: Publisher Summary This chapter presents the theory of atom interferometry based on optical pulses. The interference of magnetic spin states used in magnetic resonance and later generalized to electronically excited states of atoms is a mature field. Consequently, the wealth of theoretical and experimental techniques that have been developed for over a half century can be exploited for atom interferometry. The fundamental starting point of an atom interferometry based on optical pulses is that light can be used to detect the motion of atoms. Changes in the velocity of individual atoms are registered essentially through changes in the frequency of atomic resonances due to the Doppler effect. This chapter is concerned mainly with the high precision interferometers with long measurement times. It discusses interference of atoms in the ground state and analyzes momentum transfer based on stimulated Raman transitions. The chapter also discusses several applications of these techniques such as in gravitational acceleration, gradiometry, and gyroscopes.

Principles of calculating alignment signals in complex resonant optical interferometers

Abstract: In the long-baseline laser interferometers that are now under construction to measure gravitational waves, the alignment of the optical components with respect to the incoming laser beam is crucial for maintaining maximum phase sensitivity. We present a basic formalism to calculate the effects of misalignment and beam distortions analytically in an arbitrarily complex optical system, including coupled cavities and Michelson interferometer configurations coupled with cavities. The electromagnetic field is decomposed into a superposition of higher-order Gaussian modes, while misaligned and distorting optical components along with free-space propagators are represented by matrix operators that act on the state vectors in this basis. We show how to deduce useful alignment signals generally, in order to design angular control systems.

Interferometer with air turbulence compensation

Abstract: An improved interferometer measuring system that corrects for errors in the determination of the position of a measurement reflector along a measurement path due to the presence of an atmosphere (e.g. atmospheric turbulence) along the path is disclosed. The system includes a two-wavelength interferometer for measuring the atmosphere and a basic length interferometer for a basic measurement of a change in position of the measurement reflector. A calibration procedure for correcting the basic measurements made by the basic length interferometer uses first and second correction coefficients related to the average refractivity of the atmosphere and the change in the refractivity of the atmosphere, respectively. The coefficients can be determined by interferometric measurements or from a combination of interferometric measurements and data from an atmospheric sensor(s), including a humidity sensor. The two-wavelength interferometer can include a pulsed laser source, a compact reference path element, and path length adjustment element. An algorithm is disclosed for efficiently determining the phase difference between the two beams of the two-wavelength interferometer. Beam combining techniques and apparatus for combining the beams of the two-wavelength interferometer and the basic length measurement interferometer while preserving the polarization of the laser beams are also disclosed. The data obtained from the two-wavelength interferometer can be corrected, based on measurements made by the basic length interferometer, for aging due to the movement of the reflecting mirror subsequent to measurement of the atmosphere by the two-wavelength interferometer.

Atom Interferometry Based on Separated Light Fields

Abstract: Publisher Summary This chapter provides an overview of the atom interferometry based on separated light fields. Less than a decade after the first atom interferometers were demonstrated, a wide variety of different types of atom interferometers has been brought into operation. It is believed that the class of the atom interferometers based on separated light fields has proven themselves to be versatile, flexible devices, well understood theoretically and particularly well suited to measurements of fundamental effects that improve understanding of quantum mechanics. Measurements of atomic constants and properties also profit from the high sensitivity and signal-to-noise ratio of interferometric measurements with the Borde interferometer. Among the more mature applications is the use of Borde interferometry for an optical frequency standard, with perspectives for limits of relative precision and accuracy in the range of 10−15. This chapter discusses the four-beam Borde interferometer and the pulsed interferometer. It also discusses precision determination of physical quantities and applications of atom interferometry in optical frequency standards.

Improved multistage wide band laser frequency stabilization

Abstract: Suppression of laser frequency fluctuations is an essential technology for planned interferometric detectors for astrophysical gravitational waves. Because of the low degree of residual frequency noise which is ultimately required, control topologies comprising two or more cascaded loops are favored. One such topology, used in the Laser Interferometer Gravitational-Wave Observatory 40 m interferometer, relied on electro-optic Pockels cell phase correction as a fast actuator for the final stage. This actuation method proved susceptible to spurious amplitude modulation effects, which provided an unintended parasitic feedback path. An alternate arrangement, which achieves comparably effective frequency stabilization without using a phase correcting Pockels cell, was introduced and successfully tested.

Optimal detection strategies for measuring the stochastic gravitational radiation background with laser interferometric antennas

Abstract: Issues pertaining to the optimal strategy for detecting the stochastic gravitational wave background (SGWB) with laser interferometric antennas are discussed. Analyzed are the dependence of detection sensitivity on the relative orientation of interferometers, the interferometer design, and the inherent noise of the detectors. Previously Michelson, Flanagan, and Christensen thoroughly studied such topics. This paper addresses a few remaining issues for the optimal detection of the SGWB with laser interferometers. The optimal orientation of a pair of interferometers depends on both the noise characteristics of the detectors and their physical location on the surface of the Earth. Given a pair of detectors the maximum sensitivity for detecting the SGWB also depends on the transfer function of the interferometers; the relatively narrow band dual recycling interferometers are the best choice. Correlated noise in two antennas located at a single site complicates the detection strategy, but an optimistic attitude is called for given the considerable relative size of the correlated signal. The Laser Interferometric Gravitational Wave Observatory offers exciting prospects for placing limits on the strength of the SGWB.

How an interferometer extracts and amplifies power from a gravitational wave

Abstract: The operation of an interferometric gravitational wave detector is described in terms of the power flow through the device. I show how to identify the mechanical power absorbed by the interferometer from the gravitational wave and describe the power gain provided by the interferometer using the classical theory of parametric transducers. I discuss the power relationships involved in the optical heterodyne process at the output photodiode. I compare various possible definitions of the cross section of an interferometer with the definition used in the description of a resonant-mass gravitational wave detector.

Generalized Talbot-Lau Atom Interferometry

Abstract: Publisher Summary This chapter describes a particular form of a grating interferometer called the generalized Talbot-Lau (GTL) interferometer. The chapter first identifies a significant weakness (low throughput) of its progenitor form, separated beam envelope (SBE) interferometry, outlines the operating principles of the GTL interferometry, and shows how GTL interferometry remedies this weakness. The GTL interferometry is based on a unique form of interference intimately associated with Fresnel diffraction that occurs when Fraunhofer diffraction orders overlap. This effect was originally discovered in the optical domain using lenses and gratings, and is called the Talbot effect. Its diffraction pattern consists of the so-called Fourier and Fresnel fringes that, surprisingly, are actually multiply “aliased” near self-images of a grating's periodic complex amplitude transmission function. The chapter introduces the Talbot effect and gives a brief historical outline of work contributing to its understanding. It also introduces the related Lau effect and the Talbot interferometer. The chapter also shows how these can be combined to create generalized lens-free Talbot-Lau interferometers, suitable for de Broglie wave interferometry.

Classical and Quantum Atom Fringes

Abstract: Publisher Summary This chapter presents an overview of an attempt to exploit the unique possibilities of atomic beams and their interactions with light fields for fundamental physics. The overview starts with a short description of the experimental apparatus and then describes a classical experiment: a three grating moire imaging device based on classical ray optics. This classical device is a very sensitive inertial sensor, capable even of surpassing present-day commercial sensors. The chapter describes the three grating de Broglie wave atom interferometer based on diffraction at standing light waves and subsequently discusses the similarities between the classical moire apparatus and the quantum apparatus, the interferometer. The chapter comments on the new features one might expect in the study of coherent motion in periodic structures made of light called the light crystals. Starting from the similar and well-developed fields of dynamical diffraction in neutron, electron, and X-ray physics, the chapter gives an introduction to the different regimes accessible by the experiment and shows the first realizations of some of the expected effects.

Refining molecular potentials using atom interferometry

Abstract: We present a theoretical study of the index of refraction of argon for the propagation of sodium matter waves. The sensitivity of the index of refraction to the details of the molecular potential curve is analyzed. Our calculations reveal velocity-dependent oscillations in the index of refraction that may be detectable, particularly at low temperatures, in atom interferometry measurements. A procedure for refining molecular potential curves is outlined. {copyright} {ital 1997} {ital The American Physical Society}

Three-beam atom interferometer

Abstract: We present an atom interferometer based on the interference of three partial matter waves in three different internal and external states. Coherent laser excitation acts as a beamsplitter to create a superposition state of the ground state and two Zeeman sublevels of the metastable state of magnesium atoms. The interference pattern of the output ports shows high contrast and the characteristics of three-beam interferences as known from optical interferometry. In comparison to two-beam interferometry a reduction of the fringe width of (32±8)% is observed. This offers various possibilities for improved measurements of quantum-mechanical phases due to the internal atomic-state sensitive coupling of external potentials. This is demonstrated for the interaction of magnesium atoms with an external magnetic field. © 1997 The American Physical Society.

Differential rotationally shearing interferometer: implementation concept

Abstract: A new type of interferometer, a differential rotationally shearing interferometer, differs from the traditional rotationally shearing interferometer in that the angle of rotation is infinitesimal or, at least, very small A differential rotationally shearing interferometer may be used for the detection of wavefront asymmetry even when its asymmetry is very small We present an implementation concept for the differential rotationally shearing interferometer, based on the Mach-Zehnder interferometer One of the important advantages of the new interferometer is that the polarization problems do not arise do the small angle of rotation between the two wavefronts

Atom interferometry--dispersive index of refraction and rotation induced phase shifts for matter-waves

Abstract: This thesis describes recent advances in the use of atom interferometers. The advances comprise two new techniques that will advance the ability of atom interferometers to make precision measurements and two experiments that demonstrate the extraordinary sensitivity of atom interferometers to rotations and to atom-atom interactions, respectively. A novel scheme is described whereby multiple velocity components of an atomic beam contribute constructively to an atomic interference fringe pattern of large intensity. This multiplexing effect will allow the measurement of large dispersive phases in cases where the fringe would otherwise have damped out to zero contrast. Amplitude diffraction gratings, the atom-optical elements which make up our atom interferometer, have been manufactured with unprecedented phase uniformity, or coherence. A technique that utilizes registration marks to minimize drifts in the lithography of these gratings is described. We have measured the sensitivity of our atom interferometer to rotations. Our results agree within experimental uncertainty of 1% with the theory predicted by the Sagnac effect. Further, we demonstrated a sensitivity four orders of magnitude better than that previously seen in an atom interferometer, approaching the sensitivity of the best commercially available laser gyroscopes. We have studied the velocity dependent index of refraction for sodium matter-waves passing through a dilute sample of Argon gas. Atom interferometers are the only devices able to detect the collision induced phase shift in atom-atom scattering. The phase shift was measured as a function of the velocity, or energy, of the incident sodium atomic beam allowing determination of the mid to long range interatomic potential. Thesis Supervisor: Dr. David E. Pritchard Title: Professor of Physics

Reconstruction of the Joint State of a Two-Mode Bose-Einstein Condensate

Abstract: We propose a scheme to reconstruct the state of a two-mode Bose-Einstein condensate, with a given total number of atoms, using an atom interferometer that requires beam splitter, phase shift, and nonideal atom counting operations The density matrix in the number-state basis can be computed directly from the probabilities of different counts for various phase shifts between the original modes, unless the beam splitter is exactly balanced Simulated noisy data from a two-mode coherent state are produced and the state is reconstructed, for 49 atoms The error can be estimated from the singular values of the transformation matrix between state and probability data

Atomic interferences in a comoving magnetic field

Abstract: The use of comoving magnetic fields in Stern-Gerlach atom interferometry allows, in principle, one to reach a range of very low kinetic energies (a few tens of neV); it also allows the device to be used as an interference filter for atomic waves. The technique used to produce such fields moving at atomic velocities is described. Experimental interference patterns obtained with a beam of ${\mathrm{H}}^{*}(2S)$ atoms are in good agreement with the calculations, which clearly demonstrates the feasibility of the method.

Collapse and revival of the fringe pattern in a multiple-beam atom interferometer

Abstract: We report on the observation of collapse and revival of the fringe pattern in a multiple-beam atom interferometer, when the drift time between the beam splitting processes is varied. The atomic beam splitters are realized with laser pulses pumping the atoms into velocity selective dark states. For small drift times, the interference signal shows the sharply peaked Airy function-like pattern characteristic for multiple-beam interference. The fringe pattern collapses for larger drift times due to a recoil phase shift increasing quadratically with the transverse atomic momentum. When the total interaction time reaches an integer multiple of the inverse two-photon recoil energy in frequency units, the original fringe pattern is revived.

Oriented atoms in weak magnetic fields

Abstract: This article reviews the early investigations of Series on the resonance absorption and fluorescence of light by samples of oriented atoms dagger subjected to static and oscillatory magnetic fields. These investigations include experiments on optical-radiofrequency double resonance, light beats in double resonance, circulation of coherence in optical pumping, and time-biasing in level-crossing spectroscopy. It then describes some selected laser spectroscopy experiments involving the interaction of optically oriented atoms with static magnetic fields that were stimulated by the earlier work of Series, including experiments on hyperfine structure quantum beats, cascade quantum beats, ground-state quantum beats in transmission, and optogalvanic detection of atomic coherences. Finally, it describes some current work which uses static magnetic fields to manipulate the external variables (momentum and position) of laser-cooled oriented atoms, with applications in the rapidly developing field of atom optics and atom interferometry.

Atom Interferometry and the Quantum Theory of Measurement

Abstract: Publisher Summary This chapter discusses atom interferometry and the quantum theory of measurement. The interferometry that is supremely elegant and profoundly practical part of conventional optics is deeply enriched by the advent of neutron and atom interferometry for several reasons. The shorter de Broglie wavelength of massive particles makes possible new devices such as the matter–wave gyroscope, whose sensitivities, in principle, far exceed those of their electromagnetic predecessors, such as the laser gyroscope. The first half of the chapter discusses the role of complementarity and Welcher Weg information in the context of two modern versions of the Young's double-slit experiment. The second half of the chapter addresses the more practical aspect of how a macroscopic device with many degrees of freedom affects the measurement of a microscopic object. The macroscopic device is a Stern–Gerlach interferometer in which two partial beams of spln-1/2 atoms are macroscopically separated and then reunited.

Multiple beam atom interferometer : theory and experiment

Abstract: We first give a detailed account of the theory of atom interferometers based on a sequence of laser pulses pro- jecting the atomic wave packets onto a spatially separating dark superposition state. We then describe the experimen- tal realization of a multiple beam atom interferometer based on this method. In our experiment, we observe an interfer- ence signal that shows the sharply peaked Airy-function like pattern characteristic for multiple beam interference. Besides this fringe sharpening effect, we observe a further significant difference compared to the signal of a conventional two-beam atom interferometer. When the time between the beamsplit- ting pulses is varied, we observe collapse and revival of the fringe pattern, which is caused by a recoil phase shift increas- ing quadratically with the transverse atomic momentum.