Showing papers on "Atom interferometer published in 2002"

Formation of a Matter-Wave Bright Soliton

Abstract: We report the production of matter-wave solitons in an ultracold lithium-7 gas. The effective interaction between atoms in a Bose-Einstein condensate is tuned with a Feshbach resonance from repulsive to attractive before release in a one-dimensional optical waveguide. Propagation of the soliton without dispersion over a macroscopic distance of 1.1 millimeter is observed. A simple theoretical model explains the stability region of the soliton. These matter-wave solitons open possibilities for future applications in coherent atom optics, atom interferometry, and atom transport.

Microchip traps and Bose-Einstein condensation

Abstract: The article gives an overview of the rapidly evolving field of magnetic microchip traps (also called ‘atom chips’) for neutral atoms Special attention is given to Bose–Einstein condensation in such traps, to the particular properties of microchip trap potentials, and to practical considerations in their design Scaling laws are developed, which lead to an estimate of the ultimate confinement that chip traps can provide Future applications such as integrated atom interferometers are discussed

A Preliminary Measurement of the Fine Structure Constant Based on Atom Interferometry

Abstract: Using an atom interferometer method, we measure the recoil velocity of a cesium atom due to the coherent scattering of a photon. This measurement is used to obtain a value of /MCs and the fine structure constant, α. The current fractional uncertainty is Δα/α = 7.4 × 10-9.

Atomic clocks and inertial sensors

Abstract: We show that the language of atom interferometry provides a unified picture for microwave and optical atomic clocks as well as for gravito-inertial sensors. The sensitivity and accuracy of these devices is now such that a new theoretical framework common to all these interferometers is required that includes: (a) a fully quantum mechanical treatment of the atomic motion in free space and in the presence of a gravitational field (most cold-atom interferometric devices use atoms in ``free fall'' in a fountain geometry); (b) an account of simultaneous actions of gravitational and electromagnetic fields in the interaction zones; (c) a second quantization of the matter fields to take into account their fermionic or bosonic character in order to discuss the role of coherent sources and their noise properties; (d) a covariant treatment including spin to evaluate general relativistic effects. A theoretical description of atomic clocks revisited along these lines is presented, using both an exact propagator of atom waves in gravito-inertial fields and a covariant Dirac equation in the presence of weak gravitational fields. Using this framework, recoil effects, spin-related effects, beam curvature effects, the sensitivity to gravito-inertial fields and the influence of the coherence of the atom source are discussed in the context of present and future atomic clocks and gravito-inertial sensors.

Method of phase extraction between coupled atom interferometers using ellipse-specific fitting

Abstract: We present a method of analysis involving ellipse-specific fitting of sinusoidally coupled data from two gravimeters in a gradiometer configuration. This method permits rapid extraction of induced gradient phase shifts in the presence of common-mode vibrational phase noise. Gravity gradients can be accurately measured in the presence of large vibrational accelerations.

The LISA response function

Abstract: The orbital motion of the Laser Interferometer Space Antenna (LISA) introduces modulations into the observed gravitational wave signal. These modulations can be used to determine the location and orientation of a gravitational wave source. The complete LISA response to an arbitary gravitational wave is derived using a coordinate free approach in the transverse-traceless gauge. The general response function reduces to that found by Cutler (PRD 57, 7089 1998) for low frequency, monochromatic plane waves. Estimates of the noise in the detector are found to be complicated by the time variation of the interferometer arm lengths.

Parameter Estimation for Galactic Binaries by the Laser Interferometer Space Antenna

Abstract: We calculate how accurately parameters of the short-period binaries (10-4 Hz f 10-2 Hz) will be determined from the gravitational waves by the Laser Interferometer Space Antenna (LISA). In our analysis, the chirp signal, , is newly included as a fitting parameter, and dependence on the observation period or wave frequency is studied in detail. Implications for gravitational wave astronomy are also discussed quantitatively.

Lock acquisition of a gravitational-wave interferometer

Abstract: Interferometric gravitational-wave detectors, such as the Laser Interferometer Gravitational Wave Observatory (LIGO) detectors currently under construction, are based on kilometer-scale Michelson interferometers, with sensitivity that is enhanced by addition of multiple coupled optical resonators. Reducing the relative optic motions to bring the system to the resonant operating point is a significant challenge. We present a new approach to lock acquisition, used to lock a LIGO interferometer, whereby the sensor transformation matrix is dynamically calculated to sequentially bring the cavities into resonance.

Adaptive thermal compensation of test masses in advanced LIGO

Abstract: As the first generation of laser interferometric gravitational wave detectors nears operation, research and development has begun on increasing the sensitivity of the instrument while utilizing the existing infrastructure. In the laser interferometer gravitational wave observatory (LIGO), significant improvements are being planned for installation around 2007, increasing strain sensitivity through improved suspensions and test mass substrates, active seismic isolation and higher input laser power. Even with the highest quality optics available today, however, finite absorption of laser power within transmissive optics, coupled with the tremendous amount of optical power circulating in various parts of the interferometer, results in critical wavefront deformations which would cripple the performance of the instrument. A method of active wavefront correction via direct thermal actuation on optical elements of the interferometer is discussed. A simple nichrome heating element suspended off the face of an affected optic will, through radiative heating, remove the gross axisymmetric part of the original thermal distortion. A scanning heating laser will then be used to remove any remaining non-axisymmetric wavefront distortion, generated by inhomogeneities in absorption of the substrate, thermal conductivity, etc. A proof-of-principle experiment has been constructed at MIT, selected data of which are presented.

Unequal arm space-borne gravitational wave detectors

Abstract: Unlike ground-based interferometric gravitational wave detectors, large space-based systems will not be rigid structures. When the end stations of the laser interferometer are freely flying spacecraft, the armlengths will change due to variations in the spacecraft positions along their orbital trajectories, so the precise equality of the arms that is required in a laboratory interferometer to cancel laser phase noise is not possible. However, using a method discovered by Tinto and Armstrong, a signal can be constructed in which laser phase noise exactly cancels out, even in an unequal arm interferometer. We examine the case where the ratio of the armlengths is a variable parameter, and compute the averaged gravitational wave transfer function as a function of that parameter. Example sensitivity curve calculations are presented for the expected design parameters of the proposed LISA interferometer, comparing it to a similar instrument with one arm shortened by a factor of 100, showing how the ratio of the armlengths will affect the overall sensitivity of the instrument.

Gravitational decoherence of atomic interferometers

Abstract: We study the decoherence of atomic interferometers due to the scattering of stochastic gravitational waves. We evaluate the “direct” gravitational effect registered by the phase of the matter waves as well as the “indirect” effect registered by the light waves used as beam-splitters and mirrors for the matter waves. Considering as an example the space project HYPER, we show that both effects are negligible for the presently studied interferometers.

Testing the world's largest monolithic perfect crystal neutron interferometer

Abstract: Silicon perfect crystal neutron interferometers have some remarkable advantages compared to other matter wave interferometers, e.g. large beam separation, a lot of sample space and easy sample handling without the need of vacuum. In this paper we present a 45° 6-plate interferometer which considerably enlarges the utilizable interferometer space. The path length of the coherent beams reaches 21 cm, the beam separation 5 cm and the enclosed beam area 80 cm2. The 6-plate design allows a verification of how the path length influences the beam coherence and it opens new applications, e.g. measurement of the neutron–electron scattering length or Which-Way experiments. In a first series of visibility measurements, using a scanning slit and a CCD camera, 65% visibility was achieved with an 8×8 mm2 slit and 69% visibility with 4×4 mm2. The large interferometer and the two smaller interferometer loops show the same visibilities, therefore the increased path lengths does not reduce beam coherence. Finally we demonstrate in a combined action of two non-absorbing phase shifters how Which-Way information and visibility can be modulated in the 6-plate interferometer.

Differential wavelength-scanning heterodyne interferometer for measuring large step height.

Abstract: An interferometer based on the differential heterodyne configuration and wavelength-scanning interferometry for measuring large step heights is presented. The proposed interferometer is less sensitive to environmental disturbances than other interferometers and can accurately measure interference phases. A tunable diode laser is utilized to illuminate the interferometer and thus solve the phase ambiguity problem. Counting the interference fringes as the wavelength is scanned through a known change in wavelength directly determines the step height. Three gauge blocks of different lengths, 5, 10, and 50 mm, are individually wrung on a steel plate to simulate large step heights. Comparing the results measured by the proposed interferometer with those by the gauge block interferometer reveals that the accuracy is approximately 100 nm.

High-contrast Mach–Zehnder lithium-atom interferometer in the Bragg regime

Abstract: We have constructed an atom interferometer of the Mach–Zehnder type, operating with a supersonic beam of lithium. Atom diffraction uses Bragg diffraction on laser standing waves. With first-order diffraction, our apparatus has given a large signal and a very good fringe contrast (74%), which we believe to be the highest ever observed with thermal atom interferometers. This apparatus will be applied to high-sensitivity measurements.

Large-angle adjustable coherent atomic beam splitter by Bragg scattering

Abstract: Using a ``monochromatic'' (single-axial-velocity) and slow (250 m/s) beam of metastable helium atoms, we realize up to eighth-order Bragg scattering and obtain a splitting angle of 6 mrad at low laser power (3 mW). This corresponds to a truly macroscopic separation of 12 mm on the detector. For fifth-order scattering, we have observed several oscillations of the splitting ratio when varying the laser power (``Pendell\"osung oscillations''). The large splitting angle, the adjustable splitting ratio, and the cleanness of the split beams, with $200\ensuremath{-}\ensuremath{\mu}\mathrm{m}$ rms width each, make the beam splitter ideal for a large-enclosed-area atom interferometer.

Scalar Aharonov-Bohm effect for ultracold atoms

Abstract: The scalar Aharonov-Bohm effect with a time-dependent magnetic field was investigated for ultracold sodium atoms using the time-domain atom interferometer. The 38 interference fringes with almost the same amplitude verified the nondispersivity of this effect. The measured phase shift as a function of the strength of the applied magnetic field agreed with the predicted one within an accuracy of 3%. With a weak magnetic field orthogonal to the quantization axis, the phase shift was in proportion to the variation of the strength of the resultant magnetic field.

Theory of a one-dimensional double-X-junction atom interferometer

Abstract: The dynamics of an atom waveguide X-junction beam splitter becomes truly one dimensional in a regime of low temperatures and densities and large positive scattering lengths where the transverse mode becomes frozen and the many-body Schr\"odinger dynamics becomes exactly soluble via a generalized Fermi-Bose mapping theorem. We analyze the interferometric response of a double-X-junction interferometer of this type due to potential differences between the interferometer arms.

Hydrogen atom interferometer with short light pulses

Abstract: We report the realization of a hydrogen atom interferometer experiment using light as the atomic beam splitter. The wave packets of hydrogen atoms excited to the metastable 2S state are coherently split up and later recombined with the help of intense nanosecond light pulses. The pulses are generated by a novel phase-coherent source. These experiments can be seen as a step towards a precision measurement of the recoil energy of a hydrogen atom when absorbing a photon and thus of /mhydrogen.

Dynamic models of Fabry-Perot interferometers.

Abstract: Long-baseline, high-finesse Fabry-Perot interferometers can be used to make distance measurements that are precise enough to detect gravity waves. This level of sensitivity is achieved in part when the interferometer mirrors are isolated dynamically, with pendulum mounts and high-bandwidth cavity length control servos to reduce the effects of seismic noise. We present dynamical models of the cavity fields and signals of Fabry-Perot interferometers for use in the design and evaluation of length control systems for gravity-wave detectors. Models are described and compared with experimental data.

Quantum-limited optical phase detection at the 10(-10)-rad level.

Abstract: Interferometric detection of gravitational waves at a level of astrophysical interest is expected to require measurement of optical phase differences of ≤10-10 rad. A fundamental limit to the phase sensing is the statistics of photon detection—Poisson statistics for light in a coherent state. We have built a laboratory-scale interferometer to achieve and investigate the phase detection sensitivity required for the Laser Interferometer Gravitational-Wave Observatory. With 70 W of circulating power, we have obtained a phase sensitivity of 1.28×10-10 rad/Hz at frequencies above 600 Hz, limited by quantum noise. Below 600 Hz, excess noise above the quantum limit is seen, and we present our investigations into the sources of this excess. Compared with the results of previous such experiments, the phase sensitivity over the full 100-Hz–10-kHz band of interest has been improved by factors of up to 100, with a factor-of-2.5 improvement in the quantum-limited level.

Gravitational waves in plasmas

Abstract: Various aspects of gravitational wave propagation in plasmas and vacuum are discussed First, we analyse single particle trajectories, study the resonant interaction of gravitational waves with photons, and show that photons can be strongly energized by gravitational waves Second, this exchange of energy between the photons and the gravitational waves is treated statistically, using a kinetic equation for photons Gravitational wave instabilities induced by intense photon beams are considered The effects are very much dependent on the gravitational wave dispersion in the plasma medium, and in particular, on its turbulent state

Extension of gravity-wave interferometer operation to low frequencies

Abstract: Experiments relating to concepts for extending interferometer operation, particularly at low frequencies, are discussed. This includes work with suspensions connected by a suspension-point interferometer. A new concept for achieving similar frequency extension without requiring an additional interferometer between suspensions is outlined, as well as a technique for improving positioning of laser beams relative to centres of gravity of test masses in gravity-wave interferometers and other instruments.

Planck-scale dissipative effects in atom interferometry

Abstract: Atom interferometers can be used to study phenomena leading to irreversibility and dissipation, induced by the dynamics of fundamental objects (strings and branes) at a large mass scale. Using an effective, but physically consistent description in terms of a master equation of Lindblad form, the modifications of the interferometric pattern induced by the new phenomena are analyzed in detail. We find that present experimental devices can, in principle, provide stringent bounds on the new effects.

A precision measurement of the fine structure constant

Abstract: Using an atom interferometer method based on adiabatic transfer between atomic states, we measure the recoil frequency shift frec = h/(mCsλ 2 eff) of cesium due to the absorption of a photon of effective inverse wavelength 1/λeff = 1/λ330 + 1/λ430, where λ330 and λ430 are the wavelengths of the D1 transitions between the F =3 and F =4 hyperÞne ground states of the 6S1/2 energy level and the F 0=3 hyperÞne 6P1/2 excited state, respectively. We report a value of frec = 15 006.276 9996(874) Hz, where the single standard deviation uncertainty includes both the systematic and statistical uncertainties after averaging more than 2 800 data points. With independent measurements of the Rydberg constant, the proton to electron mass ratio, the cesium to proton mass ratio, and the wavelengths for the D1 transition of cesium, we derive a value for the Þne structure constant α−1 = 137.035 999 710(427)(401), where the Þrst error bar is the combined uncertainty, equivalent to a fractional error of 3.1 × 10−9, from both this and the above mentioned independent measurements and the second value is the contribution to the uncertainty from just this work.

Long-range atom-metal-surface interaction and interference of atomic states

Abstract: The effect of long-range interaction of metastable hydrogen atoms with a metal surface is experimentally studied. The suggested experimental scheme uses the interaction as a component of an atomic interferometer. Qualitative and quantitative estimates of the atom-surface interaction are obtained for various experimental designs.

Measuring Atomic Properties with an Atom Interferometer

Abstract: Two experiments are presented which measure atomic properties using an atom interferometer. The interferometer splits the sodium de Broglie wave into two paths, one of which travels through an interaction region. The paths are recombined, and the interference pattern exhibits a phase shift depending on the strength of the interaction. In the first experiment, the interaction involves a gas. De Broglie waves traveling through the gas experience a phase shift represented by an index of refraction. By measuring the index of refraction at various wavelengths, the predicted phenomenon of glory oscillations in the phase shift has been observed for the first time. The index of refraction has been measured for sodium atoms in gases of argon, krypton, xenon, and nitrogen over a wide range of wavelength. These measurements offer detailed insight into the interatomic potential between sodium atoms and the gases. Theoretical predictions of the interatomic potentials are challenged by these results, which should encourage a renewed effort to better understand these potentials. The second experiment measures atomic polarizability with an atom interferometer. Here, the interaction is with an electric field; the atom experiences a phase shift proportional to its energy inside the field. Previously, this method was used to perform the most accurate (< 1%) measurement of sodium polarizability. The precision was limited, however, by the spread of velocities in the atomic beam—the phase shift is different depending on velocity, and the interference pattern is washed out. This thesis presents a new technique to “rephase” the interference pattern at large applied fields, and demonstrates a measurement that is free of this limitation. In addition, most of the systematic errors that plagued the previous polarizability measurement are eliminated by the new technique, and an order of magnitude improvement in precision now appears quite feasible. The remaining systematic errors can be eliminated by measuring the ratio of polarizabilities between two different atoms, a comparison whose precision is better by another order of magnitude. Thesis Supervisor: David E. Pritchard Title: Professor of Physics

Study on a Novel Single Frequency Laser Interferometer

Abstract: The common optical path arrangement is adopted in the single frequency laser interferometer. The interference patterns are shifted spatially by using optical devices such as polarization beam splitter, and 1/4 wave plate. The interference output signals of three channels are extracted in phase differing 90 in order. Then the signals will be compared and amplified, thus "zero shift" of light intensity appeared in convenient single frequency laser interferometer is solved. The measurement stability and repetitiveness of the laser interferometer is improved by means of convenient mode inhibiting technique. The resolution of the laser interferometer is improved by using optical path difference doubling technique.

Magnetic guiding of cold neutral atoms using a V-shaped current-carrying conductor

Abstract: A new scheme to magnetically guide cold, neutral atoms using a V-shaped current-carrying conductor is proposed. The spatial distributions of the magnetic fields, potentials and forces generated by the V-shaped current-carrying conductor are calculated, and the relationship between the magnetic field and the parameters of the V-shaped current-carrying conductor are analyzed in detail. Our study shows that the V-shaped current-carrying conductor proposed here can be used to guide cold atoms in the weak-field-seeking state, and to construct various atom-optical elements, such as atomic funnel, atomic beam-splitter and atom interferometer and so on, and even to realize a single-mode atomic waveguiding under certain conditions.