Atom interferometry in a static electric field: Measurement of the Aharonov-Casher phase

Consecutive, phase-coherent, near-resonant optical excitations of atoms have been used to realize an atom interferometer with a beam of thermal calcium atoms. We have measured the topological phase shift due to the interaction of a static electric field with the magnetic dipole moment of a moving atom (Aharonov-Casher effect). The observed phase shift was proportional to the electric field and, within our experimental uncertainty, independent of the particle's velocity. The measured value of the phase shift has been found to agree with the predicted one within a relative uncertainty of 2.2%.Dedicated to H. Walther on the occasion of his 60th birthday     

Interferometry with Ca atoms

Separated field excitation of a calcium atomic beam using four traveling laser fields represents two distinct atom interferometers utilizing the internal degrees of freedom of the atoms. Phase shifts between the atomic partial waves have been realized by phase shifts of the laser wave fields, by the ac-Stark shift, and by rotation of the interferometer (Sagnac effect). One particular interferometer can be selected by interaction of the atomic waves with extra laser fields. We furthermore report on the preparation of a laser cooled and deflected calcium atomic beam that can be utilized to largely increase the sensitivity of the interferometer.     

Measuring gravitational effect of superintense laser by spin-squeezed Bose—Einstein condensates interferometer

We consider an extremely intense laser, enclosed by an atom interferometer. The gravitational potential generated from the high-intensity laser is solved from the Einstein field equation under the Newtonian limit. We compute the strength of the gravitational force and study the feasibility of measuring the force by the atom interferometer. The intense laser field from the laser pulse can induce a phase change in the interferometer with Bose-Einstein condensates. We push up the sensitivity limit of the interferometer with Bose-Einstein condensates by spin-squeezing effect and determine the sensitivity gap for measuring the gravitational effect from intense laser by atom interferometer.     

The magnesium ramsey interferometer: Applications and prospects

In this paper it will be shown that an atom interferometer, based on the coherent splitting of the atomic wavefunction by four travelling waves (Ramsey interferometer), may be explained by a purely mechanical interpretation. As our first application of this Ramsey interferometer we have measured the phase shifts respectively optical length changes in a magnesium atomic beam caused by the acceleration of the partial atomic wave in one arm of the interferometer. This acceleration was achieved by the dipole force exerted by an off-resonant crossing laser beam which interacted with the ground state part of the wavefunction only. Further applications of this interferometer and improvements due to laser cooling will be discussed.     

Ramsey-Bordé interferometer and embedded Ramsey interferometer with molecular matter waves of 39K2

A matter wave interferometer based on a molecular beam of K₂ has been designed for observation of both exits: with molecules in the electronically excited state and in the ground state. In addition to the excited state fluorescence the molecular ground state population is detected with a further laser. Two transitions to different electronic states were employed for this purpose and their usefulness is compared. Under the present experimental conditions both interferometer exits show a superposition of different interference patterns due to the influence of transverse and longitudinal overlaps of the interfering matter waves. The interference patterns have been analyzed to be composed of a contribution caused by a two beam splitter Ramsey interference and Ramsey-Bordé pattern with four beam splitters. This overlap of interference signals influences the suitability of the matter wave interferometer for phase measurements of the interferences.     

光和原子关联与量子计量

物理量的测量与单位标准的统一推动了计量学的发展.量子力学的建立,激光技术的发明以及原子与分子物理学的发展,在原理与技术上进一步刷新了计量学的研究内涵,特别是激光干涉与原子频标技术的发展,引起了计量学革命性的飞跃.基于激光干涉的引力波测量、激光陀螺仪,基于原子干涉的原子钟、原子陀螺仪等精密测量技术相继诞生,一个以量子物理为基础,探索与开拓物理量精密测量方法与技术的新的科学分支——量子计量学(Quantum Metrology)已然兴起.干涉是计量学中最常用的相位测量方法.量子干涉技术,其相位测量精度能够突破标准量子极限的限制,是量子计量学与量子测量技术的核心研究内容.本文重点介绍近几年我们在量子干涉方面所取得的新开拓与新发展,主要内容包括基于原子系综中四波混频过程的SU(1,1)型光量子关联干涉仪和基于原子系综中拉曼散射过程的光-原子混合干涉仪.     

Vibration-induced phase noise in Mach–Zehnder atom interferometers

The high inertial sensitivity of atom interferometers has been used to build accelerometers and gyrometers, but this property makes these interferometers very sensitive to the laboratory seismic noise. This seismic noise induces a phase noise which is large enough to reduce the fringe visibility in many cases. We develop here a model calculation of this phase noise applicable to a wide class of Mach–Zehnder atom interferometers and we apply this model to our thermal lithium interferometer. We are thus able to explain the observed dependence of the fringe visibility on the diffraction order. The dynamical model developed in the present paper should be very useful to further reduce this phase noise in atom interferometers and this reduction should open the way to improved interferometers. PACS 03.75.Dg; 39.20.+q; 42.50.Vk     

利用原子干涉仪的相位调制进行绝对转动测量

提出一种基于原子干涉仪的相位调制进行绝对转动测量的方法.以π/2-π-π/2构型的空间型原子干涉仪为例,通过对拉曼激光进行相位调制,然后在动量谱空间测量转动对原子速度谱的调制周期,获得原子干涉仪相对惯性空间的绝对转动.文章对于采用该法进行角速度测量的测量范围以及对相位调制频率的要求进行了分析,对于散粒噪声限下的转动测量灵敏度及其影响因素进行了仿真. 关键词： 原子干涉仪 原子陀螺 相位调制 绝对转动测量     

Absolute geodetic rotation measurement using atom interferometry

We demonstrate a cold-atom interferometer gyroscope which overcomes accuracy and dynamic range limitations of previous atom interferometer gyroscopes. We show how the instrument can be used for precise determination of latitude, azimuth (true north), and Earth's rotation rate. Spurious noise terms related to multiple-path interferences are suppressed by employing a novel time-skewed pulse sequence. Extended versions of this instrument appear capable of meeting the stringent requirements for inertial navigation, geodetic applications of Earth's rotation rate determination, and tests of general relativity.     

Long phase coherence time and number squeezing of two Bose-Einstein condensates on an atom chip

We measure the relative phase of two Bose-Einstein condensates confined in a radio frequency induced double-well potential on an atom chip. We observe phase coherence between the separated condensates for times up to approximately 200 ms after splitting, a factor of 10 longer than the phase diffusion time expected for a coherent state for our experimental conditions. The enhanced coherence time is attributed to number squeezing of the initial state by a factor of 10. In addition, we demonstrate a rotationally sensitive (Sagnac) geometry for a guided atom interferometer by propagating the split condensates.     

Atom interferometry measurement of the atom-surface van der Waals interaction

Using a nano-scale grid as a phase-shifting component, an atom interferometer has been utilized to study atom-surface van der Waals (VdW) interactions. We report phase shifts on the order of 0.2 rad, with a few percent uncertainty. We also report the velocity-dependent attenuation of atomic de Broglie wave amplitude that occurs in conjunction with the observed phase shifts. From these data we deduce the strength of the VdW potential and its dependence on the atom-surface separation. We discuss how our measurements can be used to set limits on the strength of non-Newtonian gravity at short length scales and we discuss the possibility of measuring the atom-surface interactions over a larger range of atom-surface distances. We also compare our results to several theoretical predictions for the VdW potential of Li near a variety of surfaces.     

用于原子干涉仪的拉曼光的制备

原子干涉仪是利用原子物质波的特性而实现的干涉仪,广泛应用于精密测量领域.在原子干涉仪中,通过拉曼光对原子进行相干操作,拉曼光的质量直接影响着干涉仪的技术指标.基于注入锁定技术,采用普通半导体激光器、声光调制器,实现了功率、频率和位相稳定的拉曼光的制备,并对拉曼光的相位噪声技术指标进行了测试.     

基于原子干涉仪的微观粒子弱等效原理检验

等效原理是广义相对论的两个基本假设之一,也是爱因斯坦对弱等效原理的推广.目前,大量实验证明弱等效原理在一定的实验精度内是成立的.将引力与标准模型统一起来的新理论都要求弱等效原理破缺,因此更高精度的弱等效原理检验具有重要的科学意义.本文介绍了原子干涉仪的原理,回顾了利用原子干涉仪开展微观粒子弱等效原理检验实验研究的历史和现状,介绍了双组分原子干涉仪检验弱等效原理实验涉及的振动噪声抑制、拉曼光移频与相位噪声抑制、四波双衍射拉曼跃迁原子干涉、信号探测与数据处理等关键问题及研究进展,分析了高精度微观粒子弱等效原理检验研究的发展趋势,介绍了长基线原子干涉仪、空间原子干涉仪、超冷原子源以及纠缠原子源制备等方面的研究动态,展望了微观粒子弱等效原理检验研究的发展前景.     

Atom Michelson interferometer on a chip using a Bose-Einstein condensate

An atom Michelson interferometer is implemented on an "atom chip." The chip uses lithographically patterned conductors and external magnetic fields to produce and guide a Bose-Einstein condensate. Splitting, reflecting, and recombining of condensate atoms are achieved by a standing-wave light field having a wave vector aligned along the atom waveguide. A differential phase shift between the two arms of the interferometer is introduced by either a magnetic-field gradient or with an initial condensate velocity. Interference contrast is still observable at 20% with an atom propagation time of 10 ms.     

Dispersion compensation for atom interferometry

A new technique for maintaining high contrast in an atom interferometer is used to measure large de Broglie wave phase shifts. Dependence of an interaction induced phase on the atoms' velocity is compensated by applying an engineered counterphase. The counterphase is equivalent to a rotation, is precisely determined by a frequency, and can be used to measure phase shifts due to interactions of unknown strength. Phase shifts of 150 rad (5 times larger than previously possible) have now been measured in an atom beam interferometer, and we suggest that this technique can enable comparisons of atomic polarizability with precision of one part in 10,000.     

A matter-wave interferometer based on the dc-Stark effect

We present a new separated beam atom interferometer in which the recombination of the atomic wave packet is due to the dc-Stark interaction of an induced atomic dipole with a cylindrically symmetric electric field of a charged wire. The fringe period shows a weak power-law dependence on the de Broglie wavelength and the polarizability of the particles. We present a semiclassical theoretical model for this interferometer which resembles the measured performance of the interferometer without free parameters. A discussion of possible applications of this interferometer for atoms and molecules is given. Received: 20 November 1998 / Published online: 8 September 1999     

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

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. Received: 22 November 2001 / Revised version: 10 February 2002 / Published online: 24 April 2002     

Active phase stabilization in a two-fiber interferometer

We report on the frequency spectrum of phase fluctuations of a two fiber interferometer in a normal laboratory environment. A feedback system in connection with a piezo regulator is used for compensation of the fluctuations. The resulting stability of the compensator has been measured.     

Atom interferometry measurement of the electric polarizability of lithium

Using an atom interferometer, we have measured the static electric polarizability of ⁷Li α=(24.33 ±0.16)×10^-30 m³ = 164.2±1.1 atomic units with a 0.66% uncertainty. Our experiment, which is similar to an experiment done on sodium in 1995 by Pritchard and co-workers, consists in applying an electric field on one of the two interfering beams and measuring the resulting phase-shift. With respect to Pritchard's experiment, we have made several improvements which are described in detail in this paper: the capacitor design is such that the electric field can be calculated analytically; the phase sensitivity of our interferometer is substantially better, near 16 mrad/ ; finally our interferometer is species selective so that impurities present in our atomic beam (other alkali atoms or lithium dimers) do not perturb our measurement. The extreme sensitivity of atom interferometry is well illustrated by our experiment: our measurement amounts to measuring a slight increase Δv of the atom velocity v when it enters the electric field region and our present sensitivity is sufficient to detect a variation Δv/v ≈6 ×10^-13.     

Ein Interferometer für langsame Neutronen

After discussing the feasibility and possible usefulness of a neutron interferometer, we describe an arrangement whereby Fresnel interferences have been obtained for neutrons with wavelengths of about 4.4 Å in a 10 meter flight path with a 0.01 mm entrance slit, using two glass prisms instead of the Fresnel biprism. A useful separation of the two coherent beams of 0.06 mm has been reached. Possible improvements of the method are discussed.