We investigated the Raman pulse duration effect in a gravity gradiometer with two atom interferometers. Since the two atom clouds in the gradiometer experience different gravitational fields, it is hard to compensate the Doppler shifts of the two clouds simultaneously by chirping the frequency of a common Raman laser, which leads to an appreciable phase shift. When applied to an experiment measuring the Newtonian gravitational constant G, the effect contributes to a systematic offset as large as -49ppm in Nature 510, 518 (2014). Thus an underestimated value of G measured by atom interferometers can be partly explained due to this effect.
We present a compact high-resolution gravity gradiometer based on dual Rb-85 atom interferometers using stimulated Raman transitions. A baseline L=44.5 cm and an interrogation time T=130 ms are realized in a sensor head with volume of less than 100 liters. Experimental parameters are optimized to improve the short-term sensitivity while a rejection algorithm relying on inversion of the Raman wave vector is implemented to improve the long-term stability. After an averaging time of 17000 s, a phase resolution of 104 μrad is achieved, which corresponds to a gravity gradient resolution of 0.86 E. …
We present a gradiometer based on matter-wave interference of alkaline-earth-metal atoms, namely $^{88}$Sr. The coherent manipulation of the atomic external degrees of freedom is obtained by large-momentum-transfer Bragg diffraction, driven by laser fields detuned away from the narrow $^1$S$_0$-$^3$P$_1$ intercombination transition. We use a well-controlled artificial gradient, realized by changing the relative frequencies of the Bragg pulses during the interferometer sequence, in order to characterize the sensitivity of the gradiometer. The sensitivity reaches $1.5 \times 10^{-5}$ s$^{-2}$ fo…
An atom interferometer using a Bose-Einstein condensate of $^{87}$Rb atoms is utilized for the measurement of magnetic field gradients. Composite optical pulses are used to construct a spatially symmetric Mach-Zehnder geometry. Using a biased interferometer we demonstrate the ability to measure small residual forces in our system at the position of the atoms. These are a residual magnetic field gradient of 15$\pm$2 mG/cm and and an inertial acceleration of 0.08$\pm$0.02 m/s$^2$. Our method has important applications in the calibration of precision measurement devices and the reduction of syste…
We characterize the performance of a gravimeter and a gravity gradiometer based on the $^{1}$S$_{0}$-$^3$P$_0$ clock transition of strontium atoms. We use this new quantum sensor to measure the gravitational acceleration with a relative sensitivity of $1.7\times10^{-5}$, representing the first realisation of an atomic interferometry gravimeter based on a single-photon transition. Various noise contributions to the gravimeter are measured and characterized, with the current primary limitation to sensitivity seen to be the intrinsic noise of the interferometry laser itself. In a gravity gradiome…
We demonstrate an atom interferometer operating on the $^1S_0-{}^3P_0$ clock transition of $^{87}$Sr atoms in a "magic" optical guide, where the light shift perturbations of the guiding potential are canceled. As a proof-of-principle demonstration, a Mach-Zehnder interferometer is set horizontally to map the acceleration introduced by the focused optical guide. This magic guide interferometer on the clock transition is applicable to atomic elements where magic wavelengths can be found. Possible applications of the magic guide interferometer, including a hollow-core fiber interferometer and gra…
Atom interferometry is a powerful experimental technique that can be employed to search for the oscillation of atomic transition energies induced by ultralight scalar dark matter (ULDM). Previous studies have focused on the sensitivity to ULDM of km-length atom gradiometers, where atom interferometers are located at the ends of very long baselines. In this work, we generalize the treatment of the time-dependent signal induced by a linearly-coupled scalar ULDM candidate for vertical atom gradiometers of any length and find correction factors that especially impact the ULDM signal in short-basel…
We investigate the effect of coherent population trapping (CPT) in an atom inter-ferometer gravimeter based on the use of stimulated Raman transitions. We find that CPT leads to significant phase shifts, of order of a few mrad, which may compromise the accuracy of inertial measurements. We show that this effect is rejected by the k-reversal technique, which consists in averaging inertial measurements performed with two opposite orientations of the Raman wavevector k, provided that internal states at the input of the interferometer are kept identical for both configurations.
We present a single-source dual atom interferometer and utilize it as a gradiometer for precise gravitational measurements. The macroscopic separation between interfering atomic wave packets (as large as 16 cm) reveals the interplay of recoil effects and gravitational curvature from a nearby Pb source mass. The gradiometer baseline is set by the laser wavelength and pulse timings, which can be measured to high precision. Using a long drift time and large momentum transfer atom optics, the gradiometer reaches a resolution of $3 \times 10^{-9}$ s$^{-2}$ per shot and measures a 1 rad phase shift …
We present an atom interferometry technique in which the beamsplitter is split into two separate operations. A microwave pulse first creates a spin-state superposition, before optical adiabatic passage spatially separates the arms of that superposition. Despite using a thermal atom sample in a small ($600 \, μ$m) interferometry beam, this procedure delivers an efficiency of $99\%$ per $\hbar k$ of momentum separation. Utilizing this efficiency, we first demonstrate interferometry with up to $16\hbar k$ momentum splitting and free-fall limited interrogation times. We then realize a single-sourc…
MAGIS-100 is a next-generation quantum sensor under construction at Fermilab that aims to explore fundamental physics with atom interferometry over a 100-meter baseline. This novel detector will search for ultralight dark matter, test quantum mechanics in new regimes, and serve as a technology pathfinder for future gravitational wave detectors in a previously unexplored frequency band. It combines techniques demonstrated in state-of-the-art 10-meter-scale atom interferometers with the latest technological advances of the world's best atomic clocks. MAGIS-100 will provide a development platform…
We report on the realization of a matter-wave interferometer based on single-photon interaction on the ultra-narrow optical clock transition of strontium atoms. We experimentally demonstrated its operation as a gravimeter and as a gravity gradiometer. No reduction of interferometric contrast was observed up to an interferometer time $2T=10$ ms, limited by geometric constraints of the apparatus. In the gradiometric configuration, the sensitivity approaches the shot noise limit. Single-photon interferometers represent a new class of high-precision sensors that could be used for the detection of …
Atom interferometers in optical cavities benefit from strong laser intensities and high-quality wavefronts. The laser frequency pairs that are needed for driving Raman transitions (often generated by phase modulating a monochromatic beam) form multiple standing waves in the cavity, resulting in a periodic spatial variation of the properties of the atom-light interaction along the cavity axis. Here, we model this spatial dependence and calculate two-photon Rabi frequencies and ac Stark shifts. We compare the model to measurements performed with varying cavity and pulse parameters such as cavity…
We demonstrate a proof-of-principle of direct Earth gravity gradient measurement with an atom interferometer-based gravity gradiomter using a single proof mass of cold 87 rubidium atoms. The atomic gradiometer is implemented in the so-called double-loop configuration, hence providing a direct gravity gradient dependent phase shift insensitive do DC acceleration and constant rotation rate. The atom interferometer (AI) can be either operated as a gravimeter or a gradiomter by simply adding an extra Raman $π$-pulse. We demonstrate gravity gradient measurements first using a vibration isolation pl…
We present an observation of competition effect among multiple quantum paths in a Raman-type Mach-Zehnder atom interferometer. By measuring the contrast of interference fringes, the competition effect among multiple interference paths is experimentally investigated. Due to the phase competition, the contrast periodically oscillates when modulating either the phase or the interrogation time between Raman pulses. The multiple quantum paths form because of the imperfect population transfer efficiency in stimulated Raman transitions, and are verified by modulating the duration of Raman pulses. The…
A modified Michelson interferometer type Raman laser system for atom interferometers
我们研制了一种改进的迈克耳孙干涉仪型喇曼激光系统，用于操纵冷~（87）Rb原子进行干涉。采用调频连续波技术来确定光程差，从而将其补偿为零，以最大限度地减少共模噪声的影响。在6.834 GHz处的拍频信号的线宽（半峰全宽）被测量到由频谱分析仪的分辨率带宽限制的1Hz。在166 MHz处测量的相位噪声的均方根相位方差为0.015 rad 2，这主要是由于我们的性能较差的射频微波源。经过适当的改进，我们计划将该激光系统应用于原子干涉仪，用于加速度和旋转测量。
It is shown that using beam splitters with non-equal wave vectors results in a new recoil diagram which is qualitatively different from the well-known diagram associated with the Mach-Zehnder atom interferometer. We predict a new asymmetric Mach-Zehnder atom interferometer (AMZAI) and study it when one uses a Raman beam splitter. The main feature is that the phase of AMZAI contains a quantum part proportional to the recoil frequency. A response sensitive only to the quantum phase was found. A new technique to measure the recoil frequency and fine structure constant is proposed and studied outs…
Compared to light interferometers, the flux in cold-atom interferometers is low and the associated shot noise large. Sensitivities beyond these limitations require the preparation of entangled atoms in different momentum modes. Here, we demonstrate a source of entangled atoms that is compatible with state-of-the-art interferometers. Entanglement is transferred from the spin degree of freedom of a Bose-Einstein condensate to well-separated momentum modes, witnessed by a squeezing parameter of -3.1(8) dB. Entanglement-enhanced atom interferometers open up unprecedented sensitivities for quantum …
We propose and demonstrate a method for calibrating atomic trajectories in a large-area dual-atom-interferometer gyroscope. The atom trajectories are monitored by modulating and delaying the Raman transition, and they are precisely calibrated by controlling the laser orientation and the bias magnetic field. To improve the immunity to the gravity effect and the common phase noise, the symmetry and the overlapping of two large-area atomic interference loops are optimized by calibrating the atomic trajectories and by aligning the Raman-laser orientations. The dual-atom-interferometer gyroscope is…
Using the technique of point source atom interferometry, we characterize the sensitivity of a multi-axis gyroscope based on free-space Raman interrogation of a single source of cold atoms in a glass vacuum cell. The instrument simultaneously measures the acceleration in the direction of the Raman laser beams and the component of the rotation vector in the plane perpendicular to that direction. We characterize the sensitivities for the magnitude and direction of the rotation vector measurement, which are 0.033 $^{\circ}/\mathrm{s}$ and 0.27 $^{\circ}$ with one second averaging time, respectivel…
We report the first realization of large momentum transfer (LMT) clock atom interferometry. Using single-photon interactions on the strontium ${}^1S_0 - {}^3P_1$ transition, we demonstrate Mach-Zehnder interferometers with state-of-the-art momentum separation of up to $141\,\hbar k$ and gradiometers of up to $81\,\hbar k$. Moreover, we circumvent excited state decay limitations and extend the gradiometer duration to 50 times the excited state lifetime. Because of the broad velocity acceptance of the interferometry pulses, all experiments are performed with laser-cooled atoms at a temperature o…
We realize a Mach-Zehnder-type dual-atom-interferometer gyroscope with an interrogation arm of 40 cm length and the interference area up to 1.2 cm$^2$. The precise angular alignment of the large-scale separated Raman lasers is demonstrated by seeking the phase intersection of Ramsey-Bord$\acute{e}$ interferometers after the gravity effect is compensated and by decoupling the velocity dependent crosstalk phase shifts, and applied to build the Mach-Zehnder atom interferometer. Then a compact inertial rotation sensor is realized based on dual large-area Mach-Zehnder atom interferometers by precis…
An N-atom Collective State Atomic Interferometer with Ultra-High Compton Frequency and Ultra-Short de Broglie Wavelength, with root-N Reduction in Fringe Width
We focus on the fact that light-pulse atom interferometers measure the atoms' acceleration with only three data points per drop. As a result, the measured effect of the gravity gradient is systematically larger than the true one, an error linear with the gradient and quadratic in time almost unnoticed so far. We show how this error affects the absolute measurement of the gravitational acceleration $g$ as well as ground and space experiments with gradiometers based on atom interferometry such as those designed for space geodesy, the measurement of the universal constant of gravity and the detec…
We proposed the European Laboratory for Gravitation and Atom-interferometric Research (ELGAR), an array of atom gradiometers aimed at studying space-time and gravitation with the primary goal of observing gravitational waves (GWs) in the infrasound band with a peak strain sensitivity of $3.3 \times 10^{-22}/\sqrt{\text{Hz}}$ at 1.7 Hz. In this paper we detail the main technological bricks of this large scale detector and emphasis the research pathways to be conducted for its realization. We discuss the site options, atom optics, and source requirements needed to reach the target sensitivity. W…
We perform the experimental demonstration of the method proposed in [Phys. Rev. A 91, 063615 (2015)] to extract the differential phase in dual atom interferometers. From a single magneto-optical trap, we generate two atomic sources, vertically separated and free-falling synchronously, with the help of an accelerated lattice. We drive simultaneous Raman interferometers onto the two sources, and use the correlation with the vibration signal measured by a seismometer to extract the phase of each interferometer. We demonstrate an optimal sensitivity of the extracted differential phase between the …
Fine-structure Raman interferometry with metastable barium for magnetically resilient inertial sensing
Department of Physics, Institute of Science Tokyo（东京科学大学物理系）；Institute of Integrated Research, Institute of Science Tokyo（东京科学大学综合研究学院）；Product Development Center, Japan Aviation Electronics Industry, Ltd.（日本航空电子工业有限公司产品开发中心）
A new approach to the theory of atoms' interaction with chirped Raman pulses is developed. When the pulses have sufficiently close effective wave lengths, which are smaller than the atomic cloud size, equations for the family of the matrix elements of the atomic density matrix in the Wigner representation are derived. The solution, involving linear (in the pulse duration) phase corrections, is obtained for the rectangular pulse. The interferometric part of the atoms' excitation is calculated.
A point source atom interferometer (PSI) is a device where atoms are split and recombined by applying a temporal sequence of Raman pulses during the expansion of a cloud of cold atoms behaving approximately as a point source. Unlike a conventional light pulse atom interferometer, the PSI can produce a signal that corresponds to multi-axis rotation only, independent of acceleration. In addition, it can be used to measure acceleration along one direction, independent of rotation. Here, we describe a modified PSI that can be used to measure multi-axis rotation and multi-axis acceleration. Specifi…
Coriolis effect is an important error source in the weak equivalence principle (WEP) test using atom interferometer. In this paper, the problem of Coriolis error in WEP test is studied theoretically and experimentally. In theoretical simulation, Coriolis effect is analyzed by establishing an error model. The measurement errors of Eotvos coefficient (eta) in WEP test related to experimental parameters, such as horizontal-velocity difference and horizontal-position difference of atomic clouds, horizontal-position difference of detectors and rotation compensation of Raman laser's mirror are calcu…
We report simultaneous conjugate Ramsey-Bordé interferometers with a sample of low-mass (lithium-7) atoms at 50 times the recoil temperature. We optically pump the atoms to a magnetically insensitive state using the $2S_{1/2} - 2P_{1/2}$ line. Fast stimulated Raman beam splitters address a broad velocity class and unavoidably drive two conjugate interferometers that overlap spatially. We show that detecting the summed interference signals of both interferometers, using state labeling, allows recoil measurements and suppression of phase noise from vibrations. The use of "warm" atoms allows for …
Atom Optics for Multidimensional Raman Interferometry
A-Knows Lab, State Key Laboratory of Precision Measurement Technology and Instruments, Department of Precision Instruments, Tsinghua University（清华大学精密仪器系精密测量技术与仪器全国重点实验室A-Knows实验室）；The Key Laboratory of Quantum Precision Measurement of Zhejiang Province, School of Physcis and Optical Engineering, Zhejiang University of Technology（浙江工业大学物理与光学工程学院浙江省量子精密测量重点实验室）；School of Physics and Astronomy, Shanghai Jiao Tong University（上海交通大学物理与天文学院）；Tsung-Dao Lee Institute, Shanghai Jiao Tong University（上海交通大学李政道研究所）
We present an observation of zero to $π$ phase flips induced by Rabi oscillation in an unbalanced Ramsey atom interferometer. The phase shift and visibility are experimentally investigated by modulating either the polarization or duration of Raman lasers, and they are well explained by a theoretical model. In an atom interferometer, the $π$-phase flips are caused not only by the sign of Rabi frequency but also by the Rabi oscillation. Considering the $π$-phase flips, we propose the composite-light-pulse sequences for realizing the large-momentum-transfer beam splitter and mirror, which have th…
