Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Optical and Quantum Sensing and Precision Metrology II

Improving the sensitivity grating-echo atom interferometers for measurements of gravity

Gehrig Carlse, Jaskaran Randhawa, Alexander Pouliot, Thomas Vacheresse, Eduardo Ramos, Adam C. Carew, Anantharaman Kumarakrishnan

Published Mar 13, 2024• 0 citations
Publisher

Abstract

Precision measurements of gravitational acceleration g have far reaching applications in navigation and sensing as well as for tests of general relativity. Grating-echo atom interferometers (AIs) utilize simple setups and distinctive excitation schemes that involve a single excitation laser, and do not require velocity selection. They have demonstrated measurements of gravity precise to 75 parts per billion (ppb) by dropping laser-cooled atomic samples through ~ 1 cm. Here we describe progress toward realizing a cold atom gravimeter using an echo AI designed for drop heights of ~30 cm. The experimental technique involves illuminating the falling sample of laser-cooled rubidium atoms with two standing wave (sw) pulses separated by time t = T. The sw pulses are composed of two traveling-wave components, each having a wave vector of magnitude k = 2π/λ. Momentum state interference produces one-dimensional density gratings with a period λ/2 immediately after each excitation pulse. These gratings dephase due to the velocity distribution of the sample along the sw axis. The AI uses an echo technique to cancel the effect of velocity dephasing and observe a rephased density grating in the vicinity of the echo time τ = 2Τ. The grating contrast and phase are measured by coherently backscattering a traveling wave readout pulse from the sample. The grating phase, measured with respect to a vibrationally stabilized inertial reference frame, scales as 2kgΤ2. A drawback of echo AIs is the signal-to-noise ratio, which is limited by the contrast of the grating and systematic effects due the refractive index of the sample. Here, we review improvements to the experimental design and investigate methods of improving the signal-to-noise ratio by optimizing the atom-field coupling. We describe progress toward realizing our goals of increasing the grating contrast and the backscattered signal. The improved contrast is expected to allow the experiment to be carried out at a lower density to reduce corrections due to the refractive index. We discuss a variety of excitation schemes for achieving a target precision of a few ppb.

DOI
10.1117/12.3012377

Related papers

Techniques for Inertial Sensing Using Atomic Matter Wave Lattices

Gehrig Carlse

This dissertation describes the development of a suite of interlinked techniques for precision metrology with matter wave lattices realized in a ceiling-to-floor non-magnetic atom trapping apparatus. This work involves the development of a single-state atom interferometer that relies on the observation of density gratings formed in the atomic ground state of a laser-cooled sample. These gratings, the result of Kapitza-Dirac diffraction of momentum states following a standing wave optical excitation pulse, typically dephase according to their velocity distribution, and motional properties of the sample, including the local value of gravitational acceleration g, are imprinted on the grating contrast and phase. These features can be extracted by coherently backscattering a travelling wave readout field applied within the thermal coherence time of the sample and measuring the grating free-induction decay. Alternatively, a grating echo, resulting from the application of two standing wave pulses separated by t=T_{21}, can be detected using the same backscattering method in the vicinity of the echo time t=2T_{21} on time scales defined by the transit of cold atoms out of the standing wave beam volume. This dissertation presents five main experimental results that impact a new generation of cold atom quantum sensors. Firstly, we investigate a technique for measuring the magnetic moments and sublevel distributions of laser-cooled gases. Secondly, we study optical channell-ing which can be used to increase the scattering efficiency of optical lattices and the sensitivity of grating-echo interferometers. Thirdly, we describe Bragg scattering of a readout pulse from optical lattices and develop a technique to optimize this process in dilute gas lattices, leading to increased signal strengths in echo interferometers. Fourthly, we demonstrate a novel "Ramsey" velocimeter which can measure sample center-of-mass velocity with a precision of 600 µm/s. Finally, we present a measurement of g which represents the first realization of a frequency domain echo-type gravimeter, with a sensitivity to g of 2 parts per million. We outline the basis for improving the precision of these sensors to realize devices capable of measuring g with a sensitivity of 10 parts per billion and probing velocities more precisely than all other atomic velocimeters.

•Dec 15, 2025•0 citations

Demonstration of improved sensitivity of echo interferometers to gravitational acceleration

Carson Mok, B. Barrett, Adam C. Carew +3 more

We have developed two configurations of an echo interferometer that rely on standing-wave excitation of a laser-cooled sample of rubidium atoms. Both configurations can be used to measure acceleration $a$ along the axis of excitation. For a two-pulse configuration, the signal from the interferometer is modulated at the recoil frequency and exhibits a sinusoidal frequency chirp as a function of pulse spacing. In comparison, for a three-pulse stimulated-echo configuration, the signal is observed without recoil modulation and exhibits a modulation at a single frequency as a function of pulse spacing. The three-pulse configuration is less sensitive to effects of vibrations and magnetic field curvature, leading to a longer experimental time scale. For both configurations of the atom interferometer (AI), we show that a measurement of acceleration with a statistical precision of 0.5% can be realized by analyzing the shape of the echo envelope that has a temporal duration of a few microseconds. Using the two-pulse AI, we obtain measurements of acceleration that are statistically precise to 6 parts per million (ppm) on a 25 ms time scale. In comparison, using the three-pulse AI, we obtain measurements of acceleration that are statistically precise to 0.4 ppm on a time scale of 50 ms. A further statistical enhancement is achieved by analyzing the data across the echo envelope so that the statistical error is reduced to 75 parts per billion (ppb). The inhomogeneous field of a magnetized vacuum chamber limited the experimental time scale and resulted in prominent systematic effects. Extended time scales and improved signal-to-noise ratio observed in recent echo experiments using a nonmagnetic vacuum chamber suggest that echo techniques are suitable for a high-precision measurement of gravitational acceleration $g$. We discuss methods for reducing systematic effects and improving the signal-to-noise ratio. Simulations of both AI configurations with a time scale of 300 ms suggest that an optimized experiment with improved vibration isolation and atoms selected in the ${m}_{F}=0$ state can result in measurements of $g$ statistically precise to 0.3 ppb for the two-pulse AI and 0.6 ppb for the three-pulse AI.

arXiv:1307.1902•Physical Review A•Aug 20, 2013•16 citations

Prospects for Precise Measurements with Echo Atom Interferometry

B. Barrett, Adam C. Carew, Hermina C. Beica +3 more

Echo atom interferometers have emerged as interesting alternatives to Raman interferometers for the realization of precise measurements of the gravitational acceleration g and the determination of the atomic fine structure through measurements of the atomic recoil frequency ω q . Here we review the development of different configurations of echo interferometers that are best suited to achieve these goals. We describe experiments that utilize near-resonant excitation of laser-cooled rubidium atoms by a sequence of standing wave pulses to measure ω q with a statistical uncertainty of 37 parts per billion (ppb) on a time scale of ∼50 ms and g with a statistical precision of 75 ppb. Related coherent transient techniques that have achieved the most statistically precise measurements of atomic g-factor ratios are also outlined. We discuss the reduction of prominent systematic effects in these experiments using off-resonant excitation by low-cost, high-power lasers.

arXiv:1606.06831•Atoms•Jun 27, 2016•23 citations

Measuring the atomic recoil frequency using a modified grating-echo atom interferometer

B. Barrett, A. Carew, Scott Beattie +1 more

We describe progress toward a precise measurement of the recoil energy of an atom measured using a modified grating-echo atom interferometer (AI) that involves three standing-wave (sw) pulses. With this technique, an additional sw pulse is used to shift the phase of excited momentum states, which produces a modulation in the contrast of the interference pattern. The signal exhibits narrow fringes that revive periodically at twice the two-photon recoil frequency, $2{\ensuremath{\omega}}_{q}$, as a function of the onset time of the pulse. Experiments are performed using samples of laser-cooled rubidium atoms with temperatures $\ensuremath{\lesssim}$5 $\ensuremath{\mu}$K in a nonmagnetic apparatus. We demonstrate a measurement of ${\ensuremath{\omega}}_{q}$ with a statistical uncertainty of 37 parts per ${10}^{9}$ (ppb) on a time scale of $\ensuremath{\sim}$45 ms in 14 h. Further statistical improvements are anticipated by extending this time scale and narrowing the signal fringe width. However, the total systematic uncertainty is estimated to be $\ensuremath{\sim}$6 parts per ${10}^{6}$ (ppm). We describe methods of reducing these systematic errors.

arXiv:1209.5624•Physical Review A•Mar 25, 2013•21 citations

Atom-interferometric techniques for measuring uniform magnetic field gradients and gravitational acceleration

B. Barrett, I. Y. Chan, Anantharaman Kumarakrishnan

We discuss techniques for probing the effects of a constant force acting on cold atoms using two configurations of a grating echo-type atom interferometer. Laser-cooled samples of ${}^{85}$Rb with temperatures as low as 2.4 $\ensuremath{\mu}$K have been achieved in a new experimental apparatus with a well-controlled magnetic environment. We demonstrate interferometer signal lifetimes approaching the transit time limit in this system ($\ensuremath{\sim}270$ ms), which is comparable to the time scale achieved by Raman interferometers. Using these long time scales, we experimentally investigate the influence of a homogeneous magnetic field gradient using two- and three-pulse interferometers, which enable us to sense changes in externally applied magnetic field gradients as small as $\ensuremath{\sim}4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$ G/cm. We also provide an improved theoretical description of signals generated by both interferometer configurations that accurately models experimental results. With this theory, absolute measurements of $B$ gradients at the level of $3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ G/cm are achieved. Finally, we contrast the suitability of the two- and three-pulse interferometers for precision measurements of the gravitational acceleration, $g$.

arXiv:1104.4577•Physical Review A•Dec 19, 2011•27 citations

Probing gravity with trapped atoms: the optical lattice atom interferometer

Cristian Daniel Panda

Atom interferometers are quantum mechanical devices sensitive to gravitational and inertial forces, with applications in fundamental physics and inertial sensing in the field. Their performance is currently limited by the interrogation time available to freely falling atoms in Earth’s gravitational field, as well as noise due to mechanical and acoustic vibrations. Our experiment probes gravitational potentials by holding, rather than dropping, atoms. We realize an interrogation time of 20 seconds by suspending the spatially separated atomic wave packets in an optical lattice. This record coherence is enabled by the smooth lattice wave fronts, which are mode-filtered by an optical cavity. This trapped geometry suppresses phase variance due to vibrations by three to four orders of magnitude, overcoming the dominant noise source in atom-interferometric gravimeters. The later part of the talk describes recent progress in characterizing and reducing dephasing of the interferometer. An upgraded optical lattice interferometer experiment is currently being commissioned, with the goal of increased sensitivity to gravity.

Optical and Quantum Sensing and Precision Metrology•Mar 4, 2021•0 citations
Precision measurements of gravitational acceleration g have far reaching applications in navigation and sensing as well as for tests of general relativity. Grating-echo atom interferometers (AIs) utilize simple setups and distinctive excitation schemes that involve a single excitation laser, and do not require velocity selection. They have demonstrated measurements of gravity precise to 75 parts per billion (ppb) by dropping laser-cooled atomic samples through ~ 1 cm. Here we describe progress toward realizing a cold atom gravimeter using an echo AI designed for drop heights of ~30 cm. The experimental technique involves illuminating the falling sample of laser-cooled rubidium atoms with two standing wave (sw) pulses separated by time t = T. The sw pulses are composed of two traveling-wave components, each having a wave vector of magnitude k = 2π/λ. Momentum state interference produces one-dimensional density gratings with a period λ/2 immediately after each excitation pulse. These gratings dephase due to the velocity distribution of the sample along the sw axis. The AI uses an echo technique to cancel the effect of velocity dephasing and observe a rephased density grating in the vicinity of the echo time τ = 2Τ. The grating contrast and phase are measured by coherently backscattering a traveling wave readout pulse from the sample. The grating phase, measured with respect to a vibrationally stabilized inertial reference frame, scales as 2kgΤ2. A drawback of echo AIs is the signal-to-noise ratio, which is limited by the contrast of the grating and systematic effects due the refractive index of the sample. Here, we review improvements to the experimental design and investigate methods of improving the signal-to-noise ratio by optimizing the atom-field coupling. We describe progress toward realizing our goals of increasing the grating contrast and the backscattered signal. The improved contrast is expected to allow the experiment to be carried out at a lower density to reduce corrections due to the refractive index. We discuss a variety of excitation schemes for achieving a target precision of a few ppb.
This dissertation describes the development of a suite of interlinked techniques for precision metrology with matter wave lattices realized in a ceiling-to-floor non-magnetic atom trapping apparatus. This work involves the development of a single-state atom interferometer that relies on the observation of density gratings formed in the atomic ground state of a laser-cooled sample. These gratings, the result of Kapitza-Dirac diffraction of momentum states following a standing wave optical excitation pulse, typically dephase according to their velocity distribution, and motional properties of the sample, including the local value of gravitational acceleration g, are imprinted on the grating contrast and phase. These features can be extracted by coherently backscattering a travelling wave readout field applied within the thermal coherence time of the sample and measuring the grating free-induction decay. Alternatively, a grating echo, resulting from the application of two standing wave pulses separated by t=T_{21}, can be detected using the same backscattering method in the vicinity of the echo time t=2T_{21} on time scales defined by the transit of cold atoms out of the standing wave beam volume. This dissertation presents five main experimental results that impact a new generation of cold atom quantum sensors. Firstly, we investigate a technique for measuring the magnetic moments and sublevel distributions of laser-cooled gases. Secondly, we study optical channell-ing which can be used to increase the scattering efficiency of optical lattices and the sensitivity of grating-echo interferometers. Thirdly, we describe Bragg scattering of a readout pulse from optical lattices and develop a technique to optimize this process in dilute gas lattices, leading to increased signal strengths in echo interferometers. Fourthly, we demonstrate a novel "Ramsey" velocimeter which can measure sample center-of-mass velocity with a precision of 600 µm/s. Finally, we present a measurement of g which represents the first realization of a frequency domain echo-type gravimeter, with a sensitivity to g of 2 parts per million. We outline the basis for improving the precision of these sensors to realize devices capable of measuring g with a sensitivity of 10 parts per billion and probing velocities more precisely than all other atomic velocimeters.
We have developed two configurations of an echo interferometer that rely on standing-wave excitation of a laser-cooled sample of rubidium atoms. Both configurations can be used to measure acceleration aaa along the axis of excitation. For a two-pulse configuration, the signal from the interferometer is modulated at the recoil frequency and exhibits a sinusoidal frequency chirp as a function of pulse spacing. In comparison, for a three-pulse stimulated-echo configuration, the signal is observed without recoil modulation and exhibits a modulation at a single frequency as a function of pulse spacing. The three-pulse configuration is less sensitive to effects of vibrations and magnetic field curvature, leading to a longer experimental time scale. For both configurations of the atom interferometer (AI), we show that a measurement of acceleration with a statistical precision of 0.5% can be realized by analyzing the shape of the echo envelope that has a temporal duration of a few microseconds. Using the two-pulse AI, we obtain measurements of acceleration that are statistically precise to 6 parts per million (ppm) on a 25 ms time scale. In comparison, using the three-pulse AI, we obtain measurements of acceleration that are statistically precise to 0.4 ppm on a time scale of 50 ms. A further statistical enhancement is achieved by analyzing the data across the echo envelope so that the statistical error is reduced to 75 parts per billion (ppb). The inhomogeneous field of a magnetized vacuum chamber limited the experimental time scale and resulted in prominent systematic effects. Extended time scales and improved signal-to-noise ratio observed in recent echo experiments using a nonmagnetic vacuum chamber suggest that echo techniques are suitable for a high-precision measurement of gravitational acceleration ggg. We discuss methods for reducing systematic effects and improving the signal-to-noise ratio. Simulations of both AI configurations with a time scale of 300 ms suggest that an optimized experiment with improved vibration isolation and atoms selected in the mF=0{m}_{F}=0mF​=0 state can result in measurements of ggg statistically precise to 0.3 ppb for the two-pulse AI and 0.6 ppb for the three-pulse AI.
Echo atom interferometers have emerged as interesting alternatives to Raman interferometers for the realization of precise measurements of the gravitational acceleration g and the determination of the atomic fine structure through measurements of the atomic recoil frequency ω q . Here we review the development of different configurations of echo interferometers that are best suited to achieve these goals. We describe experiments that utilize near-resonant excitation of laser-cooled rubidium atoms by a sequence of standing wave pulses to measure ω q with a statistical uncertainty of 37 parts per billion (ppb) on a time scale of ∼50 ms and g with a statistical precision of 75 ppb. Related coherent transient techniques that have achieved the most statistically precise measurements of atomic g-factor ratios are also outlined. We discuss the reduction of prominent systematic effects in these experiments using off-resonant excitation by low-cost, high-power lasers.
We describe progress toward a precise measurement of the recoil energy of an atom measured using a modified grating-echo atom interferometer (AI) that involves three standing-wave (sw) pulses. With this technique, an additional sw pulse is used to shift the phase of excited momentum states, which produces a modulation in the contrast of the interference pattern. The signal exhibits narrow fringes that revive periodically at twice the two-photon recoil frequency, $2{\ensuremath{\omega}}_{q}$, as a function of the onset time of the pulse. Experiments are performed using samples of laser-cooled rubidium atoms with temperatures $\ensuremath{\lesssim}$5 $\ensuremath{\mu}$K in a nonmagnetic apparatus. We demonstrate a measurement of ${\ensuremath{\omega}}_{q}$ with a statistical uncertainty of 37 parts per 109{10}^{9}109 (ppb) on a time scale of $\ensuremath{\sim}$45 ms in 14 h. Further statistical improvements are anticipated by extending this time scale and narrowing the signal fringe width. However, the total systematic uncertainty is estimated to be $\ensuremath{\sim}$6 parts per 106{10}^{6}106 (ppm). We describe methods of reducing these systematic errors.
We discuss techniques for probing the effects of a constant force acting on cold atoms using two configurations of a grating echo-type atom interferometer. Laser-cooled samples of 85{}^{85}85Rb with temperatures as low as 2.4 $\ensuremath{\mu}$K have been achieved in a new experimental apparatus with a well-controlled magnetic environment. We demonstrate interferometer signal lifetimes approaching the transit time limit in this system ($\ensuremath{\sim}270$ ms), which is comparable to the time scale achieved by Raman interferometers. Using these long time scales, we experimentally investigate the influence of a homogeneous magnetic field gradient using two- and three-pulse interferometers, which enable us to sense changes in externally applied magnetic field gradients as small as $\ensuremath{\sim}4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$ G/cm. We also provide an improved theoretical description of signals generated by both interferometer configurations that accurately models experimental results. With this theory, absolute measurements of BBB gradients at the level of $3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ G/cm are achieved. Finally, we contrast the suitability of the two- and three-pulse interferometers for precision measurements of the gravitational acceleration, ggg.
Atom interferometers are quantum mechanical devices sensitive to gravitational and inertial forces, with applications in fundamental physics and inertial sensing in the field. Their performance is currently limited by the interrogation time available to freely falling atoms in Earth’s gravitational field, as well as noise due to mechanical and acoustic vibrations. Our experiment probes gravitational potentials by holding, rather than dropping, atoms. We realize an interrogation time of 20 seconds by suspending the spatially separated atomic wave packets in an optical lattice. This record coherence is enabled by the smooth lattice wave fronts, which are mode-filtered by an optical cavity. This trapped geometry suppresses phase variance due to vibrations by three to four orders of magnitude, overcoming the dominant noise source in atom-interferometric gravimeters. The later part of the talk describes recent progress in characterizing and reducing dephasing of the interferometer. An upgraded optical lattice interferometer experiment is currently being commissioned, with the goal of increased sensitivity to gravity.