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Contemporary atomic clocks and atom interferometers provide measurements of frequency and gravity with unprecedented precision. Atom interferometers based on the intercombination transitions of alkaline-earth and alkaline-earth-like atoms operate at the intersection of these two devices and represent an emerging technology with a broad range of applications for fundamental physics tests. Here, work is presented towards the realization of a dual-species strontium and cadmium atom interferometer, which possess intercombination transitions in the visible and UV regions, respectively. A complete baseline, continuous-wave UV laser package for cadmium has been developed and characterized, including for the ultranarrow clock transition at 332 nm. A state-of-the-art vacuum apparatus for cadmium has been designed, which has been thoroughly numerically simulated and optimised considering the challenges arising when working with such low wavelengths. The future prospects of the cadmium-strontium interferometer are presented, including for tests of the weak equivalence principle and gravitational time-dilation-induced decoherence. In particular, the suitability of the developed laser systems for large-momentum-transfer single-photon gravimetry is analysed, suggesting gains in sensitivity up to 100 are possible.
We present the status of our optical frequency reference based on Ramsey-Bord{\'e} interferometry using the $^1$S$_0$ $\rightarrow$ $^3$P$_1$ intercombination line in strontium. Next to the current state of the atom interferometer based on a thermal atomic beam, we will present details of our compact and high-flux atomic oven, the cavity-stabilised laser system at $689$~nm and outline the anticipated noise contributions and systematic shifts of the transition frequency.
This work is supported by the German Space Agency (DLR) with funds provided by the Federal Ministry of Economics and Technology (BMWi) under grant number DLR50WM1852 and by the German Federal Ministry of Education and Research within the program quantum technologies - from basic research to market under grant number 13N15725.
We present a recent progress towards experiments with hydrogen atoms at ultra-low energies, nearly at rest planned by an international collaboration GRASIAN* (Gravity, Spectroscopy and Interferometry with Atoms and Neutrons, https://grasian.eu/). We will probe the ultralow-energy domain with hydrogen, the lightest and simplest of neutral atoms, which has served as a test probe of the fundaments of physics throughout the era of modern physics. The thermal motion of atoms has set limits to the accuracy of experiments. Therefore, using hydrogen atoms nearly at rest one expects to obtain unprecedented levels of precision.
I will report an atom interferometer based on quasi-Bragg diffraction in a fountain of 87-rubidium Bose-Einstein Condensate. We demonstrated interferometers with momentum transfers to the atoms up to 200 photon recoils. We investigated the limitations of the beam splitters due to, spontaneous emission and the limited efficiency of the quasi-Bragg diffraction. In particular, we propose a comprehensive study of parasitic interferometers due to the inherent multiport feature of the quasi-Bragg beam splitters. We show that these parasitic interferometers can distort the estimation of the interferometer phase shift and visibility. The impact of these effects will be discussed and the insight gained from these investigations should guide the development of very large base atom interferometers.
In matter wave lensing magnetic and optical harmonic potentials are used to collimate and focus matter waves. One of its key applications which I am interested in is atom lithography. By phase imprinting a design on these harmonic potentials, it can be transferred to the trapped atoms. With matter wave lensing we get a real time control of the size of these patterns which can be transferred to a suitable substrate.
We use rubidium 87 as the atomic source for creating matter waves or Bose Einstein Condensate. Rubidium atoms are evaporative cooled to form BECs in a crossed optical dipole trap. By choosing an appropriate frequency of the quadratic potential, we can focus the cloud and reduce its size after phase masking using an optical potential, which in turn can be transferred to a rubidium sensitive substrate.
We investigate the strength and linewidth of a transition between two RF-Dressed ground
states for Rubidium-87 in a non-uniform magnetic field. The linewidth of the selected transition
is broadened due to a mismatch of trapping potentials. This arises from a difference in Land´e
g-factor magnitude between the two hyperfine ground states. A scheme is presented wherein the
magnetic field dependence of the transition frequency between two RF-dressed Rubidium-87
states is reduced by the introduction of a microwave dressing field, increasing coherence times
and reducing transition linewidth [1]. Preliminary measurements are presented with the outlook
of incorporating this method into the operation of a chip-based atom interferometer [2].
Gravimeters based on atom interferometry not only offer the ability to measure the value of local acceleration g with high accuracy but also help validate highly relevant principles such as the Weak Equivalence Principle. Broadly speaking, the implementation of such a device comprises the following steps: Preparation of the atoms in a defined state, splitting and recombining the wave atomic function, and measurements of the different phases acquired by the atom’s wave function due to gravity. Every element requires components to be implemented such as a vacuum system, including the interferometric region, a laser system for the cooling, control, and detection of atoms, and a control system to control the experiment. This work shows the progress in the implementation of the first dual quantum gravimeter based on 133Cs and 87Rb atoms.
Title: High-precision atom interferometer GAIN
Authors: B. Leykauf, H.Thaivalappil Sunilkumar, V. Schkolnik, and A. Peters
The atom interferometer GAIN uses interfering ensembles of laser-cooled Rb-87 atoms in a fountain setup to precisely and accurately measure local gravity. Our instrument’s performance was compared to falling corner-cube and superconducting gravimeters during several measurement campaigns at geodetic observatories, demonstrating sensitivities better than 100 nm/s²/√Hz, long-term stability better than 1 nm/s² and an accuracy comparable with the best classical instruments.
Beyond its capabilities as a gravimeter, we will present the results of a test of the Continuous Spontaneous Localization (CSL) collapse model we recently performed. Furthermore, we will report on improvements implemented into the apparatus, including a new modularized laser system and FPGA-based laser stabilization.
There are a number of models that aim to reconcile the observed accelerating expansion of the universe with our current understanding of general relativity. One interesting model proposes the existence of a scalar field that is screened in regions of high matter density and can therefore go unnoticed in experiments performed on Earth – colloquially referred to as the ‘chameleon field’.
In 2015 Burrage et al showed that atoms inside a vacuum chamber are too small to screen the chameleon field and could therefore be used as a probe to measure it. Since then a number of experimental searches have been undertaken using cold atoms, but have so far failed to observe its existence.
Here, we describe a number of upgrades to our experiment at Imperial College that improve our precision and reduce systematic sources of errors. We are now planning a series of experiments that will probe the remaining region in parameter space where a signature of the elusive chameleon field may exist.
A Cesium (Cs) Bose-Einstein Condensate in an optical trap with the magnetic field as free tuning parameter offers exciting possibilities including tunable matter-wave interferometry which is planned to perform using optical double-well potential. The scattering length of Cs can be controlled using Feshbach coils in the practical range of magnetic field numbers for tuning the atom-atom interactions below an atomchip which adds compactness but increases the complexity. Cs being heavier than other possible candidates like Rubidium associates shorter De Broglie wavelength indicating sensitive equipment which can probe change in gravity for fundamental and environmental research.
Metric descriptions of gravitation, among them general relativity as today’s established theory, are founded on assumptions summarized in the Einstein equivalence principle (EEP). Its violation would hint at unknown physics and could be a leverage for the development of quantum gravity. Atomic clocks are excellent systems to probe aspects of EEP connected to (proper) time and have evolved into a working horse for tests of local position invariance (LPI). Even though the operational definition of time requires localized and idealized clocks, quantum systems like atoms allow for spatial superpositions that are inherently delocalized. While quantum experiments have tested other aspects of EEP, no competitive test of LPI has been performed or proposed allowing for an intrinsic delocalization. We extend the concepts for tests of the universality of clock rates (one facet of LPI) to atom interferometry generating delocalized quantum clocks. The proposed test depends on proper time with a favorable scaling and is, in contrast to fountain clocks, robust against initial conditions and recoil effects. It enables optical frequencies so that the projected sensitivity exceeds the one of state-of-the-art localized clocks. These results extend our notion of time, detached from classical and localized philosophies.
Are top sensitivity Sagnac gyroscopes suitable to fundamental physics tests?
Precision measurements of the Earth rotation make it possible to investigate fundamental physics, as they contain general relativity terms, such as de Sitter and Lense Thirring, and can provide unique data to investigate possible Lorentz violations. These measurements require high sensitivity, usually parametrised as the fraction of the average Earth rotation rate; the limit to be reached to study fundamental physics is 1 part in 10^9 and long term continuous operation. Present high sensitivity ring laser gyroscope have already fulfilled those requirements, and the sensitivity target has been demonstrated.
The GINGER (Gyroscopes IN General Relativity) project focuses on fundamental physics, using an array of Ring Laser Gyroscopes (RLG). The GINGER apparatus and its potentiality will be described.
Towards a levitated atom interferometer with potassium Matthias Kolb*a, Thomas Weigner a, Samuel Rind a, Thomas Spielauer a, Philipp Haslinger a a Vienna Center for Quantum Science and Technology, Atominstitut, TU Wien, Stadionallee 2, 1020 Vienna, Austria * matthias.kolb@tuwien.ac.at We develop a setup suitable for cavity-enhanced levitated atom interferometry, which is capable of very long interaction times [1, 2]. By holding atoms in a lattice, short- ranging potentials can be measured, enabling high precision experiments allowing to search for new physics and light induced interactions [3–5]. The small hyperfine splittings simplify the generation of laser frequencies needed for cooling the bosonic isotopes 39K and 41K from a single laser using acousto-optic modulators. The experiment consists of a transfer chamber separated by a valve to a science chamber, which facilitates the insertion of samples, e.g. test masses to measure their effect on the potassium atoms, but also allows for inserting electron sources to perform experiments to realize coherent interactions between atoms and electrons [6].
MAGIS-100 is a strontium atom interferometer with a baseline of 100 m under construction at Fermilab that aims to explore fundamental physics. AION is a UK initiative to develop this technology further. AION project has established five strontium atom interferometry laboratories nationwide, and a 10 m prototype is planned. Both projects will search for the ultralight dark matter fields and lead the technology for a future kilometre-scale detector that would be sensitive to gravitational waves from known sources. To achieve this, MAGIS 100 and AION will have to demonstrate the shot-noise limited detection, the ability to launch atoms for tens of meters, maintain the record-breaking spatial separation of the wave packets, and account for multiple systematic uncertainties.
As part of UK input to MAGIS-100 and a future AION-10 experiment, the University of Liverpool is contributing to the development of a phase-shear detection platform. The phase-shear detection method is a novel technique which imprints the interference fringes across the atom cloud allowing single-shot measurements of the phase and contrast, increasing the repetition rate of the experiment and better control of the systematics, such as Coriolis force. The phase-shear platform design, specifications, and integration into the experiment's detection system are presented.
The Matter-wave Atomic Gradiometer Interferometric Sensor (MAGIS-100) is a 100m vertical baseline detector under construction at Fermilab. It works closely with the Atom Interferometry Observatory Network (AION), a UK-based program with the initial goal of constructing a 10m detector. Both programs will use the latest strontium atomic interferometry techniques to search for dark matter, test quantum mechanics, and investigate the feasibility of constructing future kilometre baseline detectors.
The University of Liverpool deliverable for MAGIS and AION is the phase-shear detection platform, a UHV chamber housing a tip-tilt mirror that corrects for the Coriolis effect and allows for phase shear readout. The tip-tilt mirror is rotated by amplified piezoelectric actuators, whose motion will be measured by strain gauges. The strain gauge signal is sent to a piezo controller, which completes the servomotor system and allows for the precise movement of the mirror. The testing of this system is presented, as well as the future plans to implement MAGIS.
The Atom Interferometer Observatory and Network (AION) project aims to develop a next-generation differential atom interferometer for the detection of ultra-light dark matter and mid-frequency range gravitational waves, complementing the peak sensitivities of other experiments i.e., LISA, LIGO, and Virgo. The project is comprised of various stages, starting with a 10 m baseline atom interferometer paving the way to a 100 m detector and eventually a km-scale terrestrial detector with the final stage being the development of a satellite-based detector. The project is a multidisciplinary initiative bringing together researchers from seven institutions from all over the UK. In this work, I present the role of my team at Imperial College London in this collaboration which is to improve the sensitivity of the detector by performing spin-squeezing on the atoms. Spin squeezing involves the entanglement of many atoms to reduce the spin measurement noise (which obeys Heisenberg’s uncertainty principle) in one direction (i.e. Jy) while increasing the noise in the other direction (i.e. Jz) and allows measurements below the standard quantum limit. As a consequence, the resolution of the interferometer increases as the noise in the differential phase measurement is reduced.
Many quantum optics experiment, including but not limited to large-baseline atom interferometers, require a mechanically robust optical distribution system. Particularly for space-based missions, such as MAGIS Space or AEDGE, compactness also plays a crucial role.
We have developed an optical bench technology that is both compact and exhibits a high mechanical stability when exposed to mechanical loads and temperature fluctuations. Benches made using this toolkit have a proven track-record of many successful sounding rocket missions, such as the MAIUS cold-atom missions.
It will further be employed for the upcoming NASA-DLR BECCAL mission, a multi-user experimental facility aboard the ISS, which, among other things, will be able to perform atom interferometry along two separate axes, and can serve as a technological pathfinder to demonstrate major experimental and technological capabilities. For BECCAL, we have improved upon our toolkit, which includes an increase in functional density and an expansion to new wavelengths. We have constructed multiple prototypes that have undergone rigorous testing to assess technological readiness.
Our work is supported by the German Space Agency DLR with funds provided by the Federal Ministry for Economic Affairs and Energy (BMWi) under grant number 50 WP 1433, 50 WP 1703 and 50 WP 2103.
The 15m high Very Long Baseline Atom Interferometry (VLBAI) facility
in Hannover, Germany, aims for sub nm/s^2 gravity measurement sensitivities. Using light-pulse atom interferometry, the VLBAI facility enables to perform accurate measurements of inertial effects thus making it a useful device for metrology and tests of fundamental physics. The sensitivity of light-pulse atom interferometers depends on several factors one of which being the freefall time. A second-long free fall of the atoms allows to reach acceleration sensitivities of 1nm/s2, comparable to the best classical superconducting gravimeters. At the VLBAI facility, a freefall time of 2.8s can be reached. In addition, excellent control over the environment and a large atomic flux is necessary to reduce systematic effects and achieve shot-noise limited sensitivities.
We present the current status of the VLBAI facility and outline its
distinguishing aspects that will include sources of ultracold ytterbium
and rubidium, a 10m long UHV baseline magnetically shielded to below 1.5nT/m, and a inertial reference seismic attentuation system.
"AION (Atom Interferometer Observatory and Network) and MAGIS (Matter-wave Atomic Gradiometer Interferometric Sensor) are experiments utilising strontium atoms to search for ultra-light dark matter and mid-band gravitational waves. Both experiments have embarked on building a series of atom interferometers ranging from 10 m to 1 km baselines, with MAGIS currently constructing the 100 m detector at Fermilab and AION planning to build the 10 m detector at The University of Oxford. Technical features and parameters are shared between AION and MAGIS intending to establish a quantum sensors network.
The University of Liverpool is responsible for developing the phase-shear detection platform for AION and MAGIS, employing a piezo-driven retro reflection mirror inside the ultra-high vacuum chamber. The ultimate target is high-precision control of 50 nrad which will be achieved by an optical feedback system to track the angle of the retro-reflection mirror via an optical lever.
Rutherford Appleton Laboratory hosts one of five strontium labs in the AION consortium currently working on the 2D and 3D strontium magneto-optical traps and a 1064 nm dipole trap. The ultimate goal is to achieve strontium interferometry with the potential to test the out-of-vacuum phase-shear imaging platform in collaboration with the University of Liverpool."
Rubidium-85 Interferometry at the University of Liverpool: A previously decommissioned frequency standard fountain, repurposed for atom interferometry at the National Physical Laboratory with the University of Liverpool, has been relocated to Liverpool and is currently being prepared for an upgraded laser system. The device will serve as a prototype detector to test for fundamental physics concepts beyond the standard model and can act as a test stand for quantum technology and inertial sensing applications. The set-up is capable of trapping and cooling ~108 rubidium-85 atoms in a 3D MOT from a low-velocity intense source, followed by launching using a moving molasses configuration, and an interferometry sequence in a ~1 m magnetically shielded region.
A significant upgrade to laser power and frequency control for the cooling, repumper and Raman systems is underway. The interferometer is in a fountain configuration, so the upgrade also includes the ability to launch atoms, improved state selection, incorporation of an active vibration control system and a new detection system. Progress on the fountain, upgrading the laser system, and the planned new vacuum chamber will be reported.
Long baseline atom interferometers offer an exciting opportunity to explore mid-frequency gravitational waves. In this work we survey the landscape of possible contributions to the total `gravitational wave background' in this frequency band and advocate for targeting this observable. Such an approach is complimentary to searches for resolved mergers from individual sources and may have much to reveal
about the Universe. We find that the inspiral phases of stellar-mass compact binaries cumulatively produce a signal well within reach of the proposed AION-km and AEDGE experiments. Hypothetical populations of dark sector exotic compact objects, harbouring just a tiny fraction of the dark energy density, could also generate signatures
unique to mid- and low-frequency gravitational wave detectors, providing a novel means to probe complexity in the dark sector.
Atom interferometry provides a powerful tool to probe fundamental physics due to its incredible sensitivity to changes in local gravitational potential and atomic transition energies. New compact atom interferometry experiments such as AION-10 hope to constrain the presence of small oscillating signals from scalar ultra-light dark matter and other new physics by taking measurements over a long integration time. However, the sensitivity of this class of quantum sensors means that backgrounds from sources of nearby mass need to be considered carefully to ensure the success of the experiment. This poster will detail work we have done to calculate the simulated phase response of a differential atom interferometer taking measurements in a busy environment and how the backgrounds from local moving masses contribute to the spectral features of the signal. We also demonstrate a rudimentary method for mitigating these backgrounds by masking the noise to recover the characteristic features of an oscillating signal in the frequency domain.
We propose a laboratory experiment to detect the fifth force mediated by a new light scalar field. The symmetron is a light scalar field which couples quadratically to matter, with a symmetry-breaking potential that takes the form of a symmetric double-well. As the characteristic phase transition of the symmetron field occurs, topological defects or 'domain walls' can form. It is hoped that by designing and manufacturing a topologically-tailored vacuum chamber, we can ensure that these domain walls are long-lived by pinning them to the interior of the chamber. A good vacuum will result in a very low density environment in which the symmetron can couple with gravitational strength, and the effects of the scalar field on a matter particle are potentially observable via a particle experiment involving cold atoms. As a cloud of cold atoms approaches the domain wall, it will experience the fifth force mediated by the scalar field and will be deflected or reflected off the domain wall. This deflection or reflection is a signature of the fifth force and could constrain some previously unconstrained parts of the dark sector.
The search for violations of the Einstein equivalence principle and dark matter is a driving force for atom interferometery. A scalar, light dilaton field constitutes such a basic but consistent extension to known physics. While recent works focus on the coupling of matter to gravity and dilaton fields, we include the propagation of the light essential to manipulate the atoms. In particular, we derive modified Maxwell equations including an expanded gravitational and dilaton field. We show that to leading order the dilaton has no influence on the phase of the electromagnetic field, and only modifies the wave vector via gravity. We transfer this result to various classes of atom interferometers and show that the coupling to the dilaton field is solely given via the atom's mass, whereas the modified light propagation also enters via gravity.
Nowadays, matter-wave interferometry has become a powerful technique for measuring acceleration, gravity gradient, and constant rotation with enormous precision. Here, we explore an atom interferometer which is highly sensitive to unknown constant angular acceleration. By modeling rotation with fixed axis and constant angular acceleration, we employ atom-interferometric scheme based on a sequence of five Raman laser pulses. For a small enough initial angular velocity, we have found that the interferometer has a very high contrast, more precisely it is reduced only by a correction scaling with the sixth order of this initial angular velocity. On the other hand, the leading term of the interferometer phase is linearly proportional to the angular acceleration and scales with the fourth power of the total interferometer time. In addition, we have investigated the feasibility of the proposed scheme for the typical ground- and space-based configurations, such as a rotating platform on earth and satellites.
We analyze the possibility of the leptonic mixing matrix having a Wolfenstein form at the Grand Unified Theory scale. The renormalization group evolution of masses and mixing angles from the high scale to electroweak scale, in certain new physics scenarios, can significantly alter the form of the leptonic mixing matrix. In the past it as shown that such significant enhancement implies that the leptonic mixing matrix at high scale can be the same or similar in structure to the quark one. We thoroughly analyze this hypothesis in the light of the latest neutrino oscillation data as well as other constraints such as those coming from neutrinoless double beta decay. We show that such an ansatz, at least within the context of minimal supersymmetric models, is no longer compatible with the latest experimental data.
Multi-messenger studies involving Gravitational Waves
1,2F.C. Pîslan, 1L.I. Caramete, 1A. Caramete
1 Institute of Space Science, Romania
2 Faculty of Physics, University of Bucharest, Romania
Recently, with the first discovery of gravitational waves, the multi-messenger studies involving observations on the same astrophysical event with photons, neutrinos and gravitational waves really began in full.
One proposed approach is to follow electromagnetic observations of potential candidate sources for merging (like for instance of TXS 0506+056) and to model their gravitational wave emission and make predictions regarding the possible merging time or observational potential for present and future gravitational wave observatories. Using known observed parameters of potential candidate sources, such as masses, redshift, orbital separation, coordinates etc. and modelling the ones that are not yet observed, like spin or orbital separation we also simulated the potential waveform of the gravitational waves emitted in the interaction of the binary system and analyzed the waveform changes when certain parameters are modified, as well as the feasibility of actually detecting its merging phase. These studies can lead to limits on the potential detection of the future gravitational wave observatories or actual predictions for the present ones.
Simulating space-borne atom interferometers for Earth Observation and tests of General Relativity
Christian Struckmann, Ernst M. Rasel, Peter Wolf, Naceur Gaaloul
Quantum sensors based on the interference of matter waves provide an exceptional performance to test the postulates of General Relativity by comparing the free-fall acceleration of matter waves of different composition. Space-borne quantum tests of the universality of free fall (UFF) promise to exploit the full potential of these sensors due to long free-fall times, and to reach unprecedented sensitivity beyond current limits.
In this contribution, we present a simulator for satellite-based atom interferometry and demonstrate its functionality in designing the STE-QUEST mission scenario, a satellite test of the UFF with ultra-cold atoms to 10^-17 as proposed to the ESA Medium mission frame [https://arxiv.org/abs/2211.15412]. Moreover, we will highlight the possibility of this simulator to design Earth Observation missions going beyond state of the art such as the CARIOQA concept [https://arxiv.org/abs/2211.01215].
This work is supported by DLR funds from the BMWi (50WM2263A-CARIOQA-GE and 50WM2253A-(AI)^2).
We present a systematic approach to calculate all relativistic phase shift effects in Bragg-type light-pulse matter wave interferometer (MWI) experiments up to (and including) order 𝒪(𝑐−2), placed in a weak gravitational field. The whole analysis is derived from first principles and even admits test of General Relativity (GR) apart from the usual Einstein Equivalence Principle (EEP) tests, consisting of universality of free fall (UFF) and local position invariance (LPI) deviations, by using the more general „parameterized post-Newtonian“ (PPN) formalism. We collect general phase shift formulas for a variety of well-known MWI schemes and present how modern experimental setups could measure PPN induced deviations from GR without the use of macroscopic test masses. This procedure should be seen as a way to easily calculate certain phase contributions, without having to redo all relativistic calculations in new MWI setups and come up with possibly new measurement strategies.
"Based on our previous work, we evaluate the possibility of implementing
and testing quantum walk algorithms and quantum neural network algorithms
using as hardware the optical lattice made by interfering cold atoms.
Recent evidence for the implementation of qubit gates using atomic
interferometry opens the possibility to address the qubit-environment
interaction noise problem that we also encounter on data analysis of
gravitational wave signals on quantum computers.
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