Atom Interferometry Research Articles

Digital stabilization of an I/Q modulator in the carrier suppressed single-sideband mode for atom interferometry

We present an all-digital method for stabilizing the phase biases in an electro-optic I/Q modulator for carrier-suppressed single-sideband (CS-SSB) modulation. Using programmable logic on the Red Pitaya STEMlab 125-14 platform, we digitally generate and demodulate an auxiliary radio-frequency tone whose beat with the optical carrier probes the I/Q modulator’s phase imbalances. We implement a multiple-input, multiple-output integral feedback controller that accounts for unavoidable cross-couplings in the phase biases to lock the error signals at exactly zero, where optical power fluctuations have no impact on phase stability. We demonstrate >23dB suppression of the optical carrier relative to the desired sideband at +3.4GHz over a period of 15 h and over temperature variations of 20°C.

Black hole spectroscopy with ground-based atom interferometer and space-based laser interferometer gravitational wave detectors

Gravitational wave (GW) detection allows us to test general relativity in entirely new regimes. A prominent role takes the detection of quasi-normal modes (QNMs), which are emitted after the merger of a binary black hole (BBH) when the highly distorted remnant emits GWs to become a regular Kerr black hole (BH). The BH uniqueness theorems of Kerr black hole solutions in general relativity imply that the frequencies and damping times of QNMs are determined solely by the mass and spin of the remnant BH. Therefore, detecting QNMs offers a unique way to probe the nature of the remnant BH and to test general relativity. We study the detection of a merging BBH in the intermediate-mass range, where the inspiral–merger phase is detected by space-based laser interferometer detectors TianQin and LISA, while the ringdown is detected by the ground-based atom interferometer (AI) observatory AION. The analysis of the ringdown is done using the regular broadband mode of AI detectors as well as the resonant mode optimizing it to the frequencies of the QNMs predicted from the inspiral–merger phase. We find that the regular broadband mode allows constraining the parameters of the BBH with relative errors of the order 10−1 and below from the ringdown. Moreover, for a variety of systems considered, the frequencies and the damping times of the QNMs can be determined with relative errors below 0.1 and 0.2, respectively. We further find that using the resonant mode can improve the parameter estimation for the BBH from the ringdown by a factor of up to three. Utilizing the resonant mode significantly limits the detection of the frequency of the QNMs but improves the detection error of the damping times by around two orders of magnitude.

Optical frequency filtering for Raman beams.

We present an optical filter that is appropriate for use with Raman beams in atomic interferometry. This is a filter that lets the light of the two frequencies of the Raman pair go through and rejects spurious frequencies that may be close to the atomic resonance and cause decoherence. We characterized the filter's performance optically and also by shining the light into atoms in a Ramsey sequence, to look for decoherence effects from photon scattering. We found that it is safe to use tapered amplifiers in single and double pass for light amplification in the Raman beams since the pedestal of emission has a negligible effect, which can be further reduced by the use of the filter we present.

Quectonewton Local Force Sensor.

We report on the realization of a quantum sensor based on trapped atom interferometry in an optical lattice for the measurement of atom-surface interactions, with sub-micrometer-level control of the mean atom-surface separation distance. The force sensor reaches a short-term sensitivity of 3.4×10^{-28} N at 1s and a long-term stability of 4qN (4×10^{-30} N). We perform force measurements in the 0-300 μm range, and despite significant stray forces caused by adsorbed atoms on the surface, we obtain evidence of the Casimir-Polder force.

Improved frequency shift compensation technique and pulse sequence for multi-loop atom interference experiments

With the rapid development of atom interference technology, multi-loop atom interferometers are widely used in the high-precision measurement of various physical constants and testing of various gravity-related effects. However, in ground-based multi-loop atom interference experiments, the systematic error contribution by classical effects is an important factor that affects the experimental measurement accuracy and gravitational effect detection. Based on this, we used the atomic wave-function evolution-phase accumulation method to provide a high-order interference phase of multi-loop atom interferometers in an inhomogeneous gravitational field containing Earth’s rotation. Furthermore, we propose a new scheme that combines optimised frequency-shift compensation technology with an improved pulse sequence to eliminate systematic errors due to the gravity gradient, Earth’s rotation, and their coupling effect with the pulse duration, as well as the coupling effect of laser detuning with the pulse duration. This study lays a theoretical foundation for experiments on multi-loop atom interferometers with higher precision.

Atom interferometer measures centimeter-scale gravity

Atom interferometer measures centimeter-scale gravity

Design and implementation of a high-performance miniaturized multi-layer magnetic shielding spherical shell with minimal pores based on target magnetic field

Achieving the spin-exchange relaxation-free (SERF) state in atomic comagnetometers (ACMs) necessitates a stable and weak magnetic environment. This paper presents the design of a miniaturized permalloy magnetic shielding spherical shell (MSSS) with minimal apertures, tailored to meet these requirements. By employing a combination of analytical solutions and finite element analysis (FEA), we achieved superior magnetic shielding while maintaining a compact form factor. The analytical solution for the shielding factor indicated that a four-layer permalloy sphere shell with optimized air gaps was necessary. A numerical analysis model of the MSSS was developed and validated using COMSOL software, confirming the suitability of the air gaps. The size, shape, and orientation of the openings in the perforated sphere shell were meticulously designed and optimized to minimize residual magnetism. The optimal structure was fabricated, resulting in triaxial shielding factors of 47619, 52631, and 21739, meeting the anticipated requirements. A comparison of simulation results with experimental tests demonstrated the efficacy of the design methodology. This study has significant implications for ultra-sensitive magnetic field detection devices requiring weak magnetic field environments, such as atomic gyroscopes, magnetometers, atomic interferometers, and atomic clocks.

The Benefits of Future Quantum Accelerometers for Satellite Gravimetry

AbstractWe investigate the benefits of future quantum accelerometers based on cold atom interferometry (CAI) on current and upcoming satellite gravity mission concepts. These mission concepts include satellite‐to‐satellite tracking (SST) in a single‐pair (GRACE‐like) and double‐pair constellation as well as satellite gravity gradiometry (SGG, single satellite, GOCE‐like). Regarding instruments, four scenarios are considered: current‐generation electrostatic (GRACE‐, GOCE‐like), next‐generation electrostatic, conservative hybrid/CAI and optimistic hybrid/CAI. For SST, it is shown that temporal aliasing poses currently the dominating error source in simulated global gravity field solutions independent of the investigated instrument and constellation. To still quantify the advantages of CAI instruments on the gravity functional itself, additional simulations are performed where the impact of temporal aliasing is synthetically reduced. When neglecting temporal aliasing, future accelerometers in conjunction with future ranging instruments can substantially improve the retrieval performance of the Earth's gravity field (depending on instrument and constellation). These simulation results are further investigated regarding possible benefit for hydrological use cases where these improvements can also be observed (when omitting temporal aliasing). For SGG, it is demonstrated that, with realistic instrument assumptions, one is still mostly insensitive to time‐variable gravity and not competitive with the SST principle. However, due to the improved instrument sensitivity of quantum gradiometers compared to the GOCE mission, static gravity field solutions can be improved significantly.

Perspective on Quantum Sensors from Basic Research to Commercial Applications

Quantum sensors represent a new generation of sensors with improved precision, accuracy, stability, and robustness to environmental effects compared to their classical predecessors. After decades of laboratory development, several types of quantum sensors are now commercially available or are part-way through the commercialization process. This paper provides a brief description of the operation of a selection of quantum sensors that employ the principles of atom–light interactions and discusses progress toward packaging those sensors into products. This paper covers quantum inertial and gravitational sensors, including gyroscopes, accelerometers, gravimeters, and gravity gradiometers that employ atom interferometry, nuclear magnetic resonance gyroscopes, atomic and spin-defect magnetometers, and Rydberg electric field sensors.

Scalar gravitational Aharonov–Bohm effect: Generalization of the gravitational redshift

The Aharonov–Bohm effect is a quantum mechanical phenomenon that demonstrates how potentials can have observable effects even when the classical fields associated with those potentials are absent. Initially proposed for electromagnetic interactions, this effect has been experimentally confirmed and extensively studied over the years. More recently, the effect has been observed in the context of gravitational interactions using atom interferometry. Additionally, recent predictions suggest that temporal variations in the phase of an electron wave function will induce modulation sidebands in the energy levels of an atomic clock, solely driven by a time-varying scalar gravitational potential. In this study, we consider the atomic clock as a two-level system undergoing continuous Rabi oscillations between the electron's ground and excited state. We assume the photons driving the transition are precisely frequency-stabilized to match the transition, enabling accurate clock comparisons. Our analysis takes into account, that when an atom transitions from its ground state to an excited state, it absorbs energy, increasing its mass according to the mass-energy equivalence principle. Due to the mass difference between the two energy levels, we predict that an atomic clock in an eccentric orbit experiencing a time-varying gravitational potential, will exhibit a constant frequency redshift relative to a ground clock, corresponding to the orbit's average gravitational redshift. Additionally, modulation sidebands will appear, and detecting these predicted sidebands would confirm the scalar gravitational Aharonov–Bohm effect.

Matter-wave interferometry based on barrier beam splitters

In this letter, we explore the use of barriers as coherent beam splitters for the construction of matter-wave interferometers. The effect of barrier shape and width, wave-packet width, and interatomic interaction on the interference signal is comprehensively investigated. Numerical simulations demonstrate the feasibility of constructing an atom interferometer utilizing deep-cooled Bose-Einstein condensates with barrier beam splitters. Such an interferometer exhibits the capability to measure acceleration with an accuracy of up to 10−8 g within a single measurement cycle.

Pathfinder experiments with atom interferometry in the Cold Atom Lab onboard the International Space Station

Deployment of ultracold atom interferometers (AI) into space will capitalize on quantum advantages and the extended freefall of persistent microgravity to provide high-precision measurement capabilities for gravitational, Earth, and planetary sciences, and to enable searches for subtle forces signifying physics beyond General Relativity and the Standard Model. NASA’s Cold Atom Lab (CAL) operates onboard the International Space Station as a multi-user facility for fundamental studies of ultracold atoms and to mature space-based quantum technologies. We report on pathfinding experiments utilizing ultracold 87Rb atoms in the CAL AI. A three-pulse Mach–Zehnder interferometer was studied to understand the influence of ISS vibrations. Additionally, Ramsey shear-wave interferometry was used to manifest interference patterns in a single run that were observable for over 150 ms free-expansion time. Finally, the CAL AI was used to remotely measure the Bragg laser photon recoil as a demonstration of the first quantum sensor using matter-wave interferometry in space.

All-semiconductor-based systems for atom interferometry experiments in space

Quantum atomic sensors based on atom interferometry (AI) have recently led to the development of new techniques for the measurement of inertial forces, finding important applications in both fundamental physics and applied research. As these types of sensors have begun to mature, they have received increasing interest for deployment in the field and even in space. There has been significant effort in the past in reducing the size and complexity of the system for applications in size, weight, and power (SWaP) challenging environments such as space. Here, we report on a design and assembly of a low-SWaP all-semiconductor-based laser and optical system (LOS) suitable for operating an AI system for potential space applications.

Accurate and efficient Bloch-oscillation-enhanced atom interferometry

Bloch oscillations of atoms in optical lattices are a powerful technique that can dramatically boost the sensitivity of atom interferometers to a wide range of signals by large momentum transfer. To leverage this method to its full potential, an accurate theoretical description of losses and phases is required, going beyond existing treatments. Here, we present a comprehensive theoretical framework for Bloch-oscillation-enhanced atom interferometry and verify its accuracy through comparison with a numerical solution of the Schrödinger equation. Our approach establishes design criteria to reach the fundamental efficiency and accuracy limits of large momentum transfer using Bloch oscillations and allows us, in a broader context, to define the fundamental efficiency limit of the transport of neutral atoms using optical lattices. We compare these limits to the capabilities of current state-of-the-art experiments and make projections for the next generation of quantum sensors. Published by the American Physical Society 2024

Violation of the equivalence principle induced by oscillating rest mass and transition frequency, and its detection in atom interferometers

We present a theoretical investigation of the expected experimental signals produced by freely falling atoms with time oscillating mass and transition frequency. These oscillations could be produced in a variety of models, in particular, models of scalar dark matter nonuniversally coupled to the standard matter such as axionlike particles and dilatons. Performing complete and rigorous calculations, we show that, on one hand, two different atomic species would accelerate at a different rate, and, on the other hand, they would produce a nonzero differential phase shift in atom interferometers (AI). The former would produce observable signals in equivalence principle tests like the recent MICROSCOPE mission, and we provide a corresponding sensitivity estimate, showing that MICROSCOPE can reach beyond the best existing searches in the axionlike particle case. We also compare the expected sensitivity of two future AI experiments, namely the AION-10 gradiometer and an isotope differential AI considered for MAGIS-100, that we will refer to as SPID. We show that the SPID setup would be more sensitive to these dark matter fields compared to the gradiometer one, assuming equivalent experimental parameters. Published by the American Physical Society 2024

Atom interferometry at arbitrary orientations and rotation rates

The exquisite precision of atom interferometers has sparked the interest of a large community for uses ranging from fundamental physics to geodesy and inertial navigation. However, their implementation for onboard applications is still limited, not least because rotation and acceleration are intertwined in a single phase shift, which makes the extraction of a useful signal more challenging. Moreover, the spatial separation of the wave packets due to rotations leads to a loss of signal. We present an atom interferometer operating over a large range of random angles, rotation rates and accelerations. A model of the expected phase shift allows us to untangle the rotation and acceleration signals. We also implement a real-time compensation system using fiber-optic gyroscopes and a rotating reference mirror to maintain the full contrast of the interferometer. We demonstrate a single-shot sensitivity to acceleration of 24 μg for rotation rates reaching 14° s−1.

Constellation design and performance of future quantum satellite gravity missions

Temporal aliasing is currently the largest error contributor to time-variable satellite gravity field models. Therefore, the evolution of sensor technologies has to be complemented by strategies to reduce temporal aliasing errors. The most straightforward way to improve temporal aliasing is through extended satellite constellations because they improve the observation geometry and increase the achievable temporal resolution. Therefore, strategies to optimize the design of larger satellite constellations are investigated in this contribution. A complete constellation modeling procedure is presented, starting from primary design variables (such as the required targeted resolutions) and concluding with concrete orbital elements for the individual satellites. In parallel, it is evaluated if improved instrument sensitivities based on quantum technologies (cold atom interferometry) can be fully exploited in the case of larger constellations. For this, future quantum satellite gravity missions adopting the gradiometry concept (similar to the GOCE mission) and the low-low satellite-to-satellite tracking concept (similar to GRACE/-FO) are simulated on optimized constellations with up to 6 satellites/pairs. The retrieval performance of a 6-pair mission in terms of the global equivalent water height RMS can be improved by a factor of roughly 3 compared to an inclined double-pair mission. 3D-gradiometry intrinsically has a better de-aliasing behavior but has extremely high accuracy requirements for the gradiometer (about 10 µEotvos) and the attitude reconstruction to be of any benefit. All simulations show that when incorporating improved sensor technologies, such as future quantum sensing instruments in extended constellations, temporal aliasing will remain the dominant error source by far, up to five orders of magnitude larger than the instrument errors. Therefore, improving sensor technologies has to go hand in hand with larger satellite constellations and improved space–time parameterization strategies to further reduce temporal aliasing effects.Graphical

Evaluation of the systematic error induced by quadratic Zeeman effect using hyperfine-ground-state-exchange method in a long-baseline dual-species atom interferometer

Evaluation of the systematic error induced by quadratic Zeeman effect using hyperfine-ground-state-exchange method in a long-baseline dual-species atom interferometer

Atom interferometer using spatially localized beam splitters

Atom interferometer using spatially localized beam splitters

High-performance silicon photonic single-sideband modulators for cold-atom interferometry.

The laser system is the most complex component of a light-pulse atom interferometer (LPAI), controlling frequencies and intensities of multiple laser beams to configure quantum gravity and inertial sensors. Its main functions include cold-atom generation, state preparation, state-selective detection, and generating a coherent two-photon process for the light-pulse sequence. To achieve substantial miniaturization and ruggedization, we integrate key laser system functions onto a photonic integrated circuit. Our study focuses on a high-performance silicon photonic suppressed-carrier single-sideband (SC-SSB) modulator at 1560 nanometers, capable of dynamic frequency shifting within the LPAI. By independently controlling radio frequency (RF) channels, we achieve 30-decibel carrier suppression and unprecedented 47.8-decibel sideband suppression at peak conversion efficiency of -6.846 decibels (20.7%). We investigate imbalances in both amplitudes and phases between the RF signals. Using this modulator, we demonstrate cold-atom generation, state-selective detection, and atom interferometer fringes to estimate gravitational acceleration, g ≈ 9.77 ± 0.01 meters per second squared, in a rubidium (87Rb) atom system.