A Background-Free Search for Physics Beyond the Standard Model Using Atom Interferometry Description This presentation outlines an experimental architecture adapting a large-baseline atom interferometer with a macroscopic electrostatic potential to perform a background-free search for anomalous gauge-gravity scalar couplings. Searching for Beyond Standard Model (BSM) physics at the intersection of gravity and electromagnetism is traditionally hindered by severe kinematic degeneracies, specifically the quadratic Stark shift. This proposed architecture transforms a mathematically degenerate quantum measurement problem into an achievable array of classical control requirements utilizing a "Four-Pillar" metrological approach: Geometric Exponential Suppression: Utilizing a Faraday tube to exponentially decay vector leakage fields, physically breaking the parity degeneracy. Double-Difference Lock-In Quadrature: A 4-point measurement cycle that algebraically annihilates gigaradian inertial gravitational phases and active high-pass filters low-frequency drift. Mid-Fringe Sweeping: Injecting an active optical phase shift to defeat fringe-peak rectification bias caused by massive environmental vibration noise. Optimal Spin-Squeezing: Utilizing Quantum Non-Demolition (QND) measurements to surpass the Standard Quantum Limit, achieving a ~20 dB noise reduction. The protocol is rigorously validated through ab initio 1D Split-Step Fourier Method (SSFM) simulations and a Monte Carlo noise engine, which successfully extracted a 28.2 μrad target signal with >10σ statistical confidence against extreme macroscopic drift. A statistically significant detection using this pristine null test would carry profound fundamental implications, including the breakdown of local gauge invariance, Equivalence Principle violations, and new empirical constraints on screened scalars and the Standard-Model Extension (SME). Full preprint paper:Cagnani, I. (2026). A Background-Free Search for Physics Beyond the Standard Model Using Atom Interferometry. Zenodo. https://doi.org/10.5281/zenodo.18896187
A Background-Free Search for Physics Beyond the Standard Model Using Atom Interferometry Description This presentation outlines an experimental architecture adapting a large-baseline atom interferometer with a macroscopic electrostatic potential to perform a background-free search for anomalous gauge-gravity scalar couplings. Searching for Beyond Standard Model (BSM) physics at the intersection of gravity and electromagnetism is traditionally hindered by severe kinematic degeneracies, specifically the quadratic Stark shift. This proposed architecture transforms a mathematically degenerate quantum measurement problem into an achievable array of classical control requirements utilizing a "Four-Pillar" metrological approach: Geometric Exponential Suppression: Utilizing a Faraday tube to exponentially decay vector leakage fields, physically breaking the parity degeneracy. Double-Difference Lock-In Quadrature: A 4-point measurement cycle that algebraically annihilates gigaradian inertial gravitational phases and active high-pass filters low-frequency drift. Mid-Fringe Sweeping: Injecting an active optical phase shift to defeat fringe-peak rectification bias caused by massive environmental vibration noise. Optimal Spin-Squeezing: Utilizing Quantum Non-Demolition (QND) measurements to surpass the Standard Quantum Limit, achieving a ~20 dB noise reduction. The protocol is rigorously validated through ab initio 1D Split-Step Fourier Method (SSFM) simulations and a Monte Carlo noise engine, which successfully extracted a 28.2 μrad target signal with >10σ statistical confidence against extreme macroscopic drift. A statistically significant detection using this pristine null test would carry profound fundamental implications, including the breakdown of local gauge invariance, Equivalence Principle violations, and new empirical constraints on screened scalars and the Standard-Model Extension (SME). Full preprint paper:Cagnani, I. (2026). A Background-Free Search for Physics Beyond the Standard Model Using Atom Interferometry. Zenodo. https://doi.org/10.5281/zenodo.18896187
Atom interferometry provides a unique platform for testing fundamental physics. Building on the successful realization of the gravitational Aharonov-Bohm (gAB) effect in a large-baseline atom interferometer, I propose a next-generation experiment adapting this precise setup by adding a controllable electric potential. This experiment enables a background-free search for Beyond Standard Model (BSM) physics manifesting as a phenomenological composition-dependent coupling to both a gravitational and an electric potential (LBSM∝qφgφe). I show that the analogous Standard Model (SM) effect, a gravitationally-modified Stark shift, vanishes identically due to parity conservation; as the atomic ground state has even parity, the expectation value of this interaction is zero. To detect the target microradian-scale signal beneath milliradian-scale technical noise and gigaradian-scale inertial backgrounds, the experimental design integrates three crucial solutions: (1) a simultaneous dual-isotope (85Rb/87Rb) interferometer to reject technical common-mode noise, (2) optimal spin-squeezed states providing N−2/3 sensitivity scaling to surpass the Standard Quantum Limit, and (3) a four-point differential quadrature (±V0,±keff) to algebraically cancel the dominant inertial phase and all k-odd systematics. A Monte Carlo analysis validates this complete protocol's robustness against systematics and projects a realistic path to a 5-sigma discovery within a 3-month integration time. This model-independent search, particularly sensitive to neutron-coupled forces like U(1)B−L gauge bosons, constitutes a high-precision null test that further solidifies the Aharonov-Bohm intuition that potentials are more fundamental than fields.
Gravity plays a central role in our understanding of the Earth and the Universe. It is the dominant force at astronomic scales, shaping star systems and galaxies. It is also a pivotal field in the geosciences, allowing access to the physical shape of the Earth, defining height systems, and tracking mass transport, for example water in climate change research, inside volcanoes, or along seismic faults. Finally, it could become a crucial resource for engineering, opening the way to a renewal of underground exploration techniques, both for natural resources and civil engineering legacy. In fundamental physics, gravity nevertheless remains a riddle. From its origins to the first direct detection of gravitational waves in 2015, the theory of general relativity has accumulated successes. Our understanding of the microscopic world, through quantum mechanics and the standard model of particle physics is a similar success story, culminating with the detection of the BEH boson in 2012. Nevertheless, unification theories remain inaccessible and testing both the hypotheses and predictions of our theories remains the safest way towards the discovery of new physics. Here, key research areas relate to tests of the universality of free fall, at the heart of general relativity theory, or the creation of macroscopic superposition states of massive particles, a genuine marker of the quantum world. Novel applications in the geosciences also require improved gravity sensors. For multiple applications in engineering and geodesy, the ideal device is easily transportable and has low energy consumption. Nevertheless, higher-order references are necessary to enable an accurate definition of a gravity standard across the world. Such gravity references could also be combined with state-of-the-art laser gyroscopes into quantum Earth observatories. In this manuscript, we introduce a new generation of matter wave sensors based on very long baseline atom interferometry (VLBAI). Exploring the properties of massive quantum objects at the scales of meters and seconds, they will provide new insights into fundamental physics questions and serve as testbeds for novel atomic inertial sensors on ground and in space. We provide the motivation and working principles for absolute gravity sensing with VLBAI, and discuss in particular the specific trade-offs arising from the use of an extended baseline in atom interferometry. We also present the core design of the Hannover VLBAI facility. Finally, we demonstrate that through a unique and carefully characterized 10 m-long magnetically shielded baseline, this devices offers the required environment for next-generation atomic gravity reference sensors and tests of fundamental physics.
Very Long Baseline Atom Interferometry (VLBAI) corresponds to ground-based atomic matter-wave interferometry on large scales in space and time, letting the atomic wave functions interfere after free evolution times of several seconds or wave packet separation at the scale of meters. As inertial sensors, e.g., accelerometers, these devices take advantage of the quadratic scaling of the leading order phase shift with the free evolution time to enhance their sensitivity, giving rise to compelling experiments. With shot noise-limited instabilities better than 10−9 m/s2 at 1 s at the horizon, VLBAI may compete with state-of-the-art superconducting gravimeters, while providing absolute instead of relative measurements. When operated with several atomic states, isotopes, or species simultaneously, tests of the universality of free fall at a level of parts in 1013 and beyond are in reach. Finally, the large spatial extent of the interferometer allows one to probe the limits of coherence at macroscopic scales as well as the interplay of quantum mechanics and gravity. We report on the status of the VLBAI facility, its key features, and future prospects in fundamental science.
Quantum non-demolition measurement with an off-resonance polarized probe is a widely utilized technique for atomic sensors. Typically, QND instruments read out spin states through optical polarimetry using a linearly off-resonance probe in atomic media. This optical read-out process offers high accuracy, with potential applications in biomagnetism, inertial navigation and new physics exploration beyond the standard model. It was observed that previously unexplored spin-alignment polarization induced by the far-detuned off-resonance linear probe in an ultrasensitive optical polarimetry. The evolution of probe-generated multipole moments exacerbates probe noise due to strong magnetic couplings. A method was demonstrated to decouple spin-alignment from magnetic fields by manipulating the multipole moments in zero fields. A suppression of the probe noise by 8.2 dB at 1 Hz and 10.4 dB at 10 Hz with the proposed method, reaching the standard quantum limit, was achieved. The realized shot-noise-limited optical polarimetry shows significant potential for advancing the performance of atomic sensors, particularly in applications requiring ultra-high sensitivity, such as precision measurements and quantum metrology. These findings provide a pathway toward enhanced sensor precision in diverse scientific and technological applications.
Atom interferometry is a quantum sensor technology that uses ultra-cold atoms placed in entangled quantum states to detect minute changes in local fields arising from gravitational waves and ultra-light dark matter. Their extreme sensitivity to accelerations has been demonstrated for measurements of Newton’s gravitation constant, tests of the Equivalence Principle, and measurement of local gravity gradients. The search for ultra-light dark matter and measurements of gravitational waves requires interferometer baselines greater than approximately 100 m. In understanding the fundamental systematics and backgrounds of these detectors, we have discovered that atmospheric and seismic effects, even though physically decoupled from the atoms which are in vacuum and free-fall, are still detectable by the quantum phase of the atoms. From a different perspective these “noise” sources are also interesting signals that we may be able to understand better with these sensor platforms leading to cross-disciplinary studies in Earth sciences.