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A Background-Free Search for Physics Beyond the Standard Model Using Atom Interferometry

Cagnani, Ivan

Published Nov 21, 2025• 0 citations
Publisher

Abstract

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 ($\mathcal{L}_{BSM} \propto q \varphi_g \varphi_e$). 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 ($^{85}$Rb/$^{87}$Rb) 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 ($\pm V_0, \pm k_{\text{eff}}$) 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.

DOI
10.5281/zenodo.17722600

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A Background-Free Search for Physics Beyond the Standard Model Using Atom Interferometry

Ivan Cagnani

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

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Gravitational waves and ultralight dark matter are among the most compelling frontiers in fundamental physics, motivating proposals for very-long-baseline atom interferometerssuch as AION1, MAGIS2, AICE3 and AEDGE4 that aim to detect at frequencies at which ground-based5 and space-borne6 laser interferometers lose sensitivity. Very-long-baseline atom interferometers look for signals by comparing the quantum phase evolution of widely separated atomic ensembles interrogated by a common laser. However, their performance depends critically on suppressing noise sources, particularly laser phase noise. The experimental validation of such noise rejection remains an important challenge. Here we demonstrate a prototype differential atom interferometer based on the single-photon clock transition of fermionic 87Sr. Thus, we obtain a gradiometer configuration with a species intrinsically suited to kilometre-scale and space-baseline operation. The instrument operates at the standard quantum limit7 with no excess noise beyond atom shot noise. The differential configuration maintains quantum-limited sensitivity in the presence of several radians of artificially injected laser phase noise per shot, which emulates the conditions expected in a very-long-baseline atom interferometer. We also demonstrate the recovery of coherent oscillatory signals across a broad frequency range under fully phase-randomized conditions, a capability that is inaccessible to a single interferometer operating in the same regime. These results provide an experimental validation of the noise-immune measurement principle underlying very-long-baseline atom interferometers and mark an important step towards next-generation quantum sensors for gravitational-wave detection and searches for ultralight dark matter8,9.

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Abstract Gravitational waves and ultralight dark matter are among the most compelling frontiers in fundamental physics, motivating proposals for very-long-baseline atom interferometerssuch as AION 1 , MAGIS 2 , AICE 3 and AEDGE 4 that aim to detect at frequencies at which ground-based 5 and space-borne 6 laser interferometers lose sensitivity. Very-long-baseline atom interferometers look for signals by comparing the quantum phase evolution of widely separated atomic ensembles interrogated by a common laser. However, their performance depends critically on suppressing noise sources, particularly laser phase noise. The experimental validation of such noise rejection remains an important challenge. Here we demonstrate a prototype differential atom interferometer based on the single-photon clock transition of fermionic 87 Sr. Thus, we obtain a gradiometer configuration with a species intrinsically suited to kilometre-scale and space-baseline operation. The instrument operates at the standard quantum limit 7 with no excess noise beyond atom shot noise. The differential configuration maintains quantum-limited sensitivity in the presence of several radians of artificially injected laser phase noise per shot, which emulates the conditions expected in a very-long-baseline atom interferometer. We also demonstrate the recovery of coherent oscillatory signals across a broad frequency range under fully phase-randomized conditions, a capability that is inaccessible to a single interferometer operating in the same regime. These results provide an experimental validation of the noise-immune measurement principle underlying very-long-baseline atom interferometers and mark an important step towards next-generation quantum sensors for gravitational-wave detection and searches for ultralight dark matter 8,9 .

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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\mathcal{L}_{BSM} \propto q \varphi_g \varphi_eLBSM​∝qφg​φe​). 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 (85^{85}85Rb/87^{87}87Rb) interferometer to reject technical common-mode noise, (2) optimal spin-squeezed states providing N−2/3^{-2/3}−2/3 sensitivity scaling to surpass the Standard Quantum Limit, and (3) a four-point differential quadrature (±V0,±keff\pm V_0, \pm k_{\text{eff}}±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_{B-L}B−L​ gauge bosons, constitutes a high-precision null test that further solidifies the Aharonov-Bohm intuition that potentials are more fundamental than fields.
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
The gravitational Aharonov-Bohm (GAB) effect serves as the gravitational counterpart to the electromagnetic Aharonov-Bohm effect. Despite the concept's inception in 1967, a rigorous experimental test of the GAB effect remains elusive. While recent endeavors with ground-based apparatus show promise in uncovering hints of the GAB effect, we propose a precise yet practical experiment to deterministically measure the GAB phase shift using cold atom interferometry in a microgravity environment, such as an orbital space station or drop tower. We conduct a thorough analysis of the experiment's principles and derive key parameters. Our calculations suggest that it is feasible to precisely measure a significant GAB phase shift within known engineering constraints. Additionally, our design of the cold atom interferometer possesses a unique sensitivity to potential but insensitivity to force, which can be further refined to effectively mitigate adverse effects associated with nonzero inertial forces acting on the cold atoms. These endeavors will ultimately pave the way for experimental exploration into the quantum nature of gravity.
Atom interferometers provide a powerful means of realizing quantum coherent systems with increasingly macroscopic extent in space and time. These systems provide an opportunity for a variety of novel tests of fundamental physics, including ultralight dark matter searches and tests of modifications of gravity, using long drop times and microgravity environments. However, as experiments operate with longer periods of free fall and become sensitive to smaller background effects, key questions start to emerge about the fundamental limits to future atom interferometry experiments. We study the effects on atomic coherence from hard-to-screen backgrounds due to baths of ambient particles with long-range forces, such as gravitating baths and charged cosmic rays. Our approach---working in the Heisenberg picture for the atomic motion---makes proper inclusion of the experimental apparatus feasible and clearly shows how to handle long-range forces. We find that these potential backgrounds are likely negligible for the next generation of interferometers, as aggressive estimates for the gravitational decoherence from a background bath of dark matter particles gives a decoherence timescale on the order of years.
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 10−910^{-9}10−9 m/s2^22 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 101310^{13}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.
Gravitational waves and ultralight dark matter are among the most compelling frontiers in fundamental physics, motivating proposals for very-long-baseline atom interferometerssuch as AION1, MAGIS2, AICE3 and AEDGE4 that aim to detect at frequencies at which ground-based5 and space-borne6 laser interferometers lose sensitivity. Very-long-baseline atom interferometers look for signals by comparing the quantum phase evolution of widely separated atomic ensembles interrogated by a common laser. However, their performance depends critically on suppressing noise sources, particularly laser phase noise. The experimental validation of such noise rejection remains an important challenge. Here we demonstrate a prototype differential atom interferometer based on the single-photon clock transition of fermionic 87Sr. Thus, we obtain a gradiometer configuration with a species intrinsically suited to kilometre-scale and space-baseline operation. The instrument operates at the standard quantum limit7 with no excess noise beyond atom shot noise. The differential configuration maintains quantum-limited sensitivity in the presence of several radians of artificially injected laser phase noise per shot, which emulates the conditions expected in a very-long-baseline atom interferometer. We also demonstrate the recovery of coherent oscillatory signals across a broad frequency range under fully phase-randomized conditions, a capability that is inaccessible to a single interferometer operating in the same regime. These results provide an experimental validation of the noise-immune measurement principle underlying very-long-baseline atom interferometers and mark an important step towards next-generation quantum sensors for gravitational-wave detection and searches for ultralight dark matter8,9.
Abstract Gravitational waves and ultralight dark matter are among the most compelling frontiers in fundamental physics, motivating proposals for very-long-baseline atom interferometerssuch as AION 1 , MAGIS 2 , AICE 3 and AEDGE 4 that aim to detect at frequencies at which ground-based 5 and space-borne 6 laser interferometers lose sensitivity. Very-long-baseline atom interferometers look for signals by comparing the quantum phase evolution of widely separated atomic ensembles interrogated by a common laser. However, their performance depends critically on suppressing noise sources, particularly laser phase noise. The experimental validation of such noise rejection remains an important challenge. Here we demonstrate a prototype differential atom interferometer based on the single-photon clock transition of fermionic 87 Sr. Thus, we obtain a gradiometer configuration with a species intrinsically suited to kilometre-scale and space-baseline operation. The instrument operates at the standard quantum limit 7 with no excess noise beyond atom shot noise. The differential configuration maintains quantum-limited sensitivity in the presence of several radians of artificially injected laser phase noise per shot, which emulates the conditions expected in a very-long-baseline atom interferometer. We also demonstrate the recovery of coherent oscillatory signals across a broad frequency range under fully phase-randomized conditions, a capability that is inaccessible to a single interferometer operating in the same regime. These results provide an experimental validation of the noise-immune measurement principle underlying very-long-baseline atom interferometers and mark an important step towards next-generation quantum sensors for gravitational-wave detection and searches for ultralight dark matter 8,9 .