arXiv subjects

Hendrik Ulbricht

Publications and source records attributed to Hendrik Ulbricht.

At least 19 recordsLinked to original sources

arXiv2026

Maximizing Nonclassicality of Massive Objects via Quantum Zeno Effect

For testing quantum mechanics in the macroscopic domain, a major challenge is to devise effective means for enhancing the observable nonclassical signatures despite the ubiquitous presence of environmental decoherence. Toward this goal, we invoke the Quantum Zeno Effect (QZE) for achieving a tunable amplification of an inherently nonclassical quantum disturbance induced by any measurement. Such an enhancement of otherwise small and decoherence-suppressed nonclassicality can arise from the cumulative quantum disturbances generated by repetitive measurements, with the tunability of amplification controlled by the number of measurements. To evidence this, we formulate a testable loophole-free scheme using a massive oscillator, where the system preparation requires trapping and ground-state cooling of a massive object. The required measurements can be realized through a beam-splitter-type interaction between the mechanical oscillator and an optical field, followed by photon detection. Our analysis shows that such amplification, suitably quantified in terms of a testable witness, remains appreciably observable even in the realistic regimes of optomechanical damping, and for sufficiently large masses, thus enabling the demonstration of QZE in the macroscopic domain.

quant-ph↗

arXiv2026

A Levitated-Magnet Vector Force Sensor for Spin-Dependent Exotic Interactions

We present a magnetically levitated ferromagnetic vector force sensor that enables selective searches for spin-dependent exotic interactions mediated by beyond-Standard-Model bosons. A defining feature of spin-dependent exotic interactions is that they can generate forces with distinct directional signatures set by the relative spin configuration of the interacting bodies. We show that our sensor resolves these signatures by mapping forces along different axes onto distinct translational modes with different resonance frequencies, thereby separating interaction channels within the same coupling class. As a representative example, we study parity-violating axial-vector--vector interactions mediated by a spin-1 $Z'$ boson between a sensing and a driving levitated ferromagnet. Using a matched-filter likelihood analysis, we show that a setup based on an already demonstrated experiment can probe the pure electron--electron coupling $g_A^e g_V^e$ in the previously inaccessible force range $λ\lesssim 1\,\mathrm{cm}$, corresponding to mediator masses $M_{Z'} \gtrsim 10^{-5}\,\mathrm{eV}/c^2$. Our results establish levitated ferromagnets as a promising platform for millimeter-scale searches for spin-dependent fifth forces and for resolving the multiple effective potentials associated with a given coupling class.

hep-ph↗

arXiv2026

Detection of the Earth Tides by Diamagnetic Levitation

The detection of mass distributions and mass transport via gravity mapping is a key geophysical tool for understanding the structure and dynamics of the earth. Changes in mass distribution, driven by natural processes and human activity (e.g., extraction of oil, gas, and minerals), contribute to observable phenomena such as sea-level rise (3 mm per year), increased flooding, landslides, and ice mass loss (hundreds of giga-tons per year). These processes generate gravity variations detectable by gravimeters and gradiometers on ground and in space. Current instruments achieve sensitivities of 10-100 micro-GAL per square root of Hz and enable applications including hydrocarbon exploration, volcanic monitoring, and subsurface detection. They also measure Earth tides (100-300 micro-GAL amplitude), requiring long-term stability over days. However, existing systems are limited by size (more than 8 kg) and cost (more than 100,000 USD), restricting widespread deployment. Here we demonstrate a levitated mechanical sensor (LOMS) with a demonstrated sensitivity of 18 micro-GAL, a large dynamical range, and an integration time of 6 s, with an expected sensitivity of smaller than 200 nano-GAL per square root of Hz in a volume of only a few cubic cm. We resolve earth tide signals, demonstrating stability comparable to state-of-the-art instruments. Unlike conventional accelerometers (micro-g sensitivity, low stability), our device operates as a true gravimeter. Its compact size and low projected cost enable scalable deployment, including drone-based surveys (10-100 m altitude), distributed sensor networks, and multipixel gravity imaging arrays. This platform enables high-resolution, cost-effective gravity mapping with potential for large-scale geophysical monitoring.

physics.geo-ph↗

arXiv2026

Rotational Quantum Tunneling of a Magnetic Dipole in a Superconducting Trap

We study the quantum dynamics of the rotational degree of freedom of a nano-magnet trapped in a superconducting trap. The nano-magnet is modeled as a magnetic dipole with magnetization pinned to the easy axis of the particle. The magnetic trap then leads to a potential barrier that hinders free rotation of the particle, but through which it can tunnel. We identified rest-gas scattering as the most important decoherence mechanism at low temperatures. A shape of the particle sufficiently close to perfect rotational symmetry about the rotational axis can protect the rotational tunneling against this decoherence mechanism, and we identify experimentally feasible parameter regimes where rotational tunneling should be observable.

quant-ph↗

arXiv2026

Magnetic Levitation as a New Probe of Non-Newtonian Gravity

We present MORRIS (Magnetic Oscillatory Resonator for Rare-Interaction Studies) and propose the first tabletop search for non-Newtonian gravity due to a Yukawa-like fifth force using a magnetically levitated particle. Our experiment comprises a levitated sub-millimeter magnet in a superconducting trap that is driven by a time-periodic source. Featuring short-, medium-, and long-term stages, MORRIS will admit increasing sensitivities to the force coupling strength $α$, optimally probing screening lengths of $λ\sim 1\,\mathrm{mm}$. Our short-term setup provides a proof-of-principle study, with our medium- and long-term stages respectively constraining $α\lesssim 10^{-4}$ and $α\lesssim 10^{-5}$, leading over existing bounds. Our projections are readily recastable to concrete models predicting the existence of fifth forces, and our statistical analysis is generally applicable to well-characterized sinusoidal driving forces. By leveraging ultralow dissipation and heavy test masses, MORRIS opens a new window onto tests of small-scale gravity and searches for physics beyond the Standard Model.

hep-ph↗

arXiv2025

Macroscopic Quantum Resonators Path Finder (MAQRO-PF) White Paper

Optically levitated particles are used in a wide range of experiments to explore both fundamental physics and to act as sensors to a variety of external forces. One field of particular interest that these particles can be used to investigate is quantum mechanics. Previous research has yet to set an absolute upper bound on the size of objects that can be prepared in a quantum superposition. Exploring this limit involves allowing ever-larger objects to freely and coherently evolve to assess if their behaviour matches quantum or classical theoretical predictions. However, the long free evolution times required for these behaviours to be visible result in the experiments being gravitationally limited. Space based platforms therefore become the next key step in these investigations. In this white paper, we shall discuss our proposal for an optical levitation experiment in space that will explore the fundamental upper size limits of quantum mechanics. We shall cover the scientific motivation behind these investigations, then summarize the current status of our designs for the satellite. We will then review the aspects of the payload that require further development, then summarize the current estimates of the payload's requirements.

quant-ph↗

arXiv2025

Oligonucleotide selective detection by levitated optomechanics

This study examines the detection of oligonucleotide-specific signals in sensitive optomechanical experiments. Silica nanoparticles were functionalized using ZnCl$_2$ and 25-mers of single-stranded deoxyadenosine and deoxythymidine monophosphate which were optically trapped by a 1550 nm wavelength laser in vacuum. In the optical trap, silica nanoparticles behave as harmonic oscillators, and their oscillation frequency and amplitude can be precisely detected by optical interferometry. The data was compared across particle types, revealing differences in frequency, width and amplitude of peaks with respect to motion of the silica nanoparticles which can be explained by a theoretical model. Data obtained from this platform was analyzed by fitting Lorentzian curves to the spectra. Dimensionality reduction detected differences between the functionalized and non-functionalized silica nanoparticles. Random forest modeling provided further evidence that the fitted data were different between the groups. Transmission electron microscopy was carried out, but did not reveal any visual differences between the particle types.

physics.optics↗

arXiv2025

Cryogenic pressure sensing with an ultrafast Meissner-levitated microrotor

Magnetically levitated spinning rotors are key elements in important technologies such as navigation by gyroscopes, energy storage by flywheels, ultra-high vacuum generation by turbomolecular pumps, and pressure sensing for process control. However, mechanical rotors are typically macroscopic and limited to room temperature and low rotation frequencies. In particular, sensing pressure at low temperatures remains a technological challenge, while emerging quantum technologies demand a precise evaluation of pressure conditions at low temperatures to cope with quantum-spoiling decoherence. To close this gap, we demonstrate wide range pressure sensing by a spinning rotor based on a micromagnet levitated by the Meissner effect at 4.2 Kelvin. We achieve rotational speeds of up to 138 million rotations per minute, resulting in very high effective quality factors, outperforming current platforms. Beside sensing applications, we envision the use of levitated rotors for probing fundamental science including quantum mechanics and gravity, enabled by ultralow torque noise.

quant-ph↗

arXiv2025

A Spin-Based Pathway to Testing the Quantum Nature of Gravity

A key open problem in physics is the correct way to combine gravity (described by general relativity) with everything else (described by quantum mechanics). This problem suggests that general relativity and possibly also quantum mechanics need fundamental corrections. Most physicists expect that gravity should be quantum in character, but gravity is fundamentally different to the other forces because it alone is described by spacetime geometry. Experiments are needed to test whether gravity, and hence space-time, is quantum or classical. We propose an experiment to test the quantum nature of gravity by checking whether gravity can entangle two micron-sized crystals. A pathway to this is to create macroscopic quantum superpositions of each crystal first using embedded spins and Stern-Gerlach forces. These crystals could be nanodiamonds containing nitrogen-vacancy (NV) centres. The spins can subsequently be measured to witness the gravitationally generated entanglement. This is based on extensive theoretical feasibility studies and experimental progress in quantum technology. The eventual experiment will require a medium-sized consortium with excellent suppression of decoherence including vibrations and gravitational noise. In this white paper, we review the progress and plans towards realizing this. While implementing these plans, we will further explore the most macroscopic superpositions that are possible, which will test theories that predict a limit to this.

quant-ph↗

arXiv2025

Enhancement of the effects due to the Schrödinger-Newton equation

The Schrödinger-Newton (SN) equation introduces a nonlinear self-gravitational term to the standard Schrödinger equation, offering a paradigmatic model for semiclassical gravity. However, the small deviations it predicts from standard quantum mechanics pose significant experimental challenges. We propose a novel method to amplify such deviations through periodic modulation of the trapping frequency in a levitated mechanical oscillator. We identify specific regimes where the SN-induced effects on the dynamics of second moments are significantly enhanced-by up to six orders of magnitude compared to unmodulated setups. We show that this protocol remains feasible within current magnetic levitation technologies and enables distinguishability between standard and SN dynamics using measurable quantities such as the position variance. Our results pave the way for a viable experimental test of the SN equation, offering a new route to probe the interface between quantum mechanics and gravity.

quant-ph↗

arXiv2025

Measuring Decoherence Due to Quantum Vacuum Fluctuations

The interaction of a particle with vacuum fluctuations--which theoretically exist even in the complete absence of matter--can lead to observable irreversible decoherence if it were possible to switch on and off the particle charge suddenly. We compute the leading order decoherence effect for such a scenario and propose an experimental setup for its detection. Such a measurement might provide further insights into the nature of vacuum fluctuations and a novel precision test for the decoherence theory.

quant-ph↗

arXiv2025

The path towards measuring the gravitational field of proton bunches at accelerators

The Newtonian law describing the gravitational interaction of non-relativistic (slowly moving) gravitating matter, has been tested in many laboratory experiments with very high precision. In contrast, the post Minkowskian predictions for the gravitational field of ultra-relativistic matter, dominated by momentum instead of rest mass, have not been tested directly yet. The intense ultra-relativistic proton beam in the LHC storage ring offers the potential to test general relativity and alternative gravitational theories in this parameter regime for the first time in controlled lab-scale experiments. If successful, this would open the road to a novel use case of the LHC, where non-trivial gravitational physics could be studied likely in a parasitic mode, without the necessity of dedicated filling patterns. While the technical challenges are formidable, they should also lead to the development of ultra-high-sensitive acceleration sensors with abundant applications in other parts of science and technology. The present document summarizes the status of the theoretical studies in this direction, points out the challenges, and possible ways of addressing them. It was submitted as a contribution to the European Strategy for Particle Physics (ESPP) 2026 Update.

hep-ex↗

arXiv2025

Long-Baseline Atom Interferometry

Long-baseline atom interferometry is a promising technique for probing various aspects of fundamental physics, astrophysics and cosmology, including searches for ultralight dark matter (ULDM) and for gravitational waves (GWs) in the frequency range around 1~Hz that is not covered by present and planned detectors using laser interferometry. The MAGIS detector is under construction at Fermilab, as is the MIGA detector in France. The PX46 access shaft to the LHC has been identified as a very suitable site for an atom interferometer of height $\sim 100$m, sites at the Boulby mine in the UK and the Canfranc Laboratory are also under investigation, and possible sites for km-class detectors have been suggested. The Terrestrial Very-Long-Baseline Atom Interferometry (TVLBAI) Proto-Collaboration proposes a coordinated programme of interferometers of increasing baselines.

hep-ex↗

arXiv2025

Creation of a black hole bomb instability in an electromagnetic system

The amplification and generation of electromagnetic radiation by a rotating metallic or lossy cylinder, first theorized by Zeldovich in the 1970s, is tightly connected to the concepts of quantum friction, energy extraction from rotating black holes and runaway mechanisms such as black hole bombs. Despite recent advances including acoustic analogues of the Zeldovich effect and the observation of a negative resistance in a low-frequency electromagnetic model, actual positive signal amplitude gain, the spontaneous generation of electromagnetic waves and runaway amplifi- cation effects have never been experimentally verified. Here, we demonstrate experimentally that a mechanically rotating metallic cylinder not only definitively acts as an amplifier of a rotating elec- tromagnetic field mode but also, when paired with a low-loss resonator, becomes unstable and acts as a generator, seeded only by noise. The system exhibits an exponential runaway amplification of spontaneously generated electromagnetic modes thus demonstrating the electromagnetic analogue of Press and Teukolskys black hole bomb. The exponential amplification from noise supports theoretical investigations into black hole instabilities and is promising for the development of future experiments to observe quantum friction in the form of the Zeldovich effect seeded by the quantum vacuum.

quant-ph↗

arXiv2025

An experimental platform for levitated mechanics in space

Conducting levitated mechanical experiments in extreme conditions has long been the aim of researchers, as it allows for the investigation of new fundamental physics phenomena. One of the great frontiers has been sending these experiments into the micro-g environment of space, with multiple proposals calling for such a platform. At the same time, levitated sensors have demonstrated a high sensitivity to external stimuli which will only improve in low-vibrational conditions. conditions This paper describes the development of a technology demonstrator for optical and magnetic trapping experiments in space. Our payload represents the first concrete step towards future missions with aims of probing fundamental physical questions: matter-wave interferometry of nanoparticles to probe the limits of macroscopic quantum mechanics, detection of Dark Matter candidates and gravitational waves to test physics beyond the Standard Model, and accelerometry for Earth-observation.

physics.ins-det↗

arXiv2025

Generation of classical non-Gaussian distributions by squeezing a thermal state into non-linear motion of levitated optomechanics

We report on an experiment achieving the dynamical generation of non-Gaussian states of motion of a levitated optomechanical system. We access intrinsic Duffing-like nonlinearities by thermal squeezing of an oscillator's state of motion by rapidly switching the frequency of its trap. We characterize the experimental non-Gaussian state versus expectations from simulations and give prospects for the emergence of genuine nonclassical features.

quant-ph↗

arXiv2025

Metrology of Gravitational Effects with Mechanical Quantum Systems

Mechanical quantum systems, such as resonators and levitated particles, offer unique opportunities for quantum metrology. Particularly, their significant mass and quantum-level control enable applications in measuring gravitational effects. This article highlights key challenges, alongside potential solutions to advance precision sensing and quantum-gravitational research.

quant-ph↗

arXiv2024

Ultralight dark matter detection with levitated ferromagnets

Levitated ferromagnets act as ultraprecise magnetometers, which can exhibit high quality factors due to their excellent isolation from the environment. These instruments can be utilized in searches for ultralight dark matter candidates, such as axionlike dark matter or dark-photon dark matter. In addition to being sensitive to an axion-photon coupling or kinetic mixing, which produce physical magnetic fields, ferromagnets are also sensitive to the effective magnetic field (or "axion wind") produced by an axion-electron coupling. While the dynamics of a levitated ferromagnet in response to a DC magnetic field have been well studied, all of these couplings would produce AC fields. In this work, we study the response of a ferromagnet to an applied AC magnetic field and use these results to project their sensitivity to axion and dark-photon dark matter. We pay special attention to the direction of motion induced by an applied AC field, in particular, whether it precesses around the applied field (similar to an electron spin) or librates in the plane of the field (similar to a compass needle). We show that existing levitated ferromagnet setups can already have comparable sensitivity to an axion-electron coupling as comagnetometer or torsion balance experiments. In addition, future setups can become sensitive probes of axion-electron coupling, dark-photon kinetic mixing, and axion-photon coupling, for ultralight dark matter masses $m_\mathrm{DM}\lesssim\mathrm{feV}$.

hep-ph↗