arXiv subjects

Peter Asenbaum

Publications and source records attributed to Peter Asenbaum.

13 recordsLinked to original sources

arXiv2025

Magnetic recoil interferometer in a uniform gravitational field. Comment on Observation of the quantum equivalence principle for matter-waves

The calculation of the phase shift of a matter-wave interferometer looks different for different coordinate choices or the addition of a uniform gravitational field, but the final result of the observable phase shift does not depend on the coordinate choices or the uniform gravitational field. We find that the phase shift observed in ``Observation of the quantum equivalence principle for matter-waves'' is a magnetic recoil phase shift, similar to the recoil phase shift in light-pulse interferometers. Recoil phase shifts are inversely proportional to the inertial mass and do not depend on the gravitational mass. Our analysis highlights the difference between magnetic and gravitational acceleration in quantum mechanics.

quant-ph↗

arXiv2024

Matter waves and clocks do not observe uniform gravitational fields

In a uniform gravitational field, classical test objects fall universally. Any reference object or observer will fall in the same universal manner. Therefore, a uniform gravitational field cannot create dynamics between observers and classical test objects. The influence of a uniform gravitational field on matter waves and clocks, however, is described inconsistently throughout research and education. To illustrate, we discuss the behavior of a matter-wave interferometer and a clock redshift experiment in a uniform gravitational field. As a consistent formulation of the equivalence principle implies, a uniform gravitational field has no observable influence on these systems and is physically equivalent to the absence of gravity.

quant-ph↗

arXiv2024

Remote sensing of a levitated superconductor with a flux-tunable microwave cavity

We present a cavity-electromechanical system comprising a superconducting quantum interference device which is embedded in a microwave resonator and coupled via a pick-up loop to a 6 $\mu$g magnetically-levitated superconducting sphere. The motion of the sphere in the magnetic trap induces a frequency shift in the SQUID-cavity system. We use microwave spectroscopy to characterize the system, and we demonstrate that the electromechanical interaction is tunable. The measured displacement sensitivity of $10^{-7} \, \mathrm{m} / \sqrt{\mathrm{Hz}}$, defines a path towards ground-state cooling of levitated particles with Planck-scale masses at millikelvin environment temperatures.

quant-ph↗

arXiv2022

Inference of gravitational field superposition from quantum measurements

Experiments are beginning to probe the interaction of quantum particles with gravitational fields beyond the uniform-field regime. In non-relativistic quantum mechanics, the gravitational field in such experiments can be written as a superposition state. We empirically demonstrate that alternative theories of gravity can avoid gravitational superposition states only by decoupling the gravitational field energy from the quantum particle's time evolution. Furthermore, such theories must specify a preferred quantum reference frame in which the equations of motion are valid. To the extent that these properties are theoretically implausible, recent experiments provide indirect evidence that gravity has quantum features. Proposed experiments with superposed gravitational sources would provide even stronger evidence that gravity is nonclassical.

quant-ph↗

arXiv2020

Physically significant phase shifts in matter-wave interferometry

Many different formalisms exist for computing the phase of a matter-wave interferometer. However, it can be challenging to develop physical intuition about what a particular interferometer is actually measuring or about whether a given classical measurement provides equivalent information. Here we investigate the physical content of the interferometer phase through a series of thought experiments. In low-order potentials, a matter-wave interferometer with a single internal state provides the same information as a sum of position measurements of a classical test object. In high-order potentials, the interferometer phase becomes decoupled from the motion of the interferometer arms, and the phase contains information that cannot be obtained by any set of position measurements on the interferometer trajectory. This phase shift in a high-order potential fundamentally distinguishes matter-wave interferometers from classical measuring devices.

physics.atom-ph↗

arXiv2020

A 40 W, 780 nm laser system with compensated dual beam splitters for atom interferometry

We demonstrate a narrow-linewidth 780 nm laser system with up to 40 W power and a frequency modulation bandwidth of 230 MHz. Efficient overlap on nonlinear optical elements combines two pairs of phase-locked frequency components into a single beam. Serrodyne modulation with a high-quality sawtooth waveform is used to perform frequency shifts with > 96.5 % efficiency over tens of MHz. This system enables next-generation atom interferometry by delivering simultaneous, Stark-shift-compensated dual beam splitters while minimizing spontaneous emission.

physics.atom-ph↗

arXiv2020

Atom-interferometric test of the equivalence principle at the $10^{-12}$ level

Does gravity influence local measurements? We use a dual-species atom interferometer with $2\,\text{s}$ of free-fall time to measure the relative acceleration between $^{85}$Rb and $^{87}$Rb wave packets in the Earth's gravitational field. Systematic errors arising from kinematic differences between the isotopes are suppressed by calibrating the angles and frequencies of the interferometry beams. We find an E\"otv\"os parameter of $\eta = [1.6\; \pm\; 1.8\; \text{(stat)}\; \pm \; 3.4 \; \text{(sys)}] \times 10^{-12}$, consistent with zero violation of the equivalence principle. With a resolution of up to $1.4 \times 10^{-11} \, g$ per shot, we demonstrate a sensitivity to $\eta$ of $5.4 \times 10^{-11}\,/\sqrt{\text{Hz}}$.

physics.atom-ph↗

arXiv2017

Effective inertial frame in an atom interferometric test of the equivalence principle

In an ideal test of the equivalence principle, the test masses fall in a common inertial frame. A real experiment is affected by gravity gradients, which introduce systematic errors by coupling to initial kinematic differences between the test masses. We demonstrate a method that reduces the sensitivity of a dual-species atom interferometer to initial kinematics by using a frequency shift of the mirror pulse to create an effective inertial frame for both atomic species. This suppresses the gravity-gradient-induced dependence of the differential phase on initial kinematic differences by a factor of 100 and enables a precise measurement of these differences. We realize a relative precision of $Δg / g \approx 6 \times 10^{-11}$ per shot, which improves on the best previous result for a dual-species atom interferometer by more than three orders of magnitude. By suppressing gravity gradient systematic errors to below one part in $10^{13}$, these results pave the way for an atomic test of the equivalence principle at an accuracy comparable with state-of-the-art classical tests.

physics.atom-ph↗

arXiv2016

Phase shift in atom interferometry due to spacetime curvature

We present a single-source dual atom interferometer and utilize it as a gradiometer for precise gravitational measurements. The macroscopic separation between interfering atomic wave packets (as large as 16 cm) reveals the interplay of recoil effects and gravitational curvature from a nearby Pb source mass. The gradiometer baseline is set by the laser wavelength and pulse timings, which can be measured to high precision. Using a long drift time and large momentum transfer atom optics, the gradiometer reaches a resolution of $3 \times 10^{-9}$ s$^{-2}$ per shot and measures a 1 rad phase shift induced by the source mass.

physics.atom-ph↗

arXiv2015

Cavity-assisted manipulation of freely rotating silicon nanorods in high vacuum

Optical control of nanoscale objects has recently developed into a thriving field of research with far-reaching promises for precision measurements, fundamental quantum physics and studies on single-particle thermodynamics. Here, we demonstrate the optical manipulation of silicon nanorods in high vacuum. Initially, we sculpture these particles into a silicon substrate with a tailored geometry to facilitate their launch into high vacuum by laser-induced mechanical cleavage. We manipulate and trace their center-of-mass and rotational motion through the interaction with an intense intra-cavity field. Our experiments show optical forces on nanorotors three times stronger than on silicon nanospheres of the same mass. The optical torque experienced by the spinning rods will enable cooling of the rotational motion and torsional opto-mechanics in a dissipation-free environment.

quant-ph↗

arXiv2014

Real-time single-molecule imaging of quantum interference

The observation of interference patterns in double-slit experiments with massive particles is generally regarded as the ultimate demonstration of the quantum nature of these objects. Such matter-wave interference has been observed for electrons, neutrons, atoms and molecules and it differs from classical wave-physics in that it can even be observed when single particles arrive at the detector one by one. The build-up of such patterns in experiments with electrons has been described as the "most beautiful experiment in physics". Here we show how a combination of nanofabrication and nanoimaging methods allows us to record the full two-dimensional build-up of quantum diffraction patterns in real-time for phthalocyanine molecules PcH2 and their tailored derivatives F24PcH2 with a mass of 1298 amu. A laser-controlled micro-evaporation source was used to produce a beam of molecules with the required intensity and coherence and the gratings were machined in 10 nm thick silicon nitride membranes to reduce the effect of van der Waals forces. Wide-field fluorescence microscopy was used to detect the position of each molecule with an accuracy of 10 nm and to reveal the build-up of a deterministic ensemble interference pattern from stochastically arriving and internally hot single molecules.

quant-ph↗

arXiv2013

Cavity cooling of free silicon nanoparticles in high-vacuum

Laser cooling has given a boost to atomic physics throughout the last thirty years since it allows one to prepare atoms in motional states which can only be described by quantum mechanics. Most methods, such as Doppler cooling, polarization gradient cooling or sub-recoil laser cooling rely, however, on a near-resonant and cyclic coupling between laser light and well-defined internal states. Although this feat has recently even been achieved for diatomic molecules, it is very hard for mesoscopic particles. It has been proposed that an external cavity may compensate for the lack of internal cycling transitions in dielectric objects and it may thus provide assistance in the cooling of their centre of mass state. Here, we demonstrate cavity cooling of the transverse kinetic energy of silicon nanoparticles propagating in genuine high-vacuum (< 10^8 mbar). We create and launch them with longitudinal velocities even down to v < 1 m/s using laser induced thermomechanical stress on a pristine silicon wafer. The interaction with the light of a high-finesse infrared cavity reduces their transverse kinetic energy by more than a factor of 30. This is an important step towards new tests of recent proposals to explore the still speculative non-linearities of quantum mechanics with objects in the mass range between 10^7 and 10^10 amu.

quant-ph↗

arXiv2010

Master Equation for the Motion of a Polarizable Particle in a Multimode Cavity

We derive a master equation for the motion of a polarizable particle weakly interacting with one or several strongly pumped cavity modes. We focus here on massive particles with complex internal structure such as large molecules and clusters, for which we assume a linear scalar polarizability mediating the particle-light interaction. The predicted friction and diffusion coefficients are in good agreement with former semiclassical calculations for atoms and small molecules in weakly pumped cavities, while the current rigorous quantum treatment and numerical assessment sheds a light on the feasibility of experiments that aim at optically manipulating beams of massive molecules with multimode cavities.

quant-ph↗