arXiv subjects

Jaimy Plugge

Publications and source records attributed to Jaimy Plugge.

5 recordsLinked to original sources

arXiv2025

A Sub-kHz Mechanical Resonator Passively Cooled to 6 mK

Highly coherent mechanical resonators are invaluable to ultrasensitive detection techniques by enabling detection of small forces. Studying mechanical resonators in a thermal equilibrium state at millikelvin temperatures provides a promising path to increase their coherence time. Here, we passively cool a 700 Hz massive (1.5 ng) mechanical cantilever down to 6.1(4) mK by means of nuclear demagnetization, as confirmed by detecting its thermal motion via a lock-in based detection scheme. At the lowest temperatures the thermal motion of the resonator is still clearly distinguishable from the background noise. Our data analysis confirms that at these temperatures the motion is still thermally distributed. These results pave the way for passive cooling low-frequency resonators to the sub-millikelvin regime, which would enable new tests of quantum mechanics and advances in ultrasensitive force detection.

quant-ph↗

arXiv2025

Superconducting flux concentrator coils for levitation of particles in the Meissner state

Magnetic levitation of superconductors is a promising platform to study quantum mechanics in the large-mass limit. One major limitation is the weak trapping potential, which results in low vibrational eigenfrequencies and increased susceptibility to low-frequency noise. While generating strong magnetic fields is relatively straightforward, creating a tightly confined harmonic potential - essentially achieving a large magnetic field gradient - remains a significant challenge. In this work, we demonstrate a potential solution using superconducting cores that concentrate magnetic flux into arbitrarily small volumes. We show the ability to trap superconducting particles using an anti-Helmholtz coil configuration incorporating these cores. However, we observe rapid damping of the levitated particle motion due to flux trapping within the cores, occurring once the lower critical field is exceeded locally. To investigate this mechanism, we employ diamond NV center magnetometry and detect substantial remanent fields persisting after high-current operation of the coils. Finally, we discuss possible strategies to mitigate this effect and improve the levitation properties.

quant-ph↗

arXiv2024

Current experimental upper bounds on spacetime diffusion

A consistent theory describing the dynamics of quantum systems interacting on a classical space-time was recently put forward by Oppenheim et al..[1, 2]. Quantum states may retain their coherence, at the cost of some amount of stochasticity of the spacetime metric, characterized by a spacetime diffusion parameter. Here, we report existing experimental upper bounds on such space-time diffusion, based on a review of several types of experiments with very low force noise over a broad range of test masses from single atoms to several kilograms. We find an upper bound at least 15 orders of magnitude lower as compared to the initial bounds for explicit models presented by Oppenheimn et al. The results presented here provide a path forward for future experiments that can help evaluate classical-quantum theories

quant-ph↗

arXiv2023

Measuring gravity with milligram levitated masses

Gravity differs from all other known fundamental forces since it is best described as a curvature of spacetime. For that reason it remains resistant to unifications with quantum theory. Gravitational interaction is fundamentally weak and becomes prominent only at macroscopic scales. This means, we do not know what happens to gravity in the microscopic regime where quantum effects dominate, and whether quantum coherent effects of gravity become apparent. Levitated mechanical systems of mesoscopic size offer a probe of gravity, while still allowing quantum control over their motional state. This regime opens the possibility of table-top testing of quantum superposition and entanglement in gravitating systems. Here we show gravitational coupling between a levitated sub-millimeter scale magnetic particle inside a type-I superconducting trap and kg source masses, placed approximately half a meter away. Our results extend gravity measurements to low gravitational forces of attonewton and underline the importance of levitated mechanical sensors. Specifically, at a frequency of 26.7 Hz, a mass of 0.4 mg and showing Q-factors in excess of 10$^7$, we obtained a force noise of 0.5 $fN\sqrt{Hz}$ . We simultaneously detect the other 5 rotational and translational degrees of freedom.

quant-ph↗

arXiv2022

Magnetic cooling and vibration isolation of a sub-kHz mechanical resonator

We report recent progress towards the realization of a sub-mK, low-vibration environment at the bottom stage of a dry dilution refrigerator for use in mechanical tests of quantum mechanics. Using adiabatic nuclear demagnetization, we have cooled a silicon cantilever force sensor to $T\approx 1$ mK. The temperature of the tip-holder of the cantilever chip was determined via a primary magnetic flux noise thermometer. The quality factor of the cantilever continues to increase with decreasing temperature, reaching $Q\approx 4\cdot 10^4$ at $2$ mK. To demonstrate that the vibration isolation is not compromised, we report the detection of the thermal motion of the cantilever down to $T \approx 20$ mK, only limited by the coupling to the SQUID readout circuit. We discuss feasible improvements that will allow us to probe unexplored regions of the parameter space of continuous spontaneous localization models.

quant-ph↗