325 research outputs found
Testing collapse models with levitated nanoparticles: the detection challenge
We consider a nanoparticle levitated in a Paul trap in ultrahigh cryogenic
vacuum, and look for the conditions which allow for a stringent
noninterferometric test of spontaneous collapse models. In particular we
compare different possible techniques to detect the particle motion. Key
conditions which need to be achieved are extremely low residual pressure and
the ability to detect the particle at ultralow power. We compare three
different detection approaches based respectively on a optical cavity, optical
tweezer and a electrical readout, and for each one we assess advantages,
drawbacks and technical challenges
Probing modified gravity with magnetically levitated resonators
We present an experimental procedure, based on Meissner effect levitation of neodymium ferromagnets, as a method of measuring the gravitational interactions between milligram masses. The scheme consists of two superconducting lead traps, with a magnet levitating in each trap. The levitating magnets behave as harmonic oscillators and, by carefully driving the motion of one magnet on resonance with the other, we find that it should easily be possible to measure the gravitational field produced by a 4 mg sphere, with the gravitational attraction from masses as small as 30 μg predicted to be measurable within a realistic measurement time frame. We apply this acceleration sensitivity to one concrete example and show the abilities of testing models of modified Newtonian dynamics
Non-interferometric test of the Continuous Spontaneous Localization model based on rotational optomechanics
The Continuous Spontaneous Localization (CSL) model is the best known and
studied among collapse models, which modify quantum mechanics and identify the
fundamental reasons behind the unobservability of quantum superpositions at the
macroscopic scale. Albeit several tests were performed during the last decade,
up to date the CSL parameter space still exhibits a vast unexplored region.
Here, we study and propose an unattempted non-interferometric test aimed to
fill this gap. We show that the angular momentum diffusion predicted by CSL
heavily constrains the parametric values of the model when applied to a
macroscopic object
Upper Bounds on Spontaneous Wave-Function Collapse Models Using Millikelvin-Cooled Nanocantilevers
6siCollapse models predict a tiny violation of energy conservation, as a consequence of the spontaneous collapse of the wave function. This property allows us to set experimental bounds on their parameters. We consider an ultrasoft magnetically tipped nanocantilever cooled to millikelvin temperature. The thermal noise of the cantilever fundamental mode has been accurately estimated in the range 0.03 – 1 K, and any other excess noise is found to be negligible within the experimental uncertainty. From the measured data and the cantilever geometry, we estimate the upper bound on the continuous spontaneous localization collapse rate in a wide range of the correlation length rC. Our upper bound improves significantly previous constraints for r_C > 10^−6 m, and partially excludes the enhanced collapse rate suggested by Adler. We discuss future improvements.openopenVinante, A.; Bahrami, M.; Bassi, A.; Usenko, O.; Wijts, G.; Oosterkamp, T.H.Vinante, A.; Bahrami, Mohammad; Bassi, Angelo; Usenko, O.; Wijts, G.; Oosterkamp, T. H
Testing Dissipative Collapse Models with a Levitated Micromagnet
We present experimental tests of dissipative extensions of spontaneous wave
function collapse models based on a levitated micromagnet with ultralow
dissipation. The spherical micromagnet, with radius m, is levitated
by Meissner effect in a lead trap at K and its motion is detected by a
SQUID. We perform accurate ringdown measurements on the vertical translational
mode with frequency Hz, and infer the residual damping at vanishing
pressure Hz. From this upper limit we derive improved
bounds on the dissipative versions of the CSL (continuous spontaneous
localization) and the DP (Di\'{o}si-Penrose) models with proper choices of the
reference mass. In particular, dissipative models give rise to an intrinsic
damping of an isolated system with the effect parameterized by a temperature
constant; the dissipative CSL model with temperatures below 1 nK is ruled out,
while the dissipative DP model is excluded for temperatures below K.
Furthermore, we present the first bounds on dissipative effects in a more
recent model, which relates the wave function collapse to fluctuations of a
generalized complex-valued spacetime metric.Comment: 10 pages, 7 figure
Amplification of electromagnetic waves by a rotating body
In 1971, Zel'dovich predicted the amplification of electromagnetic (EM) waves
scattered by a rotating metallic cylinder, gaining mechanical rotational energy
from the body. Since then, this phenomenon has been believed to be unobservable
with electromagnetic fields due to technological difficulties in meeting the
condition of amplification, that is, the cylinder must rotate faster than the
frequency of the incoming radiation. Here, we show that this key piece of
fundamental physics has been hiding in plain sight for the past 60 years in the
physics of induction generators. We measure the amplification of an
electromagnetic field, generated by a toroid LC-circuit, scattered by an
aluminium cylinder spinning in the toroid gap. We show that when the Zel'dovich
condition is met, the resistance induced by the cylinder becomes negative
implying amplification of the incoming EM waves. These results reveal the
connection between the concept of induction generators and the physics of this
fundamental effect that was believed to be unobservable, and hence open new
prospects towards testing the Zel'dovich mechanism in the quantum regime, as
well as related quantum friction effects.Comment: 5 pages and 3 figure plus supplementary fil
Feedback cooling of the normal modes of a massive electromechanical system to submillikelvin temperature
We apply a feedback cooling technique to simultaneously cool the three
electromechanical normal modes of the ton-scale resonant-bar gravitational wave
detector AURIGA. The measuring system is based on a dc Superconducting Quantum
Interference Device (SQUID) amplifier, and the feedback cooling is applied
electronically to the input circuit of the SQUID. Starting from a bath
temperature of 4.2 K, we achieve a minimum temperature of 0.17 mK for the
coolest normal mode. The same technique, implemented in a dedicated experiment
at subkelvin bath temperature and with a quantum limited SQUID, could allow to
approach the quantum ground state of a kilogram-scale mechanical resonator.Comment: 4 pages, 4 figure
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