859 research outputs found
Data for "Testing dissipative collapse models with a levitated micromagnet"
No full textData for the journal article: Vinante, A, Gasbarri, G, Timberlake, C, Toros, M & Ulbricht, H 2020, 'Testing dissipative collapse models with a levitated micromagnet', Physical Review Research.</span
Collisional Models for a Quantum Particle in a Gas
No full textIn the last decades important steps has been made to understand the quantum behaviour of a test particle in a gas. However the most refined theoretical collisional models proposed so far seem not to be in agreement with each other. The open dabate about which model is the one that correctly describes a particle in a gas is a witness that the validity of these models is still unclear. A better understanding of the quantum behavior of a test particle in a gas is not only desirable, but would also help in understanding the non-classical process of decoherence, which is believed to be of crucial importance in the quantum-classical transition.
The broad objective of this study is to analyze the validity of collisional models for the motion of a tracer particle affected by the presence of a background gas.
We start with a critical review of the state of the art in quantum collisional models. Then, we study a very simple system, which is exactly solvable: A two-particle system interacting via a Dirac delta potential in one dimension. We analyze the interaction and estimate the collision time for Gaussian wave packets.
Then, we focus on the main problem of this thesis: the dynamics of a test particle in a quantum gas. We first tackle it with an original technique that combines the Hartree variational method with stochastic calculus techniques. In this way we properly describe the non dissipative behavior of the test particle, and we gather interesting insight on the dissipative process. Eventually, we provide a microscopic derivation of the collisional dynamics for a test particle in a rarefied thermal bath. We, shows the limits of this approach, providing necessary conditions for the validity of collisional equation
General Galilei Covariant Gaussian Maps
No full textWe characterize general non-Markovian Gaussian maps which are covariant under Galilean transformations. In particular, we characterize translational and Galilean covariant maps and show that they reduce to the known Holevo result in the Markovian limit. We apply the results to discuss measures of macroscopicity based on classicalization maps, specifically addressing dissipation, Galilean covariance and non-Markovianity. We further suggest a possible generalization of the macroscopicity measure defined in Nimmrichter and Hornbergerl. [Phys. Rev. Lett. 110, 16 (2013)]
Colored and dissipative continuous spontaneous localization model and bounds from matter-wave interferometry
No full textMatter-wave interferometry is a direct test of the quantum superposition principle for massive systems, and of collapse models. Here we show that the bounds placed by matter-wave interferometry depend weakly on the details of the collapse mechanism. Specifically, we compute the bounds on the CSL model and its variants, provided by the the KDTL interferometry experiment of Arndt's group [Phys. Chem. Chem. Phys., 2013, 15, 14696-14700], which currently holds the record of largest mass in interferometry.
We also show that the CSL family of models emerges naturally by considering a minimal set of assumptions. In particular, we construct the dynamical map for the colored and dissipative Continuous Spontaneous Localization (cdCSL) model, which reduces to the CSL model and variants in the appropriate limits. In addition, we discuss the measure of macroscopicity based on the cdCSL model
Mass-coupled relativistic spontaneous collapse models
No full textCurrently there is not a satisfactory relativistic spontaneous collapse model. Here we show the impossibility of a simple generalization of the continuous spontaneous collapse (CSL) model to the relativistic framework. We consider a mass coupled model as in the non-relativistic limit this gives the CSL model. We show that a Lorentz covariant collapse equation cannot simultaneously satisfy the following conditions: (i) to avoid a divergent rate of energy, (ii) to prevent superluminal signalling
Coherent scattering in non relativistic quantum mechanics
No full textIn this paper we give a pedagogical explanation of coherence effects in non relativistic scattering processes. Coherent scattering is important not only because it is a clear manifestation of the wave character of the interaction in these regimes, but also because it helps in increasing the cross section and thus the observable effects. We show under which conditions a particle scatters coherently on a multi-particle system. In a nutshell, in order to have coherent scattering, the incident particle has not to resolve the internal structure of the composite system. We show that the above condition is satisfied when the de Broglie length of the incident particle is much larger than the size of the system
Gravitational decoherence and the possibility of its interferometric detection
No full textWe present a general master equation describing the quantum dynamics of a scalar bosonic field interacting with an external weak and stochastic gravitational field. The dynamics predicts decoherence both in position and in energy-momentum. We show how the master equation reproduces, thus generalizing, the previous results in the literature by taking appropriate limits. We estimate the effect of gravitational decoherence in atom interferometers, providing also a straightforward way to assess the magnitude of the effect
Nanoparticle interferometer by throw and catch
No full textMatter wave interferometry with increasingly larger masses could pave the way to understanding the nature of wavefunction collapse, the quantum to classical transition, or even how an object in a spatial superposition interacts with its gravitational field. In order to improve upon the current mass record, it is necessary to move into the nanoparticle regime. In this paper, we provide a design for a nanoparticle Talbot–Lau matter wave interferometer that circumvents the practical challenges of previously proposed designs. We present numerical estimates of the expected fringe patterns that such an interferometer would produce, considering all major sources of decoherence. We discuss the practical challenges involved in building such an experiment, as well as some preliminary experimental results to illustrate the proposed measurement scheme. We show that such a design is suitable for seeing interference fringes with 106 amu SiO2 particles and that this design can be extended to even 108 amu particles by using flight times below the typical Talbot time of the system
Iodine nutrition status, thyroid function in the first trimester of pregnancy and pregnancy progression in women residing in an area of know moderate iodine deficiency
No full textBACKGROUND: 1) To assess thyroid function in a group of women in the first trimester of pregnancy who reside in a geographic area of moderate iodine deficiency. 2) To assess the usefulness of early pregnancy screening.
METHODS: The study population included 240 women in the first trimester of pregnancy residing in the same valley in the Appenine Mountains (Casentino, Tuscany) characterized by a known moderate iodine deficiency. TSH, FT3, FT4, urinary iodine level, and anti-thyroid peroxidase autoantibodies (anti-TPO antibodies) were added to the tests included in the regional prescription pad for the first blood draw and data on thyroid disease and the use of iodized salt was also recorded.
RESULTS: Of the 240 women examined, 55 (23%) had a TSH value over 2.5 mUI/L (NV= 2.51-9.89). A urinary iodine level of under 150μg/L was found in 170 women (70%). The median urinary iodine level in women using iodized salt was 103 μg/L, while that in women not using it was 110μg/L (not a significant statistical difference). None of the women included in the study were taking iodine-containing supplements.
CONCLUSIONS: In an area of known moderate iodine deficiency 23% of the women presented TSH values over 2.5 mUI/L and 70% of the women presented urinary iodine deficiency in the first trimester of pregnancy. This makes the case for thyroid function screening and strengthening of iodine supplementation at the beginning of pregnancy
Talbot-Lau effect beyond the point-particle approximation
No full textRecent progress in matter-wave interferometry aims to directly probe the quantum properties of matter on ever increasing scales. However, in order to perform interferometric experiments with massive mesoscopic objects, taking into account the constraints on the experimental setups, the pointlike-particle approximation needs to be cast aside. In this work, we consider near-field interferometry based on the Talbot effects with a single optical grating for large spherical particles beyond the point-particle approximation. We account for the suppression of the coherent grating effect and, at the same time, the enhancement of the decoherence effects due to scattering and absorption of grating photons
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