Catalogue Search | MBRL
Are you sure you want to remove the book from the shelf?
{{itemTitle}}
35,393
result(s) for
"Wave functions."
Sort by:
Variational approach to quantum spin liquid in a Rydberg atom simulator
Recently the Rydberg blockade effect has been utilized to realize quantum spin liquid (QSL) on a kagome lattice. Evidence of QSL has been obtained experimentally by directly measuring non-local string order. In this paper, we report a Bardeen–Cooper–Schrieffer (BCS)-type variational wave function study of the spin liquid state in this model. This wave function is motivated by mapping the Rydberg blockade model to a lattice gauge theory, where the local gauge conservations replace the role of constraints from the Rydberg blockade. We determine the variational parameter from the experimental measurement of the Rydberg atom population. Then we compare the predictions of this deterministic wave function with the experimental measurements of non-local string order. Combining the measurements on both open and closed strings, we extract the fluctuations only associated with the closed-loop as an indicator of the topological order. The prediction from our wave function agrees reasonably well with the experimental data, with only one fitting parameter determined by measurement of Rydberg atom population. Our variational wave function provides a simple and intuitive picture of the QSL in this system that can be generalized to similar spin liquid phases in other lattice geometry.
Journal Article
Contextual Wavefunction collapse: an integrated theory of quantum measurement
This paper is an in depth implementation of the proposal (Ellis 2012 Ann. Phys. NY 327 1890-932) that the quantum measurement issue can be resolved by carefully looking at top-down contextual effects within realistic measurement contexts. The specific setup of the measurement apparatus determines the possible events that can take place. The interaction of local heat baths with a quantum system plays a key role in the process. In contrast to the usual attempts to explain quantum measurement by decoherence, we argue that the heat bath follows unitary time evolution only over limited length and time scales (Drossel 2017 His. Phil. Sci. B 58 12-21) and thus leads to localization and stochastic dynamics of quantum particles that interact with it. We show furthermore that a theory that describes all the steps from the initial arrival of the quantum particle to the final pointer deflection must use elements from classical physics. This proposal also provides a contextual answer to the puzzle of the origin of the arrow of time when quantum measurements take place: it derives from the cosmological direction of time. Overall, our proposal is for contextual wavefunction collapse.
Journal Article
Transformation to a geminal basis and stationary conditions for the exact wave function therein
We show the transformation from a one-particle basis to a geminal basis, transformations between different geminal bases demonstrate the Lie algebra of a geminal basis. From the basis transformations, we express both the wave function and Hamiltonian in the geminal basis. The necessary and sufficient conditions of the exact wave function expanded in a geminal basis are shown to be a Brillouin theorem of geminals. The variational optimization of the geminals in the antisymmetrized geminal power (AGP), antisymmetrized product of geminals (APG) and the full geminal product (FGP) wave function ansätze are discussed. We show that using a geminal replacement operator to describe geminal rotations introduce both primary and secondary rotations. The secondary rotations rotate two geminals in the reference at the same time due to the composite boson nature of geminals. Due to the completeness of the FGP, where all possible geminal combinations are present, the FGP is exact. The number of parameters in the FGP scale exponentially with the number of particles, like the full configuration interaction (FCI). Truncation in the FGP expansion can give compact representations of the wave function since the reference function in the FGP can be either the AGP or APG wave function.
Journal Article
Was David Bohm a Wave Function Realist?
One of the more radical ideas to have emerged in recent metaphysics of quantum theory is wave function realism, according to which the fundamental spatial framework of the world is one of very many dimensions. At first sight this idea sounds similar to the notion of a multidimensional implicate order the physicist David Bohm proposed on the basis of quantum theory in the 1980s. This paper briefly considers Bohm’s various attempts to provide a realist interpretation of the wave function in order to clarify whether or not Bohm was anticipating and even endorsing wave function realism with his implicate order theory. The underlying question is what quantum theory — and non-locality in particular — is trying to tell us about the more fundamental nature of the physical world.
Journal Article
Vibrations of an Elastic Half-Space
We report on the resolution of the vibration problem for a homogeneous and isotropic elastic half-space (the Lamb problem), with application to the seismic tensorial force. We assume a homogeneous and isotropic half-space with a localized force which produces vibrations. The solution is achieved by introducing vector plane-wave functions. Explicit results are given for an isotropic tensorial force and a half-space with free surface. The contribution of the Rayleigh surface waves to vibrations is analyzed in the special case of a temporal-impulse force, where the solution exhibits unphysical features, as expected: it extends over the entire free surface and time domain, with a (scissor-like) double-wall propagating both in the future and the past.
Journal Article
Consciousness and the Measurement Problem in Quantum Mechanics
The idea that consciousness is somehow needed to collapse the wave function was emphasized especially by Eugene Wigner in 1961 and has recently been discussed by e.g. David Chalmers and Kelvin McQueen. We revisit the reasons why the idea was proposed in the first place and briefly consider Chalmers and McQueen’s discussion.
Journal Article
Characterizing the spontaneous collapse of a wavefunction through entropy production
We investigate the phenomenology leading to the non-conservation of energy of the continuous spontaneous localization (CSL) model from the viewpoint of non-equilibrium thermodynamics, and use such framework to assess the equilibration process entailed by the dissipative formulation of the model (dCSL). As a paradigmatic situation currently addressed in frontier experiments aimed at investigating possible collapse theories, we consider a one-dimensional mechanical oscillator in a thermal state. We perform our analysis in the phase space of the oscillator, where the entropy production rate, a non-equilibrium quantity used to characterize irreversibility, can be conveniently analyzed. We show that the CSL model violates Clausius law, as it exhibits a negative entropy production rate, while the dCSL model reaches equilibrium consistently only under certain dynamical conditions, thus allowing us to identify the values—in the parameter space—where the latter mechanism can be faithfully used to describe a thermodynamically consistent phenomenon.
Journal Article
Intermolecular Interactions between Serine and C60, C59Si, and C59Ge: a DFT Study
The study of intermolecular interactions is of great importance. This study attempted to quantitatively examine the interactions between Serine (C
3
H
7
NO
3
) and fullerene nanocages, C
60
, in vacuum. As the frequent introduction of elements as impurities into the structure of nanomaterials can increase the intensity of intermolecular interactions, nanocages doped with silicon and germanium have also been studied as adsorbents, C
59
Si and C
59
Ge. Quantum mechanical studies of such systems are possible in the density functional theory (DFT) framework. For this purpose, various functionals, such as B3LYP-D3, ωB97XD, and M062X, have been used. One of the most suitable basis functionals for the systems studied in this research is 6-311G (d), which has been used in both optimization calculations and calculations related to wave function analyses. The main part of this work is the study of various analyses that reveal the nature of the intermolecular interactions between the two components introduced above. The results of conceptual DFT, natural bond orbital, non-covalent interactions, and quantum theory of atoms in molecules were consistent and in favor of physical adsorption in all systems. Germanium had more adsorption energy than other dopants. The HOMO–LUMO energy gaps were as follows: C
60
: 5.996, C
59
Si: 5.309 and C59Ge: 5.188 eV at B3LYP-D3/6–311 G (d) model chemistry. The sensitivity of the adsorption increased when an amino acid molecule interacted with doped C
60
, and this capability could be used to design nanocarrier to detect Serine amino acid.
Journal Article