Interpretation of wave function by coherent ensembles of trajectories

We re-use some original ideas of de~Broglie, Schrödiger, Dirac and Feynman to revise the ensemble interpretation of wave function in quantum mechanics. To this end we introduce coherence (auto-concordance) of ensembles of quantum trajectories in the space-time. The coherence condition accounts phases proportional to classical action, which are in foundation of the Feynman path integral technique. Therefore, our interpretation is entirely based on well-known and tested concepts and methods of wave mechanics. Similarly to other ensemble interpretations our approach allows us to avoid all problems and paradoxes related to wave function collapse during a measurement process. Another consequence is that no quantum computation or quantum cryptography method will ever work if it assumes that a particular q-bit represents the entire wave function

Interpretation of Wave Function by Coherent Ensembles of Trajectories

We re-use some original ideas of de Broglie, Schrödiger, Dirac and Feynman to revise the ensemble interpretation of wave function in quantum mechanics. To this end we introduce coherence (auto-concordance) of ensembles of quantum trajectories in the space-time. The coherence condition accounts phases proportional to classical action, which are in foundation of the Feynman path integral technique. Therefore, our interpretation is entirely based on well-known and tested concepts and methods of wave mechanics. Similarly to other ensemble interpretations our approach allows us to avoid all problems and paradoxes related to wave function collapse during a measurement process. Another consequence is that no quantum computation or quantum cryptography method will ever work if it assumes that a particular q-bit represents the entire wave function

Interacting electrons in a one-dimensional random array of scatterers - A Quantum Dynamics and Monte-Carlo study

The quantum dynamics of an ensemble of interacting electrons in an array of random scatterers is treated using a new numerical approach for the calculation of average values of quantum operators and time correlation functions in the Wigner representation. The Fourier transform of the product of matrix elements of the dynamic propagators obeys an integral Wigner-Liouville-type equation. Initial conditions for this equation are given by the Fourier transform of the Wiener path integral representation of the matrix elements of the propagators at the chosen initial times. This approach combines both molecular dynamics and Monte Carlo methods and computes numerical traces and spectra of the relevant dynamical quantities such as momentum-momentum correlation functions and spatial dispersions. Considering as an application a system with fixed scatterers, the results clearly demonstrate that the many-particle interaction between the electrons leads to an enhancement of the conductivity and spatial dispersion compared to the noninteracting case.Comment: 10 pages and 8 figures, to appear in PRB April 1

The semiclassical tool in mesoscopic physics

Semiclassical methods are extremely valuable in the study of transport and thermodynamical properties of ballistic microstructures. By expressing the conductance in terms of classical trajectories, we demonstrate that quantum interference phenomena depend on the underlying classical dynamics of non-interacting electrons. In particular, we are able to calculate the characteristic length of the ballistic conductance fluctuations and the weak localization peak in the case of chaotic dynamics. Integrable cavities are not governed by single scales, but their non-generic behavior can also be obtained from semiclassical expansions (over isolated trajectories or families of trajectories, depending on the system). The magnetic response of a microstructure is enhanced with respect to the bulk (Landau) susceptibility, and the semiclassical approach shows that this enhancement is the largest for integrable geometries, due to the existence of families of periodic orbits. We show how the semiclassical tool can be adapted to describe weak residual disorder, as well as the effects of electron-electron interactions. The interaction contribution to the magnetic susceptibility also depends on the nature of the classical dynamics of non-interacting electrons, and is parametrically larger in the case of integrable systems.Comment: Latex, Cimento-varenna style, 82 pages, 21 postscript figures; lectures given in the CXLIII Course "New Directions in Quantum Chaos" on the International School of Physics "Enrico Fermi"; Varenna, Italy, July 1999; to be published in Proceeding

The Many-Worlds Interpretation of Quantum Mechanics: Psychological versus Physical Bases for the Multiplicity of "Worlds"

This unpublished 1990 preprint argues that a crucial distinction in discussions of the many-worlds interpretation of quantum mechanics (MWI) is that between versions of the interpretation positing a physical multiplicity of worlds, and those in which the multiplicity is merely psychological, and due to the splitting of consciousness upon interaction with amplified quantum superpositions. It is argued that Everett's original version of the MWI belongs to the latter class, and that most of the criticisms leveled against the MWI, in particular that it is illogical or incoherent, are not valid against such "psychological-multiplicity" versions. Attempts to derive the quantum-mechanical probabilities from the many-worlds interpretation are reviewed, and Everett's initial derivation is extended in an attempt to show that these are the unique possible probabilities. But there remains a challenge for proponents of the MWI: to show that their interpretation requires probabilities, rather than merely nonprobabilistic indeterminacy. A 2002 preface, revised in 2004, briefly discusses the extent to which I still agree with the claims in the paper. While its derivation of probabilities used, and failed to justify, noncontextuality, I still agree with the paper's general interpretation of the MWI, though not with the MWI itself