Quantum mechanics, including quantum field theory, is a fundamental theory in physics which describes nature at the smallest scales of atoms and subatomic particles.

40926 Results for the subject "Quantum Physics":

AbstractAlong with exploring some of the necessary conditions for the chemistry of our world given what we know about quantum mechanics, I will also discuss a different reductionist challenge than is usually considered in debates on the relationship of chemistry to physics. Contrary to popular belief, classical physics does not have a reductive relationship to quantum mechanics and some of the reasons why reduction fails between classical and quantum physics are the same as for why reduction fails between chemistry and quantum physics. However, a neoreductionist can accept that classical physics has some amount of autonomy from quantum mechanics, but still try to maintain that classical+quantum physics taken as a whole reduces chemistry to physics. I will explore some of the obstacles lying in the neoreductionist's path with respect to quantum chemistry and thereby hope to shed more light on the conditions necessary for the chemistry of our world.

Robert C. Bishop Publication date: 2010/05/01AbstractQuantum computers hold great promises for the future of computation. In this paper, this new kind of computing device is presented, together with a short survey of the status of research in this field. The principal algorithms are introduced, with an emphasis on the applications of quantum computing to physics. Experimental implementations are also briefly discussed.

B. Georgeot Publication date: 2006/04/01AbstractThe theme of phenomenology and quantum physics is here tackled by examining some basic interpretational issues in quantum physics. One key issue in quantum theory from the very beginning has been whether it is possible to provide a quantum ontology of particles in motion in the same way as in classical physics, or whether we are restricted to stay within a more limited view of quantum systems, in terms of complementary but mutually exclusive phenomena. In phenomenological terms we could describe the situation by saying that according to the usual interpretation of quantum theory (especially Niels Bohr's), quantum phenomena require a kind of epoché (i.e. a suspension of assumptions about reality at the quantum level). However, there are other interpretations (especially David Bohm's) that seem to re-establish the possibility of a mind-independent ontology at the quantum level. We will show that even such ontological interpretations contain novel, non-classical features, which r *Read more...*

AbstractWe discuss some physics of quantum gravity on the basis of a hybrid model of lattice gravity, particularly in the strong-coupling region. As a clue to explore the region, we make a comparison between QCD and quantum gravity. Although we do not know what are ‘physical states’ in highly curved space except for a few cases, we can get several hints on the physics by analogy with QCD; a physical picture of quantum spacetime is obtained, which is consistent with the so-called spacetime foam.

Hiroyuki Hagura Publication date: 2004/03/01Mike Lazaridis is the man behind the top-selling BlackBerry. Not content with sitting back and counting the dollars, he is pumping upwards of C$150 million into blue sky quantum physics research. He tells Paul Marks what drew him to the strange world of quantum entanglement, and why quantum physics is essential to the future of consumer electronics

Paul Marks Publication date: 2008/03/08Quantum cryptography relies on the inherent weirdness of quantum physics to create stronger cryptographic keys. So, what happens when cryptography moves from mathematics into physics?

Danny Bradbury Publication date: 2006/01/01AbstractBy combining advanced device modeling with computational physics, microscopic changes in quantum many-body interactions of quantum dots are described as a function of macroscopic device parameters without a priori assumption on the confining potential. In planar coupled quantum dot structures, spin control can be achieved by modulating exchange interaction with an external gate as in conventional field effect transistors. These new features, coupled with recent advances in quantum dot physics constitute the basic ingredients for a solid state technology for quantum information processing.

Jean-Pierre Leburton Publication date: 2003/05/01AbstractThe goal of physics simulation using controllable quantum systems (“physics imitation”) is to exploit quantum laws to advantage, and thus accomplish efficient simulation of physical phenomena. In this Note, we discuss the fundamental concepts behind this paradigm of information processing, such as the connection between models of computation and physical systems. The experimental simulation of a toy quantum many-body problem is described.

G. Ortiz Publication date: 2002/03/01Highlights•Karl Popper entered the community (“though collective”) of quantum physicists between 1950s and 1960s.•He proposed a new interpretation of quantum mechanics based on the “propensity interpretation” of probabilities.•His influence on physicists concerned with quantum foundations (e.g. D. Bohm, A. Landé, H. Margenau) was remarkable.•Feyerabend early critique of Popper was developed in the context of foundations of quantum physics.

Flavio Del Santo Publication date: 2019/05/17AbstractThe role of topology in elementary quantum physics is discussed in detail. It is argued that attributes of classical spatial topology emerge from properties of state vectors with suitably smooth time evolution. Equivalently, they emerge from considerations on the domain of the quantum Hamiltonian, this domain being often specified by boundary conditions in elementary quantum physics. Examples are presented where classical topology is changed by smoothly altering the boundary conditions. When the parameters labelling the latter are treated as quantum variables, quantum states need not give a well-defined classical topology, instead they can give a quantum superposition of such topologies. An existing argument of Sorkin based on the spin-statistics connection and indicating the necessity of topology change in quantum gravity is recalled. It is suggested therefrom and our results here that Einstein gravity and its minor variants are effective theories of a deeper description with *Read more...*

Highlights•Explains relevance of unsolved inertial frame physics to space drive ambitions.•Updates space drive findings; benefits, challenges, approaches, and unsolved physics.•Comparatively lists type, status, issues, and references of 25 space drive inquiries.•Reviews inertial frame physics (Riemannian, optical-mechanical analogy, quantum).•Begins thought experiments to reassess inertial frames in context of space drives.

Marc G. Millis Publication date: 2017/09/01Publisher SummaryThis chapter discusses that the matrix logic algebra serves as a unifying link between fundamental physics and logic. One of the key reasons for such an assumption is that both quantum physics and matrix logic are built around a similar mathematical construct. In quantum physics, the wave functions do not represent an observable quantity; only the square of modulo of a wave function has physical meaning ||Ψ||2 = <Ψ* | Ψ>, where Ψ* is the conjugate transpose of Ψ. Similarly, in matrix logic, the logic vectors also represent logically unobservable quantities, yielding observable values through the application of the bilinear valuation device. To measure a physically observable quantity or to infer a logically observable quantity, corresponding operator between the two adjoint bra and ket vectors is introduced. In quantum physics an act of measurement, projects a pure state out of the mixed state of a quantum system, whereas the bilinear logic closure a *Read more...*

AbstractCreation and annihilation operators are used in quantum physics as the building blocks of linear operators acting on Hilbert spaces of many body systems. In quantum physics, pairing operators are defined in terms of those operators. In this paper, spectral properties of pairing operators are studied. The numerical ranges of pairing operators are investigated. In the context of matrix theory, the results give the numerical ranges of certain infinite tridiagonal matrices.

N. Bebiano Publication date: 2004/04/01AbstractFollowing a review of the frame of local quantum physics some remarks concerning the incorporation of principles of general relativity are made. The possibility of developing a theory of events by accepting irreversibility on a fundamental level is suggested.

Rudolf Haag Publication date: 1991/01/01AbstractWe review recent theoretical advances in cold atom physics concentrating on strongly correlated cold atoms in optical lattices. We discuss recently developed quantum optical tools for manipulating atoms and show how they can be used to realize a wide range of many body Hamiltonians. Then, we describe connections and differences to condensed matter physics and present applications in the fields of quantum computing and quantum simulations. Finally, we explain how defects and atomic quantum dots can be introduced in a controlled way in optical lattice systems.

D. Jaksch Publication date: 2005/01/01AbstractDuality, the equivalence between seemingly distinct quantum systems, is a curious property that has been known for at least three quarters of a century. In the past two decades it has played a central role in mapping out the structure of theoretical physics. I discuss the unexpected connections that have been revealed among quantum field theories and string theories. Written for a special issue of Studies in History and Philosophy of Modern Physics.

Joseph Polchinski Publication date: 2017/08/01AbstractBy using the method of few-body physics, the energy spectra of low-lying states of a negatively charged exciton X− (trion) in a GaAs quantum dot with a parabolic confinement have been calculated to obtain the low-lying eigenenergy values as a function of the dot size and the electron-to-hole effective mass ratio. The dependence of the binding energy of the ground state of the trion on the quantum dot radius is obtained.

Wenfang Xie Publication date: 2000/07/01AbstractA theoretical investigation on how the band structure of bulk semiconductors specifically affects the quantum confinement in quantum dots is presented, using Ge as an example. The intrinsic difference of the quantum confinement of different symmetrical valence states may bring some completely new physics as the quantum dot size decreases.

Shang Yuan Ren Publication date: 1997/05/01AbstractThe report analyzes the weak absorption problem of the quantum mechanics fundamental laws by the students of the Polytechnic schools and teaching. The problem is that in the famous courses of General physics (including lectures Feynman) emphasizes the exotic nature of quantum mechanics. This section of General physics is presented as a tool for solving only problems in atomic and nuclear physics. This is largely due to the lack of research results of quantum regularities at the macro-processes. The aim of presented study was to search for previously unknown quantum effects in the macro-processes. A positive outcome of these studies would present to students the fundamental and unique features of the quantum approach. In the research the author of this paper was able to establish previously unknown manifestations of quantum regularities in the wind gusts formation. The fundamental nature of these manifestations was obtained for a representative set of geographic points of the Ea *Read more...*

AbstractWe propose methods for observation of the quasi-stationary states of neutrons, localized near a curved mirror surface. The bounding effective well is formed by the centrifugal potential and the mirror's optical potential. This phenomenon is an example of an exactly solvable “quantum bouncer” problem that can be studied experimentally. It could provide a new tool for studying fundamental neutron–matter interactions, neutron quantum optics and surface physics effects. The feasibility of observation of such quantum states has been proven in first experiments.

R. Cubitt Publication date: 2009/12/01