68,666 research outputs found
Quantum Physics from A to Z
This is a collection of statements gathered on the occasion of the Quantum
Physics of Nature meeting in Vienna.Comment: 3 pages, Quantum Physics of Nature (QUPON) Conference, Vienna,
Austria, May 22nd-26th, 2005; v4: more contribution
Quantum physics meets biology
Quantum physics and biology have long been regarded as unrelated disciplines,
describing nature at the inanimate microlevel on the one hand and living
species on the other hand. Over the last decades the life sciences have
succeeded in providing ever more and refined explanations of macroscopic
phenomena that were based on an improved understanding of molecular structures
and mechanisms. Simultaneously, quantum physics, originally rooted in a world
view of quantum coherences, entanglement and other non-classical effects, has
been heading towards systems of increasing complexity. The present perspective
article shall serve as a pedestrian guide to the growing interconnections
between the two fields. We recapitulate the generic and sometimes unintuitive
characteristics of quantum physics and point to a number of applications in the
life sciences. We discuss our criteria for a future quantum biology, its
current status, recent experimental progress and also the restrictions that
nature imposes on bold extrapolations of quantum theory to macroscopic
phenomena.Comment: 26 pages, 4 figures, Perspective article for the HFSP Journa
Correlations in Quantum Physics
We provide an historical perspective of how the notion of correlations has
evolved within quantum physics. We begin by reviewing Shannon's information
theory and its first application in quantum physics, due to Everett, in
explaining the information conveyed during a quantum measurement. This
naturally leads us to Lindblad's information theoretic analysis of quantum
measurements and his emphasis of the difference between the classical and
quantum mutual information. After briefly summarising the quantification of
entanglement using these and related ideas, we arrive at the concept of quantum
discord that naturally captures the boundary between entanglement and classical
correlations. Finally we discuss possible links between discord and the
generation of correlations in thermodynamic transformations of coupled harmonic
oscillators.Comment: 10 pages, 1 figure. Submitted to Int. J. Mod. Phys. B, special issue
"Classical Vs Quantum correlations in composite systems" edited by L. Amico,
S. Bose, V. Korepin and V. Vedra
Quantum Physics and Computers
Recent theoretical results confirm that quantum theory provides the
possibility of new ways of performing efficient calculations. The most striking
example is the factoring problem. It has recently been shown that computers
that exploit quantum features could factor large composite integers. This task
is believed to be out of reach of classical computers as soon as the number of
digits in the number to factor exceeds a certain limit. The additional power of
quantum computers comes from the possibility of employing a superposition of
states, of following many distinct computation paths and of producing a final
output that depends on the interference of all of them. This ``quantum
parallelism'' outstrips by far any parallelism that can be thought of in
classical computation and is responsible for the ``exponential'' speed-up of
computation.
This is a non-technical (or at least not too technical) introduction to the
field of quantum computation. It does not cover very recent topics, such as
error-correction.Comment: 27 pages, LaTeX, 8 PostScript figures embedded. A bug in one of the
postscript files has been fixed. Reprints available from the author. The
files are also available from
http://eve.physics.ox.ac.uk/Articles/QC.Articles.htm
Measurement in Quantum Physics
The conceptual problems in quantum mechanics -- related to the collapse of
the wave function, the particle-wave duality, the meaning of measurement --
arise from the need to ascribe particle character to the wave function. As will
be shown, all these problems dissolve when working instead with quantum fields,
which have both wave and particle character. Otherwise the predictions of
quantum physics, including Bell's inequalities, coincide with those of the
standard treatments. The transfer of the results of the quantum measurement to
the classical realm is also discussed.Comment: 34 pages, in Latex, revised and expanded version with an extra
appendix on decoherenc
Time Asymmetric Quantum Physics
Mathematical and phenomenological arguments in favor of asymmetric time
evolution of micro-physical states are presented.Comment: Tex file with 2 figure
- …