EGAS41 - Swansea University

41 st EGAS CP 102 Gdańsk 2009
Discreteness and chance in atomic physics
G. von Oppen
Institut fuer Optik und Atomare Physik, Technical University Berlin,
D-10653 Berlin, Germany
E-mail: oppen@physik.tu-berlin.de,
The discrete structure of matter (atoms) and fields (quanta) implies that free atoms cannot
be observed continuously. Rather, they are observed by detecting discrete elementary
events triggered by spontaneous quantum jumps or particle impact. The occurrence of
these elementary events is governed by the laws of chance.
In this contribution we discuss the fundamental change from continuity to discreteness
and from determinism to chance, which characterizes the transition from classical to
quantum measurements. The quantized structure of the process of observation opens a
new perspective on the relation between classical and quantum physics. Since the process
of observation is quantized, the objects of physics do not evolve purely dynamically,
but are exposed also to influences occurring spontaneously. This influence of chance is
fundamental. It gives rise to thermal and statistical noise in precision measurements, and
in quantum physics it has to be taken into account by introducing quantum jumps.
A purely dynamic evolution is possible only, if idealized experimental conditions are
assumed. In classical dynamics one assumes that the objects can be observed continuously.
In this case, the objects are not disturbed by spontaneously occurring events. Quantum
dynamics applies to the opposite extreme. Quantum objects are unobservable [1]. The
quantum dynamic evolution breaks down, if the object interacts spontaneously with the
environment and, hence, becomes observable. By accepting quantum jumps in theory and
noise in experimental physics as fundamental ingredients, we are led to the conclusion that
quantum and classical dynamics apply to opposite extremes on a scale of observability
[2]. However, the two theories are related by correspondence rules.
In contrast to our conclusion, quantum dynamics is often considered as a generalization
of classical mechanics [3], and one concludes that only the uncertainty relations give rise
to experimental uncertainties, even if the measurements are performed on macroscopic
(continuously observable) bodies [4]. From our point of view, this conclusion is wrong,
because the presence of thermal and statistical noise due to the observability of the body
is disregarded.
The new insight into the quantum-classical relation necessitates a revision of the world
picture of physics. The unobservable objects of quantum dynamics have to be considered
as unstructured entities embedded in an observable environment. Classical model systems
are justified only within the framework of the correspondence rules. We conjecture
that ultimately quantum dynamics has a purely mathematical foundation. The correspondence
between the classical world of particles and fields moving in space and time
and the quantum world may guide the way to the appropriate algebraic structure. Some
speculative investigations on a metric quaternion algebra have been performed.
References
[1] G. v. Oppen, Phys. Usp. 166, 661 (1996)
[2] G. v. Oppen, Eur. Phys. J., Special Topics 144, 3 (2007)
[3] A. Messiah, Quantum Mechanics, (North Holland Publ. Comp., Amsterdam 1970)
[4] C. M. Caves et al., Rev. Mod. Phys. 52, 341 (1980)
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