Woensdag 17 november 2004
Spreker: 
Mikhail Katsnelson (RU)

Titel: 
Quantum dynamics and decoherence in nanoscale spin systems

Tijd: 
11:00  12:00

Plaats: 
CK N4 (N3045)

Vanaf half 11 is er koffie en chocola in de Weylkamer
(N2046).
Abstract
Whereas microworld is considered now as a quantum one, macroscopic objects are
classical. Moreover, according to Bohr's complementary principle, the existence
of classical measuring devices is necessary for the existence of quantum physics
itself. It is not easy to understand, however, what is the boundary between
quantum and classical.
Another (and closely related) problem is a status of von Neumann's postulate
about the change of the state of quantum system after the measurement. These
problems are treated now in a framework of "quantum physics of open systems",
i.e., the systems interacting with an environment. The interaction leads, in
particular, to the "decoherence". For example, this is the main obstacle for
physical realization of quantum computers.
Nanoscale spin systems (e.g., magnetic molecules) are typical examples of open
quantum systems where the interaction with an environment is comparable with
typical energies of the system itself. Basing on this example, some general
problems will be discussed, such as: what are real criteria of decoherence and
"classicality"; why the superposition principle does now work for large objects;
what is the von Neumann measurement in distributed quantum systems and how it is
connected with a concept of "broken" symmetry; a relevance of the concept of
"quantum entanglement" in quantum manybody theory.