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Q: Fachverband Quantenoptik und Photonik

Q 16: Quanteneffekte (Interferenz und Korrelationen)

Q 16.4: Vortrag

Montag, 19. März 2007, 17:15–17:30, 5E

Decoherence measurements and visualisation of the quantum-classical border using an electron interferometer — •Peter Sonnentag and Franz Hasselbach — Institut für Angewandte Physik, Universität Tübingen, Auf der Morgenstelle 10, 72076 Tübingen

The incompatibility of the quantum mechanical superposition principle with our everyday experience of a classical world has been a longstanding problem, nowadays being solved by the theory of decoherence. To investigate decoherence experimentally, we used free electrons interacting by Coulomb force with a truly macroscopic and theoretically nontrivial environment, the electron and phonon gas inside a semiconducting plate. The electron beam in a biprism interferometer is split into two parts which travel over the plate at the same, small height, but laterally separated. The induced currents inside the plate encounter ohmic resistance, leading to Joule heating which quantum-mechanically means a disturbance of the electron and phonon gas [1]. As this disturbance is different for the two paths of the beam electron, entanglement between beam electron and plate is formed, leading to a decrease in fringe visibility. The experiment also allows for an intuitive explanation in terms of which-path information.

Our results are quantitatively compared with different theoretical calculations. Furthermore, our modification of the original proposal [1] enabled us to directly visualize the quantum-classical border in single interferograms.

[1] J. R. Anglin, W. H. Zurek, Phys. Rev. A 55 (1997) 4041.