Quantum Computation and Information Seminar 

18/02/2005, 15:00 — 16:00 — Room P4.35, Mathematics Building
Beatrix Hiesmayr, U Vienna

Thermodynamical versus optical complementarity

The complementarity principle and the closely related concept of duality in interferometric devices was phrased by Niels Bohr in an attempt to express the most fundamental difference between classical and quantum physics. The well known statement that “the observation of an interference pattern and the acquisition of which–way information are mutually exclusive”, has been discussed for many years at a qualitative level. But only recently, quantitative statements for this long known “interferometric duality” have become available. In this talk I am going to investigate physical situations for which the visibility ("the wave-like property") and the predictability ("the particle-like property") can be analytically computed. This includes interference pattern of various types of double-slit experiments, but also oscillations due to particle mixing (e.g. the neutral kaon system) and also Mott scattering experiments of identical particles or nuclei. All these two-state systems belonging to distinct fields of physics can be treated via the generalized complementarity relation in a unified way. Surprisingly, this concept can also be applied to thermodynamical systems and thus one obtains new physical insights into usually complicated thermodynamical models, such as viewing a phase transition simply as a change from an effective single slit diffraction to a double slit interference.