Karl Kraus (physicist)
Karl Kraus ( born March 21, 1938 in Vrchlabí ( German Hohenelbe / Giant Mountains ), † June 9, 1988 in Würzburg ) was a German theoretical physicist who made major contributions to the foundations of quantum physics has done.
Life and work
Kraus was born in 1938 in Hohenelbe / Giant Mountains, today Vrchlabí. After the war, he grew up in and attended local schools Elsterwerda. He studied 1955 to 1960 at the Humboldt University of Berlin (East) and the Free University of Berlin ( West) physics. There he was in 1962 received his doctorate with a dissertation on Kurt Just about Lorentzinvariante theory of gravitation. Kraus then moved on as an assistant to Günther Ludwig at the University of Marburg, where he qualified in 1966. In 1971 he accepted a professorship at the Physics Institute of the University of Würzburg, where he founded a mathematical-physical Working Group on the theme of the foundations of quantum theory. 1980 Kraus spent a sabbatical year at the University of Austin in John Archibald Wheeler, Arno Böhm, George Sudarshan, William Wootters and Wojciech Zurek.
Throughout his academic life Kraus dealt with the question of the connection between the non-locality of the quantum world and the obvious location of our classical world. In this context, he has researched and published on the Einstein - Podolsky-Rosen effect and time again on issues of the measurement process in quantum theory, the problem was in his opinion largely ignored by the founders of quantum theory in the Copenhagen interpretation.
Important publications on the measurement process in quantum theory of Kraus were:
- Measuring processes in quantum mechanics I. Continuous observation and the watchdog effect.
- Measuring processes in quantum mechanics II The classical behavior of measuring instruments.
- States, Effects, and Operations.
In that book States, Effects, and Operations Kraus led to the description of the measurement process in quantum mechanics for the first time the concept and mathematical formalism of quantum operation, a, a special mapping of density matrices. The representation used by him in this regard is now known as the Kraus representation, Kraus operator formalism or operator -sum formalism, and is now frequently used in the context of developments in the field of quantum information. The Kraus representation is based on a theorem of WF Stinespring on completely positive mappings of finite-dimensional C * - algebras. For a modern proof of the Kraus representation, which instead of the set of Stinespring on a theorem of M.-D. Choi is supported, see eg M. Nielsen, I. Chuang.
The treated by Kraus questions about the foundations of quantum theory are a current area of research today. New theoretical advances are discussed in E. Joos, HD Zeh, C. Kiefer, D. Giulini, J. Kupsch, I.-O. Stamatescu. The combination of these decoherence theories with modern experiments, as described in particular by the groups of Serge Haroche (Paris) and Anton Zeilinger (Innsbruck, Vienna) were started, maybe can help the measurement process in quantum theory, and thus the relationship between quantum and classical future to better understand the world.
Except for mathematics and physics Kraus had a special interest in biology, earned it an extensive knowledge and even published some biological work. Karl Kraus died in 1988 at age 50 from the effects of tumor disease.