Quantum Decoherence and Entanglement

It is still an open question how a classical world evolves out of quantum nature. Dephasing and decoherence play an important role in this respect and will be a main topic of this project. Most experimental investigations will be done by neutron interferometry where different (nearly) classical and non-classical quantum states can be produced and analyzed. Inhomogeneous materials and magnetic noise fields will be used to destroy the coherence of such quantum states. But during the last decade it has been shown that most of these decoherence effects only virtually destroy these quantum states because proper error correction methods can retrieve the original quantum state at least to a large extent. A more detailed analysis shows that, in addition to these retrievable effects, unavoidable quantum losses appear which may be essential for real dephasing. These unavoidable quantum losses (reflections, diffractions, energy exchanges) will be investigated in detail. Dephasing effects concerning dynamical and topological phases will be investigated separately. The connection to dephasing effects of entangled systems and of different degrees of freedom in single particle systems (contextuality) will be addressed. Additional measurements with a novel neutron resonator system and with ultra-cold neutrons are planned as well. This project has been formulated in close connection to a partner project submitted by Mr R. Bertlmann from the University of Vienna, where mostly theoretical aspects of decoherence will be treated. Both projects should be carried out in an "entangled" manner to guarantee a high efficiency for the scientific outcome.

It is still an open question how a classical world evolves out of quantum nature. Dephasing and decoherence play an important role in this respect and will be a main topic of this project. Most experimental investigations will be done by neutron interferometry where different (nearly) classical and non-classical quantum states can be produced and analyzed. Inhomogeneous materials and magnetic noise fields will be used to destroy the coherence of such quantum states. But during the last decade it has been shown that most of these decoherence effects only virtually destroy these quantum states because proper error correction methods can retrieve the original quantum state at least to a large extent. A more detailed analysis shows that, in addition to these retrievable effects, unavoidable quantum losses appear which may be essential for real dephasing. These unavoidable quantum losses (reflections, diffractions, energy exchanges) will be investigated in detail. Dephasing effects concerning dynamical and topological phases will be investigated separately. The connection to dephasing effects of entangled systems and of different degrees of freedom in single particle systems (contextuality) will be addressed. Additional measurements with a novel neutron resonator system and with ultra-cold neutrons are planned as well. This project has been formulated in close connection to a partner project submitted by Mr R. Bertlmann from the University of Vienna, where mostly theoretical aspects of decoherence will be treated. Both projects should be carried out in an "entangled" manner to guarantee a high efficiency for the scientific outcome.