SFB 668

 

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16.5.2017, 17:00
Jungiusstr. 11, Hörsaal AP

SFB 668 - Kolloquium

Prof. Dr. M. Katsnelson (Radboud University, Nijmegen, Netherlands):

Decoherence in quantum spin systems

Decoherence in quantum spin systems M. I. Katsnelson Radboud University, Nijmegen, Netherlands One of the basic questions of quantum mechanics is the "origin of classical": why superposition principle does not work in the macroworld and what preserve Shroedinger cat from being in the superposition of alive and dead states. "Decoherence program" suggests an answer on this question based on the idea that superposition of quantum states can be destroyed by interaction with an environment and only some special states ("pointer states") survive. I will review this issue emphasizing difficulties and open problems. I will also consider a concept of "decoherence wave" which arises after a local measurement in a distributed quantum system. Magnetic clusters at the surface probed via spin-polarized STM is a good system to probe these issues of a fundamental importance. The talk is based on the works [1-9]. [1] M. I. Katsnelson, V. V. Dobrovitski, and B. N. Harmon, Propagation of local decohering action in distributed quantum systems. PHYS REV A 62, 022118 (2000) [2] M. I. Katsnelson, V. V. Dobrovitski, and B. N. Harmon, Neel state of an antiferromagnet as a result of a local measurement in the distributed quantum systems. PHYS REV B 63, 212404 (2001) [3] S. D. Hamieh and M. I. Katsnelson, Quantum entanglement dynamics and decoherence wave in spin chains at finite temperatures. PHYS REV A 72, 032316 (2005) [4] S. Yuan, M. I. Katsnelson, and H. De Raedt, Giant enhancement of quantum decoherence by frustrated environments. JETP LETT 84, 99 (2006) [5] S. Yuan, M. I. Katsnelson, and H. De Raedt, Evolution of a quantum spin system to its ground state: Role of entanglement and interaction symmetry. PHYS REV A 75, 052109 (2007) [6] S. Yuan, M. I. Katsnelson, and H. De Raedt, Decoherence by a spin thermal bath: Role of spin-spin interactions and initial state of the bath. PHYS REV B 77, 184301 (2008) [7] S. Yuan, M. I. Katsnelson, and H. De Raedt, Origin of the canonical ensemble: Thermalization with decoherence. J PHYS SOC JAPAN 78, 094003 (2009) [8] H. C. Donker, H. De Raedt, and M. I. Katsnelson, Decoherence wave in magnetic systems and creation of Neel antiferromagnetic state by measurement. PHYS REV B 93, 184426 (2016) [9] H. C. Donker, H. De Raedt, and M. I. Katsnelson, Decoherence and pointer states in small antiferromagnets: A benchmark test. SCIPOST PHYS 2, 010 (2017)

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