Phase Transitions and Quantum Measurements
| Autor: | Allahverdyan, A., Balian, R., Nieuwenhuizen, T.M., Adenier, G., Khrennikov, A.Y. |
|---|---|
| Přispěvatelé: | Yerevan Physics Institute, Yerevan State University, Service de Physique Théorique (SPhT), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS), Institute for Theoretical Physics [Amsterdam] (IFTA), University of Amsterdam [Amsterdam] (UvA), Quantum Condensed Matter Theory (ITFA, IoP, FNWI) |
| Jazyk: | angličtina |
| Rok vydání: | 2015 |
| Předmět: |
Physics
[PHYS]Physics [physics] Phase transition Quantum Physics Spins Condensed matter physics Condensed Matter - Mesoscale and Nanoscale Physics Statistical Mechanics (cond-mat.stat-mech) Phonon Relaxation (NMR) FOS: Physical sciences Magnetization Mesoscale and Nanoscale Physics (cond-mat.mes-hall) Symmetry breaking Quantum Physics (quant-ph) Quantum Condensed Matter - Statistical Mechanics Spin-½ |
| Zdroj: | Quantum Theory: Reconsideration of Foundations-3: Växjö, Sweden, 6-11 June 2005, 47-58 STARTPAGE=47;ENDPAGE=58;TITLE=Quantum Theory: Reconsideration of Foundations-3 |
| Popis: | In a quantum measurement, a coupling $g$ between the system S and the apparatus A triggers the establishment of correlations, which provide statistical information about S. Robust registration requires A to be macroscopic, and a dynamical symmetry breaking of A governed by S allows the absence of any bias. Phase transitions are thus a paradigm for quantum measurement apparatuses, with the order parameter as pointer variable. The coupling $g$ behaves as the source of symmetry breaking. The exact solution of a model where S is a single spin and A a magnetic dot (consisting of $N$ interacting spins and a phonon thermal bath) exhibits the reduction of the state as a relaxation process of the off-diagonal elements of S+A, rapid due to the large size of $N$. The registration of the diagonal elements involves a slower relaxation from the initial paramagnetic state of A to either one of its ferromagnetic states. If $g$ is too weak, the measurement fails due to a ``Buridan's ass'' effect. The probability distribution for the magnetization then develops not one but two narrow peaks at the ferromagnetic values. During its evolution it goes through wide shapes extending between these values. Comment: 12 pages, 2 figures |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|