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Macroscopic Superposition in Quantum Systems

Abad, Tahereh | 2019

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 52263 (04)
  4. University: Sharif University of Technology
  5. Department: Physics
  6. Advisor(s): Karimipour, Vahid
  7. Abstract:
  8. Quantum mechanics provides a deep understanding of atoms and their interaction with light. As long as we consider only microscopic systems on the scale of an atomic radius, objections to quantum properties such as quantum superposition are nevertheless rare, mainly because of the overwhelming experimental evidence. When it comes to macroscopic systems, many things are not clear anymore. For example,everyday objects of macroscopic size do not exist in superposition of their different states. The reason is that a quantum system interacts with its environment locally,which destroys non-local quantum correlation within the system, larger objects interact with the environment more intensively and therefore lose these correlations more rapidly. With recent progresses in experimental physics, it is nowadays possible to investigate quantum effects in macroscopic scale such as interference in Young’s Double Slit Experiment for molecules and macromolecules and will continue to larger and larger systems. In this thesis, we study the relevant subject; It may be possible, to appear a macroscopic quantum superposition in the quantum phase transition point.The scale of divergence of correlation length in classical phase transition, may appear here in some form of divergence of macroscopic superposition. We study two separated physical systems, namely Ising model in transverse field, and Rydberg atoms subject to the stimulated Raman adiabatic passage. In two cases we show that in the critical point, the system is a macroscopic superposition of its particles. We also show that using the interaction Hamiltonian that only addresses each pair of particles once, the system may become entangled over long distances. For this purpose we study quantum states generated by a sequence of nearest neighbor bipartite entangling operations along an uncorrelated spin chain. We conclude macroscopic quantum superposition only occurs over the entire chain if the nearest neighbor interaction is maximally entangling
  9. Keywords:
  10. Macroscopic Quantum System ; Quantum Fisher Information ; Quantum Phase Transition ; Matrix Product State ; Rydberg Blockade ; Stimulated Raman Adiabatic Passage

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