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Fundamental Study of Entanglement and its Application in Chirality Problem

Taher Ghahramani, Farhad | 2014

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 46418 (03)
  4. University: Sharif University of Technology
  5. Department: Chemistry Science
  6. Advisor(s): Shafiee, Afshin
  7. Abstract:
  8. The origin of life is one of the fundamental problems of the science, which is not yet answered appositely. The building blocks of life’s molecules, including nucleic acids (DNA and RNA) and proteins, are composed of carbohydrates and amino acids. At the chemical level, these building blocks have definite chirality. This phenomenon is known as biological homochirality. Due to the fact that this phenomenon has taken place in the early stages of life, it is believed that the life’s origin is to a great extent connected to the origin of biological homochirality. Like every other system, at the microscopic level, life’s molecules are composed of atoms which are governed by the lows of quantum theory. From the quantum perspective, under the adiabatic conditions, the problem can be formulized in terms of the one-dimensional dynamics of a particle in the symmetric double-well potential. At not too high temperatures, the chiral states -localized in the minima of two wells- are expressed as the superposition of energy eigenstates. The crucial question is that why the chiral states, which are not stationary states, are stable (stabilization problem), and beyond this, for life’s molecules, why one of these chiral states are more stable than the other one (discrimination problem). At the early days of the development of quantum theory, the stabilization problem was posed by Hund, which later dubbed as Hund paradox. Numerous attempts have been made to explain the stabilization of the chiral states. In 1970s, it has been theoretically shown that parity-violating weak interactions, resulted from the exchange of the bosons between electrons and nuclei of chiral molecules, destroy the degeneracy of the chiral states, making the double-well potential asymmetric. Nevertheless, the calculations showed that the difference due to the weak interactions is not sufficient to explain the stability of the chiral states. In 1980s, the effect of environment on the dynamics of the quantum system is formulized within the framework of decoherence theory. According to this theory, interaction between system and environment can demolish the coherence between certain states of system and leads to the emergence of those states. In this way, it has been qualitatively shown that the chiral states can stabilized in the course of the collision of environmental particles. In this thesis, we show that, within the framework of decoherence theory, molecular chiral states can stabilize in the course of the interaction with the circular-polarized light. Then, by introducing the chiral interactions into the molecular Hamiltonian we examine the discrimination problem for an ensemble of chiral molecules in a biological environment
  9. Keywords:
  10. Hund Paradox ; Decoherence ; Life Origin ; Biological Homochirality ; Chiral Interactions

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