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- Type of Document: M.Sc. Thesis
- Language: Farsi
- Document No: 55592 (04)
- University: Sharif University of Technology
- Department: Physics
- Advisor(s): Bahrampour, Alireza
- Abstract:
- Systems with permutation symmetry are prevalent in physics. In practical applications of quantum information, we frequently deal with multipartite quantum states that are invariant under permutations. These states may have complex structures that are hard to deal with due to quantum correlations between the parties. Luckily, symmetry can lead to independence. An important aspect of our research is to study the useful tools to harness symmetry in quantum information, to efficiently tackle the complexity.A representative example of such tools, is the quantum de Finetti theorem, which tells us that one part of a symmetric state can be treated as a mixture of identically prepared quantum states that have no correlation between the parties.After studying exchangeability and classical de Finetti Theorems, we analyze the quantum versions of this theorem. Regarding the application of these theorems in quantum communications, we address the security proof of (particulary continuous variable) quantum key distribution protocols against coherent attacks. Indeed, we claim that the coherent attacks are not stronger than collective attacks. Finally, with respect to the previous studies, we will point out a problem regarding exploiting the symmetry of invariance under the action of unitary operators in Gaussian continuous variable quantum key distribution with homodyne detection
- Keywords:
- Coherent Attacks ; Collective Attacks ; De Finetti Reduction Theorem ; De Finetti Theorem ; Permutation Symmetry
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