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Entanglement and State Transfer through Quantum Spin Chains

Zare Harofteh, Mohammadnabi | 2023

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 56691 (04)
  4. University: Sharif University of Technology
  5. Department: Physics
  6. Advisor(s): Memarzadeh, Laleh; Langari, Abdollah
  7. Abstract:
  8. In this thesis, we will examine quantum state and entanglement transfer. Quantum state and entanglement transfer are requirements for the development of quantum technology. Transferring the output state of a quantum processor to the next processor, which can be at an arbitrary distance from the first processor, is one of the direct applications of quantum state transfer. On the other hand, entanglement transmission is a necessary prerequisite for quantum protocols. For example, preparing the entangled pair in a laboratory and transferring one share of an entangled pair to another place in order to create entanglement between different points is essential for building quantum networks. Also, the need to transport entangled pairs produced in a laboratory to other locations to perform quantum protocols is obvious. These topics are the focus of this thesis. After reviewing the fundamentals and recent achievements, we specifically investigate the spin-1/2 XY chain placed in a (non-uniform) local magnetic field for quantum state and entanglement transfer. First, we consider the local magnetic fields, only on the initial and final spins. Within an analytical solution we are able to find the optimal magnetic fields for maximum quantum state transfer, which are symmetric with respect to the middle of chain. Moreover, the analytical solution is used to benchmark the numerical solution approach. The optimal values of magnetic fields and time for quantum state and entanglement transfer in chains up to length N=20 are calculated using an optimization algorithm. Using simulation data and machine learning approach, optimal values of magnetic fields and time for chains up to length N=50 are obtained. Our results show that the local magnetic fields increase the entanglement transfer of an entangled pair in the chain and the fidelity between the transferred and expected states
  9. Keywords:
  10. Spin Chain ; Entanglement ; Optimization ; Machine Learning ; Remote State Preparation ; State Transfer ; Quantum Entanglement

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