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Low-Temperature Coherence Properties of Z2 Quantum Memory

Cheraghi, Hadi | 2011

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 43110 (04)
  4. University: Sharif University of Technology
  5. Department: physics
  6. Advisor(s): Karimipour, Vahid; Memarzadeh Esfahani, Laleh
  7. Abstract:
  8. Quantum memory which stores the coherent information of logical qubits, is an essential ingredient of quantum information processings. Each logical basis should be encoded on macroscopically distinct physical states since otherwise the indistinguishability of logical bases is easily destroyed by local errors.On the other hand, the memory must be able to have superposition of macroscopically distinct states of physical qubits. To maintain such superposition is very difficult. First, if the size of the memory is infinite, such macroscopic superposition is impossible since superposition of different phases is just a classical mixture of them in an infinite system. Second, even in finite systems, such macroscopic superposition is usually very unstable. Therefore, how to balance those two contradictory demands?
    In The project, We investigate low-temperature coherence properties of the quantum memory which is capable of storing the information of a single logical qubit. We show that the memory has superposition of macroscopically distinct states for some values of a control parameter and at sufficiently low temperature, and that the code states of this memory have no instability except for the inevitable one. However, we also see that the coherence power of this memory is limited by space and time. We also briefly discuss the RVB memory, which is an improvement of the quantum memory
  9. Keywords:
  10. Superposition Principle ; Coherence Theory ; Quantum Memory ; Logical Qubits ; Logical Basic ; Quantum Error

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