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Retrieving Lost Quantum Information Due to Non-Unital Noise by Partial Access to the Environment

Shirazi Zamani, Ali | 2022

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 55005 (04)
  4. University: Sharif University of Technology
  5. Department: Physics
  6. Advisor(s): Memarzadeh Esfahani, Laleh
  7. Abstract:
  8. One of the main obstacles in constructing quantum computers and implementations of quantum computations and communications protocols, is the occurrence of quantum noise. In fact, due to the unavoidable interaction of the system and its surrounding environment, errors always occur and the system should be protected against noise or we need to find a way to detect the errors and correct them. Regarding the importance of the subject, intensive investigations have been done in this direction. Different approaches for correcting quantum errors are introduced. In this thesis, we focus on an approach based on collecting information from the environment. It has been shown that for a class of noise, with access to the environment quantum information can be recovered and full correction is possible. This class of noise in two-dimensional Hilbert-space is described by unital channels. For these multi-qubit quantum channels, quantum information correction with partial access to the environment has been discussed.In this thesis we focus on channels which are not convex combinations of unitary channels. For channels which are not convex combinations of unitary channels, full recovery of quantum information with a feedback control scheme is not possible and one should find the optimal measurement and recovery of information. First we study the fully correlated two-qubit amplitude damping noise. In this model we analyze the role of correlation in noise in error correction with a feedback-control scheme and discuss the possibility of recovering information with partial access to the environment. Then we introduce four different models of noise on two qubit systems emerging from their interaction with a thermal bath in Born-Markov approximation. In each model we discuss the optimal measurement and optimal recovery map and elaborate on the performance of the feedback control scheme on recovery of quantum information in terms of noise parameter
  9. Keywords:
  10. Quantum Noise ; Error Correction ; Lost Data Recovery ; Quantum Error Correction ; Correlated Errors

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