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研究生： 洪若慈
Jo-Tzu Hung
論文名稱： Spin Qubit Decoherence and Entanglement Induced by 1D Quantum Spin Baths
自旋量子位元與一維自旋環境交互作用之消相干與糾纏態研究
指導教授： 陳柏中
Pochung Chen
口試委員:
學位類別： 碩士
Master
系所名稱： 理學院 - 物理學系
Department of Physics
論文出版年： 2008
畢業學年度： 96
語文別： 英文
論文頁數： 43
中文關鍵詞： 密度矩陣重整化群 、量子資訊
外文關鍵詞： Density matrix renormalization group, DMRG, Quantum information
相關次數： 點閱：1  下載：0 
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    • Spin decoherence induced by spin baths has become an important subject in the field of quantum information science and quantum computing. In this work, the Heisenberg XXZ spin chain, which has a rich phase diagram, functions as a spin bath. I investigate spin-1/2 qubit decoherence as well as entanglement by mean of time-dependent density matrix renormalization group (t-DMRG). I find that induced decoherence and entanglement crucially depends on the phase
    of the spin bath. Moreover, for various interaction types and coupling strengths between the qubit(s) and the spin bath, the induced decoherence and entanglement differs. These show that there is a competition between the induced decoherence and entanglement. Finally, I stimulate two-qubit (dis)entanglement dynamics via a common bath and entanglement sudden death is also observed.

    1 Introduction 2 Numerical approach: density matrix renormalization group 2.1 Density matrix renormalization group 2.1.1 DMRG algorithms 2.1.2 Physical quantities in DMRG 2.1.3 Wavefunction transformation 2.2 Time-dependent DMRG 2.2.1 Suzuki-Trotter decomposition 2.2.2 Add qubit(s) in t-DMRG 2.2.3 Add qubit self-Hamiltonian 3 Single-qubit decoherence by 1D Heisenberg XXZ spin baths 3.1 The model 3.2 Single-qubit decoherence and Loschmidt echo 3.3 Single-qubit decoherence dynamics 3.3.1 Ising-type interaction 3.3.2 Heisenberg-type interaction 4 Two-qubit dynamics via common bath 4.1 Measure of entanglement 4.1.1 Wootters concurrence 4.2 Entanglement creation 4.2.1 Ising-type interaction 4.2.2 Heisenberg-type interaction 4.3 Disentanglement dynamics 4.4 Multi-link coupling 5 Conclusion 5.1 Summary 5.2 Future work Appendices

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