以微擾理論計算雙量子點之失相時間｜國立清華大學博碩士論文庫

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研究生：	潘正達 Cheng-Ta Pan
論文名稱：	以微擾理論計算雙量子點之失相時間 Decoherence Time of the Coupled Quantum Dots Calculated with Perturbation Theory
指導教授：	吳玉書 George Yu-Shu Wu
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：	2005
畢業學年度：	93
語文別：	英文
論文頁數：	37
中文關鍵詞：	失相、失相時間、量子點、微擾
外文關鍵詞：	decoherence, decoherence time, quantum dot, perturbation
相關次數：	點閱：2 下載：0
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我們提供兩個新穎的方法來計算雙量子點的失相時間(decoherence time)。我們所提供的方法較一些相關的計算，例如NIBA，簡潔和直觀許多；透過我們的計算方法，對於失相時間的機制可以有很好的物理解釋。由費米黃金法則(Fermi’s golden rule)，我們計算一個與兩個聲子的躍遷速率，而我們的結果和一些相關文獻的結果一致。我們也計算近似的多聲子躍遷速率，而發現一個溫度尺度可以決定何時多聲子躍遷的速率變得重要。最後，我們提供雙量子點失相時間的數值估計，當溫度離不甚遠時，則量子計算將有希望可以實現，但若溫度離太遠時，失相時間將不足夠長，以至於無法完成量子計算。

We provide two novel approaches to calculate the decoherence time of the coupled quantum dots. These two approaches are much more succinct and intuitive than the previous works such as NIBA. Our approaches provide good physical insight for the mechanism of the decoherence time. One- and two-phonon transition rates are calculated with Fermi’s golden rule and results are in agreement with relevant works. The approximate multi-phonon transition rate is obtained and we find there is a temperature scale T0 which can determine when the multi-phonon transition dominates. Numerical calculations of the decoherence time of the coupled quantum dots are given and we find the quantum computation based on coupled quantum dots can be realized at low temperature, ie. not far above T0, but otherwise the decoherence time is too short for performing quantum computation.

Chapter 1 : Introduction-----------------------------------1

Chapter 2 : Theoretical Background-------------------------3

2-1 Brief Derivation of Spin-Boson Hamiltonian with second
    quantization-------------------------------------------3
2-2 Physical Meaning of the Canonical Transformation-------4
2-3 Fermi’s Golden Rule for a Two-State System------------6

Chapter 3 : Approach I Thermodynamic Limit Approach--------8

3-1 Set up the Perturbation--------------------------------8
3-2 One-Phonon Transition Rate-----------------------------9
3-3 Two-Phonon and Multi-Phonon Transition Rate-----------14
   3-3.1 Two-Phonon Transition Rate-----------------------14
   3-3.2 Multi-Phonon Transition rate---------------------20
   3-3.3 Temperature Scale T0-----------------------------21

Chapter 4 : Approach II Average Approach------------------23

4-1 Set up the Perturbation-------------------------------23
4-2 Transition Rate---------------------------------------24
   4-2.1 Odd-Phonon Transition Rate-----------------------24
   4-2.2 Even-Phonon Transition Rate----------------------25
4-3 Estimate Decoherence Time-----------------------------27

Chapter 5 : Conclusions-----------------------------------31

Appendix A------------------------------------------------32

Appendix B------------------------------------------------35

Reference-------------------------------------------------37

                                

[1] Yuriy Makhlin et al., Rev. Mod. Phys 73, No.2, April 2001.

[2] D. P. DiVincenzo, Phys. Rev. A 51(2), 1015 (1995).

[3] A. Steane, Appl. Phys. B-Laser and Optics 64(6), 623 (1997).

[4] Tetsufumi Tanamoto, Phys. Rev A 61, 022305 (2000).

[5] A.J. Leggett et al., Rev. Mod. Phys 59, No.1, January 1987.

[6] A. Würger, Phys. Rev. B 57, 347 (1998-I).

[7] A. Würger, Phys. Rev. Lett. 78, 1759 (1997).

[8] A. Würger, J. Phys.:Condens. Matter 9, 5543 (1997).

[9] T. Holstein, Ann. Phys. (N.Y.) 8, 343 (1959)

[10] G. D. Mahan, Many-Particle Physics 3rd ed. (Plenum, New York, 2000).

[11] G. Grosso and G. P. Parravicini, Solid State Physics (Academic Press, 2000).

[12] Claude Cohen-Tannoudji et al., Atom-Photon Interactions : Basic Processes and
Applications (New York :J. Wiley, 1992).

[13] J.J. Sakurai, Modern Quantum Mechanics (Addition Wesley Longman, 1994).

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