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Generation and suppression of decoherence in NMR quantum computer

Generation and suppression of decoherence in NMR quantum computer. Mikio Nakahara (Kinki University) in collaboration with Yasushi Kondo, Shogo Tanimura, Sachiko Kitajima, Chikako Uchiyama and Fumiaki Shibata J. Phys. Soc. Jpn., 76, 074002 (2007). Plan of the talk. 1. Introduction

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Generation and suppression of decoherence in NMR quantum computer

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  1. Generation and suppression of decoherence in NMR quantum computer Mikio Nakahara (Kinki University) in collaboration with Yasushi Kondo, Shogo Tanimura, Sachiko Kitajima, Chikako Uchiyama and Fumiaki Shibata J. Phys. Soc. Jpn., 76, 074002 (2007).

  2. Plan of the talk 1. Introduction 2. A Brief Introduction to Decoherence 3. Liquid-state NMR Quantum Computer (QC) 4. Artificial decoherence and its suppression 4.1 Generation of artificial relaxation 4.2 Demonstration of bang-bang control 4.3 Theoretical Analysis 5. Decay of Entanglement due to Noise 6. Summary IICQI, Kish Island September 2007

  3. Introduction: DiVincenzo Criteria IICQI, Kish Island September 2007

  4. 2. Brief Introduction to Decoherence IICQI, Kish Island September 2007

  5. Example: Phase-Flip channel IICQI, Kish Island September 2007

  6. Bloch vector IICQI, Kish Island September 2007

  7. Alternative Formalism (ours) IICQI, Kish Island September 2007

  8. Phase-Flip channel vs phase decoherence in NMR IICQI, Kish Island September 2007

  9. Probability distributions IICQI, Kish Island September 2007

  10. 3. Liquid State NMR Quantum Computer system environment IICQI, Kish Island September 2007

  11. Cl Cl Cl 13C H Hamiltonian qubit 1 system environment qubit 2 2 1 1 2 IICQI, Kish Island September 2007

  12. Spin flip = Telegraph noise IICQI, Kish Island September 2007

  13. 4. Generation of Artificial Decoherence 4.1 Decoherence in Quantum Channel Quantum Channel Bob Alice Noise (environment) Loss of Information IICQI, Kish Island September 2007

  14. IICQI, Kish Island September 2007

  15. IICQI, Kish Island September 2007

  16. IICQI, Kish Island September 2007

  17. 2 1 1 2 4.2 Qubit Under RTN IICQI, Kish Island September 2007

  18. Experimental Procedure - + + - + + - - reference pulses + + + - - - - + - random pulses IICQI, Kish Island September 2007

  19. Artificial Transverse Relaxation: Experimental Results IICQI, Kish Island September 2007

  20. 4.3 Suppression of Decoherence Spin Echo Cancellation fails if noise changes during the cycle. IICQI, Kish Island September 2007

  21. IICQI, Kish Island September 2007

  22. F. K. Wilhelm and K. Semba, in PHYSICAL REALIZATIONS OF QUANTUM COMPUTING: Are the DiVincenzo Criteria Fulfilled in 2004? IICQI, Kish Island September 2007

  23. Artificial Transverse Relaxation+Bang-Bang control + + - + - - - + IICQI, Kish Island September 2007

  24. Suppression of artificial transverse relaxation IICQI, Kish Island September 2007

  25. 5 Theoretical Analysis5.1 Without BB pulses IICQI, Kish Island September 2007

  26. IICQI, Kish Island September 2007

  27. IICQI, Kish Island September 2007

  28. IICQI, Kish Island September 2007

  29. IICQI, Kish Island September 2007

  30. IICQI, Kish Island September 2007

  31. 5.2 With BB Pulses IICQI, Kish Island September 2007

  32. IICQI, Kish Island September 2007

  33. IICQI, Kish Island September 2007

  34. Suppression of artificial transverse relaxation IICQI, Kish Island September 2007

  35. IICQI, Kish Island September 2007

  36. 6. Decoherence in Entangled Pair IICQI, Kish Island September 2007

  37. Hamiltonian and Initial State IICQI, Kish Island September 2007

  38. IICQI, Kish Island September 2007

  39. With Bang-Bang Pulses IICQI, Kish Island September 2007

  40. IICQI, Kish Island September 2007

  41. Example: IICQI, Kish Island September 2007

  42. Summary IICQI, Kish Island September 2007

  43. IICQI, Kish Island September 2007

  44. IICQI, Kish Island September 2007

  45. system Two-spin molecule as a system and its environment • System • Environment • Interaction in between Environment →　Natural Decoherence IICQI, Kish Island September 2007

  46. Artificial decoherence (our case) ~ system 1 system 2 environment + stochastic classical field on the subsystem 2 Teklemariam et al, Phys. Rev. A 67, 062316 (2003) IICQI, Kish Island September 2007

  47. Simulation of Artificial Relaxation IICQI, Kish Island September 2007

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