Principles of Noise Assisted Transport in Networks

1. Imperial College London Principles of Noise Assisted Transport in Networks Martin B Plenio Institute for Mathematical Sciences & Quantum Optics and Laser Science Group Blackett Laboratory Imperial College London http://www.imperial.ac.uk/quantuminformation In collaboration with: Animesh Datta & Filippo Caruso (Imperial College London, UK) Alex Chin and Susana Huelga (Univ. Hertfordshire, UK)

8. Noise seems a problem here as it destroys quantum coherence

9. Weak coherent driving Weak response

10. Weak coherent driving + weak noise give a strong coherent response. Noise Stochastic resonance

11. Biological systems can use noise to improve their sensitivity to weak coherent signals Can we use this in quantum mechanics ? Noise can be good for you in quantum mechanics too for entanglement generation and preservation ! Huelga & Plenio, PRA 1999, PRA 2000 & PRL 2002 & PRL 2007 See also overview talk by Susana Huelga Friday

12. A Fundamental Experiment Clicks Time Clicks Time

13. A Fundamental Experiment

14. A Fundamental Experiment Clicks Time Clicks Time

15. Photosynthesis Green sulphur Bacteria A black smoker in the Atlantic Ocean ~ 2000m deep Y.C. Cheng and G.R. Fleming, Annu. Rev. Phys. Chem. 60, 241 (2009)

16. Exciton Transport in Photosynthesis Green sulphur Bacteria Reaction Centre CO + 2 H S 2 2 + energy CH O + H O + 2 S 2 2

17. Exciton Transport in Photosynthesis Green sulphur Bacteria Reaction Centre CO + 2 H S 2 2 + energy CH O + H O + 2 S 2 2

18. Exciton Transport in Photosynthesis Green sulphur Bacteria Reaction Centre Transfer to reaction centre CO + 2 H S 2 2 + energy CH O + H O + 2 S 2 2

19. Dephasing Exchange of excitation Transfer to reaction centre Loss of excitation Reaction Centre CO + 2 H S 2 2 + energy CH O + H O + 2 S 2 2 M.B. Plenio and S.F. Huelga, New J. Phys. 10, 113019 (2008)

20. Noise Assisted Transport and Photosynthesis More dephasing Some dephasing No dephasing Plenio & Huelga, New J. Phys. 2008 Mohseni, Rebentrost, Lloyd, Aspuru-Guzik, J. Phys. Chem. 2008

21. Physical Origin of Noise Assisted Transport

22. Exciton Transport in Photosynthesis Show Movie 1: No dephasing Initial excitation in site 1

23. Exciton Transport in Photosynthesis Two differenttime scales !

24. Destructive Interference and Invariant States Clicks Time Clicks Time

25. Destructive Interference and Invariant States = J J Reactioncenter

26. Destructive Interference and Invariant States = J J Reactioncenter Transfer efficiency

27. Noise Inhibits Destructive Interference = Decoherence inhibits destructive interference ! J J Reactionscenter Transfer efficiency Reactioncenter Reduction ofdestructive interference

28. Destructive Interference and Invariant States Two atoms in the same location: Invariant state:

29. Dephasing on site 1 only Show Movie1a: Small dephasing on site 1 only

30. Dephasing on site 1 only

31. Destructive Interference and Invariant States Different energy splitting: not invariant under Hamiltonian evolution !

32. Disorder Inhibits Destructive Interference Static disorder inhibits destructive interference ! J J Destructiveinterference Reactioncenter J J Reactioncenter Reduction ofdestructive interference

33. Disorder Inhibits Destructive Interference

34. The Hamiltonian of the FMO complex Quite strong static disorder compared to coupling strengths !

35. Bridging the gap: Enhanced transport via line broadening

36. Dephasing Noise on Site 3 only Play Movie1ab: Same amount of dephasing noise now only on site 3 Play Movie1b: Dephasing noise only on site 3

37. Dephasing Noise on Site 3 only

38. Line broadening does enhance transfer! No line broadening, No transfer!

39. Spatially Correlated Noise J J J J destructive interference destructive interference +J -J -J -J effect ofnoise enhanced effect ofnoise reduced

40. Spatially Correlated Noise dephasing with non-local correlations T=5 ps local dephasing without correlations Therefore, correlated noise does not lead to decisive improvements in this setting!

41. Loss Enhanced Transport J J destructive interference J J J J excitationlost destructive interferencereduced

42. Noise Assisted Transport and Photosynthesis More dephasing Some dephasing No dephasing

43. Dependence on Noise Strength Inhibition of coupling through dephasing Reduction of destructive interference

44. Robustness of Noise Assisted Transport optimal dephasing Two differenttime scales ! no dephasing Robustness against strong static disorder compared to coupling strengths (i.e. 20%)!

45. Entanglement Dynamics F.Caruso., A.W. Chin, A. Datta, S.F. Huelga, M.B. Plenio, to be submitted

46. |01>-|10> J J J destructive interference reduced destructive interference • Each process open additional pathways for propagation F.C., A.W. Chin, A. Datta, S.F. Huelga, M.B. Plenio, arxiv:0901.4454 (2009)

47. The Fundamental Mechanisms • Dephasing can reduce destructive interference • Energy mismatch can reduce destructive interference • Dephasing noise increases overlap of energy levels • Each process open additional pathways for propagation Plenio & Huelga, New J. Phys. 10, 113019 (2008) Caruso, Chin, Datta, Huelga, Plenio, arxiv:0901.4454 [quant-ph]

48. Can we improve solar cellsbased on this idea ? More generally: Adding the right kind of noise, to the right kind of nano-structure can improve its performance. Engineer system to generate constructive interplay between quantum dynamics and noise

49. This talk was based on Plenio & Huelga, New J. Phys. 10, 113019 (2008) Caruso, Chin, Datta, Huelga, Plenio, E-Print arXiv:0901.4454 Caruso, Chin, Datta, Huelga, Plenio, to be submitted

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