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

2. Lisbon, 8 th July 2009

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

9. Lisbon, 8 th July 2009 Weak coherent driving Weak response

10. Lisbon, 8 th July 2009 Weak coherent driving + weak noise give a strong coherent response. Stochastic resonance Noise

11. Lisbon, 8 th July 2009 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. Lisbon, 8 th July 2009 Clicks Time Clicks Time A Fundamental Experiment

13. Lisbon, 8 th July 2009 A Fundamental Experiment

14. Lisbon, 8 th July 2009 Clicks Time Clicks Time A Fundamental Experiment

15. Lisbon, 8 th July 2009 Green sulphur Bacteria Photosynthesis A black smoker in the Atlantic Ocean ~ 2000m deep Y.C. Cheng and G.R. Fleming, Annu. Rev. Phys. Chem. 60, 241 (2009)

16. Lisbon, 8 th July 2009 Green sulphur Bacteria Exciton Transport in Photosynthesis Reaction Centre CO 2 + 2 H S 2 + energy CH O 2 + 2 S + H O 2

17. Lisbon, 8 th July 2009 Green sulphur Bacteria Reaction Centre Exciton Transport in Photosynthesis CO 2 + 2 H S 2 + energy CH O 2 + 2 S + H O 2

18. Lisbon, 8 th July 2009 Transfer to reaction centre Green sulphur Bacteria Reaction Centre Exciton Transport in Photosynthesis CO 2 + 2 H S 2 + energy CH O 2 + 2 S + H O 2

19. Lisbon, 8 th July 2009 Loss of excitation Transfer to reaction centre Reaction Centre CO 2 + 2 H S 2 + energy CH O 2 + 2 S + H O 2 M.B. Plenio and S.F. Huelga, New J. Phys. 10, 113019 (2008) Exchange of excitation Dephasing

20. Lisbon, 8 th July 2009 Noise Assisted Transport and Photosynthesis No dephasing Some dephasing Plenio & Huelga, New J. Phys. 2008Mohseni, Rebentrost, Lloyd, Aspuru-Guzik, J. Phys. Chem. 2008 More dephasing

21. Lisbon, 8 th July 2009 Physical Origin of Noise Assisted Transport

22. Lisbon, 8 th July 2009 Exciton Transport in Photosynthesis Show Movie 1: No dephasing Initial excitation in site 1

23. Lisbon, 8 th July 2009 Two different time scales ! Exciton Transport in Photosynthesis

24. Lisbon, 8 th July 2009 Clicks Time Clicks Time Destructive Interference and Invariant States

25. Lisbon, 8 th July 2009 Destructive Interference and Invariant States JJ Reaction center =

26. Lisbon, 8 th July 2009 Destructive Interference and Invariant States Transfer efficiency JJ = Reaction center

27. Lisbon, 8 th July 2009 Noise Inhibits Destructive Interference Decoherence inhibits destructive interference ! Transfer efficiency Reduction of destructive interference JJ Reactions center Reaction center =

28. Lisbon, 8 th July 2009 Destructive Interference and Invariant States Invariant state: Two atoms in the same location:

29. Lisbon, 8 th July 2009 Dephasing on site 1 only Show Movie1a: Small dephasing on site 1 only

30. Lisbon, 8 th July 2009 Dephasing on site 1 only

31. Lisbon, 8 th July 2009 Destructive Interference and Invariant States not invariant under Hamiltonian evolution ! Different energy splitting:

32. Lisbon, 8 th July 2009 Static disorder inhibits destructive interference ! Disorder Inhibits Destructive Interference JJ JJ Destructive interference Reaction center Reduction of destructive interference Reaction center

33. Lisbon, 8 th July 2009 Disorder Inhibits Destructive Interference

34. Lisbon, 8 th July 2009 The Hamiltonian of the FMO complex Quite strong static disorder compared to coupling strengths !

35. Lisbon, 8 th July 2009 Increase Energy Gap of Sites 1&2 to the Rest Smaller gap Larger gap

36. Lisbon, 8 th July 2009 Bridging the gap: Enhanced transport via line broadening

37. Lisbon, 8 th July 2009 Dephasing Noise on Site 3 only Play Movie1b: Dephasing noise only on site 3 Play Movie1ab: Same amount of dephasing noise now only on site 3

38. Lisbon, 8 th July 2009 Dephasing Noise on Site 3 only

39. Lisbon, 8 th July 2009 No line broadening, No transfer!Line broadening does enhance transfer!

40. Lisbon, 8 th July 2009 JJ destructive interference -J Spatially Correlated Noise effect of noise reduced JJ destructive interference +J-J effect of noise enhanced

41. Lisbon, 8 th July 2009 local dephasing without correlations dephasing with non-local correlations T=5 ps Therefore, correlated noise does not lead to decisive improvements in this setting! Spatially Correlated Noise

42. Lisbon, 8 th July 2009 JJ destructive interference JJ Loss Enhanced Transport destructive interference reduced JJ excitation lost

43. Lisbon, 8 th July 2009 Noise Assisted Transport and Photosynthesis No dephasing Some dephasing More dephasing

44. Lisbon, 8 th July 2009 Reduction of destructive interference Inhibition of coupling through dephasing Dependence on Noise Strength

45. Lisbon, 8 th July 2009 Two different time scales ! Robustness against strong static disorder compared to coupling strengths (i.e. 20%)! optimal dephasing no dephasing Robustness of Noise Assisted Transport

46. Lisbon, 8 th July 2009 F.Caruso., A.W. Chin, A. Datta, S.F. Huelga, M.B. Plenio, to be submitted Entanglement Dynamics

47. Lisbon, 8 th July 2009 F.C., A.W. Chin, A. Datta, S.F. Huelga, M.B. Plenio, arxiv:0901.4454 (2009) |01>-|10> JJ reduced destructive interferencedestructive interference J  Each process open additional pathways for propagation

48. Lisbon, 8 th July 2009 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]

49. Lisbon, 8 th July 2009 Can we improve solar cells based 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

50. Lisbon, 8 th July 2009 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

51. Lisbon, 8 th July 2009  We move to Ulm to establish Center for Quantum Engineering  Explain VideoAbstracts