1. Advanced Optical Microscopy lecture 4. February 2013 Kai Wicker

2. Exam: written exam 26 February 2013 exact time and place will be announced by email

3. Today: The quantum world in microscopy 1. Photon anti-bunching 2. Interaction-free measurements 3. Entangled photons, parametric down-conversion 4. Beating shot-noise 5. Entangled two-photon microscopy

4. 1. Photon anti-bunching

5. Jablonski diagram Absorption… … and spontaneous emission Normal fluorescence

6. Photon anti-bunching: - only 1 photon per emitter and excitation pulse - sub-Poissonian (!) statistics 1.0 anti-bunching

7. Possible applications of photon anti-bunching: - single molecule localisation: is it really just one single molecule? - super resolution imaging exploiting sub-Poissonian statistics

8. Super resolution imaging exploiting sub-Poissonian statistics a)Pulsed excitation and synchronised detection b) + d)Two-pixel correlations c) + e)Three-pixel correlations

9. Super resolution imaging exploiting sub-Poissonian statistics a) + d)Conventional fluorescence image b) + e)Second order anti-bunching c) + f)Third order anti-bunching

10. 2. Interaction-free measurements Seeing without light

11. Mirror Transmitted light Reflected light Fabry-Perot resonator

12. Reflected light Transmitted light Reflected light Transmitted light Mirror Fabry-Perot resonator

13. Mirror Fabry-Perot resonator

14. opposite phase  cancellation Mirror Fabry-Perot resonator

15. Case 1 One mirror Case 2 Two mirrors, resonator Case 3 Two mirrors with obstacle Fabry-Perot resonator Interaction-free measurement

16. Experiment: Imaging photographic film without exposing it to light „sample“-film„detector“-film scan area

17. Experiment: Imaging photographic film without exposing it to light

18. 3. Entangled photons, parametric down- conversion

19. Coherent super-positions of states:“click”

20. Image: European Space Agency parametric down-conversion Position entanglement!

21. 4. Beating shot-noise

22. Beating shot-noise Position entanglement! Image: Alessandra Gatti, Enrico Brambilla, and Luigi Lugiato, “Quantum Imaging,” 2007 Intensity distributions are correlated, even down to Poisson noise!!

23. Identical! Quantum image: Weakly absorbing object Illumination Not correlated! Classical image: Beating shot-noise

24. Beating shot-noise imaging a weakly absorbing object

25. Simulation Sample Classical image: SNR 1.2 Quantum image: SNR 3.3

26. Beating shot-noise imaging a weakly absorbing object Experiment Sample: π -shaped titanium deposition Classical image: SNR 1.2Quantum image: SNR 1.7

27. 5. Entangled two-photon microscopy

28. Jablonski diagram NO absorption… Normal fluorescence

29. Jablonski diagram 2-photon absorption… … and spontaneous emission 2-photon fluorescence

30. Classical: -2-photon absorption requires two photons to be present simultaneously. -The probability for this grows quadratically with intensity. -It will only occur where the local intensity is high. Quantum: -2-photon absorption requires two photons to be present simultaneously. -This is achieved through temporal coincidence of entangled photons.

31. Entangled two-photon microscopy Comparisson of different imaging modalities:

32. Entangled two-photon microscopy

33. End of lecture