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Advanced Optical Microscopy lecture 4. February 2013 Kai Wicker
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Exam: written exam 26 February 2013 exact time and place will be announced by email
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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
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1. Photon anti-bunching
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Jablonski diagram Absorption… … and spontaneous emission Normal fluorescence
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Photon anti-bunching: - only 1 photon per emitter and excitation pulse - sub-Poissonian (!) statistics 1.0 anti-bunching
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Possible applications of photon anti-bunching: - single molecule localisation: is it really just one single molecule? - super resolution imaging exploiting sub-Poissonian statistics
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Super resolution imaging exploiting sub-Poissonian statistics a)Pulsed excitation and synchronised detection b) + d)Two-pixel correlations c) + e)Three-pixel correlations
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Super resolution imaging exploiting sub-Poissonian statistics a) + d)Conventional fluorescence image b) + e)Second order anti-bunching c) + f)Third order anti-bunching
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2. Interaction-free measurements Seeing without light
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Mirror Transmitted light Reflected light Fabry-Perot resonator
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Reflected light Transmitted light Reflected light Transmitted light Mirror Fabry-Perot resonator
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Mirror Fabry-Perot resonator
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opposite phase cancellation Mirror Fabry-Perot resonator
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Case 1 One mirror Case 2 Two mirrors, resonator Case 3 Two mirrors with obstacle Fabry-Perot resonator Interaction-free measurement
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Experiment: Imaging photographic film without exposing it to light „sample“-film„detector“-film scan area
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Experiment: Imaging photographic film without exposing it to light
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3. Entangled photons, parametric down- conversion
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Coherent super-positions of states:“click”
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Image: European Space Agency parametric down-conversion Position entanglement!
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4. Beating shot-noise
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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!!
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Identical! Quantum image: Weakly absorbing object Illumination Not correlated! Classical image: Beating shot-noise
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Beating shot-noise imaging a weakly absorbing object
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Simulation Sample Classical image: SNR 1.2 Quantum image: SNR 3.3
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Beating shot-noise imaging a weakly absorbing object Experiment Sample: π -shaped titanium deposition Classical image: SNR 1.2Quantum image: SNR 1.7
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5. Entangled two-photon microscopy
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Jablonski diagram NO absorption… Normal fluorescence
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Jablonski diagram 2-photon absorption… … and spontaneous emission 2-photon fluorescence
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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.
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Entangled two-photon microscopy Comparisson of different imaging modalities:
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Entangled two-photon microscopy
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End of lecture
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