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Advanced Optical Microscopy lecture 4. February 2013 Kai Wicker Exam: written exam 26 February 2013 exact time and place will be announced by email 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 1. Photon anti-bunching Normal fluorescence Jablonski diagram Absorption… … and spontaneous emission Photon anti-bunching: - only 1 photon per emitter and excitation pulse - sub-Poissonian (!) statistics 1.0 anti-bunching Possible applications of photon anti-bunching: - single molecule localisation: is it really just one single molecule? - super resolution imaging exploiting sub-Poissonian statistics Super resolution imaging exploiting sub-Poissonian statistics a) b) + d) c) + e) Pulsed excitation and synchronised detection Two-pixel correlations Three-pixel correlations Super resolution imaging exploiting sub-Poissonian statistics a) + d) b) + e) c) + f) Conventional fluorescence image Second order anti-bunching Third order anti-bunching 2. Interaction-free measurements Seeing without light Fabry-Perot resonator Mirror Transmitted light Reflected light Fabry-Perot resonator Mirror Transmitted light Reflected light Transmitted light Reflected light Transmitted light Fabry-Perot resonator Mirror Fabry-Perot resonator Mirror opposite phase cancellation Fabry-Perot resonator Case 1 One mirror Case 2 Two mirrors, resonator Case 3 Two mirrors with obstacle Interaction-free measurement Experiment: Imaging photographic film without exposing it to light „sample“-film scan area „detector“-film Experiment: Imaging photographic film without exposing it to light 3. Entangled photons, parametric downconversion Coherent super-positions of states: 𝑏 𝑎 𝜓 = 𝑎 1 𝜓 = 𝐴 + 𝐵 2 𝐴 𝐵 “click” parametric down-conversion 𝜓 = 𝜓 = 1 3 𝑟𝑒𝑑 1 𝑏𝑙𝑢𝑒 1 𝑟 1 𝑟𝑒𝑑 1 𝑑3𝑟 2 + 𝑔𝑟𝑒𝑒𝑛 −𝑟 2 𝑑 3 𝑟 𝑔𝑟𝑒𝑒𝑛 𝑏𝑙𝑢𝑒 1 𝑔𝑟𝑒𝑒𝑛 2 + 𝑏𝑙𝑢𝑒 1 𝑟𝑒𝑑 Position entanglement! 1 1 𝑟1 Image: European Space Agency 𝑔𝑟𝑒𝑒𝑛 𝑏𝑙𝑢𝑒 2 2 −𝑟 𝑟𝑒𝑑 2 2 2 4. Beating shot-noise Beating shot-noise 𝜓 = 1 𝑑3𝑟 𝑟 1 −𝑟 2 𝑑 3 𝑟 Position entanglement! Intensity distributions are correlated, even down to Poisson noise!! Image: Alessandra Gatti, Enrico Brambilla, and Luigi Lugiato, “Quantum Imaging,” 2007 Beating shot-noise Illumination Quantum Classical image: image: 𝐷1 𝑟 = 𝐼 𝑟 ± 𝐼 𝑟 Not Identical! correlated! 𝐷2 𝑟 = 𝐷 𝑟 𝐼 1𝑟 −𝑆𝑟𝑟𝑆 ± Weakly absorbing object 𝐼 𝑟 𝑆 𝑟 Beating shot-noise imaging a weakly absorbing object Beating shot-noise imaging a weakly absorbing object Simulation Sample Classical image: SNR 1.2 Quantum image: SNR 3.3 Beating shot-noise imaging a weakly absorbing object Experiment Sample: π-shaped titanium deposition Classical image: SNR 1.2 Quantum image: SNR 1.7 5. Entangled two-photon microscopy Normal fluorescence Jablonski diagram NO absorption… 2-photon fluorescence Jablonski diagram 2-photon absorption… … and spontaneous emission 2-photon fluorescence 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. Entangled two-photon microscopy Comparisson of different imaging modalities: Entangled two-photon microscopy End of lecture