Browsing by Author "Hofferberth, Sebastian"

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    Controlled multi-photon subtraction with cascaded Rydberg superatoms as single-photon absorbers
    (2021) Stiesdal, Nina; Busche, Hannes; Kleinbeck, Kevin; Kumlin, Jan; Hansen, Mikkel G.; Büchler, Hans Peter; Hofferberth, Sebastian
    The preparation of light pulses with well-defined quantum properties requires precise control at the individual photon level. Here, we demonstrate exact and controlled multi-photon subtraction from incoming light pulses. We employ a cascaded system of tightly confined cold atom ensembles with strong, collectively enhanced coupling of photons to Rydberg states. The excitation blockade resulting from interactions between Rydberg atoms limits photon absorption to one per ensemble and rapid dephasing of the collective excitation suppresses stimulated re-emission of the photon. We experimentally demonstrate subtraction with up to three absorbers. Furthermore, we present a thorough theoretical analysis of our scheme where we identify weak Raman decay of the long-lived Rydberg state as the main source of infidelity in the subtracted photon number and investigate the performance of the multi-photon subtractor for increasing absorber numbers in the presence of Raman decay.
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    Imaging single Rydberg electrons in a Bose-Einstein condensate
    (2015) Karpiuk, Tomasz; Brewczyk, Mirosław; Rzążewski, Kazimierz; Gaj, Anita; Balewski, Jonathan B.; Krupp, Alexander T.; Schlagmüller, Michael; Löw, Robert; Hofferberth, Sebastian; Pfau, Tilman
    The quantum mechanical states of electrons in atoms and molecules are distinct orbitals, which are fundamental for our understanding of atoms, molecules and solids. Electronic orbitals determine a wide range of basic atomic properties, allowing also for the explanation of many chemical processes. Here, we propose a novel technique to optically image the shape of electron orbitals of neutral atoms using electron-phonon coupling in a Bose-Einstein condensate. To validate our model we carefully analyze the impact of a single Rydberg electron onto a condensate and compare the results to experimental data. Our scheme requires only well-established experimental techniques that are readily available and allows for the direct capture of textbook-like spatial images of single electronic orbitals in a single shot experiment.