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1. Probing electronic decoherence with high-resolution attosecond photoelectron interferometry

   https://doi.org/10.1140/epjd/s10053-022-00438-y  

   Busto, David; Laurell, Hugo; Finkelstein-Shapiro, Daniel; Alexandridi, Christiana; Isinger, Marcus; Nandi, Saikat; Squibb, Richard J.; Turconi, Margherita; Zhong, Shiyang; Arnold, Cord L.; et al (July 2022, The European Physical Journal D)

   AbstractQuantum coherence plays a fundamental role in the study and control of ultrafast dynamics in matter. In the case of photoionization, entanglement of the photoelectron with the ion is a well-known source of decoherence when only one of the particles is measured. Here, we investigate decoherence due to entanglement of the radial and angular degrees of freedom of the photoelectron. We study two-photon ionization via the 2s2p autoionizing state in He using high spectral resolution photoelectron interferometry. Combining experiment and theory, we show that the strong dipole coupling of the 2s2p and 2p$$^2$$ ${}^2$states results in the entanglement of the angular and radial degrees of freedom. This translates, in angle-integrated measurements, into a dynamic loss of coherence during autoionization. Graphic Abstract 

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2. High resolution metrology of autoionizing states through Raman interferences

   https://doi.org/10.1088/1742-6596/2494/1/012003  

   Plunkett, A.; Wood, J. K.; Alarcón, M. A.; Biswas, D.; Greene, C. H.; Sandhu, A. (May 2023, Journal of Physics: Conference Series)

   Abstract Metrology of electron wavepackets is often conducted with the technique of photoelectron interferometry. However, the ultrashort light pulses employed in this method place a limit on the energy resolution. Here, weadvance ultrafast photoelectron interferometry access both high temporal and spectral resolution. The key to our approach lies in stimulating Raman interferences with a probe pulse and while monitoring the modification of the autoionizing electron yield in a separate delayed detection step. As a proof of the principle, we demonstrated this technique to obtain the components of an autoionizing nf′ wavepacket between the spin-orbit split ionization thresholds in argon. We extracted the amplitudes and phases from the interferogram and compared the experimental results with second-order perturbation theory calculations. This high resolution probing and metrology of electron dynamics opens the path for study of molecular wavepackets. 

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3. Influence of final state interactions in attosecond photoelectron interferometry

   https://doi.org/10.1103/PhysRevResearch.6.043271  

   Luo, S; Weissenbilder, R; Laurell, H; Bello, R Y; Marante, C; Ammitzböll, M; Neoričić, L; Ljungdahl, A; Squibb, R J; Feifel, R; et al (December 2024, Physical Review Research)

   Fano resonances are ubiquitous phenomena appearing in many fields of physics, e.g., atomic or molecular photoionization, or electron transport in quantum dots. Recently, attosecond interferometric techniques have been used to measure the amplitude and phase of photoelectron wave packets close to Fano resonances in argon and helium, allowing for the retrieval of the temporal dynamics of the photoionization process. In this work, we study the photoionization of argon atoms close to the $3s^{1}3p^{6}4p$autoionizing state using an interferometric technique with high spectral resolution. The phase shows a monotonic $2\pi$variation across the resonance or a nonmonotonic less than $\pi$variation depending on experimental conditions, e.g., the probe laser bandwidth. Using three different, state-of-the-art calculations, we show that the measured phase is influenced by the interaction between final states reached by two-photon transitions. Published by the American Physical Society2024 

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4. Bound and autoionizing potential energy curves in the CH molecule

   https://doi.org/10.1063/5.0177822  

   Hvizdoš, Dávid; Forer, Joshua; Kokoouline, Viatcheslav; Greene, Chris H (December 2023, The Journal of Chemical Physics)

   This article presents a method of computing bound state potential curves and autoionizing curves using fixed-nuclei R-matrix data extracted from the Quantemol-N software suite. It is a method based on two related multichannel quantum-defect theory approaches. One is applying bound-state boundary conditions to closed-channel asymptotic solution matrices, and the other is searching for resonance positions via eigenphase shift analysis. We apply the method to the CH molecule to produce dense potential-curve datasets presented as graphs and supplied as tables in the publication supplement. 

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5. Photonic Fock state generation using superradiance

   https://doi.org/10.1364/OL.468481  

   Liu, Qihang; Shen, Jung-Tsung (August 2022, Optics Letters)

   Photonic Fock states are the most basic quantum states of a radiation field, but arbitrary number states are still difficult to produce. Here we propose to use superradiant atoms in a chiral waveguide to generate multi-photon Fock states deterministically. We calculate the explicit forms of the output quantum photonic states and their correlation functions. We further establish the conditions for the output optical fields to approach the Fock states asymptotically. 

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