FYI -------- Weitergeleitete Nachricht -------- Betreff: [COST Action RQI - WG2] Online Seminar Thursday, 19th of February 10am CET - Torsten V. Zache - Non-local mass superpositions and optical clock interferometry in atomic ensemble quantum networks Datum: Fri, 13 Feb 2026 10:53:33 +0000 Von: Dennis Rätzel <dennis.raetzel@zarm.uni-bremen.de> Dear Members of Working Group WG2, I would like to invite you to the next talk of our online seminar. Date and time: Thursday, 19th of February 10am CET Speaker: Torsten V. Zache (University of Innsbruck & IQOQI) Title: Non-local mass superpositions and optical clock interferometry in atomic ensemble quantum networks Abstract: Quantum networks are emerging as powerful platforms for sensing, communication, and fundamental tests of physics. We propose a programmable quantum sensing network based on entangled atomic ensembles, where optical clock qubits emulate mass superpositions in atom and atom-Clock interferometry. Our approach uniquely combines scalability to large atom numbers with minimal control requirements, relying only on collective addressing of internal atomic states. This enables the creation of both non-local and local superpositions with spatial separations beyond those achievable in conventional interferometry. Starting from Bell-type seed states distributed via photonic channels, collective operations within atomic ensembles coherently build many-body mass superpositions sensitive to gravitational redshift. The resulting architecture realizes a non-local Ramsey interferometer, where interference patterns arising from gravitationally induced phase shifts can be observed through local measurements of network nodes. Beyond extending the spatial reach of mass superpositions, our scheme establishes a scalable, programmable platform to probe the interface of quantum mechanics and gravity, and offers a new experimental pathway to test atom and atom-clock interferometer proposals in a network-based quantum laboratory. The talk will be streamed via Zoom https://uni-bremen.zoom-x.de/j/65971273542?pwd=4C1b7x87b1HbQ09hi5WXaKTOnetmD... I am looking forward to seeing you for the talk and subsequent discussions with Torsten Zache. With kind regards, Dennis (Rätzel) University College London WG2 leader