Freiburg 2024 – scientific programme
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Q: Fachverband Quantenoptik und Photonik
Q 27: Phase Transitions
Q 27.3: Talk
Wednesday, March 13, 2024, 11:45–12:00, Aula
Phase transition and higher-order mean-field theory of chiral waveguide QED — •Kasper Jan Kusmierek1, Max Schemmer2, Sahand Mahmoodian3, and Klemens Hammerer4 — 1Institute for Theoretical Physics, Leibniz University Hannover, Germany — 2Istituto Nazionale di Ottica del Consiglio Nazionale delle Ricerche (CNR-INO), 50019 Sesto Fiorentino, Italy — 3Centre for Engineered Quantum Systems, School of Physics, The University of Sydney, Sydney, NSW 2006, Australia — 4Institute for Theoretical Physics, Leibniz University Hannover, Germany
Waveguide QED with cold atoms provides a potent platform for the study of non-equilibrium, many-body, and open-system quantum dynamics. Even with weak coupling and strong photon loss, the collective enhancement of light-atom interactions leads to strong correlations of photons arising in transmission. Here we apply an improved mean-field theory based on higher-order cumulant expansions to describe the experimentally relevant, but theoretically elusive, regime of weak coupling and strong driving of large ensembles. We determine the transmitted power, squeezing spectra and the degree of second-order coherence. In the regime of very large drive and atom numbers we observe an non-equilibrium phase transition. This reveals the important role of many-body and long-range correlations between atoms in steady state.
Keywords: Waveguide QED; Cumulant Expansion; Long-range correlations; Phase Transition