Collective optical effects of ultra-cold Rydberg atoms in optical cavities

• Applicant: Professor Dr. Sebastian Slama
• Subject Area: Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: from 2019 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 422447846

• Final Report Year: 2024

Final Report Abstract

Many-body systems with interactions are paradigmatic for a plethora of examples in different realms of nature and life. Those examples feature effects like structure formation, synchronization and phase transitions that can be explained by the collective action of all parts of the system, only. Synchronization of pacemaker cells is for instance important for a regular heartbeat. A small change of the interaction between the cells, for instance by release of adrenalin, influences the heartbeat frequency. A too large change however causes a phase transition to ventricular fibrillation. Precisely understanding the mechanisms of these systems is therefore highly relevant. The project investigates collective effects in a model system of cold atoms that interact via the light field inside an optical cavity. Several research groups have used this model system for investigating how atoms synchronize their motion, how density and spin grating arise spontaneously, and under which conditions phase transitions occur. The atoms were mostly described as effective two-level systems, and the interaction was global. The latter means that the light mode in the cavity couples far distant atoms with the same strength as closely neighboring atoms. In contrast, the interaction strength in most real systems decays with distance. The project goes beyond these restrictions and considers both multiple degenerate ground states with different interaction strength, each, and the excitation of atoms into Rydberg states. Rydberg atoms interact with each other via distance dependent potentials. The project could resolve how the distance dependent interaction influences the collective behavior of the atoms occurring in superradiance. Here, atoms normally emit light globally and collectively. The Rydberg interaction leads to a distance dependent dephasing and thus weakens the superradiant emission. The results clarify the question why superradiance was observed in some experiments with small Rydberg atom density, whereas it was not observed in others with higher densities. Moreover, the project has revealed that the existence of several ground states leads to a novel nonlinearity: A phase transition was identified from a symmetric phase to a symmetry-broken phase where the occupation of the ground states bears several stable steady-states. This is relevant as this phase can be used for pattern recognition, similar to a neural network. Small differences in the pattern of the ground state occupation are amplified and mapped to one of several final states. The pattern can then be identified in the light being emitted from the cavity.

Publications

• Posterpräsentation beim 724. WE-Heraeus-Seminar “Collective Effects and Non-Equilibrium Quantum Dynamics” (online) mit dem Titel:”Detecting atomic dynamics in a cavity- Rydberg system”
  Elmer Suarez
  
• Wissenschaftlicher Vortrag bei der „International Conference on Quantum, Atomic, Molecular and Plasma Physics, QuAMP 2021“ (online), mit dem Titel „Collective effects of Rydberg atoms in optical cavities“
  Sebastian Slama
  
• Posterpräsentation bei der DPG Frühjahrstagung Erlangen (online) mit dem Titel: "Tracking Rydberg state dynamics to study the effect of long-range dipole-dipole interactions on superradiance"
  Elmer Suarez, Philip Wolf, Patrizia Weiss & Sebastian Slama
  
• Posterpräsentation bei der ICAP 2022 mit dem Titel: "Superradiance decoherence caused by long-range Rydberg-atom pair interactions"
  Elmer Suarez
  
• Posterpräsentation bei der ITAMP winter school on AMO physics: "Superradiance and its decoherence due to long-range Rydberg atom pair-interactions"
  Elmer Suarez
  
• Superradiance decoherence caused by long-range Rydberg-atom pair interactions. Physical Review A, 105(4).
  Suarez, Elmer; Wolf, Philip; Weiss, Patrizia & Slama, Sebastian
  
• Collective atom-cavity coupling and nonlinear dynamics with atoms with multilevel ground states. Physical Review A, 107(2).
  Suarez, Elmer; Carollo, Federico; Lesanovsky, Igor; Olmos, Beatriz; Courteille, Philippe W. & Slama, Sebastian
  
• Posterpräsentation bei der DPG Frühjahrstagung in Hamburg mit dem Titel: "Collective atom-cavity coupling and non-linear dynamics with atoms with multilevel ground states"
  Suarez, E., Carollo, F., Lesanovsky, I., Olmos, B., Courteille, P. W. & Slama, S.
  
• Quantum resonant optical bistability with a narrow atomic transition: bistability phase diagram in the bad cavity regime. New Journal of Physics, 25(9), 093053.
  Rivero, D.; Pessoa, Jr C. A.; de França, G. H.; Teixeira, R. C.; Slama, S. & Courteille, Ph W.
  
• Wissenschaftlicher Vortrag bei der summer school on quantum matter, Granada, Spanien, mit dem Titel “Multi-level atoms in cavities“
  Sebastian Slama
  
• Symmetry breaking and non-ergodicity in a driven-dissipative ensemble of multilevel atoms in a cavity. Physical Review Research, 6(3).
  Hernandez, Enrique; Suarez, Elmer; Lesanovsky, Igor; Olmos, Beatriz; Courteille, Philippe W. & Slama, Sebastian
  
• Wissenschaftlicher Vortrag am Instituto de Fisica de Sao Carlos, IFSC, Universität Sao Paulo, Brasilien, mit dem Titel: „Bistability of atoms with multiple ground states in a cavity“
  Sebastian Slama
  
• Wissenschaftlicher Vortrag beim Workshop on „Quantum computing, simulations and metrology with long-range interacting systems” mit dem Titel “Pattern retrieval in a driven-dissipative ensemble of multi-level atoms in a two-mode cavity”
  Sebastian Slama
  
• Spin Self-Organization in an Optical Cavity Facilitated by Inhomogeneous Broadening. Physical Review Letters, 134(8).
  Nairn, Marc; Giannelli, Luigi; Morigi, Giovanna; Slama, Sebastian; Olmos, Beatriz & Jäger, Simon B.