Medical systems are inherently complex, exhibiting multi-scale, dynamic, adaptive, and context-dependent behavior. Understanding and modeling these systems requires specialized domain expertise together with diverse mathematical approaches to capture and represent processes across different scales.
Our research investigates how principles from complex systems theory, statistical physics, and information theory can provide a unifying foundation for AI-driven health research. We focus on bridging patient-level (microscopic) and population-level (macroscopic) modeling.
By treating patients and populations as interconnected levels of the same dynamic health system, we seek to move beyond isolated AI applications toward a coherent systems-level understanding of health and disease. This perspective supports the development of informed, interpretable, and scalable computational models for personalized medicine and precision public health.
Digital Twins for Personalised Medicine
Leading Question: How to guide and evaluate decision-making in clinical practice?
A Digital Twin is a virtual representation of a patient that can be used to predict and analyze various medical scenarios and treatments.
The origin of the Digital Twin concept is in the engineering disciplines, but recently gained a lot of attention in medical areas as tool to enable personalized healthcare. The Digital Twin incorporates high-level Machine Learning and integrates individual-level data, such as proteome and clinical characteristics, with other factors like clinical trials and population studies to create a multiscale and multimodal data set for model training.
For medical applications, black-box Machine Learning must be avoided. For the doctor to make informed decisions, it is important to enable
An intuitively interpretable decision support and
Inclusion of current evidence-based knowledge and clinical guidelines
Our unique Digital Twin platform enables a versatile and agnostic decision support system and intrinsic plus state-of-the-art interpretation techniques.
Cooperations
We work closely with medical doctors from the University Hospital and are focusing on the diagnosis of Prostate Cancer. The Urology department of the University Hospital offers a unique database of prostate cancer patients. Therefore, we are able to develop state-of-the-art machine learning pipelines and have a direct impact on the clinical patient care.
Machine Learning in Precision Public Health & Global Health
Leading Question: How to guide and evaluate design-choices in healthcare? How should population information be represented so that it remains interpretable, uncertainty-aware, and useful for decision-making?
We investigate the application of machine learning methods to public health, with a particular focus on global health in low-resource settings. Our research aims to improve the estimation of multimorbidity burden at the population level by developing advanced mathematical approaches for health data representation and population stratification. These methods support more robust epidemiological analyses and contribute to evidence-based global health research and policy-making.
Cooperations
We collaborate closely with epidemiologists at the Heidelberg Institute of Global Health and local partners at Health and Demographic Surveillance Sites (HDSS) across several African countries. These collaborations enable us to develop scientifically informed and context-aware machine learning methods with the potential to support evidence-based public health research, policy, and health system strengthening.
How can AI and machine learning improve the treatment and prognosis of brain tumors? My Master’s thesis addresses this question by focusing on the data-driven analysis of meningiomas (brain tumors) using modern machine learning techniques. In cooperation with the University Medical Center Mannheim, clinical patient data are evaluated computationally to identify patterns in the course of the disease and its treatment. The primary focus is on developing predictive models that provide forecasts regarding surgical outcomes, postoperative consequences, and tumor dynamics. Ultimately, this work aims to demonstrate how machine learning and data-driven methods can support translational medicine and personalized patient care
Anna stays with the Digital Twin group after successfully finishing her Master Thesis about an Architecture of Digital Twins of Patients in Urology and will continue her research on Digital Twins in Medicine for applications in Global Health together with partners from the Heidelberg Institute of Global Health and STRUCTURES. We wish good luck!
A new project starts in the group. The Digital Twin group consists of two members, Anna Nitscke, who wants to start her master thesis in this project. And Carlos Brandl, who starts his PhD after being a Master student at the Rydberg team. Together with Prof. Ommer from the IWR the team tries to find new ways of creating digital twins for medicine. The project is part of the collaborative CLINIC5.1 project, lead by the University Hospital and funded by the BMWK.
@article{PhysRevA.107.053310,
title = {Anomalous loss behavior in a single-component Fermi gas close to a p-wave Feshbach resonance},
author = {K. Welz and M. Gerken and B. Zhu and E. Lippi and M. Rautenberg and L. Chomaz and M. Weidemüller},
url = {https://link.aps.org/doi/10.1103/PhysRevA.107.053310},
doi = {10.1103/PhysRevA.107.053310},
year = {2023},
date = {2023-05-01},
urldate = {2023-05-01},
journal = {Phys. Rev. A},
volume = {107},
issue = {5},
pages = {053310},
publisher = {American Physical Society},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
@phdthesis{nokey,
title = {From Efimov Physics to Polarons in an Ultracold Mixture of Li and Cs Atoms},
author = {Binh Tran},
url = {https://archiv.ub.uni-heidelberg.de/volltextserver/31882/, heiDOK},
year = {2022},
date = {2022-06-30},
abstract = {This thesis reports on the reconstruction and improvement of a quantum gas experiment for studying Bose polarons as well as on theoretical investigations at the interface between Efimov physics and Fermi polarons. In both experiment and theory an ultracold mixture of fermionic 6Li and bosonic 133Cs with a large mass ratio is considered. With the improved experimental setup we realize Bose-Einstein condensates (BEC) of 133Cs with N = 10^4 atoms and molecular BECs of 6Li2 with N = 10^5 dimers. For the creation of Bose polarons we trap a small number of Li atoms in a tightly confined optical dipole trap and propose a scheme to combine them with the 133Cs BEC. In a theoretical study, employing the Born-Oppenheimer approximation, we calculate Efimov bound state energies (E < 0) in a three body Cs-Cs-Li system and in a many-body environment where two 133Cs atoms are immersed in a Fermi sea of 6Li atoms. In these systems the intraspecies scattering length determine the ground state and the Fermi sea leads to a modification of the binding energies. For the scattering states (E > 0) we calculate the induced scattering length between two 133Cs atoms mediated by the Fermi sea, and find resonant behavior. We find that for large mass ratios bound states can persist at positive energies to form quasibound states.},
keywords = {},
pubstate = {published},
tppubtype = {phdthesis}
}
This thesis reports on the reconstruction and improvement of a quantum gas experiment for studying Bose polarons as well as on theoretical investigations at the interface between Efimov physics and Fermi polarons. In both experiment and theory an ultracold mixture of fermionic 6Li and bosonic 133Cs with a large mass ratio is considered. With the improved experimental setup we realize Bose-Einstein condensates (BEC) of 133Cs with N = 10^4 atoms and molecular BECs of 6Li2 with N = 10^5 dimers. For the creation of Bose polarons we trap a small number of Li atoms in a tightly confined optical dipole trap and propose a scheme to combine them with the 133Cs BEC. In a theoretical study, employing the Born-Oppenheimer approximation, we calculate Efimov bound state energies (E < 0) in a three body Cs-Cs-Li system and in a many-body environment where two 133Cs atoms are immersed in a Fermi sea of 6Li atoms. In these systems the intraspecies scattering length determine the ground state and the Fermi sea leads to a modification of the binding energies. For the scattering states (E > 0) we calculate the induced scattering length between two 133Cs atoms mediated by the Fermi sea, and find resonant behavior. We find that for large mass ratios bound states can persist at positive energies to form quasibound states.
@phdthesis{nokey,
title = {Dynamics of anions and ultracold atoms in a hybrid atom-ion trap},
author = {Saba Zia Hassan},
url = {https://archiv.ub.uni-heidelberg.de/volltextserver/31692/, heiDOK},
year = {2022},
date = {2022-05-24},
urldate = {2022-05-24},
abstract = {In this work, the dynamics of anion-neutral interactions are studied in a hybrid atom-ion trap. An octupole radio-frequency trap is used for trapping anions, and a dark spontaneous-force optical trap is employed to create ultracold rubidium (Rb) atoms. Spatial density distributions of the ion and atom clouds are determined via photodetachment tomography and saturation absorption imaging, respectively. A method to map the ions’ translational temperature onto their time of flight to the detector is presented. This technique is applied to determine the temperature of OH−anions as they undergo laser-induced forced evaporative cooling to temperatures below 4 K. The dynamics of associative electronic detachment reaction between closed-shell anions OH−and alkali atoms are investigated where for a ground-state Rb the influence of a dipole-bound state as a reaction intermediate is observed. The interaction dynamics of Rb with OH−(H2O) are also explored, where a smaller atom-to-ion mass ratio favors sympathetic cooling via elastic collisions. For atomic O−, the detachment processes involving ground-state Rb are found to be closed and efficient anion sympathetic cooling, via ultracold Rb, is observed. These results present hybrid systems as a platform to investigate anion-neutral collision dynamics, particularly interesting for astrochemistry, fundamental physics, and quantum chemistry.},
keywords = {},
pubstate = {published},
tppubtype = {phdthesis}
}
In this work, the dynamics of anion-neutral interactions are studied in a hybrid atom-ion trap. An octupole radio-frequency trap is used for trapping anions, and a dark spontaneous-force optical trap is employed to create ultracold rubidium (Rb) atoms. Spatial density distributions of the ion and atom clouds are determined via photodetachment tomography and saturation absorption imaging, respectively. A method to map the ions’ translational temperature onto their time of flight to the detector is presented. This technique is applied to determine the temperature of OH−anions as they undergo laser-induced forced evaporative cooling to temperatures below 4 K. The dynamics of associative electronic detachment reaction between closed-shell anions OH−and alkali atoms are investigated where for a ground-state Rb the influence of a dipole-bound state as a reaction intermediate is observed. The interaction dynamics of Rb with OH−(H2O) are also explored, where a smaller atom-to-ion mass ratio favors sympathetic cooling via elastic collisions. For atomic O−, the detachment processes involving ground-state Rb are found to be closed and efficient anion sympathetic cooling, via ultracold Rb, is observed. These results present hybrid systems as a platform to investigate anion-neutral collision dynamics, particularly interesting for astrochemistry, fundamental physics, and quantum chemistry.
@phdthesis{nokey,
title = {Exploring p-wave Feshbach Resonances in Ultracold Lithium and Lithium-Cesium Mixtures},
author = {Manuel Gerken},
url = {https://archiv.ub.uni-heidelberg.de/volltextserver/31719/, heiDOK},
year = {2022},
date = {2022-05-18},
abstract = {This thesis reports on the exploration of p-wave Feshbach resonances in ultracold Li-6 and Li-6-Cs-133 gases where the pair rotation angular momentum is l=1. An improved experimental apparatus is presented, allowing atom loss spectroscopy with a magnetic field resolutions down to several milli-Gauss on three Li-6, and five Li-6-Cs-133 Feshbach resonances. A doublet structure is observed for the first time on three Li-6 p-wave Feshbach resonances. We assign the splittings to spin-spin interactions where the projection of the pair rotation angular momentum m_l splits the resonance into m_l=0 and |m_l|=1. For the first time we report on observation of spin-rotation interaction on three Li-6-Cs-133 p-wave Feshbach resonances. Here the pair-rotation couples to the atomic spins, leading to an additional splitting of the m_l=-1 and m_l=+1 projections. Via coupled channel calculations we determine the dimensionless spin rotation constant to be |gamma|=0.566(50)x10^(-3). With a simple model we show that the strength of spin-rotation coupling depends significantly on the short-range part of the electron wave functions, highlighting the potential of Feshbach resonances to provide precise information on electron and nuclear wave functions at short internuclear distance. In an additional exploratory study of losses close to a single component Fermi pwave, Feshbach resonance we find changes in qualitative loss behavior depending on the density and temperature of the gas. We separate two regimes depending on the dominance of either elastic or inelastic collisions showing three- or two-body loss behavior, respectively. Collisional losses with possible cooling efficiencies similar to classic evaporative cooling are predicted.},
keywords = {},
pubstate = {published},
tppubtype = {phdthesis}
}
This thesis reports on the exploration of p-wave Feshbach resonances in ultracold Li-6 and Li-6-Cs-133 gases where the pair rotation angular momentum is l=1. An improved experimental apparatus is presented, allowing atom loss spectroscopy with a magnetic field resolutions down to several milli-Gauss on three Li-6, and five Li-6-Cs-133 Feshbach resonances. A doublet structure is observed for the first time on three Li-6 p-wave Feshbach resonances. We assign the splittings to spin-spin interactions where the projection of the pair rotation angular momentum m_l splits the resonance into m_l=0 and |m_l|=1. For the first time we report on observation of spin-rotation interaction on three Li-6-Cs-133 p-wave Feshbach resonances. Here the pair-rotation couples to the atomic spins, leading to an additional splitting of the m_l=-1 and m_l=+1 projections. Via coupled channel calculations we determine the dimensionless spin rotation constant to be |gamma|=0.566(50)x10^(-3). With a simple model we show that the strength of spin-rotation coupling depends significantly on the short-range part of the electron wave functions, highlighting the potential of Feshbach resonances to provide precise information on electron and nuclear wave functions at short internuclear distance. In an additional exploratory study of losses close to a single component Fermi pwave, Feshbach resonance we find changes in qualitative loss behavior depending on the density and temperature of the gas. We separate two regimes depending on the dominance of either elastic or inelastic collisions showing three- or two-body loss behavior, respectively. Collisional losses with possible cooling efficiencies similar to classic evaporative cooling are predicted.
@phdthesis{,
title = {Realization of a Heisenberg XXZ spin system using Rydberg atoms},
author = {Renato Ferracini Alves },
url = {https://archiv.ub.uni-heidelberg.de/volltextserver/31511/, heiDOK},
year = {2022},
date = {2022-02-02},
urldate = {2022-02-02},
abstract = {In this thesis, we present the realization of an isolated Heisenberg XXZ spin 1/2 system with an off-diagonal disorder in the coupling constants using cold atoms in highly excited Rydberg states. We select a set of Rydberg states that interact via van der Waals interaction which can be mapped onto an interacting spin system. We investigate the out-of-equilibrium dynamics of the spin system after it has been initialized in a fully magnetized state. Following unitary evolution governed by the Heisenberg spin Hamiltonian, we measure the magnetization as a function of the evolution time. By fitting a stretched exponential function to the resulting magnetization dynamics be obtain a stretched exponent of β = 0.32 revealing a slow relaxation of the spin system, similar to what is found in spin glasses. By choice, the initial state is an eigenstate of the mean-field Hamiltonian and thus the observed relaxation indicates that the dynamics are triggered by quantum fluctuations. We find that varying the distribution of coupling constants by means of the so-called dipole blockade effect has no impact on the stretching exponent indicating that it is a universal parameter of the system independent of the microscopic details for the range of disorder explored in the experiment. It also allows us to combine the different datasets by re-scaling the time domain with the characteristic interaction strength. The combined datasets expand our measurements to two orders of magnitude in the re-scaled time-domain showing that slow dynamics is a persistent effect for long evolution times.},
keywords = {},
pubstate = {published},
tppubtype = {phdthesis}
}
In this thesis, we present the realization of an isolated Heisenberg XXZ spin 1/2 system with an off-diagonal disorder in the coupling constants using cold atoms in highly excited Rydberg states. We select a set of Rydberg states that interact via van der Waals interaction which can be mapped onto an interacting spin system. We investigate the out-of-equilibrium dynamics of the spin system after it has been initialized in a fully magnetized state. Following unitary evolution governed by the Heisenberg spin Hamiltonian, we measure the magnetization as a function of the evolution time. By fitting a stretched exponential function to the resulting magnetization dynamics be obtain a stretched exponent of β = 0.32 revealing a slow relaxation of the spin system, similar to what is found in spin glasses. By choice, the initial state is an eigenstate of the mean-field Hamiltonian and thus the observed relaxation indicates that the dynamics are triggered by quantum fluctuations. We find that varying the distribution of coupling constants by means of the so-called dipole blockade effect has no impact on the stretching exponent indicating that it is a universal parameter of the system independent of the microscopic details for the range of disorder explored in the experiment. It also allows us to combine the different datasets by re-scaling the time domain with the characteristic interaction strength. The combined datasets expand our measurements to two orders of magnitude in the re-scaled time-domain showing that slow dynamics is a persistent effect for long evolution times.
@article{tan2021,
title = {Dynamics of position disordered Ising spins with a soft-core potential},
author = {Canzhu Tan and Xiaodong Lin and Yabing Zhou and Y. H. Jiang and Matthias Weidemüller and Bing Zhu},
doi = {10.1103/PhysRevB.105.104204},
year = {2022},
date = {2022-01-01},
urldate = {2022-01-01},
journal = {Phys. Rev. B},
volume = {105},
pages = {104204},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
@article{hu2021,
title = {Observation of photon recoil effects in single-beam absorption spectroscopy with an ultracold strontium gas},
author = {Fachao Hu and Canzhu Tan and Yuhai Jiang and Matthias Weidemüller and Bing Zhu},
url = {https://doi.org/10.1088/1674-1056/ac2486},
doi = {10.1088/1674-1056/ac2486},
year = {2022},
date = {2022-01-01},
journal = {Chin. Phys. B},
volume = {31},
pages = {016702},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Scholl P, Williams H J, Bornet G, Wallner F, Barredo D, Lahaye T, Henriet L, Signoles A, Hainaut C, Franz T, Geier S, Tebben A, Zürn G, Salzinger A, Weidemüller M, Browaeys A
@article{scholl2021,
title = {Microwave-engineering of programmable XXZ Hamiltonians in arrays of Rydberg atoms},
author = {P. Scholl and H. J. Williams and G. Bornet and F. Wallner and D. Barredo and T. Lahaye and L. Henriet and A. Signoles and C. Hainaut and T. Franz and S. Geier and A. Tebben and G. Zürn and A. Salzinger and M. Weidemüller and A. Browaeys},
url = {https://doi.org/10.1103/PRXQuantum.3.020303},
doi = {10.1103/PRXQuantum.3.020303},
year = {2022},
date = {2022-01-01},
urldate = {2022-01-01},
journal = {Phys. Rev. X Quantum},
volume = {3},
pages = {020303},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
@article{schultzen2022b,
title = {Semiclassical simulations predict glassy dynamics for disordered Heisenberg models},
author = {Philipp Schultzen and Titus Franz and Clément Hainaut and Sebastian Geier and Andre Salzinger and Annika Tebben and Gerhard Zürn and Martin Gärttner and Matthias Weidemüller},
url = {https://arxiv.org/abs/2107.13314},
doi = {10.1103/PhysRevB.105.L100201},
year = {2022},
date = {2022-01-01},
urldate = {2022-01-01},
journal = {Phys. Rev. B},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
@article{schultzen2022a,
title = {Glassy quantum dynamics of disordered Ising spins},
author = {Philipp Schultzen and Titus Franz and Sebastian Geier and Andre Salzinger and Annika Tebben and Clément Hainaut and Gerhard Zürn and Matthias Weidemüller and Martin Gärttner},
url = {https://doi.org/10.1103/PhysRevB.105.L020201},
doi = {10.1103/PhysRevB.105.L020201},
year = {2022},
date = {2022-01-01},
urldate = {2022-01-01},
journal = {Phys. Rev. B},
volume = {105},
pages = {L020201},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
@article{hassan2021a,
title = {Associative detachment in anion-atom reactions involving a dipole-bound electron},
author = {Saba Zia Hassan and Jonas Tauch and Milaim Kas and Markus Nötzold and Henry López Carrera and Eric S. Endres and Roland Wester and Matthias Weidemüller},
url = {https://doi.org/10.1038/s41467-022-28382-w},
doi = {10.1038/s41467-022-28382-w},
year = {2022},
date = {2022-01-01},
urldate = {2022-01-01},
journal = {Nat. Comm.},
volume = {13},
pages = {818},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
@article{hassan2021b,
title = {Quantum state-dependent anion-neutral detachment processes},
author = {Saba Zia Hassan and Jonas Tauch and Milaim Kas and Markus Nötzold and Roland Wester and Matthias Weidemüller},
url = {https://doi.org/10.1063/5.0082734},
doi = {10.1063/5.0082734},
year = {2022},
date = {2022-01-01},
urldate = {2022-01-01},
journal = {J. Chem. Phys.},
volume = {156},
pages = {094304},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
@workingpaper{barthi2022,
title = {Ultrafast Many-Body Dynamics in an Ultracold Rydberg-Excited Atomic Mott Insulator},
author = {V. Bharti and S. Sugawa and M. Mizoguchi and M. Kunimi and Y. Zhang and S. de Léséleuc and T. Tomita and T. Franz and M. Weidemüller and K. Ohmori},
url = {https://arxiv.org/abs/2201.09590},
doi = {10.48550/arXiv.2201.09590},
year = {2022},
date = {2022-01-01},
urldate = {2022-01-01},
journal = {arXiv},
abstract = {We report the observation and control of ultrafast non-equilibrium many-body electron dynamics in Rydberg-excited spatially-ordered ultracold atoms created from a three-dimensional unity-filling atomic Mott insulator. By implementing time-domain Ramsey interferometry with attosecond precision in our Rydberg atomic system, we observe picosecond-scale ultrafast many-body dynamics that is essentially governed by the emergence and evolution of many-body correlations between long-range interacting atoms in an optical lattice. We analyze our observations with different theoretical approaches and find that quantum fluctuations have to be included beyond semi-classical descriptions to describe the observed dynamics. Our Rydberg lattice platform combined with an ultrafast approach, which is robust against environmental noises, opens the door for simulating strongly-correlated electron dynamics by long-range van der Waals interaction and resonant dipole-dipole interaction to the charge-overlapping regime in synthetic ultracold atomic crystals.},
howpublished = {arXiv e-prints: 2201.09590},
keywords = {},
pubstate = {published},
tppubtype = {workingpaper}
}
We report the observation and control of ultrafast non-equilibrium many-body electron dynamics in Rydberg-excited spatially-ordered ultracold atoms created from a three-dimensional unity-filling atomic Mott insulator. By implementing time-domain Ramsey interferometry with attosecond precision in our Rydberg atomic system, we observe picosecond-scale ultrafast many-body dynamics that is essentially governed by the emergence and evolution of many-body correlations between long-range interacting atoms in an optical lattice. We analyze our observations with different theoretical approaches and find that quantum fluctuations have to be included beyond semi-classical descriptions to describe the observed dynamics. Our Rydberg lattice platform combined with an ultrafast approach, which is robust against environmental noises, opens the door for simulating strongly-correlated electron dynamics by long-range van der Waals interaction and resonant dipole-dipole interaction to the charge-overlapping regime in synthetic ultracold atomic crystals.
@phdthesis{nokey,
title = {Rydberg Electromagnetically Induced Transparency - A vanishing linear response, resonances, and a stationary Rydberg polariton},
author = {Annika Tebben},
url = {https://archiv.ub.uni-heidelberg.de/volltextserver/30661/, heiDOK},
year = {2021},
date = {2021-10-22},
urldate = {2021-10-22},
abstract = {Rydberg electromagnetically induced transparency (Rydberg EIT) enables extremely strong optical nonlinearities, opening the possibility for photon-photon interactions and exotic states of light. Subjects of this thesis are the development and the experimental test of semiclassical models for Rydberg EIT systems on two-photon resonance. Beyond that, this thesis opens the route towards enhanced photon-photon interactions in terms of an increased interaction time. Three major results are achieved: (i) In the semiclassical regime, we extend existing models and reveal that a two-body, two-photon resonance leads to an enhanced nonlinear optical response. (ii) We develop an experimental method to rigorously test semiclassical models of Rydberg EIT. For this purpose, we go beyond previous experimental investigations and measure transmission spectra on two-photon resonance, where the linear response of the system vanishes. We identify qualitative differences between a measured absorption feature and predictions provided by a mean-field model, a Monte-Carlo rate equation simulation, and a theory based on a pairwise treatment of atomic interactions. (iii) In the quantum regime, we propose and analyze a novel scheme to endow a stationary light polariton with a Rydberg character, resulting in a stationary Rydberg polariton. Our scheme offers the prospect for polariton interactions with increased interaction time, and thus might find application in the creation of exotic states of light.},
keywords = {},
pubstate = {published},
tppubtype = {phdthesis}
}
Rydberg electromagnetically induced transparency (Rydberg EIT) enables extremely strong optical nonlinearities, opening the possibility for photon-photon interactions and exotic states of light. Subjects of this thesis are the development and the experimental test of semiclassical models for Rydberg EIT systems on two-photon resonance. Beyond that, this thesis opens the route towards enhanced photon-photon interactions in terms of an increased interaction time. Three major results are achieved: (i) In the semiclassical regime, we extend existing models and reveal that a two-body, two-photon resonance leads to an enhanced nonlinear optical response. (ii) We develop an experimental method to rigorously test semiclassical models of Rydberg EIT. For this purpose, we go beyond previous experimental investigations and measure transmission spectra on two-photon resonance, where the linear response of the system vanishes. We identify qualitative differences between a measured absorption feature and predictions provided by a mean-field model, a Monte-Carlo rate equation simulation, and a theory based on a pairwise treatment of atomic interactions. (iii) In the quantum regime, we propose and analyze a novel scheme to endow a stationary light polariton with a Rydberg character, resulting in a stationary Rydberg polariton. Our scheme offers the prospect for polariton interactions with increased interaction time, and thus might find application in the creation of exotic states of light.
@phdthesis{nokey,
title = {New approaches for cooling molecular anions to the Kelvin range},
author = {Jonas Tauch},
url = {https://archiv.ub.uni-heidelberg.de/volltextserver/30105/, heiDOK},
year = {2021},
date = {2021-06-02},
abstract = {This thesis presents two anion cooling techniques based on their interaction with photons or ultracold atoms, pushing the frontier of anion cooling beyond state-of-the-art experiments. A hybrid atom-ion trap (HAITrap) is presented, combining an octupole radio frequency (rf) trap and a dark spontaneous-force optical trap for rubidium. The anions and atoms are probed via photodetachment tomography, time-of-flight thermometry and saturation absorption imaging, respectively. The anion photodetachment via a focused far-threshold laser beam removes anions selectively by their energy. This thesis reports forced evaporative cooling of OH− via dynamically moving the beam, below 4 Kelvin in 2 seconds. A derived thermodynamic model describes the evolution of anion temperature and number, including the importance of ion-ion thermalization and resulting rf-heating in such traps. It shows experimental and theoretical framework to prepare any anionic specie in a vast energy range. This thesis also reports the sympathetic cooling and the collision dynamics of anions with ultracold rubidium in a HAITrap. The cooling is experimentally demonstrated to 30(2) Kelvin for O− and 135(8) Kelvin for OH−. The different cooling behavior is explained by their dissimilar loss channels, which are identified and quantified. These limitations can be overcome in future experiments, providing a tool to cool anions translationally and internally.},
keywords = {},
pubstate = {published},
tppubtype = {phdthesis}
}
This thesis presents two anion cooling techniques based on their interaction with photons or ultracold atoms, pushing the frontier of anion cooling beyond state-of-the-art experiments. A hybrid atom-ion trap (HAITrap) is presented, combining an octupole radio frequency (rf) trap and a dark spontaneous-force optical trap for rubidium. The anions and atoms are probed via photodetachment tomography, time-of-flight thermometry and saturation absorption imaging, respectively. The anion photodetachment via a focused far-threshold laser beam removes anions selectively by their energy. This thesis reports forced evaporative cooling of OH− via dynamically moving the beam, below 4 Kelvin in 2 seconds. A derived thermodynamic model describes the evolution of anion temperature and number, including the importance of ion-ion thermalization and resulting rf-heating in such traps. It shows experimental and theoretical framework to prepare any anionic specie in a vast energy range. This thesis also reports the sympathetic cooling and the collision dynamics of anions with ultracold rubidium in a HAITrap. The cooling is experimentally demonstrated to 30(2) Kelvin for O− and 135(8) Kelvin for OH−. The different cooling behavior is explained by their dissimilar loss channels, which are identified and quantified. These limitations can be overcome in future experiments, providing a tool to cool anions translationally and internally.
@phdthesis{nokey,
title = {Complex systems dynamics in laser excited ensembles of Rydberg atoms},
author = {Tobias Martin Wintermantel},
url = {https://archiv.ub.uni-heidelberg.de/volltextserver/29303/, heiDOK},
year = {2021},
date = {2021-01-13},
abstract = {In this thesis I present experimental and theoretical results showing that an ultracold gas under laser excitation to Rydberg states offers a controllable platform for studying the interesting complex dynamics that can emerge in driven-dissipative systems. The findings can be summarized according to the following three main insights: (i) The discovery of self-organized criticality (SOC) in our Rydberg system under facilitated excitation via three signatures: self-organization of the density to a stationary state; scale invariant behavior; and a critical response in terms of power-law distributed excitation avalanches. Additionally, we explore a mechanism inherent to our system which stabilizes the SOC state. We further investigate this stabilization via a controlled, variable driving of the system. These analyses can help answer the question of why scale invariant behavior is so prevalent in nature. (ii) A striking connection between the power-law growth of the Rydberg excitation number and epidemic spreading is found. Based on this, an epidemic network model is devised which efficiently describes the collective excitation dynamics. The importance of heterogeneity in the emergent Rydberg network and associated Griffiths effects provide a way to explain the observation of non-universal power laws. (iii) A novel quantum cellular automata implementation is proposed using atomic arrays together with multifrequency laser fields. This provides a natural framework to study the relation between microscopic processes and global dynamics, where special rules are found to generate entangled states with applications in quantum metrology and computing.},
keywords = {},
pubstate = {published},
tppubtype = {phdthesis}
}
In this thesis I present experimental and theoretical results showing that an ultracold gas under laser excitation to Rydberg states offers a controllable platform for studying the interesting complex dynamics that can emerge in driven-dissipative systems. The findings can be summarized according to the following three main insights: (i) The discovery of self-organized criticality (SOC) in our Rydberg system under facilitated excitation via three signatures: self-organization of the density to a stationary state; scale invariant behavior; and a critical response in terms of power-law distributed excitation avalanches. Additionally, we explore a mechanism inherent to our system which stabilizes the SOC state. We further investigate this stabilization via a controlled, variable driving of the system. These analyses can help answer the question of why scale invariant behavior is so prevalent in nature. (ii) A striking connection between the power-law growth of the Rydberg excitation number and epidemic spreading is found. Based on this, an epidemic network model is devised which efficiently describes the collective excitation dynamics. The importance of heterogeneity in the emergent Rydberg network and associated Griffiths effects provide a way to explain the observation of non-universal power laws. (iii) A novel quantum cellular automata implementation is proposed using atomic arrays together with multifrequency laser fields. This provides a natural framework to study the relation between microscopic processes and global dynamics, where special rules are found to generate entangled states with applications in quantum metrology and computing.
@article{tran2020fermions,
title = {Fermions meet two bosons -- the heteronuclear Efimov effect revisited},
author = {Binh Tran and Michael Rautenberg and Manuel Gerken and Eleonora Lippi and Bing Zhu and Juris Ulmanis and Moritz Drescher and Manfred Salmhofer and Tilman Enss and Matthias Weidemüller},
url = {https://doi.org/10.1007/s13538-020-00811-5},
doi = {10.1007/s13538-020-00811-5},
year = {2021},
date = {2021-01-01},
urldate = {2020-01-01},
journal = {Braz. J. Phys.},
volume = {51},
pages = {316},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
@article{signoles2019,
title = {Observation of glassy dynamics in a disordered quantum spin system},
author = {A. Signoles and T. Franz and R. Ferracini Alves and M. Gärttner and S. Whitlock and G. Zürn and M. Weidemüller},
url = {https://doi.org/10.1103/PhysRevX.11.011011},
doi = {10.1103/PhysRevX.11.011011},
year = {2021},
date = {2021-01-01},
urldate = {2021-01-01},
journal = {Phys. Rev. X},
volume = {11},
pages = {011011},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
@article{geier2021,
title = {Floquet Hamiltonian Engineering of an Isolated Many-Body Spin System},
author = {Sebastian Geier and Nithiwadee Thaicharoen and Clément Hainaut and Titus Franz and Andre Salzinger and Annika Tebben and David Grimshandl and Gerhard Zürn and Matthias Weidemüller},
url = {https://doi.org/10.1126/science.abd9547},
doi = {10.1126/science.abd9547},
year = {2021},
date = {2021-01-01},
urldate = {2021-01-01},
journal = {Science},
volume = {374},
pages = {1149},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
@article{Tebben2021,
title = {Nonlinear absorption in interacting Rydberg electromagnetically-induced-transparency spectra on two-photon resonance},
author = {Annika Tebben and Clément Hainaut and Andre Salzinger and Sebastian Geier and Titus Franz and Thomas Pohl and Martin Gärttner and Gerhard Zürn and Matthias Weidemüller},
url = {https://doi.org/10.1103/PhysRevA.103.063710},
doi = {10.1103/PhysRevA.103.063710},
year = {2021},
date = {2021-01-01},
urldate = {2021-01-01},
journal = {Phys. Rev. A},
volume = {103},
pages = {063710},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
@article{Qiao2021,
title = {Rydberg blockade in an ultracold strontium gas revealed by two-photon excitation dynamics},
author = {Chang Qiao and Canzhu Tan and Julia Siegl and Fachao Hu and Zhijing Niu and Yuhai Jiang and Matthias Weidemüller and Bing Zhu},
url = {https://doi.org/10.1103/PhysRevA.103.063313},
doi = {10.1103/PhysRevA.103.063313},
year = {2021},
date = {2021-01-01},
urldate = {2021-01-01},
journal = {Phys. Rev. A},
volume = {103},
pages = {063313},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
