Tangi Legrand
Current Organizations / Institutes
The organizations/institutes from the scholar's latest article
Tangi Legrand has a total of 22 co-authors. Here are the top co-authors by number of shared publications:
- Sebastian Hofferberth
Institute of Applied Physics, University of Bonn, Bonn, Germany
3 shared publications - Wolfgang Alt
University of Bonn
3 shared publications - Eduardo Uruñuela
University of Bonn
2 shared publications - Xin Wang
University of Bonn
2 shared publications - Alicia Keil
Institut für Theoretische Physik, Universität Tübingen, Tübingen, Germany
1 shared publication - Andrea Alberti
Universität Bonn
1 shared publication
Latest Publications
- Open Access
- 8 October 2026
- Published by Springer Nature in Scientific Reports
- Vol. 16 (1) , 31484
The PairInteraction toolkit for modeling Rydberg physics in alkali and alkaline-earth-like atoms
Rydberg atoms provide a powerful platform for exploring strongly interacting quantum systems, both in free space and in structured electromagnetic environments, with growing applications in quantum technology. Accurately modeling their single-atom properties and mutual interactions is essential for interpreting experiments and designing new architectures. We present a unified theoretical framework for Rydberg atoms and their interactions based on multi-channel quantum defect theory (MQDT) and static electromagnetic Green’s tensors. MQDT provides a precise description of Rydberg states of divalent atoms such as strontium and ytterbium, while the Green’s tensor formalism provides a general and flexible approach for calculating interactions between two Rydberg atoms in arbitrary geometries, including modifications induced by nearby surfaces. We implement this framework in an updated version of the open-source toolkit PairInteraction [Weber et al., J. Phys. B 50 (2017)]. The implementation leverages high-performance libraries and achieves speedups of one order of magnitude for pair-potential calculations compared to prior software. We demonstrate the capabilities of the toolkit through example applications to divalent atoms and show excellent agreement with experimental data for an exemplary Stark map of $$^{174}$$ Yb. The modular software architecture enables the community to extend it further.- 8 October 2026
- Published by Springer Nature in Scientific Reports
- Vol. 16 (1) , 31484
Open AccessThe PairInteraction toolkit for modeling Rydberg physics in alkali and alkaline-earth-like atoms
Rydberg atoms provide a powerful platform for exploring strongly interacting quantum systems, both in free space and in structured electromagnetic environments, with growing applications in quantum technology. Accurately modeling their single-atom properties and mutual interactions is essential for interpreting experiments and designing new architectures. We present a unified theoretical framework for Rydberg atoms and their interactions based on multi-channel quantum defect theory (MQDT) and static electromagnetic Green’s tensors. MQDT provides a precise description of Rydberg states of divalent atoms such as strontium and ytterbium, while the Green’s tensor formalism provides a general and flexible approach for calculating interactions between two Rydberg atoms in arbitrary geometries, including modifications induced by nearby surfaces. We implement this framework in an updated version of the open-source toolkit PairInteraction [Weber et al., J. Phys. B 50 (2017)]. The implementation leverages high-performance libraries and achieves speedups of one order of magnitude for pair-potential calculations compared to prior software. We demonstrate the capabilities of the toolkit through example applications to divalent atoms and show excellent agreement with experimental data for an exemplary Stark map of $$^{174}$$ Yb. The modular software architecture enables the community to extend it further. - Open Access
- 20 August 2026
- Published by American Physical Society (APS) in Physical Review X
- Vol. 16 (3) , 031045
Revealing Electron-Ytterbium Interactions through Rydberg Molecular Spectroscopy
Divalent atoms have emerged as powerful alternatives to alkalis in ultracold atom platforms, offering unique advantages arising from their two-electron structure. Among these species, ytterbium (Yb) is especially promising, yet its anionic properties and its Rydberg spectrum remain comparatively unexplored. In this work, we perform a comprehensive experimental and theoretical investigation of ultralong-range Rydberg molecules (ULRMs) of Yb 174 in 6 s n s S 1 0 Rydberg states across nearly two decades in principal quantum number n and 3 orders of magnitude in molecular binding energy. Using the Coulomb Green’s function formalism, we compute Born-Oppenheimer molecular potentials describing the Rydberg atom in the presence of a ground-state perturber and achieve quantitative agreement with high-resolution molecular spectra. This enables the extraction of low-energy electron-Yb scattering phase shifts, including the zero-energy s -wave scattering length and the positions of two spin-orbit split p -wave shape resonances. Our results provide strong evidence that the Yb − anion exists only as a metastable resonance. We additionally show the sensitivity of ULRM spectra to the atomic quantum defects, using this to determine the quantum defect of the 6 s 23 f F 1 3 state. Together, these findings establish Yb ULRMs as a powerful probe of electron-Yb interactions and lay essential groundwork for future Rydberg experiments with divalent atoms.
- 20 August 2026
- Published by American Physical Society (APS) in Physical Review X
- Vol. 16 (3) , 031045
Open AccessRevealing Electron-Ytterbium Interactions through Rydberg Molecular Spectroscopy
Divalent atoms have emerged as powerful alternatives to alkalis in ultracold atom platforms, offering unique advantages arising from their two-electron structure. Among these species, ytterbium (Yb) is especially promising, yet its anionic properties and its Rydberg spectrum remain comparatively unexplored. In this work, we perform a comprehensive experimental and theoretical investigation of ultralong-range Rydberg molecules (ULRMs) of Yb 174 in 6 s n s S 1 0 Rydberg states across nearly two decades in principal quantum number n and 3 orders of magnitude in molecular binding energy. Using the Coulomb Green’s function formalism, we compute Born-Oppenheimer molecular potentials describing the Rydberg atom in the presence of a ground-state perturber and achieve quantitative agreement with high-resolution molecular spectra. This enables the extraction of low-energy electron-Yb scattering phase shifts, including the zero-energy s -wave scattering length and the positions of two spin-orbit split p -wave shape resonances. Our results provide strong evidence that the Yb − anion exists only as a metastable resonance. We additionally show the sensitivity of ULRM spectra to the atomic quantum defects, using this to determine the quantum defect of the 6 s 23 f F 1 3 state. Together, these findings establish Yb ULRMs as a powerful probe of electron-Yb interactions and lay essential groundwork for future Rydberg experiments with divalent atoms.
- 3 January 2025
- Published by American Physical Society (APS) in Physical Review Applied
- Vol. 23 (1)
Two-color ytterbium magneto-optical trap in a compact dual-chamber setup
- 3 January 2025
- Published by American Physical Society (APS) in Physical Review Applied
- Vol. 23 (1)
Two-color ytterbium magneto-optical trap in a compact dual-chamber setup
- 5 March 2024
- Published by American Physical Society (APS) in Physical Review A
- Vol. 109 (3) , 033304
Three-dimensional imaging of single atoms in an optical lattice via helical point-spread-function engineering
We demonstrate a method for determining the three-dimensional location of single atoms in a quantum gas microscopy system using a phase-only spatial light modulator to modify the point-spread function of the high-resolution imaging system. Here, the typical diffracted spot generated by a single atom as a point source is modified to a double spot that rotates as a function of the atom's distance from the focal plane of the imaging system. We present and numerically validate a simple model linking the rotation angle of the point-spread function with the distance to the focal plane. We show that, when aberrations in the system are carefully calibrated and compensated for, this method can be used to determine an atom's position to within a single lattice site in a single experimental image, extending quantum simulation with microscopy systems further into the regime of three dimensions.
- 5 March 2024
- Published by American Physical Society (APS) in Physical Review A
- Vol. 109 (3) , 033304
Three-dimensional imaging of single atoms in an optical lattice via helical point-spread-function engineering
We demonstrate a method for determining the three-dimensional location of single atoms in a quantum gas microscopy system using a phase-only spatial light modulator to modify the point-spread function of the high-resolution imaging system. Here, the typical diffracted spot generated by a single atom as a point source is modified to a double spot that rotates as a function of the atom's distance from the focal plane of the imaging system. We present and numerically validate a simple model linking the rotation angle of the point-spread function with the distance to the focal plane. We show that, when aberrations in the system are carefully calibrated and compensated for, this method can be used to determine an atom's position to within a single lattice site in a single experimental image, extending quantum simulation with microscopy systems further into the regime of three dimensions.