A Rydberg Interaction Calculator

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Travis CI build status AppVeyor build status arXiv:1612.08053 License Documentation

Please Cite Us

Tutorial: Calculation of Rydberg interaction potentials
Sebastian Weber, Christoph Tresp, Henri Menke, Alban Urvoy, Ofer Firstenberg, Hans Peter Büchler, Sebastian Hofferberth
arXiv:1612.08053, J. Phys. B: At. Mol. Opt. Phys. 50, 133001 (2017), DOI: 10.1088/1361-6455/aa743a

See works citing pairinteraction on Google Scholar and the ADS Digital Library (preprint only).


pairinteraction was originally developed by the Rydberg Quantum Optics group at the 5th Institute of Physics and the Institute for Theoretical Physics III of the University of Stuttgart, Germany.

Currently it is maintained by developers at the Institute for Theoretical Physics III of the University of Stuttgart in Germany, the Department of Physics of the University of Otago in New Zealand, and the Department of Physics, Chemistry and Pharmacy of the University of Southern Denmark in Denmark.

The software is written in C++ and Python. It is released fully open source under the terms of the Apache License 2.0. Binary installers are made available for many systems, including several GNU/Linux distributions, Mac OS X, and Microsoft Windows. You can find them on the GitHub release page.

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Main Features

The pairinteraction software calculates pair potentials for Rydberg atoms in external fields. It supports a lot of neat features, the major of which are listed below:

  • Stark and Zeeman maps for single atom states
  • Automatic selection rules
  • Variable interatomic axis
  • Numerical and analytical methods for radial matrix elements
  • Multipole expansion to arbitrary order!
  • Electromagnetic fields in arbitrary directions including diamagnetism!

Some other convenient (non-physical) features are

  • High performance C++ backend
  • Intuitive Python interface with NumPy support
  • Parallelism using OpenMP
  • Automatic fit for C3 and C6 coefficients
  • Color code for pair state overlap on potential lines
  • MATLAB compatible data export
  • High quality plots and direct print

For further detail you can read our Doxygen code documentation.


Main window with sample configuration on Windows 10 64-bit.
Main window with sample configuration on Mac OS X El Capitan.
Stark map for a single Rydberg atom.
Quadratic Zeeman effect for a single Rydberg atom.