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Technische Universität München

Electric Dipole Moment Search with Atoms and Molecules

HeXeEDM - Overwiev

The HeXeEDM project is a dedicated test setup for developing and validating key components and methods required for future electric dipole moment (EDM) searches using atoms and molecules.
It serves as a hardware and technology platform to explore precision control of electric and magnetic fields, spin coherence, and detection techniques in a compact, modular environment.

Scientific Motivation

Searches for permanent EDMs in atomic and molecular systems provide a sensitive probe of CP violation beyond the Standard Model, directly connected to the matter–antimatter asymmetry of the Universe.
While large-scale EDM experiments already exist for neutrons and noble gases, the HeXeEDM setup is designed to enable systematic studies and hardware development for the next generation of atomic and molecular EDM searches.
The approach combines aspects of spin-precession physics, precision field control, and novel detection techniques in a flexible laboratory-scale apparatus.

Experimental Approach & Goals

Setup of the previous HeXeEDM Experiment.
  • The setup allows for controlled co-located spin systems using noble gases (helium and xenon)
  • By stabilizing and characterizing the magnetic environment with ultra-sensitive magnetometry, the experiment enables highly coherent spin precession measurements over long timescales.
  • Key components under development include:
    • High-voltage electrodes and precise electric field calibration
    • Magnetic field generation and stabilization
    • Spin manipulation (RF excitation and Ramsey interrogation)
    • Signal readout and digital data acquisition
  • The primary goal is not yet a competitive EDM limit, but rather the establishment of a precision measurement platform, including hardware, control software, and diagnostic tools.
    Insights from this test setup will directly feed into future large-scale EDM experiments at TUM

4π Magnetometry and Spatial Field Reconstruction

A central aspect of the HeXeEDM project is the implementation of 4π magnetometry — a full three-dimensional characterization of the surrounding magnetic field using distributed sensor arrays.
This technique allows the precise recording of the magnetic field environment during operation, providing valuable information to identify, quantify, and correct systematic effects that can mimic an EDM signal.

Beyond environmental monitoring, a second array of highly sensitive optically pumped magnetometers (OPMs) is used to spatially resolve the precession signal of the  He/Xe spin ensemble.
This enables:

  • reconstruction of local magnetic field distributions,
  • comparison of measured precession patterns with detailed field and spin-dynamics simulations, and
  • new insights into spin transport and coupling effects within the cell.

By combining direct field mapping and spatially resolved spin readout, the 4π-magnetometry approach provides a unique diagnostic and modeling capability, extending well beyond conventional single-channel co-magnetometry.

Contact

For collaboration, thesis opportunities, or further inquiries, please contact:

Dr. rer. nat. Florian Kuchler

Publications and finished Theses

  • Sachdeva, N. et al. New Limit on the Permanent Electric Dipole Moment of 129Xe Using 3He Comagnetometry and SQUID Detection. Phys. Rev. Lett. 123, 143003 (2019) doi: 10.1103/PhysRevLett.123.143003.
  • Terrano, W. A. et al. Frequency shifts in noble-gas comagnetometers. Phys. Rev. A 100, 012502 (2019) doi: 10.1103/PhysRevA.100.012502.
  • Kuchler, F. et al. A new search for the atomic EDM of 129Xe at FRM-II. Hyperfine Interact 237, 95 (2016) doi: 10.1007/s10751-016-1302-9.

Involved Persons and Former Members

Currently Involved persons: Dr. Florian Kuchler, Philipp Wunderl

Former Members:  

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