Long baseline Universal Matter-wave Interferometer (LUMI)

LUMI is the newest interferometer in the group. Its distinguishing features are

  • 2 m interferometer length.
  • acceptance of high mass even at high velocity.
  • acceptance of de Broglie wavelengths down to 50 fm.
  • New records in quantum macroscopicity and tests of non-standard quantum models.
  • Metrological sensitivity down to forces as tiny as 10-26 N.

With its two-meter baseline, LUMI opens a new avenue for molecular interferometry in a mass and complexity range that was inaccessible to previous interferometers. It  allow for a 100x improved sensitivity in molecule metrology due to the quadratic dependence of interferometer fringe shift on device length and transit time.

As of today, LUMI is the only matter-wave interferometer capable of demonstrating interference of particles beyond 25 000 atomic mass units, here a family of tailored oligoporphyrins[1].

Like the KDTLI and OTIMA experiments, LUMI relies on the Talbot-Lau effect, because near-field interference offers a good mass scalability and signal throughput. LUMI has the unique capability to be operated in two different modes.

  • KDTLI mode: For slow, polarizable molecules we use a nano-mechanical gratings (d = 266 nm) in position G1 and G3 to act as transmission mask for coherence preparation and fringe detection, respectively. The central phase grating G2 is formed by a green standing light wave.
  • TLI mode: For fast particles of low polarizability, the second grating G2 can also swapped in-vacuum for a nano-mechanical grating, identical to those in G1 and G3.

This interchangeability enables improved metrology of molecular properties, since it allows the device to be calibrated with atoms, whose properties are typically better understood.

We plan to upgrade the experiment to LUMI 2.0, which will replace all gratings with all-optical gratings to extend the mass range to several 100 000 amu, using metal clusters.

A key challenge to experiments with biomolecules is the development of soft beam methods for fragile molecules.   


  1. Y. Y. Fein, P. Geyer, P. Zwick, F. Kiałka, S. Pedalino, M. Mayor, S. Gerlich, and M. Arndt,
    Quantum superposition of molecules beyond 25 kDa,
    Nature Physics  (2019).
  2. F. Kiałka, B. Stickler, K. Hornberger, Y. Y. Fein, P. Geyer, L. Mairhofer, S. Gerlich, and M. Arndt,
    Concepts for long-baseline high-mass matter-wave interferometry,
    Phys. Scr. 94, 034001 (2018).