When one observes the interference of two counter-propagating waves enclosing an area, one observes a phase shift induced by the rotation of the frame of the experiment. Such an instrument is called a gyrometer. This well-known effect is called the Sagnac effect, acknowledging the French physicist who tried to demonstrate it in 1913, to test the laws of combination of the speeds of light. The Sagnac effect is a relativistic effect, somewhat analogous to Langevin’s twin paradox, but where the acceleration comes from the rotation of the frame. The Sagnac effect has also played a key role in the establishment of the theory of relativity and has led to the development of precision optical interferometers.

Sensitive rotation sensors have many applications in the navigation of vehicles such as submarines, airplanes, rockets... When the Sagnac gyrometers are sufficiently accurate, the study of the spectra of the Earth’s rotation allows to obtain information on Earthquakes and variations of the gravity field which disturb the Earth’s rotation.

Also the fundamental importance of the Sagnac effect has motivated the realization of experiments aiming at testing its validity for other than optical waves. Absolute and precision measurements remain a major challenge.

Figure Left: Schematic shape of the interferometer. Right: tomic phase shifts are measured along the two axes of the gyrometer as a function of the orientation of the rotation frame.

The team Atomic Interferometry and Inertial Sensors of SYRTE has just published in the journal Science Advances a precise test of the Sagnac effect for matter waves. A matter wave is the wave equivalent of particles, here laser cooled Cesium atoms. In the SYRTE gyrometer, the atoms are launched in such a way that their trajectories form a figure of 8 that contain a geometric surface of 11 cm2 with two sensitive measurement axes. The team was able to measure the phase shift induced by the Earth’s rotation and find agreement with the theoretical prediction at a precision level of 25 parts per million.

Beyond the importance for fundamental physics, our work opens up practical applications in seismology and geodesy.

For more information:
IACI team page: Atomic Interferometry and Inertial Sensors

The link to the article published in Science advances
Contact researcher:

Translated with www.DeepL.com/Translator (free version)
[Rémi Geiger >remi.geiger@obspm.fr]