At first sight, general relativity, theory of gravitation predicting macroscopic phenomena, and quantum mechanics, predicting the infinitely small, are irreconcilable. For example, the very notion of time differs from one theory to the other. In quantum mechanics, time is an independent external evolutionary variable, whereas in general relativity time (or rather spacetime) obeys its own dynamics.

The equivalence principle, in general relativity, stipulates that bodies of different masses fall at the same speed if they undergo the same gravity field. If this principle is already widely verified with large objects, its application to the microscopic "quantum" world raises, still nowadays, many questions. Atoms cooled down to a few thousandths of a degree above absolute zero, at the heart of quantum inertial sensors, could provide answers to these questions.

The LP2N Cold Atoms team led by Baptiste Battelier and Philippe Bouyer has developed an experiment that allows, in a unique way, to simultaneously measure the acceleration of quantum particles with different masses.

These results are published in AVS Quantum Science, in the special edition "Celebrating Roger Penrose's Nobel prize", and have been highlighted by the CNRS.

By pushing quantum sensor technology further, they expect to reach accuracies where the equivalence principle can be tested at the quantum level. This will require much colder atoms, and much more sensitive interferometers where the matter waves will propagate over greater distances.

Find the publication here.