Bloch oscillations in the field of a light wave
The University of Florence has developed a new technique for studying the force of gravity on a scale of several micrometers. The force is determined by measuring the frequency of the Bloch oscillations of atoms in an optical trap, which is a vertical standing light wave (with periodicity in the vertical direction). Bloch quantum-mechanical oscillations arise when a particle is in a periodic potential and under the influence of an additional constant force, for example, oscillations of an electron in a crystal in an external electric field.
In the experiment of G. Ferrari and his colleagues, the role of the potential was played by the dipole interaction of atoms with the periodic field of a light wave, and the external force was the force of gravity. The experiment was carried out with ultracold atoms – bosons 88 Sr, having in the ground state zero spin and nuclear magnetic moment and for this reason weakly interacting with each other and with external electromagnetic fields, which made it possible to achieve a record time of coherent Bloch oscillations – about 10 seconds. Using this technique, it is planned to perform ultra-precise measurements of the gravitational force on a micrometer scale and to check Newton’s law of gravity on a small scale.