An experiment confirmed Einstein"s theory

An international group of physicists has for the first time observed the influence of gravity on a falling quantum object, confirming the validity of Albert Einstein's theory at the microscopic level. In a groundbreaking experiment, the results of which have been published in the journal Science Advances, scientists split an atom into two parts and tracked how Earth's gravitational pull changes its quantum state.

A team from the University of Oxford and their colleagues cooled a cloud of rubidium atoms to near absolute zero and placed them on a special chip. Using microwave pulses and magnetic fields, the specialists put the particles into a state of superposition — each one began simultaneously traveling along two trajectories. One part of the atom was held in place, with the force of gravity fully compensated, while the other was allowed to fall freely, after which both branches were reunited.

Upon merging the waves, the researchers detected quantum interference, which allowed them to measure the phase difference between the stationary and falling parts of the particle. The result obtained was in precise agreement with the predictions of Einstein's equivalence principle extended to quantum objects. "This is a unique work that combines an extremely complex experiment with deep theoretical insight into one of the most fundamental questions in physics: how to bring gravity and quantum theory together into a unified understanding of how the Universe works," emphasized the lead author of the study, Professor Ron Folman from Ben-Gurion University.

The discovery does not unify the two theories, but it convincingly demonstrates that the laws of gravity remain unshakable even in the mysterious quantum world. Co-author of the work was Nobel Prize-winning physicist Professor Roger Penrose from the University of Oxford. The scientist holds the hypothesis that for sufficiently massive objects, quantum mechanics may break down. Although the current experiment did not allow testing this idea due to the small mass of atoms, the team plans to test heavier objects in the future, including nanodiamonds — carbon nanostructures possessing the same crystal lattice as ordinary diamond.

The equivalence principle, formulated by Einstein over a century ago, states that for an observer in free fall, gravity disappears — a person falling in an elevator would experience weightlessness. Until now, this rule had been repeatedly confirmed for macroscopic bodies, but verifying it on quantum particles capable of behaving like waves and existing in multiple places simultaneously had remained technically impossible. The device created by the physicists, called the "Galilean Quantum Interferometer," made it possible to overcome this barrier and for the first time peer into the junction of the two main theories of modern science.