Physicists Confirm Einstein Principle With 20,000 Rubidium Atoms After 99-Year-Old Quantum Prediction
Updated
Updated · Livescience.com · Sep 3
Physicists Confirm Einstein Principle With 20,000 Rubidium Atoms After 99-Year-Old Quantum Prediction
3 articles · Updated · Livescience.com · Sep 3
Summary
Ron Folman’s team measured, for the first time, the quantum phase shift gained by atoms falling through Earth’s gravity, using about 20,000 ultracold rubidium atoms in superposition.
Across 633 runs over 5.3 hours, the phase grew with the cube of free-fall time up to 2.4 milliseconds, matching the 1927 prediction within about 2.5%.
The setup held one branch of each atom motionless while the other moved in genuine free fall, then recombined them to reveal 13 full interference oscillations despite fading fringe contrast.
The result, published Sept. 2 in Science Advances, supports Einstein’s equivalence principle in the quantum regime, though it does not exclude every theory that predicts possible breakdowns.
Researchers next want to test rotating frames and mutually gravitating quantum systems, with heavier objects such as nanodiamonds seen as a path toward probing whether gravity itself is quantum.
What happens when half an atom falls while the rest stays still, and could this unlock the secrets of quantum gravity?
If gravity behaves normally for falling atoms, what larger objects will scientists drop next to find where Einstein's theories finally break down?
Direct Quantum Phase Measurement in Free Fall: The 2026 Breakthrough Bridging Quantum Mechanics and General Relativity
Overview
In September 2026, scientists achieved a historic first by directly measuring gravity’s effect on a falling quantum object. They cooled 20,000 rubidium-87 atoms to near absolute zero, forming a Bose-Einstein condensate that acted as a single quantum wave. Using the Quantum Galileo Interferometer, they split this wave into two paths: one held stationary by a magnetic force, the other allowed to fall freely under gravity. When the two paths were reunited, their interference revealed a quantum phase shift that grew with the cube of the fall time, matching Einstein’s predictions and confirming the equivalence principle at the quantum level with remarkable precision.