Team Observes Quantum Phase of Falling Atoms for First Time — SkimNews
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- An international team including Nobel laureate Roger Penrose has directly observed a long-predicted quantum gravity effect, publishing the findings September 2 in Science Advances.
- Researchers built a 'Quantum Galileo Interferometer' that split a rubidium atom's quantum wave into two paths — one held stationary by magnetic fields, one falling freely under gravity — then reunited the waves to measure the tiny phase shift that accumulated.
- The measured quantum phase matched predictions derived from extending Einstein's equivalence principle to quantum objects, providing what the researchers call the first direct laboratory link between quantum mechanics and Einstein's description of gravity.
- Lead author Professor Ron Folman (Ben-Gurion University) called the result a combination of 'a hard experiment with a far-reaching theoretical interpretation' on how to unify gravity and quantum theory — the two frameworks that have 'eluded all attempts at a unified theoretical framework.'
- The finding does not prove gravity itself is quantum and does not yield a unified theory; it only confirms Einstein's equivalence principle remains compatible with quantum mechanics within the range tested.
- Penrose's competing hypothesis — that quantum mechanics could eventually break down for sufficiently massive objects held in superposition long enough — remains untested by this experiment, though the group is extending the technique to nanodiamonds.
Why it matters: For theoretical physicists pursuing a unified quantum-gravity theory, the result narrows the playing field: Einstein's equivalence principle holds in the quantum domain tested, so any future unification must accommodate that constraint rather than overturn it. For Penrose's competing gravity-fails-quantum-mechanics hypothesis, the result leaves the bet alive — the rubidium atoms tested were too light and the superpositions too brief to push it to a verdict.
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