Overview
- An international team used an atom chip to split ultracold rubidium atoms into a quantum superposition, held one branch against gravity with tunable on‑chip magnetic fields, let the other branch fall, and then recombined them to read a phase difference.
- The measured phase equals the value obtained by applying Einstein’s equivalence principle to a quantum wave, providing the first direct experimental observation of that specific free‑fall quantum phase.
- The result appeared in Science Advances and the authors stress this experiment does not unify gravity with quantum mechanics nor prove that gravity itself is a quantum force.
- The work relied on precise microwave pulses, a Quantum Galileo interferometer design, and extreme coherence control, creating a technical foundation for scaling tests to larger masses and longer hold times.
- This experiment closes a long-standing empirical gap—previous quantum gravity–related studies measured gravitational effects but did not directly record the free‑fall quantum phase now observed—and sets clear targets for future, more massive tests.