Scientists have successfully measured a quantum effect predicted nearly a century ago, providing experimental confirmation that Einstein’s equivalence principle remains valid at subatomic scales. Researchers led by Ron Folman at Ben-Gurion University cooled thousands of rubidium atoms and placed them in a quantum state where each atom simultaneously traveled two different paths—one in free fall and one held stationary. When the atoms were recombined, the team detected a subtle phase difference between the two paths, matching theoretical predictions with remarkable accuracy.
The experiment, detailed in a September publication in Science Advances, employed a specialized device called the quantum Galileo interferometer. Ultra-cold atoms were manipulated using magnetic fields and radio pulses, allowing half of each atom to fall freely under Earth’s gravity while the other half remained suspended through precisely tuned magnetic forces. Over 633 experimental runs, the researchers observed 13 complete oscillation cycles as they extended the free-fall duration to approximately 2.4 milliseconds, with results agreeing with theory to within 2.5 percent.
The findings bridge two fundamental pillars of physics that have long seemed incompatible. The phase accumulation observed can be explained through two distinct approaches—one treating gravity as a force on quantum waves, and another invoking Einstein’s equivalence principle in a free-falling reference frame. Both methods yielded identical results, demonstrating that quantum mechanics and general relativity are compatible at this measurement scale. Researchers now plan to extend these tests using heavier objects and more complex quantum configurations.
Originally reported by Livescience →
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