MIT researchers have settled a century-old quantum debate between Albert Einstein and Niels Bohr by conducting a modern version of the double-slit experiment using atoms.
Why it matters: The experiment provides new insights into the wave-particle duality of light and reinforces the principles of quantum mechanics, disproving Einstein’s explanation of the experiment.
The details:
- Scientists cooled thousands of atoms to nearly absolute zero and arranged them in a lattice using laser light.
- These atoms acted as slits to scatter individual photons of light.
- The researchers adjusted the atoms’ “fuzziness”—how precisely the atom’s position was known.
- Fuzzier atoms gave more information about a photon’s path, weakening the interference pattern, while clearer atom positions strengthened the interference pattern.
The findings, published in a leading scientific journal, support Bohr’s interpretation of quantum theory and demonstrate that interference patterns weaken as more path information is available.
Cutting the strings: To further test Einstein’s disturbance theory, the team allowed atoms to float freely by turning off the lasers that initially held them in place. Despite these changes, their results remained consistent, showing that only the quantum correlations between photons and atoms affected the photon’s behavior, not the physical setup.
“Einstein and Bohr would have never thought that this is possible, to perform such an experiment with single atoms and single photons,” said Wolfgang Ketterle, who led the research team.
The big picture: This experiment arrives as the United Nations marks 2025 as the International Year of Quantum Science and Technology, commemorating nearly a century of quantum theory. By using single atoms as the tiniest slits possible, the experiment underscores the fundamental role of quantum uncertainty in the wave-particle duality of light.
