Famous Double-Slit Experiment Holds Up When Stripped To Its Quantum Essentials

Longtime Slashdot reader ndsurvivor shares a report from MIT: MIT physicists have performed an idealized version of one of the most famous experiments in quantum physics. Their findings demonstrate, with atomic-level precision, the dual yet evasive nature of light. They also happen to confirm that Albert Einstein was wrong about this particular quantum scenario. The experiment in question is the double-slit experiment, which was first performed in 1801 by the British scholar Thomas Young to show how light behaves as a wave. Today, with the formulation of quantum mechanics, the double-slit experiment is now known for its surprisingly simple demonstration of a head-scratching reality: that light exists as both a particle and a wave. Stranger still, this duality cannot be simultaneously observed. Seeing light in the form of particles instantly obscures its wave-like nature, and vice versa.

Now, MIT physicists have performed the most 'idealized' version of the double-slit experiment to date. Their version strips down the experiment to its quantum essentials. They used individual atoms as slits, and used weak beams of light so that each atom scattered at most one photon. By preparing the atoms in different quantum states, they were able to modify what information the atoms obtained about the path of the photons. The researchers thus confirmed the predictions of quantum theory: The more information was obtained about the path (i.e. the particle nature) of light, the lower the visibility of the interference pattern was. They demonstrated what Einstein got wrong. Whenever an atom is 'rustled' by a passing photon, the wave interference is diminished. 'Einstein and Bohr would have never thought that this is possible, to perform such an experiment with single atoms and single photons,' says Wolfgang Ketterle, the John D. MacArthur Professor of Physics and leader of the MIT team. 'What we have done is an idealized Gedanken experiment.' Their results appear in the journal Physical Review Letters.

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