For over 100 years, quantum physics has taught us that light can exhibit both wave-like and particle-like behavior. However, a new experiment using single atoms confirms that light cannot be seen to behave as both at the same time.
The debate about the nature of light dates back to the 17th century, with scientists like Isaac Newton and Christiaan Huygens proposing different theories. The famous double-slit experiment, devised by Thomas Young in 1801, showed that light spreads out on a wall in alternating interference patterns of light and dark. This was only possible if light waves were interacting with each other.
Albert Einstein later argued that photons also display wave-like behavior, but the uncertainty principle states that we can never observe a photon acting as both a wave and a particle simultaneously. Niels Bohr believed this “complementarity” and introduced it to explain why we cannot measure complementary properties of a quantum system at the same time.
In the latest experiment, researchers at MIT used lasers to arrange 10,000 individual atoms cooled to near absolute zero, acting as slits in the double-slit experiment. The results showed that Bohr was correct when he argued for complementarity, and Einstein had got it wrong. When they measured the “rustling” of photons on the single atoms, it weakened the diffraction pattern, demonstrating light’s particle nature.
The team also tested whether the apparatus affected the results by switching off the lasers and making a measurement within a millionth of a second of doing so. The result was always the same – light’s wave and particle properties could not be simultaneously observed.
This experiment further emphasizes the weirdness of quantum physics, where particles exhibit dual nature and we can’t measure complementary properties simultaneously.
Source: https://www.space.com/astronomy/einstein-was-wrong-slightly-about-quantum-physics-new-version-of-the-famous-double-slit-experiment-reveals