dobbeltspalteeksperimenter

Dobbeltspalteeksperimenter are experiments designed to explore wave-particle duality and quantum coherence. The best-known form is the two-slit arrangement introduced by Thomas Young in 1801, where monochromatic light passes through two narrow, closely spaced slits, yielding a pattern of alternating bright and dark fringes on a screen. This demonstrates interference, a hallmark of wave behavior.

Over the 20th century, the same setup was applied to particles such as electrons, neutrons, atoms, and even large molecules. Electron interference was demonstrated by Davisson and Germer in 1927, neutron interference by Bonse and Hartmann in 1961, and later experiments showed interference fringes for atoms and increasingly large molecules, including fullerene C60, indicating quantum coherence at macroscopic scales. In many modern versions, single particles are emitted one at a time, yet accumulate an interference pattern over time.

The physics is explained by the superposition of amplitudes. The intensity pattern for two identical slits is I ≈ I0 cos^2(π d sinθ / λ). The fringe spacing is Δx ≈ λ L / d, where λ is the wavelength, d is slit separation, and L is the distance to the screen. When a measurement is made to determine which slit the particle passes through (which-path information), the interference fringes disappear, illustrating complementarity. Variants such as delayed-choice and quantum eraser experiments further explore these ideas.

Significance: These experiments underpin the concept of wave-particle duality and quantum superposition, with implications for quantum measurement and interpretations of quantum mechanics. They remain central to quantum optics and precision metrology.