Breakdown of Classical Mechanics
Double-slit, one particle at a time.
You fire electrons one at a time through two narrow slits toward a detection screen. Each electron hits the screen as a single dot — a tiny particle impact. You let thousands of electrons accumulate over hours.
What pattern do the dots form on the screen?
An interference pattern! Each electron arrives as a single dot, but over thousands of electrons, bright and dark bands appear — exactly like a wave passing through two slits. Each electron interferes with ITSELF.
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Watch electrons arrive one by one. At first it looks random. Wait... a pattern is emerging. That's an interference pattern — from individual particles!
ψ = ψ₁ + ψ₂
The probability of arrival is |ψ₁ + ψ₂|², not |ψ₁|² + |ψ₂|² — the cross-term is interference!
Use electron waves to image objects too small for light — wave nature of particles in action
Qubits exist in superposition (both 0 AND 1), like electrons going through both slits
"Nobody understands quantum mechanics" — Richard Feynman. Even the greatest physicists find it deeply counterintuitive
“Nature is not classical, dammit. — Richard Feynman”
Quantum Slit Lab
Fire particles one at a time through slits. Adjust the number of slits, slit width, and wavelength. Watch the interference pattern build from individual particle impacts.
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Start with one slit — you get a diffraction pattern. Add a second slit — interference fringes appear! Now try detecting which slit the particle goes through — watch the pattern vanish.
The interference pattern proves particles have wave nature. But each particle arrives as a single point. The wave describes probability, not a physical oscillation.