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Glossary

Quantum glossary

Quantum tunnelling

Also: tunneling, barrier penetration

A particle crossing an energy barrier it classically could not climb over.

The wavefunction decays exponentially inside the barrier rather than stopping, so a thin enough barrier lets some of it through. Flash memory, scanning tunnelling microscopes and alpha decay all depend on it.

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Related terms

  • Wavefunction — The function ψ(x) giving the amplitude for a particle to be found at each position.
  • Schrödinger equation — The equation that governs how a quantum state changes in time.