Quantum tunnelling
= Quantum tunnelling
{wiki}
Quantum tunnelling is transmission through a <potential barrier> even when the particle energy is below the barrier height.
The <wavefunction> penetrates the classically inaccessible region; matching it to an outgoing <scattering state> on the far side gives a nonzero <transmission probability>. For a real, time-independent <potential barrier>, the transmitted <energy> equals the incident <energy>: <quantum tunnelling> does not require a temporary violation of <conservation of energy>. A <tunnel junction> turns this small <transmission probability> into a measurable <electric current>, whose sensitivity to separation makes the <scanning tunnelling microscope> possible.