Quantum tunneling
Quantum tunneling is the effect by which a particle passes through a potential energy barrier that, according to classical physics, it does not have enough energy to cross. Because a particle is described by a wave function that extends into and beyond the barrier, there is a nonzero probability of finding it on the far side. The thicker or higher the barrier, the smaller that probability.
Where it appears
Tunneling underlies many physical processes and technologies. It lets protons overcome their mutual electrical repulsion so that nuclear fusion can proceed in the Sun, and it explains the alpha decay of heavy nuclei. The scanning tunneling microscope, recognized by the 1986 Nobel Prize in Physics, images individual atoms by measuring a tiny tunneling current across a gap. In superconducting qubits, Josephson junctions rely on the tunneling of paired electrons, a phenomenon recognized by the 1973 Nobel Prize in Physics.
Sources
- The Nobel Prize in Physics 1986 (scanning tunneling microscope) (The Nobel Foundation, 1986)
- The Nobel Prize in Physics 1973 (tunneling and the Josephson effect) (The Nobel Foundation, 1973)
Cite this entry
"Quantum tunneling." postquantum.wiki. Updated July 11, 2026. https://postquantum.wiki/quantum-tunneling@misc{pqwiki-quantum-tunneling,
title = {Quantum tunneling},
howpublished = {\url{https://postquantum.wiki/quantum-tunneling}},
year = {2026},
note = {postquantum.wiki, updated 2026-07-11}
}