quantum tunneling

American  

[kwahn-tuhm tuhn-uhl-ing] / ˈkwɑn təm ˈtʌn əl ɪŋ /

noun

1. Physics. any of various phenomena of quantum mechanics in which a particle passes through a potential barrier that, according to classical mechanics, requires more energy to penetrate than the particle in fact possesses.

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quantum tunneling Scientific  

1. A quantum mechanical effect in which particles have a finite probability of crossing an energy barrier, such as the energy needed to break a bond with another particle, even though the particle's energy is less than the energy barrier. Quantum tunneling has no counterpart in classical mechanics, in which a particle can never cross an energy barrier with a higher energy level than the particle has. The emission of alpha rays in radioactive decay is a case of quantum tunneling; though the alpha particles are strongly bound to the nucleus and don't have as much energy as the bond does, they still have a finite probability of escaping the nucleus. The design of transistors and many diodes makes use of this effect.

2. See also radioactivity

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Example Sentences

The knots ultimately unraveled through quantum tunneling, a process in which particles cross energy barriers that would be insurmountable in classical physics, as if they were passing through a wall.

From Science Daily • Dec. 7, 2025

Yet in some of these cases, such reactions do happen, thanks to quantum tunneling, which allows particles to occasionally bore through energy barriers they’d never be able to climb.

From Scientific American • Apr. 4, 2023

If a proton spontaneously jumped out of its atomic bonds, in what physicists call "quantum tunneling," this could cause a cascade of sudden neuron activity.

From Salon • Apr. 30, 2021

It turns out that to get to the lower energy "true vacuum" state, the Higgs field would have to get through an enormous energy barrier through a process known as quantum tunneling.

From Science Magazine • Aug. 3, 2015

General relativity explains black holes, the bending of light and "even offers a possible explanation of the origin of our Universe - as quantum tunneling from 'nothing,'" he writes.

From Reuters • Jan. 15, 2012