Quantum tunnelling
Quantum tunnelling is a part of the theoretical branch of physics known as quantum mechanics. It states that electrons can behave like both particles and waves, and can cancel the effects of an energy barrier if the energy barrier is thin enough, due to quantum mechanics being dependent on probability. In other words, particles can travel through walls, doors, etc. if the door or wall is thin enough. The particle—usually a subatomic or quark particle such as an electron or photon—can become a wave to focus a great deal of energy on the barrier, ultimately negating it. There is also a non-zero chance that it could be found inside the barrier. However, this only noticeably works for subatomic particles, as the chance for macroscopic objects to do this is very, very low, small enough to not be thought about much.
Quantum Tunnelling Media
Animation showing the tunnel effect and its application to an STM
A simulation of a wave packet incident on a potential barrier. In relative units, the barrier energy is 20, greater than the mean wave packet energy of 14. A portion of the wave packet passes through the barrier.
A working mechanism of a resonant tunnelling diode device, based on the phenomenon of quantum tunnelling through the potential barriers
Quantum tunnelling through a barrier. The energy of the tunnelled particle is the same but the probability amplitude is decreased.
Quantum tunneling in the phase space formulation of quantum mechanics. Wigner function for tunneling through the potential barrier U(x) = 8e^{-0.25 x^2} in atomic units (a.u.). The solid lines represent the level set of the Hamiltonian H(x,p) = p^2 / 2 + U(x) .
Quantum tunnelling through a barrier. At the origin (x = 0), there is a very high, but narrow potential barrier. A significant tunnelling effect can be seen.
Quantum tunneling oscillations of probability in an integrable double well of potential, seen in phase space
Chaos-assisted tunnelling oscillations between two regular tori embedded in a chaotic sea, seen in phase space
