Tuesday, January 11, 2011

Quantum tunnelling

Quantum tunnelling refers to the quantum mechanical phenomenon where a particle tunnels through a barrier that it classically could not surmount because its total mechanical energy is lower than the potential energy of the barrier.

Quantum tunnelling is where a particle is found outside a confining potential despite it having insufficient energy to cross the barrier classically. 

Particles are confined to certain regions of space because they do not have enough energy to escape from that region. These regions are defined by potential energy curves.

The effect arises from the fact that a wavefunction does not fall abruptly to zero at the walls of a container (unless the potential is infinite), but decays exponentially inside the barrier. The result of this is that the wavefunction may be non-zero on the far side of the potential barrier and hence, by the Born interpretation of the wavefunction, there is some probability of finding the particle there. 

Quantum tunnelling occurs on an extremely small scale. We cannot directly perceive what a particle does when it tunnels so much of our understanding of the process is shaped by the language and imagery of the macroscopic world.

Quantum Tunneling has a number of applications like, it is used to explain the Alpha Decay of the Uranium Nucleus, it is used in fabricating high speed transistors and new age cooling equipments.