## Saturday, October 15, 2011

### Quantum Tunneling an Effect of Quantum Mechanics

The process by which a particle gets across a barrier that it can not classically pass is called Quantum tunneling. Related to Wave-particle duality; results from the wave nature of a particle were the probability of the particle getting through the barrier drops exponentially with the thickness of the barrier.

When the wave comes in contact with the barrier most of it bounces off the carrier but a small amount passes through the barrier; but that amount decays exponentially with the thickness of the barrier.  Such that the amplitude of the initial wave increases then the amplitude of the wave on the opposite side of the barrier increases. If the barrier thickness increases, the amplitude of the wave on the opposite side of the barrier decreases. If the energy of the initial wave increases, (wavelength decreases) the amplitude of the wave on the opposite side of the barrier increases. If the waves energy greater than that of the barrier it all passes through the barrier but with a longer wavelength For particles most of them bounce off while a few instantly get through.

Theoretically valid Quantum tunneling is at the macroscopic but the odds of it occurring are extremely small. As a result there is a non zero probability that you could run your car into a brick wall an suddenly find yourself safely on the other side. However please don’t try it because the odds that it will happen are so small as to be impossible by any reasonable definition so if try it you will die.

Tunneling gets subatomic particles across barriers they normally can not cross. The number of particles that gets across the barrier drops exponentially with the barrier thickness. The number of particles that gets across the barrier increases with the energy of the particle. Quantum tunneling is a purely quantum effect. It has no counter part in Classical mechanics. It could theoretically occur on the macroscopic scale but the odds are too small to ever see it happen.