Quantum Tunneling

The often-used description to explain the concept of quantum tunneling in layman’s terms is a man rolling a rock uphill and, upon reaching the top, pushes it downhill to  the other side of the hill (Fig. 5.1). In conventional physics, this is the only way and, perhaps, the shortest way to bring the rock to the other side. Another alternative is to go around the bend until the rock reaches the other side of the hill.

But quantum physics offers another alternative. The man can simply push the rock through the hill by tunneling through its thick structure, without destroying or demolishing any barriers along the way. The solid rock can simply pass through, as if entering a cave, and exit on the other side of the hill.

Paul Davies and John Gribbin (1992:207) describe this concept of tunneling more succinctly as follows:  

Tunneling is the quantum mechanical process by which a particle can penetrate a classically forbidden region of space (for example, passing from two separate points A and B without passing through intermediate points). The phenomenon is so named because the particle, in traveling from A to B, creates a sort of "tunnel" for itself, bypassing the usual route. 

This is really spooky and eerie. As we know, only ghosts can do this.

Quantum tunneling, originally known as “barrier penetration,” was first introduced by F. Hund in 1927. It is a concept used to express the ability of particles to barrel or tunnel through any barrier and appear on the other side, without changing or destroying the latter. Examples of these particles are the neutrinos, axions, photinos, and gravitinos, which are known as “high-density particles.” They are so subtle and tiny that they can penetrate even a block of solid lead light-years thick. 

The reason why we cannot observe this in the macroscopic level is because large-scale objects have shorter wavelengths. But researchers maintain that there is evidence that this tunneling in the world of small things is also happening in the world of big things. Larson raises this observation by citing some concrete human experiences:

Possibly you noticed a sock or two missing after you washed it, somewhere between the washing machine and the drying machine, most inexplicably leaving you one or more lone socks with no mates…What’s most curious is when the socks simply seem to vanish altogether, and all other possibilities have been investigated.  

Perhaps you’ve had an experience where you are absolutely sure that you set down your wallet or keys in a certain place, only to return and not be able to find them there. You then search around the place a bit more unsuccessfully, and return again to that same place where you first looked…and there they are. 

This inspires scientists to closely monitor events happening at the micro level. As Larson (2013) observed: “Scientists are now observing quantum behavior once thought to be relegated exclusively to submicroscopic realms such as entanglement, superposition of states, coherence, tunneling, and teleportation in our everyday world at a very human level.”