Quantum tunneling is by far one of the most interesting things I’ve ever looked into. The whole process is extremely mysterious, yet absolutely vital for life as we know it to continue. There are also aspects of it that can have strange, even harmful, consequences.
Imagine bouncing a tennis ball against a wall. For us, every single time, the ball comes back to us. However, due to the strange nature of the quantum world, there is technically a statistical possibility that the ball will end up on the other side of the wall, or even in the wall itself. Now, I didn’t say the ball would go through the wall, at least not exactly. If a weird case of macro-scale quantum tunneling took place, the ball would disappear suddenly when it approached the wall, then immediately reappear on the other side with the wall and tennis ball still perfectly in tact. Of course, there is not much of a chance that this will happen…ever. Yet, the statistical possibility still exists. It technically could happen.
The reason for this goes into the extremely probabilistic nature of the quantum world. As proven by Werner Heisenberg’s uncertainty principle, the position and momentum of a particle can not be simultaneously known. For example, if you know the position of an electron, you cannot know the velocity, and if you know the velocity, you cannot know the position. Because of this, probabilities are used to, in a sense, “guess” where a particle like an electron might be. An electron might have a higher chance of being in one place rather than another. These probabilities create what is called a “probability cloud”.
|The Probability Cloud of an Electron|
As we can see in the picture, the chances of the electron being in the center of the cloud are greater than it being away from it. However, even though the chances are incredibly small, there is a statistical possibility that the electron could be found near the edge of the cloud. This is where things begin to get strange.
Quantum tunneling is the ability of a particle, such as an electron, to travel through a barrier at an instantaneous speed. If there is a barrier of a higher energy than the electron, and an electron approaches it, we would normally assume it is impossible for the electron to breach that barrier. In fact, most times it is impossible. However, every great once in a while, the electron does something completely unexpected. In the rarest of cases, the electron simply appears on the other side of the barrier. Also, just as the tennis ball and wall example, the barrier and electron are both perfectly in tact. How can this be possible?