Joke through the wall

The concept of going through walls is really incredible and impossible in real life.

So is it really possible in quantum mechanics?

In quantum mechanics, there is a technical term for this through-wall effect, which is tunnel effect. What is the tunneling effect?

Simply put, quantum tunneling is that microscopic particles can pass through a wall higher than themselves. This is a quantum effect, which may be difficult to understand from a classical point of view. But the Schrodinger equation can be easily solved by combining the viewpoint of fluctuation in quantum mechanics.

To make it easier to understand, we can make an assumption first. If there is a wall in front, we must have enough energy to jump over it. If there is not enough energy, we will never appear on the other side of the wall. But in the quantum world, even if the energy is not enough, we can go through the wall (instead of jumping over it), which is the phenomenon of quantum tunneling. Of course,' we' here can't be macroscopic objects, but microscopic particles. Because the probability of macroscopic objects tunneling is very small, it is impossible to observe.

Discovery of quantum tunnel

Quantum tunneling is actually put forward from the process of studying radioactivity.

1896, French physicist becquerel discovered the radioactivity of uranium from his research on uranium, and then the Curies also participated in this research. Later, the three of them won the Nobel Prize in Physics.

There has always been a question about radioactivity. The most common alpha decay is heavy nuclei, that is, helium nuclei emit alpha particles. As we know, the nucleons (protons or neutrons) of the nucleus are linked together by strong interaction. How do nucleons escape from strong interactions?

In the 20th century, with the development of quantum mechanics, physicists gradually realized the uncertainty and wave-particle duality of microscopic particles, which laid the foundation for the interpretation of radioactivity. In 1927, Hont Hungary first noticed the tunneling phenomenon when calculating the ground state of double potential wells. 1928, American physicist Gamov and two other scientists independently developed the theoretical explanation of α decay. By solving the Schrodinger equation of the square barrier, they obtained the tunneling probability of particles, and further established the relationship between the energy of particles emitted during the decay process and the half-life.

Later, in a report by Gamov, Born realized the universality of tunnel effect. He believes that this phenomenon may not be limited to nuclear physics, but a relatively common phenomenon in quantum mechanics. Gradually, people discovered various quantum tunneling phenomena. The famous Josephson junction is made by the tunneling process of superconducting electrons.

Collision with wall and quantum tunneling

Although quantum tunneling is universal, it is only relative to the microscopic world. For the macro world, quantum tunneling is not applicable. Because there is no necessary condition for quantum tunneling in the macro world, that is, there is a high and low barrier, Heisenberg uncertainty and so on.

Simply put, quantum tunneling does not apply to the matter of going through walls.