Secrets of Quantum Mechanics - What is Quantum Entanglement?

About 100 years ago, scientists first thought aboutthe nature of some of the unusual properties of light. For example, the light emitted from gases when they are heated in a test tube. If you look at this light through a prism, you will notice something unusual. Not a spectrum, in which colors smoothly pass one into another, reflected in a crystal glass, but distinct lines, the colors of which do not mix, like in a rainbow. We are talking about vertical rays of light, similar to pencils - each in its own color. However, scientists could not explain such a strange property of light. The search for answers continued unsuccessfully until physicist Niels Bohr at the beginning of the twentieth century put forward the most incredible and fantastic hypothesis. Bohr was convinced that the clue to the distinct lines lies in the very heart of matter - the structure of the atom.

If you heat a gas in a test tube and look at the light coming from it through a prism, you will see non-intersecting vertical lines

Fantastic hypothesis

According to the scientist, atoms resemble tinymodels of the solar system, since electrons revolve around the core, like planets. But electrons, unlike planets, move in one definite orbit and not in any other. Bohr argued that when an atom heats up, electrons move and jump from one orbit to another. Moreover, each jump is accompanied by the release of energy in the form of light with a certain wavelength. This is where those strange vertical lines and the concept of "quantum leap" come from.

In a National Geographic documentary aboutquantum theory, physicist Brian Greene talks about the amazing properties of the quantum leap, which consist in the fact that an electron moves from one orbit immediately to another, as if not crossing the space between them. As if the Earth in an instant changed its orbits with Mars or Jupiter. Bohr believed that due to the strange properties of electrons in an atom, they emit energy in definite, indivisible portions, which are called quanta. That is why electrons can move strictlyalong certain orbits and can be either at one point or at another, but not in the middle. In everyday life, we do not come across anything like this.

If a baseball were in two placesat the same time, we might believe that the wizard is deceiving us. But in quantum mechanics, having a particle in two places at the same time is exactly what makes us think the experiment is true.

When atoms are heated, electrons begin to jump from one orbit to another.

As incredible as Bohr's assumption may seem, physicists quickly found a large amount of evidence in favor of his theory - electrons really behave according to completely different laws than the planets of the solar system or ping-pong balls. The discovery by Bohr and his colleagues, however, contradicted the well-known laws of physics and soon led to a collision with the ideas expressed by Albert Einstein.

Quantum entanglement

Einstein Couldn't Accept UncertaintyA universe flowing from quantum mechanics. The physicist believed that an object exists not only when it is being observed (as Niels Bohr argued), but all the rest of the time. The scientist wrote: "I want to believe that the moon shines even when I am not looking at it." The very idea that the reality of the universe is determined when we open and close our eyes seemed inconceivable to him. According to Einstein, quantum theory lacked something that would describe all the properties of particles, including their location, even when they are not being observed. And in 1935 it seemed to Einstein that he had found a weak point in quantum mechanics. It was an incredibly strange phenomenon, contrary to all logical ideas about the universe - quantum entanglement.

Quantum entanglement Is a theoretical assumption arising fromequations of quantum mechanics, according to which two particles can get entangled if they are close enough to each other. In this case, their properties become interrelated.

But even if you separate these particles and send tothe different ends of the world, as quantum mechanics suggests, can still remain entangled and inextricably linked. To Einstein, such a connection between particles seemed impossible, he called it so - "supernatural communication at a distance." The scientist admitted that entangled particles could exist, but believed that there was no "supernatural connection at a distance". On the contrary, everything is predetermined long before the moment of measurement.

Let's say someone took a pair of gloves, split themand put each in a separate suitcase. Then one suitcase was sent to you, and the second to Antarctica. Until the moment the suitcases are closed, you do not know which of the gloves is there. But when we open the suitcase and find the left glove in it, we will know with 100% certainty that the right glove is in the suitcase in Antarctica, even if no one has looked into it.

Niels Bohr, in turn, relied onequations proving that particles behave like two wheels that can instantly link the random results of their rotation, even when they are at a great distance from each other. So who's right?

Determine if between tangledparticles there is a "supernatural connection" as between rotating wheels, or there is no connection and the properties of the particles are predetermined, as in the case of a pair of gloves, physicist John Bell succeeded. Bell showed by sophisticated mathematical calculations that if there is no supernatural connection, then quantum mechanics is wrong. However, the theoretical physicist also proved that the problem could be solved by building a machine that would create and compare many pairs of entangled particles.

Based on Bell's instructions the physicist,quantum mechanic John Clauser has built a machine capable of doing this job. Klauser's machine could measure thousands of pairs of entangled particles and compare them in so many ways. The findings made the scientist think he made a mistake. Soon, French physicist Alain Aspe got to the heart of the Einstein-Bohr dispute.

Alain Aspe is a French physicist specializing in quantum optics, the theory of hidden parameters and quantum entanglement.

In Aspe's experiment, the measurement of one particle could directlyaffect the other only if the signal from the first particle to the second would travel at a speed exceeding the speed of light. Which, as we know, is impossible. Thus, there was only one explanation - a supernatural connection. Moreover, the experiments carried out have proven that the mathematical basis of quantum mechanics is correct.

Entanglement of quantum states is a reality.

It turns out that quantum particles can be linkeddespite the huge distances, and the measurement of one particle can really affect its distant pair, as if the space between them never existed. But No one can answer the question of how this connection works today.

Quantum entanglement of particles also does not excludethe fact that teleportation will someday become a reality. So, scientists are already teleporting hundreds of particles today, as my colleague Daria Eletskaya wrote about in more detail. Do you think scientists will be able to create a unified theory of quantum gravity? We will wait for the answer in the comments to this article, as well as in our Telegram chat.