What Is Quantum Entanglement In Physics?

By Antonia Čirjak on March 9 2020 in Did You Know

The entanglement relates to particles and describes how their fundamental properties relate to each other and how it could not have happened by chance.
The entanglement relates to particles and describes how their fundamental properties relate to each other and how it could not have happened by chance.
  • Entanglement is a concept that states that if two objects react with one another, we can find out important information about one of them by learning things about the other one.
  • This concept was mostly developed through ideas made by physicists Albert Einstein, Niels Bohr, Boris podolsky and others.
  • This concept has many uses today, including when measuring gravitational waves.

Quantum entanglement is a term used in quantum physics. The entanglement relates to particles and describes how their fundamental properties relate to each other and how it could not have happened by chance.

In simpler terms, if we know some facts about the characteristics of one particle, then we most likely know that the same thing applies to that characteristic in a different particle. This happens with particles that interact with each other.

The Conflicts In The World Of Physics

The easiest way to describe this entanglement is with an example. Imagine a pair of socks, meaning one goes on your right leg and the other on your left one. If you find just the right sock in your drawer, you can be sure that the one that is missing is for your left leg. This means that these socks are entangled; if we know something about one of them, it tells us an important fact about the other one. It sounds simple when presented this way. However, it is a big problem for quantum mechanics

First, we need to examine the differences between two schools of thought in physics. Physicists Niels Bohr and Werner Heisenberg believed that we needed to associate an object with a certain measurement for it to exist truly. If we could not do that, the object was just a possibility, not a physical existence. On the other hand, Albert Einstein and Erwin Schrödinger disagreed with this greatly. They considered this idea absurd. They compared it with the example of putting a cat inside of a box and claiming we do not know if it was dead or alive unless we take a look inside of the box.

Illustration of Erwin Schrodinger (or Schroedinger) thought experiment, where the cat is both alive and dead due to interpretations of quantum mechanics.
Illustration of Erwin Schrodinger (or Schroedinger) thought experiment, where the cat is both alive and dead due to interpretations of quantum mechanics.

Entanglement, Further Explained

Eventually, physicists Boris Podolsky and Nathan Rosen made up a thought experiment in collaboration with Albert Einstein. They published a paper in 1935 that featured the experiment that would supposedly solve the question of entanglement. This experiment dealt with two objects that interact in certain ways. They then stated that by measuring one of the objects, we are able to figure out certain information about its partner without measuring it directly. It is because of their history together, their entanglement, that this is possible. 

Bohr reacted to the paradox presented by these three physicists by suggesting that these objects did not become real until they started to interact with each other. They became real at the same time, meaning that they swapped details about each other and this interaction across a larger distance. Neither was real until one was measured. This is how quantum entanglement was explained.

Einstein disagreed with his ideas and called them “spooky,” and eventually described this as the EPR paradox, because it violates the laws of causality. However, these ideas are still very important in physics today. Throughout experiments on this phenomenon, physicists have used photons, neutrinos, electrons, and larger molecules. Entanglement is often utilized as a concept in communication, computation, and is still being researched and developed.

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