# Quantum entanglement is explained by those who “use” it.

The phenomenon that won the award This year’s Nobel Prize in Physics – L’tangle Definitely dark and mysterious for most people. But it also lies at the heart of the branch of physics known asQuantum mechanics‘, which describes the microscopic world and which is of great interest to applications, ranging from cryptography to ‘quantum’ computers, specifically, as shown in an issue of to focus Currently on newsstands. We talk about it with Simone Severini, Head of Quantum Technologies at Amazon Web Services (Aws) in Seattle, US, and author of In the land of qubits (Trèfoglie) which will be released on December 16th.

What is entanglement?
First of all, it must be said that defining entanglement without the language of mathematics is difficult. This is the beauty of mathematics: sometimes with a couple of lines you can explain complex concepts that spoken language struggles to describe.

Entanglement is now interpreted as a physical quantity, such as time or energy. It should be interpreted as a resource that can be useful in practical applications. When we talk about quantum entanglement, I like to use the synonym “quantum correlation”. Entanglement is actually a stronger correlation than any classical (that is, described by classical physics) correlation.

Quantum physics recognizes that there are strongly interconnected objects. For example, imagine two friends, Alice and Bob, each with a coin. When Alice flips her coin, she will have a 50% chance of a heads up and a 50% chance of tails. The same thing happens to Bob. When Alice and Bob flip their coins, we then have one of four possible configurations, each with a probability of 25%: heads and heads, heads and tails, tails and heads, and tails and tails. It is important to note that the outcome of Bob’s roll is not dependent on Alice’s roll, and vice versa. So here everything is clear.

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Here, now let’s imagine two special coins, coins that only exist in the realm of quantum physics. Let’s call it quantum coins. These quantum currencies have a property that is difficult to guess. Let’s say Alice flips hers and gets heads up with a probability of 50%. The two quantums are special because in this case, Bob will also get faces when he flips him over. Guaranteed, with a probability of 100%. Same thing in the case of Alice getting tails. Thus, for Alice and Bob quantum coins, only two configurations can occur, namely heads and heads or tails and tails.

The remaining two configurations, heads and tails, and tails and vertices, were excluded.

The quantum currencies described above are not a product of our imagination, but can be constructed in the physical world, for example through two photons, the basic components of light. or through atoms, the basic constituents of matter. Heads and tails can be encoded with properties of a photon or an atom. just awesome.

why all that?
A torrent of interesting things can be done with quantum correlation. There is a famous example: sharing encryption keys, or in other words, sharing passwords. Through quantitative associations, Alice and Bob can create and share passwords that are nearly impossible to guess.

But can Alice and Bob also text each other faster than light?
The answer is no.” Simply because they cannot determine the outcome of the quantum coin toss, as there is still a 50% probability.

What are quantum computers and what role does entanglement play in their work?
A quantum computer is a machine that processes information encoded in physical objects whose behavior is governed by quantum physics. Quantum computers promise, in theory, to solve some computational problems faster than any other type of computer that can be built according to the laws of physics we know today.
Quantum correlations are supposed to play a role in their behaviour, but at the moment it is not clear what exactly they are.

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Quantum teleportation has also been performed by entanglement. what is he talking about?
Quantum teleportation is a procedure that uses quantum associations and a conventional communication channel, such as a telephone, for example, to transmit a description of a quantum object from one place to another, in order to then be able to reconstruct it in a similar way.

Theoretically, the procedure was invented in 1993. One of its co-inventors was his doctoral thesis advisor, Richard Josa. The first quantum teleportation experiments were conducted in 1997 by two groups: a group in Rome led by Francesco De Martini; and a group in Innsbruck led by Anton Zellinger. Interestingly, the “sender” of quantum teleportation does not need to know what he intends to transmit.

It is very likely that quantum teleportation will one day play a major role in getting quantum computers to talk to each other. What will be called the quantum internet, or a network of interconnected quantum computers, will use quantum teleportation as the main method for transmitting information.

In Amazon Web Services, quantum technologies are used in different ways (see Focus #362). But attention is directed above all to the future. what are your plans
In general, it is difficult to predict the future of technology, especially technology that still requires a lot of science like quantum computers.

At the Amazon Web Services (AWS) quantum computing center, scientists and engineers are working to build quantum computers based on superconductors. These are electrical circuits with unique quantum properties. We chose this approach in part because it allows for fabrication techniques known in microelectronics.