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QUANTUM COMPUTING

Quantum Computing is the most innovative theme of the decade. It is a real technological revolution that, with new hardware devices and a new software approach, allows information to be represented and manipulated through "quantum bits", ie Qubits.

If the basis of classical computing is the bit, the qubit or quantum bit is the basis of quantum computing. While the former can only assume a well-defined value (“0” or “1”, “open” or “closed”, “on” or “off”), the qubit can also assume superimposed values. According to the Heisenberg Uncertainty Principle, a quantum element, such as the qubit, will never take on a well-defined value, but will always have overlapping and indeterminable states.
In the famous paradox proposed by Erwin Schrödinger to explain his theory, the cat can be both alive and dead at the same time; in the case of electrons, this principle dictates that it is impossible to determine with certainty, at the instant of time t, the energy associated with them and their position simultaneously. Therefore, according to the parameters of the system, many combinations of energies and positions will be possible, but not all. By the same principle in quantum computing, the qubit can simultaneously assume the value of 0 and 1.
This has a very important impact from the point of view of computer computing (the field of quantum computing was launched by Yuri Manin in 1980 and Richard Feyman in 1982): being able to assume more values simultaneously, the qubit allows to process a piece of greater quantity information, thus guaranteeing a greater exchange of information compared to classical computer science, limited by its binary scale.
Chris Bernhardt, the author of the book Quantum Computing for Everyone, writes: “Quantum computing is a splendid fusion of quantum mechanics and computer science, incorporating some of the most astounding ideas of twentieth-century physics in a whole new way of thinking about calculation”.
The basic principle of quantum computing is the no-cloning principle: information can neither be copied nor read with absolute precision. However it can be transferred with absolute precision as long as the original is destroyed in the process (this is the case with quantum teleportation, first obtained by Nielsen, Klinn, and LaFlamme in 1988). Each measurement made on the quantum state destroys much of the information it contains, leaving it in a base state. Finally, the coding of information can be (and will be) carried out through “non-local” correlations between different parts of the physical system based on quantum entanglement.
One might mistakenly think that these features make a computer useless, but this is where you need to start thinking outside the box.
One of the areas in which a quantum computer finds a natural place is cyber-security. It is sufficient to consider the most used encryption algorithm that currently protects any type of communication, namely the RSA. This algorithm is based on the product of two large prime numbers (today the order of magnitude of absolute security used is about 10300). The factorization of the product of these numbers is practically impossible for a classical computer, in the sense that it would normally require times probably longer than the age of the universe. There are no algorithms in the classical world capable of performing this operation efficiently.
A completely different story in the world of quantum computing where the Shor factorization algorithm was developed. Its goal is to factorize large integers into prime numbers. Using a quantum computer, the operations of the Shor algorithm become simple and the whole process can be carried out in a finite and usually short time (which can be calculated with a polynomial). With this algorithm, one could, in theory, decrypt the private encryption keys of all the most confidential messages, causing the entire telecommunications security to collapse.
But using the same quantum computers, it would be possible to adopt a new single-use block cryptography system (eg Ekert’s protocol) with the quantum distribution of the cryptographic key. This method would be, in theory, inviolable since the mere interception of a message would make it immediately unusable.

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