QUANTUM COMPUTERS

Quantum computers have always been considered a kind of “holy grail” of technological innovation, capable of revolutionising the IT world and all of society thanks to their applications. These are computers (still being developed) whose operation exploits the laws of quantum mechanics, overcoming the limits of conventional computers. The latter adopt, as a minimum unit of information, the bit, which can only assume two values (conventionally called 0 and 1).

Quantum computers too have a two-level information unit, the qubit, but with an essential difference. While the bit can only take on one of the two permitted values in a given moment, the qubit may be a combination of both, due to the superposition principle (a peculiar effect of quantum mechanics). And not just this. Thanks to the entanglement phenomenon, a kind of correlation at a distance that can be generated between quantum systems, each qubit can be correlated to another, thus multiplying the computational power. These conditions, if multiplied by a large number of qubits, make the computing power of a quantum computer incomparable to that of any classic supercomputer.
However, although there has been talk of quantum computers for more than forty years (the first to intuit their potential was the American Nobel Prize winner Richard Feynman in 1982), the technological obstacles to overcome to obtain computers for practical applications are still enormous.

In recent years, however, a strong acceleration in high-level investments and projects in the area of quantum computing has been recorded throughout the world, with the development of several promising technologies.
The first result already obtained was the creation of some examples of “quantum advantage”, i.e. the demonstration that some prototypes of quantum computers are already able to do operations in a way that is extremely more efficient than the best conventional computers (although these are, for the most part, symbolic demonstrations not linked to useful applications). INFN is strongly committed to important projects in the field of quantum computing. In particular, it is the sole non-American partner of the Superconducting Quantum Materials and Systems Center – a centre of excellence based at Fermilab in Chicago, founded in 2020, which aims to create a cutting-edge quantum computer based on superconducting technologies in the next few years. For example, the Gran Sasso laboratories are the ideal environment for measuring the effect of cosmic rays and natural radioactivity on decoherence time of quantum computers.

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