The SARS - CoV2 pandemic, better known as COVID 19, confronts the scientific community on a daily basis with a huge amount of data, clinical, health, demographic, social, and economic in nature, with the overriding goal of providing as accurate a description of the ongoing phenomenon as possible.

The main difficulty today is to be able to manage, in a short time, the data processed on a global scale (BIG DATA) and derive from it the most useful information for humanity.

For decades now, data management has been closely linked to the evolution of computerized systems, the progress of which, over time, has allowed for ever faster and higher performance processing.

When we talk about the capacity of a computer, we are used to terms such as Megabyte (106 bytes), Gigabyte (109 bytes) and, in exceptional cases, /Terabyte (1012 bytes). These quantities tell us how much data a computer can handle.

Big Data and the data traffic that develops on the Internet on a daily basis have forced the definition of new orders of magnitude; thus, the Petabyte (1015 bytes), Exabyte (1018 bytes), Zettabyte (1021 bytes) and Yottabyte (1024 bytes) have been introduced.

We have thus reached a point where even the most powerful classical calculators are beginning to experience difficulties in processing such masses of data.

To solve such difficulties, we are met, once again, by the principles of quantum mechanics, which seems to have fields of application increasingly related to everyday life.

For some years now, major computer brands, first and foremost IBM and GOOGLE, have begun in-depth studies to build a quantum computer. This is a computer that uses the laws of physics and quantum mechanics to process data, exploiting the quantum bit (qubit) as its fundamental unit (unlike electronic computing, the basis of computers as we have always known them, whose fundamental unit is instead the bit).

In particular, quantum bits have certain properties that are derived from the laws of quantum physics and on which the operation of quantum computers depends.

These properties are:

- superposition of states, that is, the simultaneous existence of all possible states of a particle or physical entity before it is measured (this means that before it is measured, a qubit can be either 0 or 1). Only by measurement can the property of the qubit be precisely defined: before the measurement takes place, therefore, the states of the qubits coexist and can be seen as a kind of "probability cloud"; this cloud will collapse and become a definite state by the time it is measured (this is the same principle perhaps known to most as Schrödinger's equation, or as "the cat-in-a-box experiment").
- entanglement, or quantum correlation, which expresses the constraint, the correlation in fact, that exists between two particles or two qubits; according to this principle, it is possible to know the state of one particle (or qubit) by measuring the other with which it has the constraint, a process that, "carried over," in computer science translates into an acceleration of computational processes.
- quantum interference, which is in fact the effect of the first principle (the superposition of states); quantum interference makes it possible to "control" the measurement of qubits based on the wavelike nature of particles (interference in fact represents the superposition of two or more waves, and depending on whether or not there is superposition between crests and vents-that is, the highest and lowest parts of the wave-constructive interference can occur, when crests or bellies coincide and form a wave that is the sum of the overlapping waves, or destructive interference, when overlapping are crest of one wave and belly of another, in which case the two waves cancel each other out).

Although endowed with extremely high computational capabilities, quantum computers still have critical issues that hinder their implementation on a commercial scale. The most prominent of these critical issues concerns the qubits: these, consist of single atoms, or small molecules, or tiny superconducting circuits, whose proper functioning is only guaranteed at very low temperatures. Cooling the qubits of a quantum computer is therefore essential to ensure their efficiency.

Assuming that these critical issues have been resolved, one wonders what the practical applications of a quantum computer might be.

First and foremost, the field of pharmaceutical chemistry for example, an industry that relies on very complex calculations to find the right combinations of molecules among the many possible ones." The three-dimensional structure of proteins and their function depends on how they fold from transcription from messenger Rna. This process, known as protein folding, is very complicated to reconstruct in detail, and high computational power could help unravel the underlying mechanisms.

Another area of application would be in complicated optimization problems. Everything done in industrial processes could be solved more efficiently. "VolksWagen for example has already worked on optimization processes for Beijing cab traffic. This is just a model, but one that shows the potential for application." Another example is scheduling or scheduling problems: "In an industry, you need to schedule the sequence of processes to be sent to the assembly line. It is an optimization problem that becomes more complicated as the number of elements considered increases. The quantum computer will be able to solve this more efficiently."

Yet another area that would benefit from the introduction of quantum computing is quantum machine learning and thus the coupling of quantum computers and artificial intelligence. "Quantum machine learning algorithms already exist that promise to be even more powerful than what we already have available."

Today there is no firm evidence of what the possible spread of quantum computers will be, but it is certain that these machines will be increasingly present where they are really needed, namely in research centers.

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