The topic of the quantum computer has recently become very popular, and talk about a breakthrough in technology does not subside, and after all, not so long ago, the success of research in the field of quantum computing was something of a fantasy. New terms have burst into the information flow and are now no less popular than artificial intelligence and machine learning. Although research has been going on for decades, last year was particularly fruitful in terms of development and eventful, when IBM brought the world the first commercial quantum computer and Google announced the achievement of quantum supremacy.

Revolutionary discoveries in modern physics that provided a new round of development of computational technologies, without exaggeration, can change the world and bring tremendous benefits to mankind, if properly applied. If you are interested in this topic and want to understand what quantum computers are, on what principle they work and why they are needed at all, then in this material we will talk about this as clearly as possible, without delving into the study of quantum mechanics and the structure of the quantum world.

## What is a quantum computer

Today, there is no need to doubt whether a quantum computer exists. If until recently it was only a figment of the imagination of scientists, now it has become a completely tangible object, and we can see what the practical implementation of the system looks like.

In simple terms, what a quantum computer is, it is a computer technology that uses the laws of quantum mechanics in its work. A machine performs certain tasks more efficiently than a simple computer that stores data in bits.

QC employs quantum algorithms that exploit effects such as superposition and quantum entanglement. For calculations, qubits (quantum particles) are used, capable of being in two states at once. That is, if a bit takes one of two possible values - 0 or 1, then a qubit is both 0 and 1, which allows the QC to process data and perform mathematical tasks thousands of times faster than usual . He does not need to sort out combinations, as does, including a supercomputer, the quantum system calculates the answer at lightning speed. These capabilities open the door to solving tasks that are not feasible today or are time-consuming.

The history of creating a new generation of computers dates back to 1981, when they first talked about using quantum systems for computing. Then it was still far from the physical implementation, the first working algorithm for QC appeared only in 1994, and the first 2-qubit machine was created in 1998 at the University of California at Berkeley. Experimental samples have been created for decades by teams of scientists from different countries, but the greatest success in this field has been achieved by IBM and Google.

The race of the leading companies is in full swing. In June 2020, Honeywell received a message that the most powerful quantum computer to date was created. The company claims that the device is twice as large as the quantum systems of IBM and Google, solving problems in minutes that would take conventional computers for millennia. Honeywell’s development impresses with a record 64 quantum volumes. The core of the system is a steel sphere the size of a basketball, cooled by liquid helium to a temperature of -262.7 ° C. It contains traps of ions formed from atoms, they stop moving under the influence of low temperatures and are controlled by laser pulses.

## What is a quantum computer for?

The rapid processing of large amounts of data using new technologies can help solve many problems and affect a wide variety of areas. For example, KK in just a few seconds will cope with the decomposition of numbers consisting of a large number of signs into prime factors (the process itself is not complicated, but it is time-consuming, this is what modern cryptography is based on), and it will also solve a number of similar problems. In addition, technologies are suitable for modeling complex situations, including calculating the physical properties of elements at the molecular level.

The main areas of application of quantum computers:

- global optimization;
- modeling of DNA molecules;
- creation of new materials;
- creation of medicines;
- improving machine learning;
- cryptography and encryption tasks (including breaking encryption algorithms and gaining access to any information).

At this stage, quantum computers are distinguished by the complexity of production and the instability of work, so so far it has only been possible to develop high-performance systems, sharpened for a single algorithm and designed for a very narrow range of tasks.

## How does a quantum computer differ from a conventional one?

For 30 years since the appearance of the concept of “quantum computing” scientific developments have allowed computing systems of this type to become a reality, albeit inaccessible to the average user. Quantum computers are based on unique behavior that is fundamentally different from the work of standard machines we are used to and is described by quantum mechanics.

The devices are capable of solving mathematical problems in a matter of seconds, the solution of which on an ordinary computer would take billions of years. According to Google, the Sycamore quantum machine performed calculations in more than three minutes, over which a standard supercomputer would pore for 10,000 years – this is called the loud term “quantum supremacy”.

A familiar computer, with which every modern person is familiar, as well as a smartphone, tablet or laptop, store information in bits that take the value 0 or 1, and any information, be it text or a picture, can be represented by zeros and ones. The fundamental difference and advantage of a quantum computer is in the operating unit used, called a qubit (or quantum bit). A qubit can be in a state of uncertainty, in other words, be in different states at the same time, by analogy with Schrödinger’s cat (the phenomenon of superposition).

A quantum computer is many times faster and more powerful than a conventional computer, while it is not suitable for most everyday tasks, since its principle of operation will be very different.

## How the computer of the future works

Now let’s take a closer look at what a high-tech system consists of. As we have already found out, the minimum unit of information in an ordinary computer is a bit that takes the value 1 or 0 (on or off), in a quantum computer these are qubits that can take all values. In this case, quantum particles depend on the measurement, which means there is no information about the qubit until the moment of its measurement, the measurement process itself also affects the value of the quantum bit, which may seem strange, but this is the case.

Due to this property of qubits (simultaneous presence in all states at once), until the time when the particle was measured, the computer will instantly sort out the possible solutions due to the existing connection between the qubits. Thus, the solution is known immediately, as soon as the initial data have been entered, that is, superposition determines the parallelism of computations, which speeds up the functioning of the algorithms at times.

A quantum computer device includes:

- control computer;
- generator of impulses affecting qubits;
- status register;
- CPU;
- a device for measuring the state of qubits.

For work between atoms, a quantum bond is provided, and the more bonds form qubits, the less the stability of the system will be. For quantum superiority over a standard computer, at least 49 qubits are required, and in this case, the stability of the system is already in question. When multiple dependencies are created, any external influences can affect them.

Due to the fragility of the bonds, the QC, consisting of several basic levels, includes the cooling of atoms to almost absolute zero, which makes it possible to protect from external processes, for this reason, a device with the provided protection of a quantum processor takes up a large amount of space.

## The principle of QC operation

The usual scheme of operation of computers, laptops, smartphones or tablets, using the digital principle, is based on the use of classical algorithms, which is fundamentally different from the principle of operation of a quantum computer. So, an ordinary computer will show the same result, regardless of how many times the calculation is run, the options are calculated sequentially.

A quantum computer uses a completely different – probabilistic principle of operation. In a sense, the system already contains all possible solutions. The result of calculations is the most probabilistic answer, and not an unambiguous one, while with each subsequent launch of the quantum algorithm, the probability of getting the correct answer grows, which means that after 3-4 quick runs you can be sure that we have come to the right decision, for example, the encryption key …

In quantum systems that use qubits in their work, with an increase in the number of particles, the number of values processed simultaneously grows exponentially.

Talking about how a quantum computer works, it is worth mentioning the coupling of qubits. If there are several qubits in the system, a change in one will also entail a change in the rest of the particles. Computing power is achieved through parallel computations.

Despite the multi-million dollar investments, quantum technologies are developing rather slowly. This is due to a large number of difficulties that scientists had to face in the process of research, including the need to build low-temperature sarcophagi with maximum isolation of the chamber with a processor from any possible external influences in order to preserve the quantum properties of the system. In addition, researchers are faced with the task of solving errors, since quantum processes and computations are of a probabilistic nature and cannot be one hundred percent correct.

The construction of stable systems is also far from ideal, and in the implementation of a quantum computer at the physical level, several solutions are used using different technologies. So the creation of a full-fledged universal quantum computer is still in the future, albeit not as distant as it seemed five years ago. Its creation is carried out by the largest companies such as IBM, Google, Intel, Microsoft, which have made a great contribution to the development of technologies, as well as some states for which this issue is of strategic importance.