When the quantum computer is invented. A quantum computer - how it works. Who invented the quantum computer

L. Fedichkin, PhD in Physics and Mathematics (Institute of Physics and Technology of the Russian Academy of Sciences.

Using the laws of quantum mechanics, you can create a fundamentally new type computing machines, which will allow solving some tasks that are inaccessible even to the most powerful modern supercomputers. The speed of many complex calculations will skyrocket; messages sent over the lines of quantum communication can neither be intercepted nor copied. Prototypes of these quantum computers of the future have already been created.

American mathematician and physicist of Hungarian descent Johann von Neumann (1903-1957).

American theoretical physicist Richard Phillips Feynman (1918-1988).

American mathematician Peter Shor, an expert in the field of quantum computing. Proposed a quantum algorithm for fast factorization of large numbers.

Quantum bit, or qubit. The states and correspond, for example, to the direction of the spin of the atomic nucleus up or down.

Quantum register is a string of quantum bits. One- or two-qubit quantum gates perform logical operations on qubits.

INTRODUCTION, OR A LITTLE ABOUT THE PROTECTION OF INFORMATION

Which software do you think has the most licenses sold in the world? I will not dare to insist that I know the correct answer, but I definitely know one wrong one: this notany of the versions Microsoft Windows... The most common operating system is outpaced by a modest product from RSA Data Security, Inc. - a program that implements an encryption algorithm with public key RSA, named after its authors - American mathematicians Rivest, Shamir and Adelman.

The fact is that the RSA algorithm is built into most of the sold operating systems, as well as many other applications used in different devices - from smartcards to cell phones... In particular, it is also available in Microsoft Windows, which means that it is obviously wider than this popular operating system... To detect traces of RSA, for example, in a browser Internet Explorer (a program for viewing www-pages on the Internet), just open the "Help" menu, enter the "About Internet Explorer" submenu and view the list of used third-party products. Another common browser, Netscape Navigator, also uses the RSA algorithm. In general, it is difficult to find a well-known high-tech firm that would not buy a license for this program. Today RSA Data Security, Inc. has already sold over 450 million (!) licenses.

Why is RSA so important?

Imagine that you need to quickly exchange a message with a person far away. Thanks to the development of the Internet, such an exchange has become available today to most people - you just need to have a computer with a modem or network card... Naturally, when exchanging information over the network, you would like to keep your messages secret from strangers. However, it is impossible to completely protect an extended communication line from eavesdropping. This means that when sending messages, they must be encrypted, and when receiving, they must be decrypted. But how can you and your interlocutor agree on which key you will use? If you send the key to the cipher on the same line, then an eavesdropping attacker can easily intercept it. You can, of course, transmit the key via some other communication line, for example, send it by telegram. But this method is usually inconvenient and, moreover, not always reliable: another line can also be tapped. It is good if you and your addressee knew in advance that you would exchange encryptions, and therefore transferred the keys to each other in advance. But what if, for example, you want to send a confidential offer to a prospective business partner or buy a product you like with a credit card in a new online store?

In the 1970s, encryption systems were proposed to solve this problem, using two types of keys for the same message: open (not requiring secrecy) and closed (highly secret). The public key is used to encrypt the message, and the private key is used to decrypt it. You send your correspondent a public key, and he encrypts his message with it. All an attacker who intercepts the public key can do is encrypt his letter and forward it to someone. But he will not be able to decipher the correspondence. Knowing the private key (it is initially stored with you), you can easily read the message addressed to you. To encrypt reply messages, you will use the public key sent by your correspondent (and he keeps the corresponding private key for himself).

This is exactly the kind of cryptographic scheme used in RSA, the most common public key encryption method. Moreover, to create a pair of public and private keys, the following important hypothesis is used. If there are two large (requiring more than a hundred decimal digits for their notation) simple numbers M and K, then finding their product N \u003d MK will not be difficult (for this it is not even necessary to have a computer: a sufficiently accurate and patient person can multiply such numbers with a pen and paper). But to solve the inverse problem, that is, knowing a large number N, decompose it into prime factors M and K (the so-called factorization problem) - almost impossible! It is with this problem that an attacker who decides to "crack" the RSA algorithm and read the information encrypted with it will face: to find out the private key, knowing the public one, you will have to calculate M or K.

To test the validity of the hypothesis about the practical complexity of factoring large numbers, special contests have been and are still being held. The decomposition of only a 155-digit (512-bit) number is considered a record. The calculations were carried out in parallel on many computers for seven months in 1999. If this task was performed on one modern personal computer, it would take about 35 years of computer time! Calculations show that using even thousands of modern workstations and the best computational algorithms known today, one 250-digit number can be factorized in about 800 thousand years, and a 1000-digit number - in 10 25 (!) Years. (For comparison, the age of the universe is ~ 10 10 years.)

Therefore, cryptographic algorithms like RSA, operating on sufficiently long keys, were considered completely reliable and were used in many applications. And everything was fine until then ... until quantum computers came along.

It turns out that using the laws of quantum mechanics, you can build computers for which the factorization problem (and many others!) Will not be difficult. It is estimated that a quantum computer with only about 10,000 quantum bits of memory is able to factor a 1000-digit number into prime factors in just a few hours!

HOW IT ALL BEGAN?

Only by the mid-1990s did the theory of quantum computers and quantum computing establish itself as new area science. As is often the case with great ideas, it is difficult to pick out a discoverer. Apparently, the Hungarian mathematician I. von Neumann was the first to draw attention to the possibility of developing quantum logic. However, at that time, not only quantum, but also ordinary, classical, computers had not yet been created. And with the advent of the latter, the main efforts of scientists turned out to be directed primarily towards the search and development of new elements for them (transistors, and then integrated circuits), and not towards the creation of fundamentally different computing devices.

In the 1960s, the American physicist R. Landauer, who worked at the IBM corporation, tried to draw the attention of the scientific world to the fact that computation is always some kind of physical process, which means that it is impossible to understand the limits of our computational capabilities without specifying what physical implementation they are. correspond. Unfortunately, at that time, among scientists, the prevailing view of computation as some kind of abstract logical procedure, which should be studied by mathematicians, not physicists.

As computers proliferated, quantum scientists came to the conclusion that it was practically impossible to directly calculate the state of an evolving system consisting of only a few dozen interacting particles, such as a methane molecule (CH 4). This is explained by the fact that for full description a complex system, it is necessary to keep in the computer memory an exponentially large (in the number of particles) number of variables, the so-called quantum amplitudes. A paradoxical situation arose: knowing the equation of evolution, knowing with sufficient accuracy all the potentials of interaction of particles with each other and the initial state of the system, it is practically impossible to calculate its future, even if the system consists of only 30 electrons in a potential well, and there is a supercomputer with rAM, the number of bits of which is equal to the number of atoms in the visible region of the Universe (!). And at the same time, to study the dynamics of such a system, you can simply set up an experiment with 30 electrons, placing them in a given potential and initial state. This, in particular, was pointed out by the Russian mathematician Yu. I. Manin, who pointed out in 1980 to the need to develop a theory of quantum computing devices. In the 1980s, the same problem was studied by the American physicist P. Benev, who clearly showed that a quantum system can perform calculations, as well as the English scientist D. Deutsch, who theoretically developed a universal quantum computer superior to the classical analogue.

The Nobel Prize laureate in physics R. Feynman, who is well known to regular readers of Science and Life, has attracted great attention to the problem of developing quantum computers. Thanks to his authoritative appeal, the number of specialists who paid attention to quantum computing has increased many times over.

Yet for a long time it was unclear whether hypothetical computing power could be used quantum computer to speed up the solution of practical problems. But in 1994, P. Shor, an American mathematician and employee of Lucent Technologies (USA), stunned the scientific world by proposing a quantum algorithm that allows fast factorization of large numbers (the importance of this problem was already discussed in the introduction). In comparison with the best of the classical methods known to date, Shor's quantum algorithm gives a multiple acceleration of computations, and the longer the factorized number, the greater the gain in speed. The fast factorization algorithm is of great practical interest for various special services that have accumulated banks of unencrypted messages.

In 1996, Shor's colleague at Lucent Technologies L. Grover proposed a quantum algorithm quick search in an unordered database. (An example of such a database is phone book, in which the names of the subscribers are arranged not alphabetically, but in an arbitrary way.) The task of searching, choosing the optimal element among numerous options is very often encountered in economic, military, engineering problems, in computer games... Grover's algorithm allows not only to speed up the search process, but also to approximately double the number of parameters taken into account when choosing the optimum.

The real creation of quantum computers was hampered by essentially the only serious problem - errors, or interference. The fact is that the same level of interference spoils the process of quantum computing much more intensively than classical ones. The ways of solving this problem were outlined in 1995 by P. Shor, who developed a scheme for encoding quantum states and correcting errors in them. Unfortunately, the topic of error correction in quantum computers is as important as it is difficult to cover in this article.

DEVICE OF A QUANTUM COMPUTER

Before telling how a quantum computer works, let us recall the main features of quantum systems (see also "Science and Life" No. 8, 1998; No. 12, 2000).

To understand the laws of the quantum world, one should not directly rely on everyday experience. In the usual way (in the everyday sense), quantum particles behave only if we constantly "peep" at them, or, more strictly speaking, we constantly measure what state they are in. But as soon as we "turn away" (stop observing), quantum particles immediately pass from a completely definite state at once into several different hypostases. That is, an electron (or any other quantum object) will be partially located at one point, partially at another, partially at a third, etc. This does not mean that it is divided into slices, like an orange. Then it would be possible to reliably isolate some part of the electron and measure its charge or mass. But experience shows that after measurement, the electron always turns out to be "safe and sound" at one single point, despite the fact that before that he managed to visit almost everywhere simultaneously. Such a state of an electron, when it is located at several points in space at once, is called superposition of quantum states and are usually described by the wave function introduced in 1926 by the German physicist E. Schrödinger. The magnitude of the value of the wave function at any point, squared, determines the probability of finding a particle at this point at a given moment. After measuring the position of the particle, its wave function contracts (collapses) to the point where the particle was detected, and then starts to spread again. The property of quantum particles to be simultaneously in many states, called quantum parallelism , used successfully in quantum computing.

Quantum bit

The main cell of a quantum computer is a quantum bit, or, in short, qubit(q-bit). It is a quantum particle with two basic states, which are denoted 0 and 1, or, as is customary in quantum mechanics, and. Two values \u200b\u200bof a qubit can correspond, for example, the ground and excited states of an atom, up and down directions of the spin of an atomic nucleus, direction of current in a superconducting ring, two possible positions of an electron in a semiconductor, etc.

Quantum register

The quantum register works almost the same as the classical one. This is a string of quantum bits, over which one- and two-bit logical operations can be performed (similar to the use of NOT, 2AND-NOT, etc., in a classical register).

The basic states of the quantum register formed by L qubits include, as in the classical one, all possible sequences of zeros and ones of length L. There can be 2 L different combinations in total. They can be considered as writing numbers in binary form from 0 to 2 L -1 and denoted. However, these basic states do not exhaust all possible values \u200b\u200bof the quantum register (in contrast to the classical one), since there are also superposition states specified by complex amplitudes related by the normalization condition. Most of the possible values \u200b\u200bof the quantum register (except for the basic ones) simply do not have a classical analogue. The states of the classical register are just a pitiful shadow of the wealth of states in a quantum computer.

Imagine that the register is external influence, for example, electrical impulses are applied to a part of the space or laser beams are directed. If it is a classical register, a pulse, which can be viewed as a computational operation, will change L variables. If it is a quantum register, then the same pulse can simultaneously transform to variables. Thus, a quantum register is, in principle, capable of processing information one times faster than its classical counterpart. From this it is immediately clear that the small quantum registers (L<20) могут служить лишь для демонстрации отдельных узлов и принципов работы квантового компьютера, но не принесут большой практической пользы, так как не сумеют обогнать современные ЭВМ, а стоить будут заведомо дороже. В действительности квантовое ускорение обычно значительно меньше, чем приведенная грубая оценка сверху (это связано со сложностью получения большого количества амплитуд и считывания результата), поэтому практически полезный квантовый компьютер должен содержать тысячи кубитов. Но, с другой стороны, понятно, что для достижения действительного ускорения вычислений нет необходимости собирать миллионы квантовых битов. Компьютер с памятью, измеряемой всего лишь в килокубитах, будет в некоторых задачах несоизмеримо быстрее, чем классический суперкомпьютер с терабайтами памяти.

It should be noted, however, that there is a class of problems for which quantum algorithms do not provide significant acceleration in comparison with classical ones. One of the first to show this was the Russian mathematician Yu. Ozhigov, who built a number of examples of algorithms that cannot be accelerated by a single clock on a quantum computer.

Nevertheless, there is no doubt that computers operating according to the laws of quantum mechanics are a new and decisive stage in the evolution of computing systems. It remains only to build them.

QUANTUM COMPUTERS TODAY

Prototypes of quantum computers exist today. True, so far experimentally it is possible to collect only small registers consisting of only a few quantum bits. For example, recently a group led by the American physicist I. Chang (IBM) announced the assembly of a 5-bit quantum computer. This is undoubtedly a great success. Unfortunately, the existing quantum systems are not yet able to provide reliable computations, since they are either insufficiently controllable, or very susceptible to noise. However, there are no physical restrictions on the construction of an effective quantum computer, it is only necessary to overcome technological difficulties.

There are several ideas and suggestions on how to make reliable and easily controllable quantum bits.

I. Chang develops the idea of \u200b\u200busing the spins of the nuclei of some organic molecules as qubits.

Russian researcher M.V. Feigelman, working at the Institute for Theoretical Physics. LD Landau RAS, suggests assembling quantum registers from miniature superconducting rings. Each ring plays the role of a qubit, and states 0 and 1 correspond to the direction of the electric current in the ring - clockwise and counterclockwise. Such qubits can be switched using a magnetic field.

At the Physico-Technological Institute of the Russian Academy of Sciences, a group led by Academician K.A. Valiev proposed two options for placing qubits in semiconductor structures. In the first case, the role of a qubit is played by an electron in a system of two potential wells created by a voltage applied to mini-electrodes on the semiconductor surface. States 0 and 1 are the positions of an electron in one of these wells. The qubit is switched by changing the voltage on one of the electrodes. In another variant, the qubit is the nucleus of a phosphorus atom inserted at a certain point in the semiconductor. States 0 and 1 are the directions of the nuclear spin along or against the external magnetic field. The control is carried out using the combined action of magnetic pulses of the resonant frequency and voltage pulses.

Thus, research is actively carried out and it can be assumed that in the very near future - in ten years - an effective quantum computer will be created.

A LOOK INTO THE FUTURE

Thus, it is quite possible that in the future, quantum computers will be manufactured using traditional methods of microelectronic technology and contain many control electrodes, resembling a modern microprocessor. In order to reduce the noise level, which is critical for the normal operation of a quantum computer, the first models will most likely have to be cooled with liquid helium. The first quantum computers are likely to be bulky and expensive devices that would not fit on a desk and were maintained by a large staff of system programmers and hardware adjusters in white coats. First, only government agencies will gain access to them, then rich commercial organizations. But the era of conventional computers began in about the same way.

And what will become of classic computers? Will they die? Unlikely. Both classical and quantum computers have their own areas of application. Although, in all likelihood, the ratio in the market will gradually shift towards the latter.

The introduction of quantum computers will not lead to the solution of fundamentally unsolvable classical problems, but will only speed up some calculations. In addition, quantum communication will become possible - the transmission of qubits over a distance, which will lead to the emergence of a kind of quantum Internet. Quantum communication will provide a protected (by the laws of quantum mechanics) from eavesdropping connection of everyone with each other. Your information stored in quantum databases will be more secure from copying than it is now. Firms producing programs for quantum computers will be able to protect them from any, including illegal, copying.

For a deeper understanding of this topic, you can read the review article by E. Riffel, V. Polak "Fundamentals of Quantum Computing" published in the journal "Quantum Computers and Quantum Computing" published in Russia (No. 1, 2000). (By the way, this is the first and so far the only journal in the world devoted to quantum computing. Additional information about it can be found on the Internet at http://rcd.ru/qc.). Having mastered this work, you will be able to read scientific articles on quantum computing.

A little more preliminary mathematical training will be required when reading the book by A. Kitaev, A. Shen, M. Vyaly "Classical and quantum computing" (Moscow: MTsNMO-CheRo, 1999).

A number of fundamental aspects of quantum mechanics that are essential for quantum computing are discussed in the book by V.V.Belokurov, O.D. Timofeevskaya, O. A. Khrustalev "Quantum teleportation is an ordinary miracle" (Izhevsk: RKhD, 2000).

RKhD Publishing House is preparing to publish in the form of a separate book a translation of A. Steen's review devoted to quantum computers.

The following literature will be useful not only cognitively, but also historically:

1) Yu. I. Manin. Computable and non-computable.

M .: Sov. radio, 1980.

2) I. von Neumann. Mathematical foundations of quantum mechanics.

Moscow: Nauka, 1964.

3) R. Feynman. Simulation of physics on computers // Quantum computer and quantum computing:

Sat. in 2 volumes - Izhevsk: RKhD, 1999.Vol. 2, p. 96-123.

4) R. Feynman. Quantum mechanical computers

// Ibid, p. 123.-156.

See in issue on the same topic

The amount of information in the world is increasing annually by 30%. In the last five years alone, humanity has been produced more data than in all previous history. IoT systems are emerging, in which each sensor sends and receives a huge amount of data every second, and analysts predict that the number of connected to the Internet of Things will soon exceed the number of human users. These colossal amounts of information need to be stored somewhere and processed somehow.

There are already supercomputers with a capacity of more than 50 petaflops (1 petaflops \u003d 1,000 trillion operations per second). However, sooner or later we will run into the physical limit of the possible processor power. Of course, supercomputers will still be able to grow in size, but this is not a solution to the problem, since size will eventually reach its limits. According to scientists, Moore's law will soon cease to be fulfilled and mankind will need new, much more powerful devices and data processing technologies. Therefore, already now large IT companies are working on the creation of a completely new revolutionary type of computers, the capacities of which will be hundreds of times higher than those that we have today. This is a quantum computer. Experts promise that thanks to him, it may be possible to find a cure for cancer, instantly find criminals, analyzing recordings from cameras, and simulate DNA molecules. Now it is even difficult to imagine what other tasks he will be able to solve.

Microsoft is trying to be at the forefront of the development of this field, studying it for twenty years, because whoever creates a quantum computer first will have an undeniable competitive advantage. Moreover, the company is working not only on the creation of "hardware", but also recently introduced a programming language that developers can use. In fact, very few people can boast that they understand the principles of this revolutionary device, for most of us it is something from the category of fantasy. So what is he like?

One of the most important parts of a computer, on which its power directly depends, is the processor, which, in turn, consists of a huge number of transistors. Transistors are the simplest parts of the system, they are somewhat similar to switches and can only be in two positions: either "on" or "off". It is from the combinations of these provisions that the binary code consisting of zeros and ones is formed, on which all programming languages \u200b\u200bare based.

Accordingly, the more powerful the computer, the more transistors are needed for its operation. Manufacturers are constantly reducing their size, trying to fit as many as possible into processors. For example, the new Xbox One X has billions of them.

Now the size of one transistor is 10 nanometers, that is, one hundred thousandth of a millimeter. But one day the physical limit will be reached, below which the transistor simply cannot be made. In order to avoid a crisis in the development of IT, scientists are working on creating a computer that will work on a completely different principle - quantum. The transistors that will make up a quantum computer can be simultaneously in two positions: "on" and "off" and, accordingly, immediately be both one and zero, this is called "superposition".

If we take 4 standard transistors (bits), then they, working together, can create 16 different combinations of ones and zeros. One at a time.

If we consider 4 quantum transistors (qubits), then they can be all 16 combinations at the same time. This is a huge savings in space and time!

But, of course, creating qubits is very, very difficult. Scientists have to deal with subatomic particles that obey the laws of quantum mechanics, develop a completely new approach to programming and language.

There are different types of qubits. Microsoft experts, for example, are working on creating topological qubits. They are incredibly fragile and easily destroyed by the slightest sound waves or heat radiation. For stable operation, they need to be constantly at a temperature of -273 ° C. However, they also have a number of advantages over other types: the information stored in them is practically not prone to errors, and, accordingly, a quantum computer based on topological qubits will be a highly reliable system.

The Microsoft quantum computer consists of three main levels: the first level is actually a quantum computer that contains qubits and is constantly at a temperature close to absolute zero; the next level is a cryogenic computer - this is also a completely new type of computer that controls a quantum computer and operates at a temperature of –268 ° C; the last level is a computer, at which a person can already work, and managing the entire system. Such computers will be 100-300 times more powerful than the most advanced supercomputers in existence today.

Today the world has come closer than ever to the invention of a real quantum computer: there is an understanding of the principle of its operation, prototypes. And at the moment when the power of ordinary computers to process all the information existing on Earth will no longer be enough, a quantum computer will appear, marking a completely new era of digital technologies.

Computers have evolved rapidly over the past decades. In fact, in the memory of one generation, they have gone from bulky lamp tubes that take up huge rooms to miniature tablets. Memory and speed increased rapidly. But the moment came when tasks appeared that were beyond the control of even super-powerful modern computers.

What is a quantum computer?

The emergence of new tasks beyond the control of conventional computers made people look for new opportunities. And, as an alternative to conventional computers, quantum appeared. A quantum computer is a computer technology based on the elements of quantum mechanics. The main provisions of quantum mechanics were formulated at the beginning of the last century. Its appearance made it possible to solve many problems of physics that did not find solutions in classical physics.

Although the theory of quanta is already in its second century, it still remains understandable only to a narrow circle of specialists. But there are also real results of quantum mechanics, to which we are already accustomed - laser technology, tomography. And at the end of the last century, the theory of quantum computing was developed by the Soviet physicist Yu. Manin. Five years later, David Deutsch unveiled the idea of \u200b\u200ba quantum machine.

Does a quantum computer exist?

But the implementation of ideas turned out to be not so easy. Periodically, there are reports that the next quantum computer has been created. Information technology giants are working on the development of such computers:

D-Wave is a Canadian company that pioneered the production of operational quantum computers. Nevertheless, there is a debate among specialists about how real these computers are and what advantages they give.
IBM - created a quantum computer, and opened access to it for Internet users to experiment with quantum algorithms. By 2025, the company plans to create a model capable of solving already practical problems.
Google - announced the release this year of a computer capable of proving quantum supremacy on conventional computers.
In May 2017, Chinese scientists in Shanghai announced that they had created the most powerful quantum computer in the world, 24 times faster than analogs in signal processing frequency.
In July 2017, at the Moscow Conference on Quantum Technologies, it was announced that a 51-qubit quantum computer had been created.

How is a quantum computer different from a conventional one?

The fundamental difference between a quantum computer in the approach to the computation process.

In a conventional processor, all calculations are based on bits that are in two states, 1 or 0. That is, all the work comes down to analyzing a huge amount of data for compliance with the specified conditions. A quantum computer is based on qubits (quantum bits). Their feature is the ability to be in state 1, 0, as well as simultaneously 1 and 0.
The capabilities of a quantum computer increase significantly, since there is no need to search for the desired answer among the multitude. In this case, the answer is selected from the already available options with a certain degree of probability of matching.

What is a quantum computer for?

The principle of a quantum computer, built on the choice of a solution with a sufficient degree of probability and the ability to find such a solution many times faster than modern computers, determines the purpose of its use. First of all, the emergence of this type of computing technology worries cryptographers. This is due to the ability of a quantum computer to compute passwords with ease. Thus, the most powerful quantum computer created by Russian-American scientists is capable of obtaining keys to existing encryption systems.

There are also more useful applied problems for quantum computers, they are related to the behavior of elementary particles, genetics, healthcare, financial markets, protecting networks from viruses, artificial intelligence, and many others that ordinary computers cannot yet solve.

How does a quantum computer work?

The device of a quantum computer is based on the use of qubits. The following are currently used as the physical execution of qubits:

rings made of superconductors with jumpers, with multidirectional current;
individual atoms exposed to laser beams;
ions;
photons;
variants of using semiconductor nanocrystals are being developed.

Quantum computer - how it works

If there is certainty in work with a classical computer, then the question of how a quantum computer works is not easy to answer. The description of the operation of a quantum computer is based on two phrases that are obscure to most:

superposition principle- we are talking about qubits that can be simultaneously in positions 1 and 0. This allows you to carry out several calculations at the same time, rather than sorting out options, which gives a big gain in time;
quantum entanglement- a phenomenon noted by A. Einstein, consisting in the relationship of two particles. In simple terms, if one of the particles has positive helicity, then the second instantly takes positive. This relationship occurs regardless of distance.

Who Invented the Quantum Computer?

The basis of quantum mechanics was presented at the very beginning of the last century, as a hypothesis. Its development is associated with such brilliant physicists as Max Planck, A. Einstein, Paul Dirac. In 1980 Yu. Antonov proposed the idea of \u200b\u200bthe possibility of quantum computing. And a year later, Richard Feineman, in theory, modeled the first quantum computer.

Now the creation of quantum computers is in the development stage, and it is even difficult to imagine what a quantum computer is capable of. But it is absolutely clear that the development of this direction will bring people many new discoveries in all fields of science, will allow them to look into the micro and macrocosm, learn more about the nature of reason and genetics.

Science does not stand still, and it would seem that what was considered yesterday mysticism is today an indisputable reality. So now, myths about parallel worlds can become a common fact in the future. It is believed that research in the field of creating a quantum computer will help arrive at this statement. Japan is in the lead, more than 70% of all studies are in this country. The essence of this discovery is better understood by those who are somehow connected with physics. But most of us graduated from high school, where a grade 11 textbook covers some of the issues of quantum physics.

How it all began

Let us recall that the beginning was laid by two main discoveries, for which their authors were awarded the Nobel Prize. In 1918, Max Planck discovered quantum, and Albert Einstein in 1921 photon. The idea of \u200b\u200bcreating a quantum computer was born in 1980, when it was proved that quantum theory was true. And ideas began to be put into practice only in 1998. Massive, and at the same time quite effective work, has been carried out only in the last 10 years.

The basic principles are clear, but with each step forward, more and more problems arise, the resolution of which takes a lot of time, although a lot of laboratories around the world are dealing with this problem. The requirements for such a computer are very high, since the measurement accuracy must be very high and the number of external influences must be minimized, each of which will distort the operation of a quantum system.

WHY DO YOU NEED A QUANTUM COMPUTER?

What does a quantum computer work on?

Everyone, to a greater or lesser extent, has an idea of \u200b\u200bhow a regular computer works. Its meaning is to use binary coding, where the presence of a certain voltage value is taken as 1, and the absence of 0., expressed as 0 or 1, is considered a bit. The work of a quantum computer is related to the concept of spin. For whom physics is limited to school knowledge, they can assert about the existence of three elementary particles and about their simple characteristics, such as mass and charge.

But physicists are constantly expanding the class of elementary particles and their characteristics, one of which is spin. And a certain direction of the spin of the particle is taken as 1, and the opposite direction to it as 0. This is similar to the device of a transistor. The main element will already be called a quantum bit or qubit. It can be photons, atoms, ions, nuclei of atoms.

The main condition here is the presence of two quantum states. A change in the state of a certain bit in an ordinary computer does not lead to a change in others, but in a quantum computer, a change in one will introduce a change in the state of other particles. This change can be controlled, and imagine that there are hundreds of such particles.

Just imagine how many times the productivity of such a machine will increase. But the creation of a complete newest computer is only a hypothesis; there is a lot of work to be done by physicists in that area of \u200b\u200bquantum mechanics, which is called multiparticle. The first mini quantum computer consisted of 16 qubits. Recently, computers using 512 qubits have been released, but they are already being used to increase the speed of performing the most complex computing operations. Quipper is a language designed specifically for such machines.

Sequence of operations

In creating a new generation computer, four directions are distinguished, which differ in that they act as logical qubits:

the direction of the spins of the particles that make up the basis of the atom;
the presence or absence of a Cooper pair in an established place in space;
what is the state of the external electron;
different states of the photon.

Now let's look at the scheme by which the computer works. To begin with, a set of qubits is taken and their initial parameters are recorded. Conversions are performed using logical operations, the resulting value is written, which is the result of the computer output. Qubits act as wires, and transformations make up logical blocks. Such a processor was proposed by D. Deutsch, who in 1995 was able to create a chain capable of performing any calculations at the quantum level. But such a system gives small errors that can be slightly reduced by increasing the number of operations involved in the algorithm.

How Does a Quantum Computer Work?

What have you achieved

So far, only two types of quantum computers have been developed, but science is not standing still. The work of both machines is based on quantum phenomena:

associated with superconductivity. When it is violated, quantization is observed;
based on such a property as coherence. The computational speed of such computers is twice as fast as the number of qubits.

The second type of those considered is considered a priority in the field of creating quantum computers.

Achievements of various countries.

In short, the achievements of the last 10 years are significant. One can note a two-qubit computer with software created in America. He also turned out to be able to release a two-qubit computer with a diamond crystal. In the role of qubits, we used the direction of the spin of nitrogen particles, its components: the nucleus and the electron. To provide significant protection, a very sophisticated system has been developed that allows you to give results with 95% accuracy.

ICQT 2017. John Martinis, Google: The Quantum Computer: Life After Moore's Law

What is all this for

We have already talked about creating quantum computers. These computers are not the result of what they were striving for, but they found their buyer. American defense company Lockheed Martin paid $ 10 million. Their acquisition is capable of finding errors in the most complex program installed on the F-35 fighter. Google wants to launch machine learning software through its acquisition.

Future

In the development of a quantum computer large companies and the state are very interested. It will lead to new discoveries in the development of a cryptographic algorithm. Time will decide whether this plays into the hands of the state or hackers. But the work on creating and recognizing crypto keys will be done instantly. Many problems associated with a bank card will be solved.

Messages will be transmitted at great speed and there will be no problem to contact any point on the globe, and maybe even beyond.

Such a computer will help to do, especially in decoding the genetic code. This will lead to the resolution of many medical problems.

And, of course, it will slightly open the door to the land of mystical secrets, parallel worlds.

The strongest shocks await us. Everything we are used to is only a part of the world that has already been given the name of Quantum Reality. To go beyond the material world will help, which constitute the principle of operation of a quantum computer.

January 29th, 2017

For me, the phrase "quantum computer" is comparable, for example, with a "photon engine", that is, it is something very complex and fantastic. However, I read now in the news - "a quantum computer is being sold to anyone who wants it." It is strange, whether under this expression they now mean something else, or is it just a fake?

Let's take a closer look ...

HOW IT ALL BEGAN?

It was not until the mid-1990s that the theory of quantum computers and quantum computing was established as a new field of science. As is often the case with great ideas, it is difficult to pick out a discoverer. Apparently, the Hungarian mathematician I. von Neumann was the first to draw attention to the possibility of developing quantum logic. However, at that time, not only quantum, but also ordinary, classical, computers had not yet been created. And with the advent of the latter, the main efforts of scientists turned out to be directed primarily towards the search and development of new elements for them (transistors, and then integrated circuits), and not towards the creation of fundamentally different computing devices.

As computers proliferated, quantum scientists came to the conclusion that it was practically impossible to directly calculate the state of an evolving system consisting of only a few dozen interacting particles, such as a molecule of methane (CH4). This is explained by the fact that for a complete description of a complex system, it is necessary to keep in the computer memory an exponentially large (in terms of the number of particles) number of variables, the so-called quantum amplitudes. A paradoxical situation arose: knowing the equation of evolution, knowing with sufficient accuracy all the potentials of interaction of particles with each other and the initial state of the system, it is practically impossible to calculate its future, even if the system consists of only 30 electrons in a potential well, and there is a supercomputer with random access memory , the number of bits of which is equal to the number of atoms in the visible region of the Universe (!). And at the same time, to study the dynamics of such a system, you can simply set up an experiment with 30 electrons, placing them in a given potential and initial state. This, in particular, was drawn by the Russian mathematician Yu. I. Manin, who pointed out in 1980 to the need to develop a theory of quantum computing devices. In the 1980s, the same problem was studied by the American physicist P. Benev, who clearly showed that a quantum system can perform calculations, as well as the English scientist D. Deutsch, who theoretically developed a universal quantum computer superior to the classical analogue.

The Nobel Prize laureate in physics R. Feynman attracted much attention to the problem of developing quantum computers. Thanks to his authoritative appeal, the number of specialists who paid attention to quantum computing has increased many times.

The basis of Shor's algorithm: the ability of qubits to store multiple values \u200b\u200bsimultaneously)

And yet, for a long time it remained unclear whether the hypothetical computing power of a quantum computer could be used to speed up solving practical problems. But in 1994, P. Shore, an American mathematician and employee of Lucent Technologies (USA), stunned the scientific world by proposing a quantum algorithm that allows fast factorization of large numbers (the importance of this problem was already discussed in the introduction). In comparison with the best of the classical methods known to date, Shor's quantum algorithm gives a multiple acceleration of computations, and the longer the factorized number, the greater the gain in speed. The fast factorization algorithm is of great practical interest for various special services that have accumulated banks of unencrypted messages.

In 1996, Shor's colleague at Lucent Technologies, L. Grover, proposed a quantum fast search algorithm in an unordered database. (An example of such a database is a telephone book, in which the names of subscribers are arranged not alphabetically, but in an arbitrary way.) The task of searching, choosing an optimal element among numerous options is very common in economic, military, engineering problems, and in computer games. Grover's algorithm allows not only to speed up the search process, but also to approximately double the number of parameters taken into account when choosing the optimum.

In simple words, then: " a quantum system gives a result that is correct only with some probability. In other words, if you count 2 + 2, then 4 will come out with only some degree of accuracy. You will never get exactly 4. The logic of its processor is not at all similar to the processor we are used to.

There are methods to calculate the result with a predetermined accuracy, naturally with an increase in the amount of computer time.
This feature determines the list of tasks. And this feature is not advertised, and the public gets the impression that a quantum computer is the same as a regular PC (the same 0 and 1), only fast and expensive. This is fundamentally not the case.

Yes, and one more thing - for a quantum computer and quantum computing in general, especially in order to use the "power and speed" of quantum computing - special algorithms and models developed specifically for the specifics of quantum computing are needed. Therefore, the complexity of using a quantum computer is not only in the presence of "hardware", but also in the compilation of new calculation methods that have not yet been used. "

And now let's move on to the practical implementation of a quantum computer: after all, a commercial 512-qubit D-Wave processor has existed for some time now!

Here, he seems to be a real breakthrough !!! And a group of reputable scientists in the equally reputable journal Physical Review convincingly testifies that the effects of quantum entanglement have indeed been discovered in D-Wave.

Accordingly, this device with good reason has the right to be called a real quantum computer, architecturally it is quite possible to further increase the number of qubits, and therefore has remarkable prospects for the future ... (T. Lanting et al. Entanglement in a Quantum Annealing Processor. PHYSICAL REVIEW X 4 , 021041 (2014) (http://dx.doi.org/10.1103/PhysRevX.4.021041))

True, a little later, another group of respectable scientists in the no less respectable journal Science, who studied the same D-Wave computing system, evaluated it purely practically: how well this device performs its computing functions. And this group of scientists, as thoroughly and convincingly as the first, demonstrates that in real test tests that are optimal for this design, the D-Wave quantum computer does not give any speed gain in comparison with ordinary, classical computers. (T.F. Ronnow, M. Troyer et al. Defining and detecting quantum speedup. SCIENCE, Jun 2014 Vol. 344 # 6190 (http://dx.doi.org/10.1126/science.1252319))

As a matter of fact, for an expensive but specialized "machine of the future" there were no problems where it could demonstrate its quantum superiority. In other words, the very meaning of the rather expensive efforts to create such a device is in great doubt ...
The results are as follows: now in the scientific community there is no longer any doubt that in the D-Wave computer processor, the work of the elements really takes place on the basis of real quantum effects between qubits.

But (and this is an extremely serious BUT) the key features in the design of the D-Wave processor are such that, in real operation, all its quantum physics does not give any advantage in comparison with an ordinary powerful computer with special software, sharpened for solving optimization problems.

Simply put, not only scientists testing D-Wave have not yet been able to see a single real problem where a quantum computer could convincingly demonstrate its computational superiority, but even the manufacturer itself has no idea what kind of task it might be ...

It's all about the design features of the 512-qubit D-Wave processor, which is assembled from groups of 8 qubits. At the same time, within these groups of 8 qubits, they all communicate directly with each other, but between these groups, the connections are very weak (ideally, ALL processor qubits should communicate directly with each other). This, of course, VERY significantly reduces the complexity of building a quantum processor ... BUT, from here a lot of other problems grow, closing in the final and on cryogenic equipment, which is very expensive to operate, cooling the circuit to ultra-low temperatures.

So what are we being offered now?

Canadian company D-Wave has announced the start of sales of its D-Wave 2000Q quantum computer, which was announced last September. Adhering to its own analogue of Moore's Law, according to which the number of transistors on an integrated circuit doubles every two years, D-Wave placed 2,048 qubits on the CPU (Quantum Processing Unit). The dynamics of growth in the number of qubits on the CPU in recent years looks like this:

2007 — 28
…
— 2013 — 512
— 2014 — 1024
— 2016 — 2048.

Moreover, unlike traditional processors, CPUs and GPUs, doubling of qubits is accompanied not by a 2-fold, but by a 1000-fold increase in performance. Compared to a computer with a traditional architecture and configuration of a single-core CPU and a 2500-core GPU, the difference in speed is 1,000 to 10,000 times. All these numbers are certainly impressive, but there are several "buts".

First, the D-Wave 2000Q is extremely expensive - $ 15 million. It is a rather massive and complex device. Its brain is a non-ferrous metal CPU called niobium, the superconducting properties of which (necessary for quantum computers) arise in a vacuum at temperatures close to absolute zero below 15 millikelvin (this is 180 times lower than the temperature in outer space).

Maintaining such an extremely low temperature requires high energy consumption, 25 kW. But still, according to the manufacturer, this is 100 times less than that of equivalent in performance traditional supercomputers. So the performance of the D-Wave 2000Q per watt of power consumption is 100 times higher. If the company manages to continue to follow its "Moore's Law", then in its future computers, this difference will grow exponentially, while maintaining power consumption at the current level.

First, quantum computers have a very specific purpose. In the case of the D-Wave 2000Q, we are talking about the so-called. adiabatic computers and solving problems of quantum normalization. They arise in particular in the following areas:

Machine learning:

Identifying statistical anomalies
- finding compressed models
- image and pattern recognition
- training of neural networks
- software verification and approval
- classification of structureless data
- diagnostics of errors in the circuit

Safety and planning

Virus and Network Hacking Detection
- resource allocation and finding optimal paths
- determination of belonging to a set
- analysis of chart properties
- factorization of integers (used in cryptography)

Financial modeling

Identifying market volatility
- development of trading strategies
- optimization of trading trajectories
- optimization of asset pricing and hedging
- portfolio optimization

Healthcare and medicine

Fraud detection (probably health insurance)
- generation of targeted ("molecular targeting") drug therapy
- optimization of [cancer] treatment with radiotherapy
- creation of protein models.

The first buyer of the D-Wave 2000Q was TDS (Temporal Defense Systems), a cyber security company. In general, D-Wave products are used by such companies and institutions as Lockheed Martin, Google, Ames Research Center at NASA, University of Southern California and Los Alamos National Laboratory at the US Department of Energy.

Thus, we are talking about a rare (D-Wave is the only company in the world that produces commercial samples of quantum computers) and expensive technology with a rather narrow and specific application. But the growth rate of its productivity is amazing, and if this dynamic continues, then thanks to the adiabatic computers D-Wave (which other companies may eventually join), real breakthroughs in science and technology can await us in the coming years. Of particular interest is the combination of quantum computers with such a promising and rapidly developing technology as artificial intelligence, especially since such an authoritative expert as Andy Rubin sees a prospect in this.

By the way, you knew that IBM Corporation allowed Internet users to connect to the universal quantum computer it built for free and experiment with quantum algorithms. This device won't have the power to crack public-key cryptographic systems, but if IBM's plans come true, more sophisticated quantum computers are just around the corner.

The quantum computer, which IBM has made available, contains five qubits: four for manipulating data, and the fifth for correcting errors during computation. Error correction is the main innovation that its developers are proud of. It will make it easier to increase the number of qubits in the future.

IBM emphasizes that its quantum computer is universal and capable of executing any quantum algorithms. This sets it apart from the adiabatic quantum computers being developed by D-Wave. Adiabatic quantum computers are designed to find optimal solutions to functions and are not suitable for other purposes.

It is believed that universal quantum computers will allow you to solve some problems that are beyond the power of conventional computers. The most famous example of such a problem is the factorization of numbers. A typical computer, even a very fast one, will take hundreds of years to find the prime factors of a large number. A quantum computer will find them using Shor's algorithm almost as quickly as multiplying integers.

The inability to quickly factor numbers into prime factors is at the heart of public key cryptographic systems. If one learns to perform this operation at the speed that quantum algorithms promise, then most of modern cryptography will have to be forgotten.

You can run Shor's algorithm on an IBM quantum computer, but until there are more qubits, there is little benefit. This will change over the next ten years. By 2025, IBM plans to build a quantum computer containing fifty to one hundred qubits. According to experts, already with fifty qubits, quantum computers will be able to solve some practical problems.

Here's a little more interesting things about computer technology: read how, but And it turns out you can and what kind of