How can a quantum computer hack modern encryption systems and reduce the cost of ammonia production?
The paradoxes and riddles of quantum physics excite the minds of scientists for a long time. Today, on the basis of the unusual properties of quantum particles, new devices and devices are being built, which can many times exceed the classical analogs by their characteristics.
Alexey Fedorov, research director of the Quantum Information Technologies group of the RCC, spoke to Acronis employees about the events in the “Quantum industry”. In this post, we provide a transcript of his lecture on quantum technologies with additions to share useful and interesting data with Acronis subscribers on Habrahabr.
Large-scale projects are being implemented in the USA, Europe, China and Russia. The quantum computer is of the greatest interest - not only universities are involved in the race to build it, but also large corporations, including Google, IBM, Microsoft and Intel. It is predicted that quantum computers can make a revolution in a number of areas, for example, in information protection, artificial intelligence and modeling new materials.
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In the modern context, quantum technologies are the methods for controlling individual quantum objects, such as atoms, photons, electrons, ions, and so on. Unlike classical systems, which are always in one of the possible states, quantum systems can be in a state of quantum superposition: they can be simultaneously in all admissible states. An example of the difference between the classical world and the quantum world can be a coin. A coin can define two states - an eagle or tails - and encode them as 0 and 1. Then the classic coin can be either in the state 0 or in the state 1. Two coins can be in one of 4 possible states at the same time. Four coins - in one of 16 states. Ten coins - in one of 1024 states.
The principle of superposition allows one “quantum coin” to be not only strictly an eagle or tail, but also to be in one of an infinite number of “intermediate” states between the tail and tail. It will be more accurate to say that a quantum coin can be in the state of an eagle and tails at the same time. At the same time, two alternatives that are incompatible from the classical point of view (a coin dropped by an eagle and a coin dropped by a tail) seem to overlap each other within a single quantum state. This is what scientists call quantum superposition, and the fact that our brain, which grew up in the classical world, is not even able to imagine - one can only get used to it. At the same time, in order to fully describe such a quantum superposition, two complex numbers are required, corresponding to each of the classically distinct alternatives. Two “quantum coins” can be in a superposition of 4 states. A 10 “quantum coins” - in a superposition of 1024 states. Such “quantum coins” are called qubits — quantum analogs of information bits. To describe a system of n quits, 2 ^ n complex numbers are required.
The main feature of quantum computing is precisely this: with an increase in the number of qubits, the number of parameters with which we operate in calculations increases exponentially. If there are even 50 qubits, the number of complex numbers needed to describe their state - 2 ^ 50 - will be so large that it will be impossible to accurately model such a system even on the most powerful supercomputer. Such a threshold is one of the possible explanations for a phenomenon called quantum supremacy or quantum advantage: the possibility of using a quantum computer to solve problems that existing classical computers are not capable of.
Quantum Quest and Quantum Race
However, to build such a computer is not easy. To do this, you need to solve a whole “quest” for managing quantum matter. At the moment, many laboratories in the world are developing new methods for managing quantum objects. The quantum race is going on at the same time both among corporations and in the scientific community. Leading developers are all new and new solutions. But the quantum race is of fundamental importance - beyond the threshold of quantum superiority we are waiting for new discoveries in completely different areas of physics: from low temperature physics to high energy physics. In addition, quantum computers also have great potential for solving practical problems; therefore, corporations are involved in its development.
What is the quest for managing quantum matter? On the one hand, it is necessary to have a sufficiently large number of qubits to provide a large state space, but, on the other hand, it is necessary to control each qubit separately. It is clear that the larger the system, the more difficult it is to manage at the level of individual individual components. This is especially important for quantum physics, but, if you think about it, it concerns other spheres of human activity. For example, if you want to create a huge and cool company, you have to hire a lot of talented people. But the more these people are, the more difficult their interactions will be, and the more difficult it will be to control them :-)
In the quantum world, the search for a balance between scale and predictability is the biggest challenge today. But, having overcome it, we will be able to develop powerful quantum computers capable of solving interesting problems. For example, IBM uses the term quantum volume - this is the number of qubit to the number of errors when performing an operation. This is a very visual measure, it shows that it is not enough just to say how many qubits are in the system; the degree of control over them is also important, which allows you to avoid mistakes. The growth of the quantum volume requires the growth of both the quantity and the “quality” of qubits.
It should always be borne in mind that the probability of errors is an inherent property of the quantum “iron”. Therefore, speaking of qubits, it is necessary to separate physical qubits and logical qubits. Physical qubits are real atoms or superconducting chains, so to say “stamped” elements. Logical qubits are those objects over which there is real control, and they can be accessed with fixed parameters without errors. The computing power of a quantum computer is ultimately determined by the number of logical qubits, which work flawlessly. In terms of quantum volume, it can be understood this way: if the level of errors is zero, then further computing capabilities (quantum volume) grows due to an increase in the number of logical qubits.
If we talk about the achievements in the field of working quantum computers, it is impossible not to mention the IBM computer on 50 qubits. He became one of the first quantum computers of this scale. The workhorse of IBM's quantum computers is superconducting qubits, which for their work must be cooled to very low temperatures. In the IBM quantum processor, individual control over each qubit is not implemented and the level of errors is rather high, but the chip itself already exists. IBM also has open 5-qubit and 16-qubit quantum computers that can be used by anyone over the Internet. In addition, in several years the corporation plans to make a system for 100 qubits. IBM recently announced the IBM System One integrated quantum computer, which is a complete device that, according to the developers, does not require any special working conditions - this brings the system closer to users, but solving practical and relevant tasks with such a computer difficult to say.
Intel is on the threshold of the same 50-qubit boundary, but uses a different technology to create qubits. And this is good, because if one of the corporations encounters problems in the implementation of its approach, the second will continue to move towards progress.
The leader of the quantum race today can be considered Google, which was demonstrated a quantum computer of 72 qubits. The basic technology at Google is the same as that of IBM - superconducting qubits. A group of scientists and developers of Google also published a number of scientific articles describing approaches to achieving quantum supremacy. So, in the near future, we can expect a demonstration of quantum superiority from the company with the help of a quantum processor developed by them.
In the academic community, a system of 51 qubits was also created — the group managed by Mikhail Lukin (a graduate of the Fiztech and the head of the International Advisory Board of the Russian Quantum Center) based on ultracold neutral atoms, as well as a system of 53 qubits from the group of Christopher Monroe of the University of Maryland, which also He is the founder of IonQ, which develops a commercial quantum computer on ions. By the way, IonQ is not the only example of a startup in the field of quantum computing - there are more than a dozen of them now.
It is obvious that China has great potential in the quantum sphere. “Celestial” is carrying out ambitious plans, planning to construct the largest quantum computer, and the developers already have 12 billion dollars to create the National Quantum Laboratory.
The D-Wave company stands somewhat apart. There are thousands of qubits in the D-Wave processor, but they work in a different mode - the quantum annealing mode. This allows you to solve with the help of such a computer, in fact, only one task. Despite the fact that companies, such as Google and Volkswagen, are already working with D-Wave, there are heated debates about the advantages of such a quantum computer company.
Despite all efforts, today quantum computers do not allow to solve so many practical problems, but the potential looks impressive. Now the development of quantum computing goes in two directions:
In any case, quantum computers allow you to operate with a large state space and this can be useful, for example, for solving search problems, optimizing various processes and modeling complex systems.
Due to the fact that IBM offers everyone to use a quantum computer, modern quantum programmers are already trained in assembling tasks and running them on small quantum computers. For example, for searching through an unordered database, the quantum algorithm has a quadratic advantage. In such a task, an unordered database can be represented as some kind of “black box”, to the input of which requests are sent (addresses of elements in this database), and the black box answers them “yes” or “no” (does the element located on given address, request requirements). Imagine that in some database the address of each element consists of n bits, and in this database there is only one element that satisfies certain conditions. To find this element, we on average need about 2 ^ n queries (more precisely 2 ^ (n-1)), since due to the disorder of the database, all we have to do is to iterate through all possible addresses (of which 2 ^ n pieces) until we are finally lucky and we don’t get to the desired item. In the case, if we have a quantum analogue of a similar black box (it is also called a “quantum oracle”), in order to get an answer we need about 2 ^ (n / 2) requests. The advantage of the “quantum search algorithm”, named after L. Grover, is due to the ability to ask many questions to the quantum box at the same time — to form a superposition of queries.
It is important to note that the task of searching in an unordered database is of a universal nature - it can reduce almost any other task (including NP-complete). However, to solve it, we need a number of queries that grow exponentially with the increasing complexity of the problem (in the example considered, it corresponds to the parameter n). Thus, you should not treat a quantum computer as an omnipotent tool capable of solving arbitrary computational problems with exponential acceleration. In some cases, its capabilities will be much more modest.
Nevertheless, the great potential is already evident today for problems from the sphere of quantum chemistry. For example, in industry, the calculation of the parameters of chemical compounds and the simulation of chemical reactions are in demand. When using classic computers, we lack the capabilities and often have to compromise with accuracy. Quantum computers can help define in detail the chain of reactions, the dynamics of processes, find catalysts for the desired reactions - all this is very useful! One of the most talked about problems today is ammonia production. This compound is actively used in fertilizers for plants, and 1-2% of all energy on earth is spent on its production (data from Quantum Computing Report and BP). If using a quantum computer it would be possible to optimize the process of ammonia production due to accurate knowledge of all parameters, then it would already have recouped all the investments that were made in technology development (remember, 1-2% of world energy).
Recently, at the junction of quantum physics and machine learning, a new direction has emerged - quantum machine learning or, as they often say, Quantum AI. At the same time, it is important that the superiority of a quantum computer over the classical ones in machine learning problems does not require a full-fledged and multiqubit quantum computer. With the help of a quantum computer, for example, it will be possible to speed up individual elements of machine learning algorithms, as well as speed up their learning process. In Google in recent years, quantum machine learning is considered one of the top trends in the entire field of quantum technology.
For the next breakthrough, however, you need not only iron, but also new fast quantum algorithms. There is notable progress. For example, to study the compound Fe2S2 using quantum chemistry algorithms it took thirty years earlier when analyzing on a quantum computer. Due to the search for a more optimal algorithm, this time was reduced to 2 minutes, taking into account the use of the same iron.
However, quantum algorithms are still not enough. So far there are still only a few dozen, and for the full development of the sphere of quantum computing, there should be much more algorithms.
A quantum computer has two sides: dark and light. Until now, we have been talking about the bright side - solving practically demanded problems that cannot be solved with the help of classic computers. But there is also a dark side: a quantum computer solves the factorization problem much better than the classical one. The complexity of this task, as is known, is one of the foundations for ensuring the persistence of common public-key cryptography algorithms. The problem of factorization is extremely difficult for a classical computer, and on a quantum one it can be effectively solved using the Shor algorithm. For example, breaking a 1024-bit RSA key will take millions of years of continuous computing on classic computers, whereas on a quantum computer this task will be solved in 10 hours (assuming that each quantum operation is performed 10 ns and that a computer is available of a sufficient number of logical qubits). So far, quantum computers do not allow anything to be hacked, because RSA requires several thousand controlled qubits to cryptanalyze. And although a potentially dangerous computer does not yet exist, the community is already thinking about protecting against possible problems in the future.
One solution is to use quantum key distribution technology, which allows two parties to exchange cryptographic keys for symmetric encryption. As you know, a single photon cannot be separated, and a quantum state cannot be copied - this is a fundamental limitation of quantum mechanics. On such a principle - the protection of transmitted data by fundamental physical laws - new devices are built. China is leading in this area on the world stage. In Russia, the technology of quantum key distribution is developed in several groups, for example, in the RCC, Moscow State University. Mv Lomonosov and ITMO. The device developed at the RCC has already been tested at Sberbank and Gazprombank.
By the level of errors in the channel, you can find out whether there was a possibility of a key compromise. If the level of errors is below the critical threshold, then it is possible to correct the errors and exclude from it information potentially available to the attacker using classical algorithms and, thus, generate the final secret key. In this case, the protected information remains inaccessible to the attacker.
The central idea is to use quantum-distributed keys in the Varnam cipher, a one-time pad. As far as is known, it is precisely such a system that is implemented in China’s most critical systems.
The second principle of protection is post-quantum cryptography. It includes a new class of public key algorithms, which are based on tasks that are computationally complex for both classical and quantum computers.
Many are interested in the question of whether a quantum computer is harmful to a blockchain. Yes it is possible. Through attacks on digital signatures, as well as through the use of Shor's quantum algorithm and the impact on consensus algorithms by Grover’s quantum algorithm. However, blockchains can also be protected by quantum key distribution or post-quantum cryptography.
Work on quantum computers continues, and today the issues of creating new hardware and developing new algorithms are equally important. This is not so easy to do, because programmers have to deal with completely new entities, and architects need to develop fundamentally new devices for controlling quantum systems. The scientific community and leading corporations are looking toward quantum computers with great optimism - there are reasons for it.
Alexey Fedorov, research director of the Quantum Information Technologies group of the RCC, spoke to Acronis employees about the events in the “Quantum industry”. In this post, we provide a transcript of his lecture on quantum technologies with additions to share useful and interesting data with Acronis subscribers on Habrahabr.
Large-scale projects are being implemented in the USA, Europe, China and Russia. The quantum computer is of the greatest interest - not only universities are involved in the race to build it, but also large corporations, including Google, IBM, Microsoft and Intel. It is predicted that quantum computers can make a revolution in a number of areas, for example, in information protection, artificial intelligence and modeling new materials.
')
In the modern context, quantum technologies are the methods for controlling individual quantum objects, such as atoms, photons, electrons, ions, and so on. Unlike classical systems, which are always in one of the possible states, quantum systems can be in a state of quantum superposition: they can be simultaneously in all admissible states. An example of the difference between the classical world and the quantum world can be a coin. A coin can define two states - an eagle or tails - and encode them as 0 and 1. Then the classic coin can be either in the state 0 or in the state 1. Two coins can be in one of 4 possible states at the same time. Four coins - in one of 16 states. Ten coins - in one of 1024 states.
The principle of superposition allows one “quantum coin” to be not only strictly an eagle or tail, but also to be in one of an infinite number of “intermediate” states between the tail and tail. It will be more accurate to say that a quantum coin can be in the state of an eagle and tails at the same time. At the same time, two alternatives that are incompatible from the classical point of view (a coin dropped by an eagle and a coin dropped by a tail) seem to overlap each other within a single quantum state. This is what scientists call quantum superposition, and the fact that our brain, which grew up in the classical world, is not even able to imagine - one can only get used to it. At the same time, in order to fully describe such a quantum superposition, two complex numbers are required, corresponding to each of the classically distinct alternatives. Two “quantum coins” can be in a superposition of 4 states. A 10 “quantum coins” - in a superposition of 1024 states. Such “quantum coins” are called qubits — quantum analogs of information bits. To describe a system of n quits, 2 ^ n complex numbers are required.
The main feature of quantum computing is precisely this: with an increase in the number of qubits, the number of parameters with which we operate in calculations increases exponentially. If there are even 50 qubits, the number of complex numbers needed to describe their state - 2 ^ 50 - will be so large that it will be impossible to accurately model such a system even on the most powerful supercomputer. Such a threshold is one of the possible explanations for a phenomenon called quantum supremacy or quantum advantage: the possibility of using a quantum computer to solve problems that existing classical computers are not capable of.
Quantum Quest and Quantum Race
However, to build such a computer is not easy. To do this, you need to solve a whole “quest” for managing quantum matter. At the moment, many laboratories in the world are developing new methods for managing quantum objects. The quantum race is going on at the same time both among corporations and in the scientific community. Leading developers are all new and new solutions. But the quantum race is of fundamental importance - beyond the threshold of quantum superiority we are waiting for new discoveries in completely different areas of physics: from low temperature physics to high energy physics. In addition, quantum computers also have great potential for solving practical problems; therefore, corporations are involved in its development.
What is the quest for managing quantum matter? On the one hand, it is necessary to have a sufficiently large number of qubits to provide a large state space, but, on the other hand, it is necessary to control each qubit separately. It is clear that the larger the system, the more difficult it is to manage at the level of individual individual components. This is especially important for quantum physics, but, if you think about it, it concerns other spheres of human activity. For example, if you want to create a huge and cool company, you have to hire a lot of talented people. But the more these people are, the more difficult their interactions will be, and the more difficult it will be to control them :-)
In the quantum world, the search for a balance between scale and predictability is the biggest challenge today. But, having overcome it, we will be able to develop powerful quantum computers capable of solving interesting problems. For example, IBM uses the term quantum volume - this is the number of qubit to the number of errors when performing an operation. This is a very visual measure, it shows that it is not enough just to say how many qubits are in the system; the degree of control over them is also important, which allows you to avoid mistakes. The growth of the quantum volume requires the growth of both the quantity and the “quality” of qubits.
It should always be borne in mind that the probability of errors is an inherent property of the quantum “iron”. Therefore, speaking of qubits, it is necessary to separate physical qubits and logical qubits. Physical qubits are real atoms or superconducting chains, so to say “stamped” elements. Logical qubits are those objects over which there is real control, and they can be accessed with fixed parameters without errors. The computing power of a quantum computer is ultimately determined by the number of logical qubits, which work flawlessly. In terms of quantum volume, it can be understood this way: if the level of errors is zero, then further computing capabilities (quantum volume) grows due to an increase in the number of logical qubits.
If we talk about the achievements in the field of working quantum computers, it is impossible not to mention the IBM computer on 50 qubits. He became one of the first quantum computers of this scale. The workhorse of IBM's quantum computers is superconducting qubits, which for their work must be cooled to very low temperatures. In the IBM quantum processor, individual control over each qubit is not implemented and the level of errors is rather high, but the chip itself already exists. IBM also has open 5-qubit and 16-qubit quantum computers that can be used by anyone over the Internet. In addition, in several years the corporation plans to make a system for 100 qubits. IBM recently announced the IBM System One integrated quantum computer, which is a complete device that, according to the developers, does not require any special working conditions - this brings the system closer to users, but solving practical and relevant tasks with such a computer difficult to say.
Intel is on the threshold of the same 50-qubit boundary, but uses a different technology to create qubits. And this is good, because if one of the corporations encounters problems in the implementation of its approach, the second will continue to move towards progress.
The leader of the quantum race today can be considered Google, which was demonstrated a quantum computer of 72 qubits. The basic technology at Google is the same as that of IBM - superconducting qubits. A group of scientists and developers of Google also published a number of scientific articles describing approaches to achieving quantum supremacy. So, in the near future, we can expect a demonstration of quantum superiority from the company with the help of a quantum processor developed by them.
In the academic community, a system of 51 qubits was also created — the group managed by Mikhail Lukin (a graduate of the Fiztech and the head of the International Advisory Board of the Russian Quantum Center) based on ultracold neutral atoms, as well as a system of 53 qubits from the group of Christopher Monroe of the University of Maryland, which also He is the founder of IonQ, which develops a commercial quantum computer on ions. By the way, IonQ is not the only example of a startup in the field of quantum computing - there are more than a dozen of them now.
It is obvious that China has great potential in the quantum sphere. “Celestial” is carrying out ambitious plans, planning to construct the largest quantum computer, and the developers already have 12 billion dollars to create the National Quantum Laboratory.
The D-Wave company stands somewhat apart. There are thousands of qubits in the D-Wave processor, but they work in a different mode - the quantum annealing mode. This allows you to solve with the help of such a computer, in fact, only one task. Despite the fact that companies, such as Google and Volkswagen, are already working with D-Wave, there are heated debates about the advantages of such a quantum computer company.
Application side of the question
Despite all efforts, today quantum computers do not allow to solve so many practical problems, but the potential looks impressive. Now the development of quantum computing goes in two directions:
- Specialized quantum computers that are aimed at solving one specific specific problem, for example, optimization problems. An example of a product is the D-Wave quantum computers.
- Universal quantum computers - which are capable of implementing arbitrary quantum algorithms. Today, there are only small prototypes of universal quantum computers — Google, IBM, and Intel are working in this direction. They lay the foundation, but do not yet allow to do something large-scale and do not know how to cope with errors.
In any case, quantum computers allow you to operate with a large state space and this can be useful, for example, for solving search problems, optimizing various processes and modeling complex systems.
Due to the fact that IBM offers everyone to use a quantum computer, modern quantum programmers are already trained in assembling tasks and running them on small quantum computers. For example, for searching through an unordered database, the quantum algorithm has a quadratic advantage. In such a task, an unordered database can be represented as some kind of “black box”, to the input of which requests are sent (addresses of elements in this database), and the black box answers them “yes” or “no” (does the element located on given address, request requirements). Imagine that in some database the address of each element consists of n bits, and in this database there is only one element that satisfies certain conditions. To find this element, we on average need about 2 ^ n queries (more precisely 2 ^ (n-1)), since due to the disorder of the database, all we have to do is to iterate through all possible addresses (of which 2 ^ n pieces) until we are finally lucky and we don’t get to the desired item. In the case, if we have a quantum analogue of a similar black box (it is also called a “quantum oracle”), in order to get an answer we need about 2 ^ (n / 2) requests. The advantage of the “quantum search algorithm”, named after L. Grover, is due to the ability to ask many questions to the quantum box at the same time — to form a superposition of queries.
It is important to note that the task of searching in an unordered database is of a universal nature - it can reduce almost any other task (including NP-complete). However, to solve it, we need a number of queries that grow exponentially with the increasing complexity of the problem (in the example considered, it corresponds to the parameter n). Thus, you should not treat a quantum computer as an omnipotent tool capable of solving arbitrary computational problems with exponential acceleration. In some cases, its capabilities will be much more modest.
Nevertheless, the great potential is already evident today for problems from the sphere of quantum chemistry. For example, in industry, the calculation of the parameters of chemical compounds and the simulation of chemical reactions are in demand. When using classic computers, we lack the capabilities and often have to compromise with accuracy. Quantum computers can help define in detail the chain of reactions, the dynamics of processes, find catalysts for the desired reactions - all this is very useful! One of the most talked about problems today is ammonia production. This compound is actively used in fertilizers for plants, and 1-2% of all energy on earth is spent on its production (data from Quantum Computing Report and BP). If using a quantum computer it would be possible to optimize the process of ammonia production due to accurate knowledge of all parameters, then it would already have recouped all the investments that were made in technology development (remember, 1-2% of world energy).
Recently, at the junction of quantum physics and machine learning, a new direction has emerged - quantum machine learning or, as they often say, Quantum AI. At the same time, it is important that the superiority of a quantum computer over the classical ones in machine learning problems does not require a full-fledged and multiqubit quantum computer. With the help of a quantum computer, for example, it will be possible to speed up individual elements of machine learning algorithms, as well as speed up their learning process. In Google in recent years, quantum machine learning is considered one of the top trends in the entire field of quantum technology.
It's not just iron
For the next breakthrough, however, you need not only iron, but also new fast quantum algorithms. There is notable progress. For example, to study the compound Fe2S2 using quantum chemistry algorithms it took thirty years earlier when analyzing on a quantum computer. Due to the search for a more optimal algorithm, this time was reduced to 2 minutes, taking into account the use of the same iron.
However, quantum algorithms are still not enough. So far there are still only a few dozen, and for the full development of the sphere of quantum computing, there should be much more algorithms.
Fears and technologies of information security
A quantum computer has two sides: dark and light. Until now, we have been talking about the bright side - solving practically demanded problems that cannot be solved with the help of classic computers. But there is also a dark side: a quantum computer solves the factorization problem much better than the classical one. The complexity of this task, as is known, is one of the foundations for ensuring the persistence of common public-key cryptography algorithms. The problem of factorization is extremely difficult for a classical computer, and on a quantum one it can be effectively solved using the Shor algorithm. For example, breaking a 1024-bit RSA key will take millions of years of continuous computing on classic computers, whereas on a quantum computer this task will be solved in 10 hours (assuming that each quantum operation is performed 10 ns and that a computer is available of a sufficient number of logical qubits). So far, quantum computers do not allow anything to be hacked, because RSA requires several thousand controlled qubits to cryptanalyze. And although a potentially dangerous computer does not yet exist, the community is already thinking about protecting against possible problems in the future.
One solution is to use quantum key distribution technology, which allows two parties to exchange cryptographic keys for symmetric encryption. As you know, a single photon cannot be separated, and a quantum state cannot be copied - this is a fundamental limitation of quantum mechanics. On such a principle - the protection of transmitted data by fundamental physical laws - new devices are built. China is leading in this area on the world stage. In Russia, the technology of quantum key distribution is developed in several groups, for example, in the RCC, Moscow State University. Mv Lomonosov and ITMO. The device developed at the RCC has already been tested at Sberbank and Gazprombank.
By the level of errors in the channel, you can find out whether there was a possibility of a key compromise. If the level of errors is below the critical threshold, then it is possible to correct the errors and exclude from it information potentially available to the attacker using classical algorithms and, thus, generate the final secret key. In this case, the protected information remains inaccessible to the attacker.
The central idea is to use quantum-distributed keys in the Varnam cipher, a one-time pad. As far as is known, it is precisely such a system that is implemented in China’s most critical systems.
The second principle of protection is post-quantum cryptography. It includes a new class of public key algorithms, which are based on tasks that are computationally complex for both classical and quantum computers.
Many are interested in the question of whether a quantum computer is harmful to a blockchain. Yes it is possible. Through attacks on digital signatures, as well as through the use of Shor's quantum algorithm and the impact on consensus algorithms by Grover’s quantum algorithm. However, blockchains can also be protected by quantum key distribution or post-quantum cryptography.
Waiting for a miracle
Work on quantum computers continues, and today the issues of creating new hardware and developing new algorithms are equally important. This is not so easy to do, because programmers have to deal with completely new entities, and architects need to develop fundamentally new devices for controlling quantum systems. The scientific community and leading corporations are looking toward quantum computers with great optimism - there are reasons for it.
Source: https://habr.com/ru/post/455559/
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