What is a quantum computer? Quantum computer: how it works
Such machines are simply necessary now in any field: medicine, aviation, space exploration. Currently, the development of computers based on quantum physics and computing technologies. The basics of operation of such a computing device are not yet available to ordinary users and are accepted as something incomprehensible. After all, not everyone is familiar with the photonic properties of elementary particles and atoms. To understand at least a little how this computer works, you need to know and understand the elementary principles of quantum mechanics. For the most part, this coherent computer is being developed for NASA.
A conventional machine performs operations using classical bits, which can take the values 0 or 1. On the other hand, a photonic computing machine uses coherent bits or qubits. They can take on the values 1 and 0 at the same time. This is what gives such computing technology its superior computing power. There are several types of computational objects that can be used as qubits.
- Nucleus of an atom.
- Electron.
All electrons have a magnetic field, as a rule, they look like small magnets and this property is called spin. If you place them in a magnetic field, they will adjust to it in the same way as a compass needle does. This is the lowest energy position, so we can call it zero or low spin. But it is possible to redirect the electron to the “one” state or to the top spin. But this requires energy. If you remove the glass from the compass, you can redirect the arrow in a different direction, but this requires force.
There are two accessories: low and high spin, which correspond to the classic 1 and 0 respectively. But the point is that photonic objects can be in two positions at the same time. When spin is measured, it will be either up or down. But before measurement, the electron will exist in a so-called quantum superposition, in which these coefficients indicate the relative probability of the electron being in one state or another.
It's quite difficult to imagine how this gives coherence machines their incredible computational power without considering the interaction of two qubits. There are now four possible states for these electrons. In a typical two-bit example, only two bits of information are needed. So two qubit contains four types of information. This means that you need to know four numbers to know the position of the system. And if you take three spins, you get eight different positions, and in a typical version you will need three bits. It turns out that the amount of information contained in N qubits is equal to 2N standard bits. The exponential function says that if, for example, there are 300 qubits, then you will have to create crazy-complex superpositions where all 300 qubits will be interconnected. Then we get 2300 classical bits, which is equal to the number of particles in the entire universe. It follows that it is necessary to create a logical sequence that will make it possible to obtain a calculation result that can be measured. That is, consisting only of standard accessories. It turns out that a coherent machine is not a replacement for conventional ones. They are only faster in calculations where it is possible to use all available superpositions. And if you just want to watch a high-quality video, chat on the Internet or write an article for work, a photon computer will not give you any priorities.
This video describes the process of a quantum computer.
If we talk in simple words, then the coherent system is designed not for the speed of calculation, but for the required quantity to achieve results, which will occur in a minimum unit of time.
The operation of a classical computer is based on information processing using silicon chips and transistors. They use binary code, which in turn consists of ones and zeros. A coherent machine works on the basis of superposition. Instead of bits, qubits are used. This allows you to not only quickly, but also make calculations as accurately as possible.
What will be the most powerful photonic computing system? For example, if a photonic computer has a thirty-qubit system, then its power will be 10 trillion computing operations per second. Currently, the most powerful two-bit computer counts one billion operations per second.
A large group of scientists from different countries developed a plan according to which the dimensions of the photonic apparatus will be close to the dimensions of a football field. He will be the most powerful in the world. This will be a kind of structure made of modules, which is placed in a vacuum. The inside of each module is ionized electric fields. It is with their help that certain parts of the circuit will be formed that will perform simple logical actions. An example of such photonic computing technology is being developed at the University of Sussex in England. The estimated cost is currently more than $130 million.
Ten years ago, D-Wave introduced the world's first coherent computer, which consists of 16 qubits. Each qubit in turn consists of a niobium crystal, which is placed in an inductor. The electric current supplied to the coil creates a magnetic field. Next, it changes the membership in which the qubit is located. Using such a machine, you can easily find out how synthetic drugs interact with blood proteins.
Or it will be possible to identify a disease such as cancer at an earlier stage.
This video contains discussions on the topic “Why does the world need a quantum computer.” Don't forget to leave your comments, questions and just
A quantum computer is a computing device that uses the phenomena of quantum superposition and quantum entanglement to transmit and process data. A full-fledged universal quantum computer is still a hypothetical device, the very possibility of building which is associated with the serious development of quantum theory in the field of many particles and complex experiments; developments in this area are associated with the latest discoveries and the achievements of modern physics. On present moment Only a few experimental systems were practically implemented, executing a fixed algorithm of low complexity.
As the editors of Science Alert write, a group of specialists from the University of Vienna were able to develop the first quantum router in history and even conducted the first tests of the new device. This is the first device that can not only receive entangled photons, but also transmit them. In addition, the circuit used in the router could become the basis for creating a quantum Internet.
Quantum computing, at least in theory, has been talked about for decades. Modern types of machines, using non-classical mechanics to process potentially unimaginable amounts of data, have been a major breakthrough. According to the developers, their implementation turned out to be perhaps the most complex technology ever created. Quantum processors operate at levels of matter that humanity only learned about 100 years ago. The potential of such computing is enormous. Using the bizarre properties of quanta will speed up calculations, so many problems that are currently beyond the capabilities of classical computers will be solved. And not only in the field of chemistry and materials science. Wall Street is also interested.
Investing in the future
CME Group has invested in Vancouver-based 1QB Information Technologies Inc., which develops software for quantum processors. Such computing will likely have the biggest impact on industries that handle large volumes of time-sensitive data, investors say. An example of such consumers are financial institutions. Goldman Sachs invested in D-Wave Systems, and In-Q-Tel is funded by the CIA. The first produces machines that do what is called “quantum annealing,” i.e., solving low-level optimization problems using a quantum processor. Intel is also investing in this technology, although it considers its implementation a matter of the future.
Why is this necessary?
The reason quantum computing is so exciting is because of its perfect combination with machine learning. Currently, this is the main application for such calculations. Part of the idea of a quantum computer is using a physical device to find solutions. Sometimes this concept explained using the example of the game Angry Birds. To simulate gravity and the interaction of colliding objects, the tablet's CPU uses mathematical equations. Quantum processors turn this approach on its head. They "throw" a few birds and see what happens. The birds are recorded in the microchip, they are thrown, what is the optimal trajectory? Then all possible solutions, or at least a very large combination of them, are tested and an answer is returned. In a quantum computer there is no mathematician, the laws of physics work instead.
How does it work?
The basic building blocks of our world are quantum mechanical. If you look at molecules, the reason they form and remain stable is the interaction of their electron orbitals. All quantum mechanical calculations are contained in each of them. Their number grows exponentially with the number of simulated electrons. For example, for 50 electrons there are 2 to the 50th power possible options. This is phenomenal, so it is impossible to calculate it today. Connecting information theory to physics can point the way to solving such problems. A 50-qubit computer can do this.
Dawn of a new era
According to Landon Downs, president and co-founder of 1QBit, a quantum processor is the ability to harness the computing power of the subatomic world, which has enormous implications for obtaining new materials or creating new drugs. There is a transition from the discovery paradigm to new era design. For example, quantum computing can be used to model catalysts that remove carbon and nitrogen from the atmosphere and thereby help stop global warming.
At the forefront of progress
The technology development community is extremely excited and active. Teams around the world in startups, corporations, universities and government labs are racing to build machines that use different approaches to processing quantum information. Superconducting qubit chips and trapped ion qubits have been created by researchers from the University of Maryland and the US National Institute of Standards and Technology. Microsoft is developing a topological approach called Station Q, which aims to exploit a non-Abelian anion that has not yet been conclusively proven to exist.
The year of a possible breakthrough
And this is just the beginning. As of the end of May 2017, the number of quantum processors that clearly do something faster or better than a classical computer is zero. Such an event would establish “quantum supremacy,” but it has not yet occurred. Although it is likely that this could happen this year. Most insiders say the clear favorite is the Google team led by UC Santa Barbara physics professor John Martini. Its goal is to achieve computational superiority using a 49-qubit processor. By the end of May 2017, the team had successfully tested a 22-qubit chip as an intermediate step toward disassembling a classic supercomputer.
Where did it all start?
The idea of using quantum mechanics to process information has been around for decades. One of the key events occurred in 1981, when IBM and MIT jointly organized a conference on the physics of computing. The famous physicist proposed building a quantum computer. According to him, quantum mechanics should be used for modeling. And this is a great task because it doesn't look so easy. The quantum processor's operating principle is based on several strange properties of atoms - superposition and entanglement. A particle can be in two states at the same time. However, when measured, it will appear in only one of them. And it is impossible to predict which one, except from the perspective of probability theory. This effect is the basis of the thought experiment of Schrödinger's cat, which is both alive and dead in a box until an observer sneaks a peek. Nothing in everyday life works this way. However, about 1 million experiments conducted since the beginning of the 20th century show that superposition does exist. And the next step is to figure out how to use this concept.
Quantum processor: job description
Classic bits can take the value 0 or 1. If you pass their string through “logical gates” (AND, OR, NOT, etc.), you can multiply numbers, draw images, etc. A qubit can take values 0, 1 or both at the same time. If, say, 2 qubits are entangled, then this makes them perfectly correlated. A quantum processor can use logic gates. T.n. The Hadamard gate, for example, places the qubit in a state of perfect superposition. When superposition and entanglement are combined with cleverly placed quantum gates, the potential of subatomic computing begins to unfold. 2 qubits allow you to explore 4 states: 00, 01, 10 and 11. The principle of operation of a quantum processor is such that the execution logical operation makes it possible to work with all positions at once. And the number of available states is 2 to the power of the number of qubits. So, if you made a 50-qubit universal quantum computer, you could theoretically explore all 1.125 quadrillion combinations at once.
Kudits
The quantum processor in Russia is seen somewhat differently. Scientists from MIPT and the Russian Quantum Center have created “qudits,” which are several “virtual” qubits with different “energy” levels.
Amplitudes
A quantum processor has the advantage that quantum mechanics is based on amplitudes. Amplitudes are similar to probability, but they can also be negative and complex numbers. So, if you need to calculate the probability of an event, you can add up the amplitudes of all possible options for their development. The idea behind quantum computing is to try to tune it so that some paths to incorrect answers have a positive amplitude and some have a negative amplitude, so they cancel each other out. And the paths leading to the correct answer would have amplitudes that are in phase with each other. The trick is to organize everything without knowing in advance which answer is correct. So the exponential nature of quantum states, combined with the potential for interference between positive and negative amplitudes, is an advantage of this type of calculation.
Shor's algorithm
There are many problems that a computer cannot solve. For example, encryption. The problem is that it is not easy to find prime factors of a 200-digit number. Even if your laptop runs great software, you may have to wait years to find the answer. So another milestone in quantum computing was an algorithm published in 1994 by Peter Shore, now a professor of mathematics at MIT. His method is to find the factors of a large number using a quantum computer that did not yet exist. Essentially, the algorithm performs operations that point to areas with the correct answer. The following year, Shor discovered a method for quantum error correction. Then many realized that this was an alternative way of computing, which in some cases could be more powerful. Then there was a surge of interest on the part of physicists in the creation of qubits and logic gates between them. And now, two decades later, humanity is on the verge of creating a full-fledged quantum computer.
The world is on the verge of another quantum revolution. The first quantum computer will instantly solve problems for which the most powerful modern device is now spending years. What are these tasks? Who benefits and who is threatened by the massive use of quantum algorithms? What is a superposition of qubits, how did people learn to find the optimal solution without going through trillions of options? We answer these questions under the heading “Simply about the complex.”
Before the quantum theory, the classical theory of electromagnetic radiation was in use. In 1900, the German scientist Max Planck, who himself did not believe in quanta and considered them a fictitious and purely theoretical construct, was forced to admit that the energy of a heated body is emitted in portions - quanta; Thus, the assumptions of the theory coincided with experimental observations. And five years later, the great Albert Einstein resorted to the same approach when explaining the photoelectric effect: when irradiated with light, an electric current arose in metals! It is unlikely that Planck and Einstein could have imagined that with their work they were laying the foundations of a new science - quantum mechanics, which would be destined to transform our world beyond recognition, and that in the 21st century scientists would come close to creating a quantum computer.
At first, quantum mechanics made it possible to explain the structure of the atom and helped to understand the processes occurring inside it. By and large, the long-standing dream of alchemists to transform atoms of some elements into atoms of others (yes, even into gold) has come true. And Einstein’s famous formula E=mc2 led to the emergence of nuclear energy and, as a consequence, the atomic bomb.
Five-qubit quantum processor from IBM
Further - more. Thanks to the work of Einstein and the English physicist Paul Dirac, a laser was created in the second half of the 20th century - also a quantum source of ultra-pure light collected into a narrow beam. Laser research has brought the Nobel Prize to more than a dozen scientists, and lasers themselves have found their application in almost all areas of human activity - from industrial cutters and laser guns to barcode scanners and vision correction. Around the same time, active research was underway on semiconductors - materials with which the flow of electric current can be easily controlled. On their basis, the first transistors were created - they later became the main building elements of modern electronics, without which we can no longer imagine our lives.
The development of electronic devices has made it possible to quickly and effectively solve many problems. computers- computers. And the gradual reduction in their size and cost (due to mass production) paved the way for computers into every home. With the advent of the Internet, our dependence on computer systems, including for communication, has become even stronger.
Richard Feynman
Dependency is growing, computing power is constantly growing, but the time has come to admit that, despite their impressive capabilities, computers have not been able to solve all the problems that we are ready to put before them. The famous physicist Richard Feynman was one of the first to talk about this: back in 1981, at a conference, he stated that it was fundamentally impossible to accurately calculate a real physical system on ordinary computers. It's all about its quantum nature! Microscale effects are easily explained by quantum mechanics and very poorly explained by the classical mechanics we are used to: it describes the behavior of large objects. It was then that, as an alternative, Feynman proposed using quantum computers to calculate physical systems.
What is a quantum computer and how is it different from the computers we are used to? It's all about how we present information.
If in conventional computers bits - zeros and ones - are responsible for this function, then in quantum computers they are replaced by quantum bits (abbreviated as qubits). The qubit itself is a fairly simple thing. It still has two fundamental values (or states, as quantum mechanics like to say) that it can take on: 0 and 1. However, thanks to a property of quantum objects called “superposition,” a qubit can take on all values that are a combination of the fundamental ones. Moreover, its quantum nature allows it to be in all these states at the same time.
This is the parallelism of quantum computing with qubits. Everything happens at once - you no longer need to go through everything possible options states of the system, which is exactly what a regular computer does. Searching large databases, compiling optimal route, the development of new drugs are just a few examples of problems whose solution can be accelerated many times over by quantum algorithms. These are those tasks where in order to find the correct answer you need to go through a huge number of options.
In addition, huge computing power and volumes are no longer needed to describe the exact state of the system. RAM, because to calculate a system of 100 particles, 100 qubits are enough, not trillions of trillions of bits. Moreover, as the number of particles increases (as in real complex systems), this difference becomes even more significant.
One of the search problems stood out for its apparent uselessness - decomposition large numbers into prime factors (that is, divisible by an integer only by themselves and one). This is called "factorization". The fact is that ordinary computers can multiply numbers quite quickly, even very large ones. However, with the inverse problem of decomposing a large number resulting from multiplying two prime numbers, conventional computers cope very poorly with the original multipliers. For example, to factor a number of 256 digits into two factors, even powerful computer it will take more than a dozen years. But a quantum algorithm that can solve this problem in a few minutes was invented in 1997 by the English mathematician Peter Shor.
With the advent of Shor's algorithm, the scientific community faced a serious problem. Back in the late 1970s, based on the complexity of the factorization problem, cryptographic scientists created a data encryption algorithm that has become widespread. In particular, with the help of this algorithm they began to protect data on the Internet - passwords, personal correspondence, banking and financial transactions. And after many years of successful use, it suddenly turned out that information encrypted in this way becomes an easy target for Shor’s algorithm running on a quantum computer. Decryption with its help becomes a matter of minutes. One thing was good: a quantum computer on which the deadly algorithm could be run had not yet been created.
Meanwhile, around the world, dozens of scientific groups and laboratories began to engage in experimental studies of qubits and the possibilities of creating a quantum computer from them. After all, it’s one thing to theoretically invent a qubit, and quite another to bring it into reality. To do this, it was necessary to find a suitable physical system with two quantum levels that can be used as the base states of the qubit - zero and one. Feynman himself, in his pioneering article, proposed using for these purposes twisted different sides photons, but the first experimentally created qubits were ions captured in special traps in 1995. Ions were followed by many other physical implementations: atomic nuclei, electrons, photons, defects in crystals, superconducting circuits - they all met the requirements.
This diversity had its merits. Driven by intense competition, various scientific groups created more and more perfect qubits and built more and more from them. complex circuits. There were two main competitive parameters for qubits: their lifetime and the number of qubits that could be made to work together.
Employees of the Laboratory of Artificial Quantum Systems
The lifetime of the qubits determined how long the fragile quantum state was stored in them. This, in turn, determined how many computational operations could be performed on the qubit before it “died.”
For efficient operation of quantum algorithms, not one qubit was needed, but at least a hundred, and working together. The problem was that the qubits didn’t really like being next to each other and protested by dramatically reducing their lifetime. To get around this incompatibility of qubits, scientists had to resort to all sorts of tricks. And yet, to date, scientists have managed to get a maximum of one or two dozen qubits to work together.
So, to the delight of cryptographers, a quantum computer is still a thing of the future. Although it is not at all as far away as it might once have seemed, because both the largest corporations like Intel, IBM and Google, as well as individual states, for which the creation of a quantum computer is a matter of strategic importance, are actively involved in its creation.
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