31 мая 2019г.
Quantum computer research.
The IDF(Industry Development Fund) under the Ministry of Industry and Trade of the Russian Federation on February 13, 2017 launched the IPI 4.0 discussion platform, where the prospects for the 4th industrial revolution in Russia will be discussed. The aim of the work is to study the structure, the principle of operation of a quantum computer. Quantum computing is one of the technologies of the 4th industrial revolution. The development of quantum computing allowed us to reconsider the possibility of implementing a quantum computer.
Demand for computing power
Moore's law expresses a certain growth trend in the performance of already existing computers. We know that computers are becoming more powerful from year to year, but behind this is a reduction in the element base, its miniaturization. Thanks to our progress in creating transistors, we can create less and less of them, and arrange everything more tightly into an elementary unit of area. However, this trend has a fundamental limit.
We can hardly create a single atom transistor. This requires at least a few atoms. However, if Moore's law continues as it continues, then in 2020 we will need to create computers with a single-atom transistor. And it seems impossible.
If we come very close to Moore's law, we will have tasks that the classical computer solves very badly. The first is the search optimization task. It is rather poorly solved on classic computers.
The second is the modeling of complex physical systems. For example, using simulation from first principles, it is very difficult to model some rather complex physical system. This requires a huge amount of resources. And even if we get close to the limit of Moore's law, we will not be able to solve such problems. Humanity would like to get a physical system that will allow solving these tasks in a more optimal way. It turns out that it exists, and it appears in the context of a quantum computer.
Quantum computer architecture
The schematic diagram of the operation of any quantum computer can be represented as follows. Its main part is a quantum register - a collection of a certain number of L qubits. Before entering information into a computer, all register qubits must be brought into basic (boolean) states. This operation is called preparation of the initial state or initialization. Further, each qubit is subjected to selective action, for example, using pulses of an external electromagnetic field, controlled by a classical computer, which will translate the basic states of certain qubits into non-ground states. In this case, the state of the entire register goes into the superposition of the basis states. While entering information into a quantum computer, the state of the input register is converted into the corresponding coherent superposition of the basic orthogonal states by means of the corresponding impulse effects. In this form, the information is then exposed to a quantum processor that performs a sequence of quantum logical operations, determined by an unitary transformation acting on the state of the entire register. By the time t, as a result of transformations, the initial quantum state becomes a new superposition, which determines the result of transforming information at the computer output.
The total of all possible operations at the input of this computer, which form the initial states, as well as carry out unitary local transformations corresponding to the calculation algorithm, methods for suppressing coherence loss - the so-called decoherence of quantum states and correcting random errors, play the same role here as “Software” in a classic computer.
Quantum computer application
Accurate modeling of molecular interactions, the search for optimal configurations for chemical reactions. Such "quantum chemistry" is too complicated. So, with the help of modern digital computers it is possible to analyze only the simplest molecules.
Chemical reactions are quantum in nature, since they form highly entangled quantum states of superposition. But fully developed quantum computers will be able to count even such complex processes without problems.
Google is already raiding this area, simulating the energy of hydrogen molecules. The result is more efficient products, from solar panels to pharmaceuticals, and especially fertilizers; Since fertilizers account for up to 2% of global energy consumption, the implications for energy and the environment will be enormous.
Cryptography
Most cyber security systems rely on the complexity of factoring large numbers into simple ones. Although digital computers, which calculate every possible factor, can cope with this, the long time required for “hacking code” results in high costs and impracticality.
Quantum computers can do this factoring exponentially more efficiently than digital computers, making modern protection methods obsolete. New methods of cryptography are being developed, which, however, take time: in August 2015, the NSA began to compile a list of quantum computing-resistant cryptographic methods that could withstand quantum computers, and in April 2016 the National Institute of Standards and Technology began a public assessment process that will last from four to six years.
Financial modeling
Modern markets are one of the most complex systems . Although we have developed many scientific and mathematical tools for working with them, they still lack the conditions that other scientific disciplines can boast of: there are no controlled conditions to conduct experiments. To solve this problem, investors and analysts turned to quantum computing. Their immediate advantage is that the randomness inherent in quantum computers is congruent to the stochastic nature of financial markets. Investors often want to evaluate the distribution of results with a very large number of randomly generated scenarios.
Another advantage that quantum computers offer is that financial transactions like arbitration can sometimes require many consecutive steps, and the number of miscalculation possibilities is far ahead of what is permissible for a regular digital computer.
Comparison of computers
Ordinary computers obey the laws of classical physics. They rely on binary numbers: one and zero. These numbers are stored and used for mathematical operations. In ordinary memory devices, each bit is determined by the charge, that is, the bit can be either one or zero.
And in quantum computers, a bit can be at the same time one and zero. The laws of quantum physics allow electrons to occupy several states simultaneously. Quantum bits or qubits thus exist in several mutually overlapping states. This superposition allows you to perform operations with many values in one fell swoop, while ordinary computers do everything consistently.At least that’s the theory. The problem is that this hypothesis has not yet been tested experimentally. Still.
Robert Koenig, a professor of the theory of complex quantum systems, together with his colleagues demonstrated the advantage of quantum computers. For this, they developed a quantum circuit that can solve a certain complex algebraic problem. The new chain has a very simple structure - it can perform only a fixed number of operations on each qubit. It is believed that such a chain has a constant depth. During the experiment, the researchers proved that the classical chain of the same depth simply could not solve the mathematical problem of their choice. Moreover, they answered the question why quantum algorithms are superior to any sequential algorithms: quantum ones use the nonlocality of quantum physics.
Prior to this work, the advantage of quantum computers was neither proven nor experimentally confirmed, despite all the theoretical calculations.
References
1. Ambainis, Andris (Spring 2014). "What Can We Do with a Quantum Computer?". Institute for Advanced Study.
2. Daniel J. Bernstein, Introduction to Post-Quantum Cryptography. Introduction to Daniel J. Bernstein, Johannes Buchmann, Erik Dahmen (editors). Post-quantum cryptography. Springer, Berlin, 2009.
3. DiVincenzo, David P. (1995). "Quantum Computation". Science.
4. "New Trends in Quantum Computation". Simons Conference on New Trends in Quantum Computation 2010: Program. C.N. Yang Institute for Theoretical Physics.
5. The National Academies of Sciences, Engineering, and Medicine (2019). Grumbling, Emily; Horowitz, Mark (eds.). Quantum Computing : Progress and Prospects (2018). Washington, DC: National Academies Press.
