What is a Quantum Computer?

A quantum computer is a type of physical device that performs high-speed mathematical and logical operations, stores, and processes quantum information in accordance with the laws of quantum mechanics. When a device processes and calculates quantum information and runs a quantum algorithm, it is a quantum computer. The concept of quantum computers stems from the study of reversible computers. The purpose of studying reversible computers is to solve the problem of energy consumption in computers. ^[1]

The characteristics of a quantum computer include fast running speed, strong ability to process information, and wide application range. Compared with ordinary computers, the more information processing, the more advantageous it is for quantum computers to perform calculations, and the more accurate the calculations will be. ^[2]

What exactly is a quantum computer

In 1982, Richard Feynman, a well-known American physicist, put forward a novel idea of using quantum system to realize general computing in a public lecture. Immediately after, in 1985, the British physicist David Dooss proposed a model of the quantum Turing machine. Richard Feynman thought at the time that if a computer composed of subsystems was used to simulate quantum phenomena, the computing time could be greatly reduced, and the concept of quantum computers was born.

The principles of quantum computers are more: A quantum computer is a type of physical device that performs high-speed mathematical and logical operations, stores, and processes quantum information in accordance with the laws of quantum mechanics. Its basic laws include the uncertainty principle, correspondence principle, and Bohr theory. It is commonly used, such as semiconductor-based electronic products, laser-burnable optical discs, nuclear magnetic resonance, and so on.
The advantages of quantum computers are more: The quantum computer's transformation of each superposition component is equivalent to a classical calculation. All these classical calculations are completed at the same time and superimposed with a certain probability amplitude to give the output of the quantum computer. This kind of calculation is called quantum parallel computing, and it is also the most important advantage of quantum computers.

Content Arrangement

Chinese name: Quantum computer
Foreign name: quantum computer
Rules: Follow the laws of quantum mechanics

Presenter: Richard Feynman
Advantage: Powerful information processing capabilities
basic unit: Qubit

Quantum computer overview

A quantum computer is simply a machine that can implement quantum computing. It is a system that uses the laws of quantum mechanics to implement mathematical and logical operations, and to process and store information. It uses quantum states as memory units and information storage forms, and uses quantum dynamics as the basis for information transmission and processing. Quantum communication and quantum computing are based on the size of various hardware components in quantum computers. A quantum computer is a physical system that stores and processes information about quantum mechanical variables. ^[1]

Just as the traditional computer realizes the distinction between 0 and 1 by the on and off of the circuit in the integrated circuit, and its basic unit is a silicon wafer, a quantum computer also has its own basic unit-qubit. Kunbit is also called qubit. It expresses 0 or 1 by the quantum two-state quantum mechanical system. For example, two orthogonal polarization directions of a photon, the spin direction of an electron in a magnetic field, or two directions of a nuclear spin, two different energy levels of a quantum in an atom, or the spatial mode of any quantum system. The principle of quantum computing is the evolution of quantum states in quantum mechanical systems. ^[1]

Quantum computer composition

Quantum computers, like many computers, are composed of many hardware and software. The software includes quantum algorithms, quantum coding, etc., and the hardware includes quantum transistors, quantum storage, and quantum effectors. ^[3]

The quantum transistor is to break the physical energy limit through the high-speed movement of electrons, so as to realize the switching function of the transistor. This transistor controls the switching speed very quickly. The transistor has a much stronger computing capacity than ordinary chips, and it has the ability to adapt to the environmental conditions used Very strong, so in the future development, transistors are an indispensable part of quantum computers. Quantum memory is a kind of high-efficiency memory. It can assign any computational information in a very short time. It is an indispensable part of quantum computers and one of the most important parts of quantum computers. A quantum computer effector is a large-scale control system that can control the operation of various components. These components occupy a major position in the development of quantum computers and play an important role. ^[3]

Quantum computer principle

A quantum computer is a computer that works based on quantum theory. Tracing to its roots is the continuous exploration of reversible machines, which has promoted the development of quantum computers. Quantum computer devices follow the basic theory of quantum computing. They process and calculate quantum information and run quantum algorithms. In 1981, Paul Benioff of Aragon National Laboratory first proposed the basic theory of quantum computing. ^[4]

1.Qubits

The basic unit of classical computer information is bits. A bit is a physical system with two states, represented by 0 and 1. In a quantum computer, the basic unit of information is a qubit. The two quantum states 0> and 1> are used instead of the classical bit states 0 and 1. Compared with bits, qubits have unique existence characteristics. They exist in the form of superposition states of two logical states, which represents the superposition of corresponding quantum states where the two states are 0 and 1. ^[4]

2.State superposition principle

The core technology of modern quantum computer models is the principle of state superposition, which belongs to a basic principle of quantum mechanics. In a system, every possible way of movement is called a state. In the micro system, the motion state of the quantum can not be determined, and it is statistically opposite to the motion state determined by the macro system. Quantum states are states of microscopic systems. ^[4]

3.Quantum entanglement

Quantum entanglement: When two particles are entangled with each other, the behavior of one particle affects the state of the other particle. This phenomenon has nothing to do with distance. In theory, even if they are far enough apart, quantum entanglement can still be detected. Therefore, when the state of one of the two particles changes, that is, when the particle is manipulated, the state of the other particle changes accordingly. ^[4]

4.Quantum parallelism

Quantum parallel computing is the most compelling advanced technology that quantum computers can surpass classical computers. Quantum computers store numbers in exponential form. By increasing the number of qubits to 300 qubits, they can store more numbers than all atoms in the universe and can perform calculations at the same time. Function calculation does not pass the classic cycle method, but can be directly obtained by unitary transformation, which greatly reduces the work loss energy and truly realizes reversible calculation. ^[4]

Quantum computer research progress

In the early 1980's, Benioff first proposed the idea of quantum computing. He designed an executable quantum Turing machine with a classic analogy.

Quantum computer principle The prototype of quantum computer. ^[5]

In 1982, Feynman developed Benioff's vision and proposed that quantum computers can simulate other quantum systems. In order to simulate the system of quantum mechanics, Feynman proposed the concept of working computers in accordance with the laws of quantum mechanics, which is considered to be the earliest idea of quantum computers. ^[5]

In a paper published by David Deutsch of Oxford University in 1985, it was proved that any physical process can be well simulated by quantum computers in principle, and proposed a new concept of quantum interference-based computer simulation, which is the "quantum logic gate" It also points out that quantum computers can be generalized, and the generation and correction of quantum computing errors. In-depth analysis and research by Zurek. But by the mid-1980s, this area of research had been left out for several reasons. First of all, because all quantum computer models at that time regarded quantum computers as an isolated system that did not interact with the external environment, not actual models. Second, there are many constraints that are not conducive to the realization of quantum computers, such as decoherence, thermal noise, etc., as pointed out by Landauer. In addition, quantum computers can be error-prone and difficult to correct. Finally, it is unclear whether quantum computers solve mathematical problems faster than classical calculations. ^[5]

In 1994, Dr. Perer Shor of AT & T discovered an efficient quantum algorithm for factorization. In 1996, S. Loyd proved Feyrman's conjecture. He pointed out that the simulation of the evolution of quantum systems will become an important use of quantum computers. Quantum computers can be built on the basis of quantum Turing machines. Since then, with the rapid development of interdisciplinary research between computer science and physics, the theoretical and experimental research of quantum computing has flourished. The development of quantum computers has begun to enter a new era, and governments and major companies in various countries have also formulated a series of research and development plans for quantum computers. ^[5]

First of all, the United States Advanced Research Projects Agency formulated a research plan called "Quantum Information Science and Technology Development Plan" version 1.0 and version 2.0 in December 2002 and April 2004. This plan details the development of quantum in the United States. The main steps and timetable of the calculation. In this plan, the United States will strive to develop a computer with 10 physical qubits in 2007 and a computer with 50 physical qubits by 2012. The US Army also plans to equip its weapons with quantum computers by 2020. ^[5]

Europe has also made active research and development in quantum computing and quantum encryption. Research on discrete and entanglement of different quantum systems (such as atoms, ions, and resonances) as well as research on quantum algorithms and information processing in the fifth framework project has been completed. At the same time, the sixth framework plan focuses on the research of quantum algorithms and encryption technology, and it is expected that by 2008, high-reliability, long-distance quantum data encryption technology will be successfully developed. ^[5]

Japan started a five-year quantum computing and information program in October 2000, focusing on the complexity of quantum computing and quantum communication, designing new quantum algorithms, developing robust quantum circuits, finding useful properties of quantum self-control, and developing quantum Calculation simulator. ^[5]

In 2007, DWave of Canada successfully developed a 16-Kbit Orion constellation quantum computer, and showed their quantum computers in California, USA and Vancouver, Canada on February 13, 2008 and February 15, respectively. ^[6]

On November 15, 2009, the National Institute of Standards and Technology developed a quantum computer that can process two Kunbit data. ^[6]

D-Wave, the world's first quantum computing company, announced on June 22, 2015 that it broke the barrier of 1,000 qubits and developed a new processor. Its qubits are two of the previous generation D-Wave processors. Times, and far beyond the qubits of DWave or any other product developed by its peers. ^[7]

On March 6, 2017, IBM announced that it will launch the world's first commercial "universal" quantum computing service IBM this year. IBM said that this service is equipped with the ability to access directly through the Internet, has a transformative role in drug development and various scientific research, and has begun to recruit consumer users. In addition to IBM, other companies, including Intel, Google, and Microsoft, are also exploring the field of practical quantum computers. ^[8]

On May 3, 2017, the computing power of the experimental prototype of the optical quantum computer constructed by the Pan Jianwei team of the Chinese Academy of Sciences has surpassed that of early computers. In addition, the Chinese scientific research team completed the manipulation of 10 superconducting qubits, successfully breaking the entanglement and complete measurement records of the world's largest digit superconducting qubit. ^[8]

Difficulties in quantum computers

1.Quantum decoherence

The coherence of quantum computing is the essence of parallel quantum computing. However, in practical situations, qubits will be affected and affected by the external environment, which will cause quantum entanglement. Quantum coherence is very susceptible to interference from quantum entanglement, which leads to a decrease in quantum coherence, which is the so-called decoherence phenomenon. In practical applications, the contact between the qubit and the outside world cannot be avoided, and the coherence of the quanta is not easily maintained. Therefore, the quantum decoherence problem is one of the important problems to be solved at present, and its solution will affect the future development of quantum computers to a certain extent. ^[9]

2.Quantum entanglement

As the smallest particle, the quantum obeys the law of quantum entanglement. Even in space, quantum may be separated, but the interaction between quantum is unavoidable. Because of this, quantum entanglement technology is associated with the field of transmission of quantum information. In a certain sense, the rapid communication speed between quantum is used to realize the transfer of information. ^[9]

3.Quantum parallel computing

The unique parallel computing of quantum computers is an important point that cannot be compared with classical computers. It is also an n-bit memory. There is only one result stored by a classic computer. But quantum computer storage results can reach 2n. Its parallel computing not only surpasses the latter in terms of storage capacity, but also has fast read speeds, and multiple reads and calculations can be performed simultaneously. It is precisely the importance of quantum parallel computing, and its effective application has become one of the keys to the development of quantum computers. ^[9]

4.Quantum cannot be cloned

Quantum non-clonability refers to the process in which there is no replication of any unknown quantum state. Since it is necessary to keep the quantum state unchanged, there is no quantum measurement and replication cannot be achieved. For quantum computers, the error correction applications and replication functions of classical computers cannot be realized. ^[9]

Quantum computer advantages

Quantum computers have powerful quantum information processing capabilities. For the currently changing information, effective information can be extracted and processed to make it new useful information. The processing of quantum information requires the storage and processing of quantum computers, and then the quantum analysis of the given information. This method can accurately predict the weather conditions. At present, the accuracy rate of weather conditions predicted by computers is 75%, but the accuracy rate can be further increased by using quantum computers to make it easier for people to travel. ^[2]

The current computer is usually attacked by a virus, which directly causes the computer to be paralyzed and the personal information to be stolen. However, due to the non-clonable quantum principle, these problems do not exist for quantum computers. When users use quantum computers, they can safely go online. Don't be afraid to leak personal information. On the other hand, quantum computers have powerful computing capabilities and can analyze a large number of different data at the same time, so they can accurately analyze financial trends in finance and play a great role in avoiding financial crisis. They can also be used in biochemical research. It plays a great role in simulating the composition of new drugs and developing drugs and chemical supplies more accurately, so that the cost of drugs and the medicinal properties of drugs can be guaranteed. ^[3]

Quantum computer application prospects

Quantum computers theoretically have the ability to simulate arbitrary natural systems and are also the key to the development of artificial intelligence. Due to the powerful ability of quantum computers in parallel operations, it has the ability to quickly complete calculations that classical computers cannot. This advantage has huge applications in the fields of encryption and deciphering. ^[1]

(1) Weather forecast: If we use a quantum computer to analyze all the information at the same time and get the results, then we can know the precise trend of the weather change, thereby avoiding a lot of economic losses. ^[1]

(2) Drug development: Quantum computers also have great advantages for the development of new drugs. Quantum computers can depict trillions of molecular compositions and choose the most likely method among them. This will improve people's ability to invent new drugs. Speed, and more personalized analysis of pharmacology. ^[1]

(3) Traffic scheduling: Quantum computers can predict traffic conditions based on existing traffic conditions, complete in-depth analysis, and perform traffic scheduling and optimization. ^[1]

(4) Confidential communication: Not only for similar aspects of our lives, because of the unclonable principle of encrypted communication for quantum computers, intruders can no longer decipher and eavesdrop without being discovered. This is the quantum computer itself. Determined by nature. ^[1]