Significance of research and development quantum computers
Studying quantum computing and quantum computers are an urgent need for social economy and science and technology development. Everyone knows that modern electronic computers were born in 1946. Half of the past half a century, due to continuous advancement of science and technology, the performance of computer has a sharp development. Only in terms of calculation speed, the speed of the first tube computer ENIAC has only 5000b / s (bit / second, ie 103), and the modern high-performance computer has a speed of up to trillion (about 1012 b / s), half The century has raised 1 billion (109) times! From this perspective, the speed of speed-rapid computer performance seems to meet the needs of social progress and economic development. But in fact, the improvement of computer performance is always on the needs of human growing information processing. Today's human social progress and economic development put forward almost endless needs to computers, and with this demand with the emergence of computers, and the spread of the Internet. We know, before the popularity of the computer in 1950, the growth rate of the information in the world is over 150 years; with the wide application of the computer, the increase in information in the information between 1950 and 1960 reached a total of 10 years; 1960 - Demna was shortened during 1992. It is expected that the amount of information will be doubled every 73 days since 2020. This shows that the improvement of computer performance is far from the demand proposed by the growth of the amount of human social information, and the current capacity of computer processing is very weak. Therefore, the development of higher performance computers is always an important topic in the information field.
Impact of quantum computers on future development of IT technology
The basic principle of electronic computers for half a century - The Trial Machine has no changes, which are all built on the "bit" operation. Specifically, a bit is one of the binary, which can be 0 or 1 in {0, 1}. In actual electronic computers, a bit is always achieved by a specific physical carrier, such as tubes, transistors or integrated circuits, etc., so the electronic computer can be regarded as a machine that uses the traditional physics principle to a large number of "bit" implementation operations. . In the half century, although the performance of the computer has changed, this principle has not changed, and the improvement of machine performance is mainly due to the size of the reduced component (physical carrier). Everyone knows that due to the continuous improvement of semiconductor technology and technology, the size of the integrated circuit has been continuously developed in accordance with the so-called "Moore Law", which has been doubled every 18 months. Performance indicators (such as computational speed, storage density, etc.) have achieved great achievements every 18 months. At present, the characteristic size of the integrated circuit has dropped to dozens of nano-level, this trend is still continuing, and it is expected to drop to several atoms, or even smaller. Then there is a new problem, and the traditional physical law is no longer applicable at the atomic surprises, follow the new quantum mechanics, we no longer make traditional computers on the scale of the atom. That is, it will reach its "physical limit" after about 20 years. It is naturally proposed as the following problem; can it be able to create a new computing machine (quantum computer) in the atomic scale in accordance with the principle of quantum mechanics? Is this machine performance beyond the traditional computer? Under the driving drive, the research task of quantum computers will naturally be present. To accomplish this task, people must solve a large number of basic theoretical issues, but also solve a large number of technical and application issues, which gives a significant opportunities and challenges to the technology community.
Basic theory of quantum computers breakthrough
Quantum computer distinguishes the characteristics of traditional computers
Under the driving of requirements, people start to explore the problem of quantum computers. The thoughts of quantum computers began in the 1970-180s, and the US C. Bennet et al., US C. Bennet, etc., in the early 1980s, P. Benioff, etc. in the early 1980s, put forward the research on the calculated quantum mechanics model, 1982 physics R.Feymann proposed a quantum computer. In 1985, British Oxford University D. Deutsh proposed the concept of quantum map foreground. Through the efforts of these scientists, the concept of quantum computers is basically formed. The basic computing unit in the conventional computer is "bit", and the basic computer unit in the quantum computer is "quantium bit". Since the unique properties, "quantum bit" has a characteristic of "bit", that is, it can not only "0" or "1", but also "0" and "1" (i.e., quantum superposition state). We know, usually a "bit" can only represent one of two possible states, and a "quantum bit" can also represent two states. It is broadcasted, and N "bits" can only represent one of 2N states, while n "quantum bit" can simultaneously represent 2N states. It can be seen that the amount of information of "quantum bit" increases the index ratio than "traditional bits". If we can operate a "quantum bit" (quantum superposition state), it means that one can operate 2N state at the same time, realize the so-called "quantum parallel", then the same operation is in the traditional computer. 2n times. The calculation speed thus improves the index! It is better than the computational speed of traditional computers, making it possible to solve problems that traditional computers cannot solve. Quantum computer current development progress
The above analysis is only to explain some of the potential and possibilities of the quantum computer, and further problems are required to find some quantum computers to calculate the specific problems, find specific algorithms that can be calculated for "quantum bits" - quantum The algorithm is satisfactory, so it is convincing. 1994 AT & T Bell Lab P.W.Shor Designed a quantum algorithm for multi-class time of large-numbered decomposition; 1995 Grover discovered a search algorithm for the database on the quantum computer, calculating the time from the classical algorithm to a square root of N. These two algorithms have a significant significance, and people call them "killer applications or use killers" because they in theory that the quantum computer can indeed solve the practical problem of traditional computers, and sweep Clear people's doubts about the calculation of quantum computer, thereby greatly improving the confidence of people developing quantum computers. Especially the Shor algorithm, everyone knows that "large number of decomposition" (the product decomposes a composite real number into two prime numbers) has always been a difficult problem of traditional computers, because it still can't find a tradition of effective (polynomial time) The computer algorithm performs a large number of decomposition. At present, the RSA cryptographic system in the Internet is based on "large decomposition", which is very difficult because of the use of modern computers, so it is very difficult to crack the RSA password. If the large number of decomposition is "not difficult" on the quantum computer, then our currently used RSA cryptographic system is easily cracked. The network security cannot guarantee. It can be seen that the research of quantum computers has a major influences. After the above theoretical problem is solved, the research of quantum computers has become very active since the mid-1990s. For example, US DARPA has funded $ 5 million to support quantum information and computing institute research quantum computing and its application. The National Science Foundation established research program "Quantum and Biologically Inspired Computing"; European Science Foundation established research plan "Quantum Information THEORY AND QUANTUM Computation (1999-2003) "; China University of Science and Technology Quantum Communication and Quantum Computer Lab has also achieved a series of research results. Quantum computers are expected to be?
Current problems in the development of quantum computer
With the above theoretical basis, the actual quantum computer can be developed next. Currently in quantum computer research is more famous: US Los Alamos National Labs, IBM, California Institute of Technology, England Oxford University. To make a quantum computer, first need to store quantum information (quantum bits) on minor particles such as electrons, atoms, etc., and can manipulate and observe it, these tasks are very difficult and difficult. First, you must find a physical carrier to store "quantum bits", which is the first difficult gate. The technical means currently adopted, and the quantum bits are stored using the atom's self-rotating axis or its energy level. For example, the Boulder National Standards Bureau captures a single ion in an electromagnetic field in a lower 273 ° C (near absolute temperature zero); Polarized Light uses polarized light to interfere with each other; Los Alamos National Laboratory is also captured ion ( Trapping ions). The second problem is how to manipulate and observe the state of a single particle. For example, IBM uses nuclear magnetic resonance techniques to indirectly observe the ionic state. So far, through the unremitting efforts of scientists and technicians, only "quantum computers" in size can be made through the above technical means. According to reports, in August 2000 IBM Almaden Research Center made five "quantum bit" (QUBITS) machines, March 2000 Los Alamos National Lab manufactures 7 quantum bits. Obviously, such a "machine" also has a considerable distance from the actual application. Quantum computer to achieve practical application
First, the state of the quantum (superimposed, superposition) is very unstable, and it is extremely susceptible to the external noise or the interference of the quantum state is formed, and the information stored in the quantum computer crashes, causing a computer error. For example, when a quantum state is observed, the state will immediately collapse for a certain set value (0 or 1). This phenomenon is physically known as Decoherence, which is the natural nature of quantum. It can be seen that the quantum calculation is very fragile, it is very easy to errors, and with the increase of the size of the machine, the reliability of the calculated reliability has dropped sharply, making it difficult to make large-scale quantum computers. In order to solve the above difficulties, the current international error correction, decentralization, and hardware architecture, etc., and has achieved some results. Another important issue is that, so far, people find two successful quantum algorithms: SHOR algorithm and Grover algorithm, we also need more quantum algorithms that can solve the actual major problems to prove on which issues are quantum computers. It is indeed superior to traditional computers.
Whether the quantum computer can be applied in the next five years
Pesson believes that the power of quantum calculation is derived from the characteristics of Quantum Interference and Quantum Entanglement, which is also the same characteristic to bring quantum calculation vulnerabilities and easy errors. Therefore, problems such as quantum error correction, decentralization, etc., are difficult to bring to the quantum calculation itself, so it is difficult to overcome. Optimists believe that the above difficulties can be overcome in a short period of time, such as the "decentralization" caused by the measurement, 1998 Los Alamos National Laboratory and IBM, identify an indirect measurement of "quantum bit" Avoid destroying the superposition state of the quantum. In 2002, the researchers of Wisconsin University believed that using the existing silicon-made techniques, it is possible to manufacture a computer with millions of quantum points (1024 × 1024) in the short term. Let us return to the question just now, when can I make practical quantum computers? Since people have different estimates for difficulties, some have been saying a few years, some have to say that it takes a few centuries, the benevolent sees benevolence, but the wise is witness, but it is the same: That is, the research of quantum computers Regardless of success or not, the research of quantum calculations will definitely bring far-reaching influence in the future life, so regardless of optimists or pessimists, they have used it as an important research topic in the 21st century, and will be highlist. Other related content:
http://lqcc.ustc.edu.cn/kp/qComputer.htm
Center for Quantum Computer Technology: http://www.qcaustralia.org/home.htm
