Andrew (Gabriel) Livshits
As with all new computers, and in particular, personal computers of all kinds, other distinct advantages and positive effects of use, brought the realization that these are the most intelligent and useful innovations carry a lot of problems and
As it turned out to correct the problem is extremely difficult, and in most cases impossible practice within acceptable financial cost
This phenomenon is particularly strengthened and extended to new industries and technology areas with the advent of the Internet
In this regard, the best prospects are the so-called quantum computers
These types of computers, common signs of which are still not fully defined and not fully investigated, as is, even at the initial stage of development, are defined and identified specific problems also need to be addressed to enhance and intensify the innovation front infrastructure projects quantum computers
Physicists have found that quantum entanglement - correlating the measurements of the physical properties of objects (such as the spin of photons), which was considered the "main force" of quantum computers, may be harmful to them. Especially the use of some of entanglement leads to the fact that these machines lose their classical counterparts. Research article appeared in the journal Physical Review Letters, and its summary is available on the website of the American Physical Society.
As part of its work, which was purely theoretical, the researchers studied a model of a quantum computer proposed by German Hans Brigelem Raussendorfom and Robert in 2001. In this model, the computer is a binary function (program), which in turn holds a measurement subsystems of a quantum system, which is the initial data of the program. The work function at each step is determined, among other things, the results of the measurements have already been made.
In any quantum computer is an element of chance, as it is based on the principles of quantum mechanics, which is based on the concept of probability. In this work, the element of chance characterized so-called geometric measure of entanglement. As a system, which took the work function of the program used a system of n qubits and entangled different subsets of the system.
As a result, the researchers were able to determine that most of the original state - a condition in which, after the program geometric entanglement measure is higher than if the task at each stage of the algorithm solved the coin toss in the air. According to the researchers, this result shows that in order to be suitable for practical research, quantum computers have to use not only the phenomenon of quantum entanglement, but other features of the microworld.
Just two groups of physicists announced the creation of systems of three entangled superconducting qubits. Such systems, in theory, make it possible to minimize the number of errors made by a quantum computer. Work of both published in the journal Nature. They are described briefly in the portal Nature News.
Entanglement - a special property of quantum systems, which is manifested in the fact that they are related to each other, even from a distance. If the status of one of the systems changes, the time changes and status of the other. This feature allows the observer to find out the status of all entangled systems, conducting measurements for some of them.
It is believed that entanglement can be useful for building a quantum computer - computing devices that can hold a lot more calculations per unit of time than conventional computers due to the fact that the quantum system simultaneously in multiple states - the so-called superposition. However, during the computation, such computers will inevitably make mistakes - due to the nature of their nature, they lose some of the information.
In order to circumvent this difficulty, to be used for computing systems of more than three qubits (quantum analogues of bits). To see if an error occurred, you need to measure, and it destroys the superposition. But if each qubit entangled with two more, one can measure the condition of two of them, while the third will continue to "work."
Authors of the two new works for the first time managed to confuse the three qubits, which are superconducting electrical circuits - they are considered the most promising designs for the development of quantum computers, how they can be handled in much the same way as with conventional electronic devices. One group was able to achieve the state of quantum entanglement GHZ, which is a superposition of three qubits in the state 0 or 1. The second team to implement the so-called state of W, where two of the three entangled qubits represent a logical value of 0, and one - 1.
While none of the groups did not show in practice how to set up the system he may correct errors.
Although entanglement three superconducting circuits is a significant achievement in making other quantum systems physics able to confuse more components. Thus, the scientists were able to create a system of eight entangled ion qubits and photonic ten. In addition, the recently proposed algorithm, theoretically allowing confuse any number of particles.
The importance and the exciting prospects for further development of the theme, actively perceived innovation community and it gave jolt to new and new research and ideas
Physicists have developed a quantum computer processing power which is capable of scaling with greatly exceed the capabilities of classical computers. The results of four independent groups of researchers to build similar devices appeared in the journal Science and the archives of Cornell University, briefly recounts the essence publications Nature News and Science Now.
The device consists of a microchip located on several glass fibers, several times crossing each other. Single photons are fed to the input of the device and are detected at the output.
Then, what conclusions will get photons depends on their interaction with each other in the overlapping areas. This interaction can be quite easy to simulate on a PC, but only as long as the photon is very small. With the growing number of computational complexity of this problem increases exponentially. At 25 to 400 channels photons measured result obtained becomes easier than calculated.
Scientists point to the fact that an optical device is actually a quantum computer, in which the calculation should be done through the interaction of photons. When modeling the behavior of photons computer solves the problem of computing the permanent of a matrix - the same problem in an optical device to perform "physically". Permanent of the matrix - is a function of the elements of this matrix are used in discrete mathematics and combinatorics. The formula for the permanent looks like a formula for the determinant of the matrix in which all the disadvantages replaced by pluses. In contrast to the permanent determinant calculation is extremely complex from a computational point of view the problem.
The main drawback of the device is its established specialization to solve one problem. While the "computer" is able to cope with only one objective - to compute the permanent, but the authors stress that the main thing when it was created - to show the potential of the devices.
To create a more conventional quantum computers are commonly used ionized atoms collected entangled quantum systems. The calculations are carried out in them by changing spins. The key difference from the classical quantum devices is that they can simultaneously be in multiple states, so calculate them are held simultaneously, rather than sequentially, and the result is probabilistic.
European physicists examined the dynamics of the behavior of the spins in the system nanomagnets by bombarding them with neutrons complexes. The work of scientists published in the journal Nature Physics, and its summary can be found on the website of the Institute Laue-Langevin name in Grenoble.
The authors studied on the basis of circular nanomagnets organic complexes, which have several metal atoms. The spins of the electrons in these systems possess unusual properties, which is explained by the strict finite size of the latter. Similar complexes are interested scientists as potential storage devices in quantum computers.
Scientists have shown that the behavior of the spins of electrons in such systems can be measured directly, without the use of computer simulation. For this physics irradiated crystalline samples neutron beam and fixed them scattering. Measurement allowed to map the magnetic moments in the complex and follow their dynamics.
Earlier mathematics from the Massachusetts Institute of Technology have shown that in quantum systems with three states of spin entanglement increases with the number of particles. This means that in the future you can create quantum systems with a large number of entangled particles simultaneously. Such systems are required for any relatively complex quantum computing.
A group of physicists from Japan, China and the United States was the first to build a practical quantum computer on the von Neumann architecture - that is, the physical separation of the quantum processor and quantum memory. The article appeared in the scientific journal Science, and its preprint available at arXiv.org.
At the moment, for the practical implementation of quantum computers (computers, which are based on the unusual properties of objects of quantum mechanics), physicists use various exotic objects and phenomena - trapped in an optical trap ions, nuclear magnetic resonance. In the new work, scientists have relied on tiny superconducting circuits - the feasibility of a quantum computer with the help of such schemes has been described in Nature in 2008.
Collected by computer scientists of quantum memory, the role of which carried two microwave cavity of the two qubit processor connected bus (also played its role cavity and superconducting qubits were the scheme), and devices for data erasure. With the help of the computer scientists realized two main algorithm - the so-called quantum Fourier transform, and the conjunction with quantum Toffoli gates.
The first algorithm is a quantum analog of the discrete Fourier transform. Its distinguishing feature is much smaller (about n2) the number of functional elements in the implementation of the algorithm in comparison with the equivalent (in the order n 2n). Discrete Fourier transform is used in various fields of human activity - from the study of partial differential equations to data compression.
In turn Toffoli quantum logic gates are the basic elements of which, with some additional requirements can be any Boolean function (program). A distinctive feature of these elements is reversible, that from the point of view of physics, among other things, to minimize heat dissipation device.
Scientists say they have created a system has one great advantage - it can be easily scaled. Thus, it can serve as a building block for future computers. According to the researchers, the new results demonstrate the promise of the new technology.
Engineers at MIT have created a graphene-based and zinc oxide nanofilamentov flexible hybrid photovoltaic cells. Description of work published in the journal Nano Letters, and its summary retold on the site of the institute.
The device consists of a monatomic layer graphene coated with a polymer layer. It hosts nanofilamenty zinc oxide-coated quantum dots of lead sulfide, or organic polymer P3HT. Graphene acts as a transparent electrode, through which receives light and the quantum dots are sinks of radiation.
Photocells this architecture has created before, but instead of graphene are commonly used indium tin oxide (ITO). The use of graphene instead of inorganic oxide to make a new device flexible.
The effectiveness of the prototype developed by the author reaches 4.2 percent, which is quite small compared with standard silicon solar cells, but comparable to the effectiveness of these experimental devices.
Previously, researchers have used the graphene to create a fully carbon photocell. As a light-absorbing substance in it were carbon nanotubes. The effectiveness of an experimental solar cell does not exceed one percent.