In quantum channels zero plus zero can equal nonzero

first_imgThe scientists account for this “superactivation” property by explaining that quantum channels have two different kinds of capacity. “Private capacity” is the rate at which a channel can send secure classical data. “Assisted capacity” is the transmission rate in which multiple symmetric channels can assist a given channel in sending quantum data. As the physicists demonstrated, a channel’s assisted capacity is always at least half as large as its private capacity. As an example of superactivation, the scientists showed that combining a private “Horodecki” channel and a symmetric channel (each with zero capacity) can give a quantum capacity of more than 0.01 qubits per channel. It’s as if each channel has the potential to activate the other, canceling the other’s reason for having zero capacity.“The effect has something to do with the existence of something called ‘private Horodecki channels,’” Smith said. “These channels have the weird property that, even though they’re too noisy to allow quantum communication, somehow they still allow you to send classical messages that are completely private. Roughly speaking, we figured out that there’s this second kind of channel – a symmetric channel – that also can’t send any quantum messages on its own, but can be used to transform the private classical communication of the Horodecki channel into noiseless quantum communication.”Superactivation raises some interesting questions about the nature of communication. For instance, you would think that the question “can this communication link transmit any information?” would have a straightforward answer. However, with quantum data, the answer may be that it depends on the context. If identifying a quantum channel’s capacity is not as straightforward as previously thought, then new ideas will be needed for designing error-correction techniques in quantum channels.These results lead to other questions, such as what the effect of combing three channels might be. The overall complexity of quantum channel capacity will keep the researchers investigating the fundamental characteristics of communication in the physical world.“First, I’d like to understand the role of privacy in this whole thing, and whether it’s necessary to achieve a superactivation,” Smith said. “In the longer term, I’d like to see if we can turn the improved understanding of quantum error correction that comes out of this into some practical ways to reduce noise in prototypes for quantum computers.”More information: Smith, Graeme and Yard, Jon. “Quantum Communication with Zero-Capacity Channels.” Science, 26 September 2008, Vol. 321. 10.1126/science.1164382.Copyright 2008 PhysOrg.com. All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of PhysOrg.com. (PhysOrg.com) — Physicists have discovered a strange characteristic of quantum communication channels. If two quantum channels each have a transmission capacity of zero, they may still have a nonzero capacity when used together. This effect, which has no classical counterpart, reveals a new complexity in the fundamental nature of quantum communication. Citation: In quantum channels, zero plus zero can equal non-zero (2008, October 6) retrieved 18 August 2019 from https://phys.org/news/2008-10-quantum-channels-equal-non-zero.html Explore further Physicists propose a second level of quantization for quantum Shannon theorycenter_img The coauthors of the study, Graeme Smith of the IBM T.J. Watson Research Center in Yorktown Heights, New York, and Jon Yard of Los Alamos National Laboratory in Los Alamos, New Mexico, have published their research in a recent issue of Science.Smith and Yard explain that one of the most important challenges in designing communication networks of any kind is taking steps to correct for noise. By decreasing noise levels in communication channels, developers can increase channel capacity, which is defined as the number of bits (or qubits, in quantum channels) that one channel can transmit. For a channel with zero capacity, no bits are transmitted.For several decades, scientists have used a well-known formula developed by Claude Shannon in 1948 for developing error-correction techniques in classical communication channels. This formula guides the design of modern communication schemes used in cell phones, the Internet, and deep-space communication. In this classical formula, capacity is additive: when two channels are used simultaneously to transmit data, the capacities of the channels are added to obtain the total capacity.But even today, physicists don’t understand quantum communication nearly as well as the classical kind. In the current study, Smith and Yard show that some pairs of zero-capacity channels can have a positive quantum capacity when used together. As the physicists explain, that would be like two cut telephone cables being able to transmit data when used together. Their finding shows two things: that quantum capacity is not additive like classical capacity, and that the quantum capacity of a single channel does not completely specify its capability for transmitting quantum information.“To me, the strange thing is that you have these two things that you would have thought were useless – I mean, you’d usually think that a zero-capacity channel was good for nothing – and when you put them together, somehow there’s a kind of synergy and they develop a very quantifiable value,” Smith told PhysOrg.com. “This doesn’t happen when you work with classical channels, and since my intuition was based on that case, I was really surprised when it happened here.” Two quantum channels that have zero capacity when used individually (orange and yellow figures) can enable communication when used together (green figure). Image credit: Graeme Smith and Jon Yard. ©2008 Science. This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.last_img read more

Entrepreneur receives funding for tornado power generator

first_img © 2012 Phys.org Michaud’s idea is to use a fan to blow some of the excess heat produced by conventional power plants, into a cylindrical hollow tower, at an angle. Doing so should create a circular air current, which he says will grow stronger as it moves higher. The higher it goes the more energy it draws due to differences in temperature. The result would be a controlled man-made tornado. To put it to good user, turbines would be installed at the base of the vortex to create electricity. The original test will be conducted at Lambton College in Ontario – the tower will be 131 feet tall with a 26 foot diameter. That should be enough to create a vortex about a foot in diameter – enough to power a small turbine. It’s just a proof of concept, Michaud notes on his site, a real-world tower would be about 25 meters in diameter, and would be capable of producing up to 200 megawatts of power using only the excess heat generated by a conventional 500 megawatt plant. Power goes up geometrically, he says, as the size of tower grows. He adds that the cost of producing electricity this way would be about 3 cents per kilowatt hour, well below the typical 4 or 5 cents for coal plants.Michaud has been investigating the idea of harnessing the power of tornado’s to provide electricity for several decades but until now has had problems being taken seriously by venture capitalists. He adds that his company built and successfully tested an AVE prototype in 2009, hinting that he has no doubts that the new tower and turbines will work as advertised.For those worried that a man-made tornado might get out of hand, escape its enclosure and wreak havoc on the nearby community, Michaud says that can’t happen because all it would take to stop the whole process would be to turn off the fan that feeds the vortex the warm air. Citation: Entrepreneur receives funding for ‘tornado’ power generator (2012, December 18) retrieved 18 August 2019 from https://phys.org/news/2012-12-entrepreneur-funding-tornado-power.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. French company uses wind turbine to create fresh watercenter_img (Phys.org)—Electrical engineer and entrepreneur Louis Michaud’s AVEtec company has received funding from PayPal cofounder Peter Thiel’s Breakout Labs program to build an experimental Atmosphere Vortex Engine (AVE). The $300,000 in startup funds is to go towards building a working engine to dispel or prove the viability of using such technology to produce electricity with virtually no carbon footprint. More information: vortexengine.ca/index.shtmlwww.breakoutlabs.org/news-even … abs-includes-an.html Explore furtherlast_img read more

Physicists propose superabsorption of light beyond the limits of classical physics

first_imgIn one potential method to realize superabsorption, a superabsorbing ring absorbs incident photons, giving rise to excitons. Credit: Higgins, et al. Citation: Physicists propose superabsorption of light beyond the limits of classical physics (2014, August 28) retrieved 18 August 2019 from https://phys.org/news/2014-08-physicists-superabsorption-limits-classical-physics.html More information: K.D.B. Higgins, et al. “Superabsorption of light via quantum engineering.” Nature Communications. DOI: 10.1038/ncomms5705 A comparison of absorption: Independent atoms (red line) absorb excitons linearly, while a proposed superabsorption scheme (green line) could absorb excitons superlinearly (ideally, N2). The yellow and blue lines represent superabsorption when accounting for costs in different ways. Credit: Higgins, et al. The ability to absorb light beyond the limits of classical physics could lead to a new class of quantum nanotechnology. One potential application is optical light or microwave sensors that could be used in future cameras or for scientific instruments. Light-harvesting technologies could also benefit by absorbing an increased number of excitons compared to conventional systems. Superabsorption could be particularly useful for wireless power transfer using light for situations where wired electrical power is impractical, such as for remote sensors or biologically implanted devices.”Eventually, harvesting sunlight in a highly efficient way might one day be possible using superabsorbing systems based on our design, but a more immediate application would be building an extremely sensitive light sensor that could form the basis of new camera technology,” said coauthor Simon Benjamin, Professor at Oxford University. “A camera sensor harnessing the power of our superbsorbing rings would have very high time and spatial resolution. And it could pave the way for camera technology that would exceed the human eye’s ability to see clearly both in dark conditions and in bright sunlight.”The physicists say that superabsorption could be experimentally demonstrated in the future in a few different ways, with possibilities including an array of quantum dots or a Bose-Einstein condensate. In the future, they plan to investigate new methods for achieving extreme light absorption.”We are working on an alternative scheme for quantum enhanced light absorption, which uses what’s called a ‘dark state’ as an efficient means of extracting energy from light, and is similar to what happens in photosynthesis, which is in contrast to superabsorption, which is very different to how natural light harvesters work,” Higgins said.”We also have plans to extend the present work by adding another effect from quantum optics, which we hope will make the proposal much easier to implement experimentally and thus realize the potential technological applications more quickly.” The key to achieving superabsorption is to use quantum engineering techniques to ensure that most state transitions take place within a specific frequency (which the scientists call the “good” frequency, in contrast with the “bad” frequencies that should be avoided). Photons can then be trapped so they are not emitted back out. Although the system would likely deviate from the “good” frequency over time, there are a few reinitialization schemes that would periodically monitor and correct the system’s frequency. (Phys.org) —In a well-known quantum effect called superradiance, atoms can emit light at an enhanced rate compared to what is possible in classical situations. This high emission rate arises from the way that the atoms interact with the surrounding electromagnetic field. Logically, structures that superradiate must also absorb light at a higher rate than normal, but so far the superabsorption of light has not been observed. Superabsorbing ring could make light work of snaps Explore further This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. © 2014 Phys.org Now in a new paper published in Nature Communications, physicists Kieran Higgins, et al., have theoretically shown that superabsorption can be demonstrated using quantum engineering techniques. Structures capable of superabsorption could have applications including solar energy harvesting, novel quantum camera pixels, and wireless light-based power transmission.”If you had a ring comprising 40 atoms, this would absorb light 10x faster than any classical approach,” Higgins, at Oxford University, told Phys.org. “The key thing in this work is that it’s a fundamentally different way of absorbing light. So if you want to design the most efficient possible absorber and you have a certain number of atoms, this is a new and better way to do it using quantum physics. The atoms behave as if there’s more of them than there actually are, which is the really cool thing.”As the physicists explain, superabsorption is the reciprocal of superradiance. Superradiance was first introduced 60 years ago by the physicist Robert Dicke, and since then has found a variety of applications, including a new class of laser. Physically, superradiance occurs when a system of excited atoms decays and moves down a ladder of states called the “Dicke” or “bright” states. As a result, light can be emitted at an enhanced rate that is proportional to the square of the number of atoms.In natural systems, light emission dominates over light absorption, which is why superabsorption has not yet been observed. But in the new paper, the scientists have shown that atoms in close proximity and with a suitable geometrical arrangement can interact with each other in such a way as to exhibit superabsorption. Journal information: Nature Communicationslast_img read more

Chinas Yutu lunar rover finds moon geography more complex than thought

first_img(Phys.org)—A team of researchers working on China’s Chang’E-3 lunar mission has found multiple distinct geographic rock layers beneath the surface of the moon, indicating a much more complex geographical history than was previously thought by most in the scientific community. In their paper published in the journal Science, the team describes their analysis of data sent back by the Yutu rover. © 2015 Phys.org More information: A young multilayered terrane of the northern Mare Imbrium revealed by Chang’E-3 mission, Science 13 March 2015: Vol. 347 no. 6227 pp. 1226-1229 . DOI: 10.1126/science.1259866AbstractChina’s Chang’E-3 (CE-3) spacecraft touched down on the northern Mare Imbrium of the lunar nearside (340.49°E, 44.12°N), a region not directly sampled before. We report preliminary results with data from the CE-3 lander descent camera and from the Yutu rover’s camera and penetrating radar. After the landing at a young 450-meter crater rim, the Yutu rover drove 114 meters on the ejecta blanket and photographed the rough surface and the excavated boulders. The boulder contains a substantial amount of crystals, which are most likely plagioclase and/or other mafic silicate mineral aggregates similar to terrestrial dolerite. The Lunar Penetrating Radar detection and integrated geological interpretation have identified more than nine subsurface layers, suggesting that this region has experienced complex geological processes since the Imbrian and is compositionally distinct from the Apollo and Luna landing sites. Journal information: Science China’s Yutu rover is still alive, reports say, as lunar panorama released Citation: China’s Yutu lunar rover finds moon geography more complex than thought (2015, March 13) retrieved 18 August 2019 from https://phys.org/news/2015-03-china-yutu-lunar-rover-moon.htmllast_img read more

Solar battery receives 20 of its energy from the sun

first_img(Left) Illustration of the new Li-I solar flow battery with an aqueous electrolyte, which compared to organic solvents has advantages in terms of performance, cost, and environmental friendliness. (Right) When the solar battery is exposed to light, the voltage that it needs from an external source immediately decreases, as the device is being charged by the solar cell. Credit: Yu, et al. ©2015 American Chemical Society Semiliquid battery competitive with both Li-ion batteries and supercapacitors (Phys.org)—Last October, researchers at Ohio State demonstrated the world’s first solar battery—a solar cell and a lithium-oxygen (Li-O2) battery combined into a single device. The main attraction of the solar battery concept is that, because it can harvest, convert, and store solar energy as chemical energy all in one device, it eliminates losses that occur when transferring electrons between multiple devices. The researchers estimate that this integration can potentially reduce overall costs by about 25%. © 2015 Phys.org Journal information: Journal of the American Chemical Society The researchers explain that the key component of the solar battery design is the electrolyte because it bridges the hydrophilic aqueous Li-I battery and the hydrophobic surface of the dye-sensitized solar cell photoelectrode. The electrolyte consists of several ingredients, including lithium iodide salt (LiI), which is essential for the battery’s electrochemical reactions, along with various additives that allow the hydrophilic electrolyte to wet the hydrophobic photoelectrode surface. This surface-wetting contact between the two components is essential for efficiently transferring charge from the solar cell to the battery.Overall, tests showed that the Li-I solar battery has a theoretical capacity (35.7 Ah/L with 2M LiI) close to that of conventional Li-I batteries, and it can be photocharged to about 91% of its theoretical capacity. It also appears to have good cyclability, retaining its full capacity for at least 25 cycles. Unfortunately, it currently takes about 16.8 hours to photocharge the device with a 0.1-mL electrolyte to its full capacity, and this long charge time is one of the biggest areas in need of improvement. The researchers plan to address this problem by improving the efficiency of the aqueous-compatible photoelectrode, among other strategies.In the future, the scientists also plan to extend some of the concepts in this solar battery design to other combinations of battery chemistry and solar cell photoelectrochemistry. One possibility is developing solar batteries that use sodium instead of lithium as the anode, since sodium has been gaining appeal due to its wide abundance and inexpensive fabrication costs.”Improving the solar battery’s photocharging rate and achieving full photocharging are among our goals,” Wu said. “We hope this technology will ultimately be commercialized for applications in grid-scale stationary solar energy conversion and storage.” Explore further This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. Although the solar-charged Li-O2 battery represented a novel and promising concept, it had a drawback: its electrolyte was made of organic solvents, which are non-aqueous and therefore not compatible with aqueous (water-based) redox flow batteries, limiting the device’s performance. Organic solvents also face problems with environmental impact and cost.Now in a new paper published in the Journal of the American Chemical Society, Ohio State Professor Yiying Wu and his research group have improved upon their original design by developing a solar battery that replaces the organic solvents with a more environmentally friendly and cost-effective iodine redox-based aqueous solution. The new version is an aqueous lithium-iodine (Li-I) solar flow battery, which integrates an aqueous Li-I redox flow battery with a dye-sensitized solar cell. This compatibility allows the device to operate at a higher voltage, improving its overall performance and bringing the solar battery a step closer to commercialization.”I think the greatest significance is the identification and demonstration of aqueous flow batteries as the platform for solar batteries,” Wu told Phys.org. “Flow batteries are flexible in materials selection. They are modular and scalable, and are being considered for applications in stationary storage, stand-alone power and electric vehicles. Our aqueous flow solar battery is an important step that brings this simultaneous solar energy conversion and storage concept closer to practical applications.”When exposed to sunlight during the charging process, the Li-I solar battery receives about 20% of its charging energy from the sun, meaning it uses 20% less energy from conventional energy sources compared to conventional Li-I batteries. The photoassisted charging process occurs when sunlight illuminates the dye molecules, causing them to become photoexcited and inject their electrons into the photoelectrode—the battery’s third electrode, in addition to the conventional cathode and anode. The photoexcited electrons supply a photovoltage to the battery, which reduces the charging voltage (which is supplied by external energy sources) to a value that is even lower than the discharging voltage. As the researchers explain, this feat would be thermodynamically impossible without the solar energy input. More information: Mingzhe Yu, et al. “Aqueous Lithium–Iodine Solar Flow Battery for the Simultaneous Conversion and Storage of Solar Energy.” Journal of the American Chemical Society. DOI: 10.1021/jacs.5b03626 Citation: Solar battery receives 20% of its energy from the sun (2015, July 14) retrieved 18 August 2019 from https://phys.org/news/2015-07-solar-battery-energy-sun.htmllast_img read more

Soildwelling fungi study shows extent of worldwide distribution

first_img Arbuscular mycorrhizal root tuber. Citation: Soil-dwelling fungi study shows extent of worldwide distribution (2015, August 28) retrieved 18 August 2019 from https://phys.org/news/2015-08-soil-dwelling-fungi-extent-worldwide.html More information: Global assessment of arbuscular mycorrhizal fungus diversity reveals very low endemism Science 28 August 2015: Vol. 349 no. 6251 pp. 970-973 DOI: 10.1126/science.aab1161ABSTRACTThe global biogeography of microorganisms remains largely unknown, in contrast to the well-studied diversity patterns of macroorganisms. We used arbuscular mycorrhizal (AM) fungus DNA from 1014 plant-root samples collected worldwide to determine the global distribution of these plant symbionts. We found that AM fungal communities reflected local environmental conditions and the spatial distance between sites. However, despite AM fungi apparently possessing limited dispersal ability, we found 93% of taxa on multiple continents and 34% on all six continents surveyed. This contrasts with the high spatial turnover of other fungal taxa and with the endemism displayed by plants at the global scale. We suggest that the biogeography of AM fungi is driven by unexpectedly efficient dispersal, probably via both abiotic and biotic vectors, including humans. © 2015 Phys.org Arbuscular mycorrhizal fungus live among 80 percent of plant roots in a symbiotic relationship with their host—the plants get assistance in obtaining nutrients, help with getting water in dry conditions and a leg up in battling pathogens. The fungi, in return, get a steady source of carbon. But, as the researchers note, little is known about the global biography of such microorganisms. They suggest a better understanding of how the microorganisms do their job and how they disperse could have important implications for better understanding our global ecosystem, helping with restoration of damaged areas, and perhaps for increasing or at least sustaining agricultural yields. To learn more, the team embarked on a study that took them to six continents and involved pulling up plants to examine their roots in forests, shrub land, grasslands, successional sites and semi-desert spots, looking for samples of fungi.In all, the team gathered 1,104 root samples, resulting in approximately 912 thousand fungus samples. Of those 836 were able to be sequenced revealing almost 250 DNA based “virtual taxa,” that could be associated with 161 unique plant species. The team also conducted ribosomal RNA testing on the samples to learn more about their evolutionary history. Arbuscular mycorrhiza seen under microscope. Flax root cortical cells containing paired arbuscules. Credit: Public Domain Explore furthercenter_img Fungi—key to tree survival in warming forest (Phys.org)—An international team of researchers has conducted a worldwide census of fungi that live in plant roots and in so doing has found them to be surprisingly broadly spread. In their paper published in the journal Science, the team describes their far-flung study, what they found and offer theories on a mystery that was also uncovered. Journal information: Science In studying their data, the researchers found that 93 percent of the fungi identified existed in the soil on more than one continent, and that 34 percent of them were found on all six continents. They also found that dispersal appeared to lessen the farther plants were from the equator and that at the local level, spatial distance and environmental conditions had an impact on the types of fungus appearing in plant roots.RNA testing showed that the dispersal of the fungi appeared to have occurred after the continents drifted apart, which caused the researchers to wonder what sort of mechanism might have been responsible for carrying the microorganisms across such great distances. They suggest it could have been a variety of elements including both biotic and abiotic vectors. This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.last_img read more

Realty scrips tower as Govt ups floor area ratio in Delhi

first_imgShares of Anant Raj jumped 9.71 per cent, DLF (7.20 per cent), Oberoi Realty (7.16 per cent) and Unitech (4.41 per cent) on the Bombay Stock Exchange. Similarly, shares of Housing Development and Infra Ltd rose 3.65 per cent, D B Realty (3.43 per cent) and Omaxe Ltd (1.20 per cent). Following the gains in these stocks, the BSE realty index was up 4.03 per cent at 1,660.73, the best among the 12 sectoral indices. ‘Led by the Delhi government’s decision to increase the Delhi city’s floor area ratio by 200 per cent, most realty sector stocks saw huge surge in buying activity,’ said Rakesh Goyal, Senior Vice President, Bonanza Portfolio Ltd. Also Read – I-T issues 17-point checklist to trace unaccounted DeMO cashFAR in respect of plots of 750-1000 sq mt size has been enhanced from the present 150 per cent to 200 per cent while the same has been increased from 120 per cent to 200 per cent for plots of 1000 sq mt and above, according to a senior Urban Development ministry official. While the Ground Coverage for plots of 750-1,000 sq mt will remain at 50 per cent, it has been increased from 40 per cent to 50 per cent for plots above 1,000 sq mt.last_img read more