Citation: Long-Lasting Quantum Memory Leads to Long-Distance Quantum Communication (2008, October 7) retrieved 18 August 2019 from https://phys.org/news/2008-10-long-lasting-quantum-memory-long-distance.html “Our work opens up new avenues for extending the coherence time of a quantum memory towards the seconds regime,” co-author Chih-Sung Chuu of the University of Heidelberg told PhysOrg.com. He added that a storage time of a few seconds could result in a communication distance of a few thousand miles.Most quantum memory devices reported to date use magneto-optical traps, rather than optical traps, to confine groups of atoms. However, the magnetic field limits the storage time by causing the atoms’ ground state to broaden. The broadening lingers even when the magnetic field is temporarily turned off during storage, and, without the magnetic field’s confinement, the atoms begin to diffuse after a few hundred microseconds. With this limited storage time, quantum communication cannot reach very long distances.By using an optical trap instead, the scientists could eliminate the negative effects of the magnetic field on storage time. The optical trap is formed by a tightly focused laser beam, which can trap atoms at a density of one trillion atoms per cubic centimeter. Then, a right-circularly polarized “write” beam of about 100,000 photons illuminates the group of atoms. Later, a left-circularly polarized “read” beam converts the quantum state of the atoms into a photon.“The ‘write’ beam probabilistically generates a quantum state in the atoms by interacting with them,” Chuu explained. “The ‘read’ beam is used to convert the quantum state into a photon, which can be detected by a single-photon detector.”In their demonstration, the scientists achieved storage times of 60 microseconds, but they explain that this is currently limited by the high temperature of the experiment. Cooling the atomic ensemble to a lower temperature (submicro-Kelvin, or very near absolute zero) could limit the thermal motion of the atoms, and extend the storage time. With cooler temperatures and by using an optical lattice for additional confinement, the physicists expect to achieve a storage time of several seconds. By increasing the storage time of a quantum memory device, the scientists have taken another step toward realizing long-distance quantum communication, which could be used to build quantum computers, among other innovations. Quantum computers could be extremely quick at solving certain problems, such as factoring, which would make them useful for applications that require large amounts of computing power. More information: Chuu, Chih-Sung; Strassel, Thorsten; Zhao, Bo; Koch, Markus; Chen, Yu-Ao; Chen, Shuai; Yuan, Zhen-Sheng; Schmiedmayer, Jörg; and Pan, Jian-Wei. “Quantum Memory with Optically Trapped Atoms.” Physical Review Letters 101, 120501 (2008).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. The basis for quantum communication is the ability to entangle two photons, A and B, where one photon, B, is sent down a transmission channel. There is also a third photon, C, which is entangled to a quantum state but not to the other two photons. A quantum state may be represented by a group of atoms that shares a superposition between two ground states (in superposition, both ground states exist simultaneously, and there is a certain probability that the atoms are in one ground state or the other).When physicists perform entanglement swapping by making a Bell state measurement on photons A and C, photon B also becomes immediately entangled to the quantum state, even though it has already traveled down the transmission channel. The site where the sent photon becomes entangled with the quantum state is called a quantum repeater. Quantum repeaters, which occur throughout the transmission channel, can generate and store entanglement in order to boost the signal, with the aim of getting the entangled state to reach the other end. Entanglement can be stored by some sort of quantum memory device until, ultimately, the quantum state is “read” by being converted into another photon.The key is that the quantum state should stay entangled with the sent photon for as long as possible, in order to maintain the quantum correlation throughout the transmission channel. Without a quantum memory, there is a small probability that quantum information can be transmitted over large distances, but the probability is exponentially dependent on the transmission length. With quantum memory, the transmission probability is only polynomially dependent on the length, greatly reducing the waiting time for a successful transmission. Physicists are currently working to improve the storage times of quantum memory devices. Recently, a team of scientists from the University of Heidelberg in Germany, the University of Science and Technology of China in Heifei, China, and the Atominstitute der Österreichischen Universitäten in Vienna, Austria, has demonstrated a new way to extend the storage time of quantum memory devices. For the first time, the scientists successfully used an optical trap to confine a group of atoms, in which the quantum state is stored. The scientists predict that the method could greatly exceed previous storage times that are on the order of microseconds. (PhysOrg.com) — Physicists have taken a step closer to realizing long-distance quantum communication, in which a quantum state is transferred from one location to another by becoming entangled with a traveling photon. Explore further Optimizing the growth of coatings on nanowire catalysts (A) In the scientists’ apparatus, the atomic ensemble is confined in an optical trap formed by a focused laser beam. This beam is overlapped with counterpropagating “write” and “read” beams. The resulting Stokes and anti-Stokes photons are detected, serving as a useful probe for quantum memory storage. (B) An absorption image of the optically trapped atoms. Image: Thorsten Strassel. 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.
Month: August 2019 Smart wound dressings could identify and destroy infectioncausing bacteria
Month: August 2019 Lenovo applies for a patent for a grip tablet keyboard
The patent application was apparently made back in 2010, but thus far, Lenovo has not made such a device available for sale. It’s not known if they plan to, or if the company decided the idea wouldn’t sell. At any rate, the dual keypads talk to the tablet wirelessly either through Bluetooth or infrared, and because they are clamped on when needed, can be placed anywhere on the tablet. Their small size also makes them much more portable than a wireless keyboard.The patent application also notes that the original design calls for a standard QWERTY keyboard, though others might be added as well and that the dual keyboards can also be placed flat on a table in front of the tablet, if desired, to serve in a more conventional way. 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. (Phys.org) — With the introduction of the tablet computer, users of such devices have been forced to make some tradeoffs regarding keyboards. Virtually all tablets make use of image display and finger touching or tapping to create a virtual keyboard, which for many, is not nearly the same as one that provides the tactile feedback of keys being pressed and released. To get around this, many have resorted to purchasing wireless keyboards, which do offer the ease of typing, but detract from the portability that is so critical to the tablet experience. Now, according to Patentbolt, Chinese hardware maker Lenovo has applied for a patent that gives users the best of both worlds. Explore further Tablet keyboard cases turn Android devices into netbooks Citation: Lenovo applies for a patent for a grip tablet keyboard (2012, May 29) retrieved 18 August 2019 from https://phys.org/news/2012-05-lenovo-patent-tablet-keyboard.html The idea is rather clever. Instead of going with a standard keyboard shape or trying to create a big overlay, Lenovo has come up with a way to clamp two tiny keyboard devices to either side of a tablet with tiny cell phone size keys on both top and bottom. Users hold onto their tablet by holding onto the keyboards, or more descriptively, their keypads. Each keypad has keys on both the top and bottom part; one has the keys for typing words and numbers, the other for control mechanisms such as the space bar, or Ctrl key. If the lettered keys are on the bottom side, users can type with their fingers as they grip. Conversely, if the keys are on the top side, they can type as they do with messaging on their cell phones, i.e. using their thumbs. © 2012 Phys.Org
China’s GM cotton farmers are losing money Journal information: Nature Citation: Chinese researchers find Bt cotton controls pests while also promoting good bugs (2012, June 14) retrieved 18 August 2019 from https://phys.org/news/2012-06-chinese-bt-cotton-pests-good.html More information: Widespread adoption of Bt cotton and insecticide decrease promotes biocontrol services, Nature (2012) doi:10.1038/nature11153AbstractOver the past 16 years, vast plantings of transgenic crops producing insecticidal proteins from the bacterium Bacillus thuringiensis (Bt) have helped to control several major insect pests and reduce the need for insecticide sprays. Because broad-spectrum insecticides kill arthropod natural enemies that provide biological control of pests, the decrease in use of insecticide sprays associated with Bt crops could enhance biocontrol services. However, this hypothesis has not been tested in terms of long-term landscape-level impacts10. On the basis of data from 1990 to 2010 at 36 sites in six provinces of northern China, we show here a marked increase in abundance of three types of generalist arthropod predators (ladybirds, lacewings and spiders) and a decreased abundance of aphid pests associated with widespread adoption of Bt cotton and reduced insecticide sprays in this crop. We also found evidence that the predators might provide additional biocontrol services spilling over from Bt cotton fields onto neighbouring crops (maize, peanut and soybean). Our work extends results from general studies evaluating ecological effects of Bt crops by demonstrating that such crops can promote biocontrol services in agricultural landscapes. Explore further © 2012 Phys.Org In their paper, the researchers report that cotton growers in China raising Bt cotton experience lower levels of bollworms than when using non genetically modified cotton and that they were able to reduce the amount of insecticide needed to control the pests as well. But perhaps more interestingly, they found that when conducting surveys in the Bt cotton fields, that many more lady bugs, spiders and other insects that feed on pests such as aphids were found, and better yet, were also more abundant in adjacent fields as well. Thus by growing Bt cotton, farmers are getting more from their fields while at the same time promoting the growth of “good” bugs that feed on other bad ones.Bt cotton is the only approved genetically modified crop being grown in China, and has been grown there since 1997. Current estimates suggest that as much as ninety five percent of all cotton now grown in that country is of the genetically modified variant, though its use is not without controversy.Most governments around the world including those in the United States, Asia, Europe and especially Africa have thus far slowed the movement of edible crops onto consumers dinner plates, fearing that some unknown disease might arise from their consumption. Even non-edible crops such as altered cotton have caused controversy due to studies being done in India that suggest that farmers that grow Bt cotton have a higher suicide rate than the rest of the country. Despite the lack of concrete proof, there persists a degree of suspicion and that has been enough to slow its use in that country.Despite the fact that genetically altered plants have been studied for decades, there is still fear among the general population that some tragedy will befall those who eat the results, thus, more research such as that being conducted in China will have to be done before common use of genetically altered crops becomes a reality. Cotton plant. Photo courtesy of USDA Natural Resources Conservation Service. (Phys.org) — Because they can modify plants to either produce better fruit or in many other cases ward off disease and pests, researchers genetically alter crop plants to increase yields without adding additional costs to the process. One such success story is Bt cotton, a strain developed in the lab and so named because it harbors Bacillus thuringiensis, a bacterium that produces a chemical harmful to some insects and thus is often used as a pesticide. Farmers in the United States have been using it since 1996, and report that since that time, average yields have been up 5% even as costs have gone down due to use less of other pesticides. Now, researchers in China are reporting that not only does planting Bt cotton reduce losses from pests, it also allows other beneficial insect populations to increase not just in the cotton fields, but in those nearby growing other crops as well. The team has published its findings in the journal Nature. 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.
Month: August 2019 Researchers use new technique to date CAIs and chondrules
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. More information: The Absolute Chronology and Thermal Processing of Solids in the Solar Protoplanetary Disk, Science, 2 November 2012: Vol. 338 no. 6107 pp. 651-655 DOI: 10.1126/science.1226919ABSTRACTTransient heating events that formed calcium-aluminum–rich inclusions (CAIs) and chondrules are fundamental processes in the evolution of the solar protoplanetary disk, but their chronology is not understood. Using U-corrected Pb-Pb dating, we determined absolute ages of individual CAIs and chondrules from primitive meteorites. CAIs define a brief formation interval corresponding to an age of 4567.30 ± 0.16 million years (My), whereas chondrule ages range from 4567.32 ± 0.42 to 4564.71 ± 0.30 My. These data refute the long-held view of an age gap between CAIs and chondrules and, instead, indicate that chondrule formation started contemporaneously with CAIs and lasted ~3 My. This time scale is similar to disk lifetimes inferred from astronomical observations, suggesting that the formation of CAIs and chondrules reflects a process intrinsically linked to the secular evolution of accretionary disks.Press release Chondrules from the chondrite Grassland, L4. Credit: Wikipedia. Explore further Citation: Researchers use new technique to date CAIs and chondrules (2012, November 2) retrieved 18 August 2019 from https://phys.org/news/2012-11-technique-date-cais-chondrules.html Chondrules younger than thought Journal information: Science © 2012 Phys.org (Phys.org)—Researchers working out of the University of Copenhagen have published a paper in the journal Science in which they claim that a new method of dating chondrules and calcium-aluminum–rich inclusions (CAIs) is more accurate than previous methods. Their dating method produces results that contradict earlier findings that have suggested that chondrules formed up to 2 million years later than CAIs; instead they say, the two materials found in meteorites formed at roughly the same time. Scientists believe that the sun and all of its orbiting bodies formed from a spinning disk approximately 4.6 billion years ago. Theory suggests the sun came first, initially surrounded by a cloud of dust and gas that over time became the planets, comets and asteroids. But for that to happen, some bit of material had to bind together first, and researchers believe two of them – chondrules and CAIs – are still present in modern meteorites. Up till now however, there has been disagreement among researchers regarding the age of such materials found in meteorite samples that have struck the Earth.Prior attempts to measure the age of materials in meteorite samples involved using techniques to discern how much aluminum 26 was present. The thinking was that differences in the levels of the isotope indicated different ages. The problem with this methodology, the new team points out, is that it ignores the possibility that objects forming in different locations might naturally have different amounts of the isotope in them.Their new technique involves isolating small amounts of lead found in a sample and then measuring the isotopic composition of both it and uranium and then calculating the age of the material using the known rate of decay of uranium. Using this method, the team calculated that both materials in a meteorite sample were approximately 4.56730 billion years old. And because their method is so precise they say the error rate of their technique is just 160,000 years.If the new method for calculating the age of chondrules and CAIs is adopted by the scientific community it will likely mean revising some ideas regarding the makeup of the early universe.
Month: August 2019 Astronomers observe mysterious dimming of a young nearby star
The red path shows an exotic looped trajectory of light through a three-slit structure, which was observed for the first time in the new study. Credit: Magaña-Loaiza et al. Nature Communications Journal information: Nature Communications (Phys.org)—Physicists have performed a variation of the famous 200-year-old double-slit experiment that, for the first time, involves “exotic looped trajectories” of photons. These photons travel forward through one slit, then loop around and travel back through another slit, and then sometimes loop around again and travel forward through a third slit. Superposition revisited: Proposed resolution of double-slit experiment paradox using Feynman path integral formalism So far, all previous versions of the experiment have produced results that appear to be accurately described by the principle of superposition. This is because looped trajectories are so rare under normal conditions that their contribution to the overall interference pattern is typically negligible, and so applying the superposition principle to those cases results in a very good approximation. Straight trajectories (green) and exotic looped trajectories (red, dashed, dotted) of light, where the red cloud near the surface depicts the near fields, which increase the probability of photons to follow looped trajectories. The graphs at left show simulations (top) and experimental results (bottom) of the large difference in interference patterns created by illuminating only one slit being treated independently (gray line) and the actual coupled system (blue line). The remarkable difference between the gray and blue lines is caused by the looped trajectories. Credit: Magaña-Loaiza et al. Nature Communications Citation: Physicists detect exotic looped trajectories of light in three-slit experiment (2017, January 6) retrieved 18 August 2019 from https://phys.org/news/2017-01-physicists-exotic-looped-trajectories-three-slit.html © 2017 Phys.org Explore further More information: Omar S. Magaña-Loaiza, Israel De Leon et al. “Exotic looped trajectories of photons in three-slit interference.” Nature Communications. DOI: 10.1038/ncomms13987 Interestingly, the contribution of these looped trajectories to the overall interference pattern leads to an apparent deviation from the usual form of the superposition principle. This apparent deviation can be understood as an incorrect application of the superposition principle—once the additional interference between looped and straight trajectories is accounted for, the superposition can be correctly applied.The team of physicists, led by Omar S. Magaña-Loaiza and Israel De Leon, has published a paper on the new experiment in a recent issue of Nature Communications. Loops of light”Our work is the first experimental observation of looped trajectories,” De Leon told Phys.org. “Looped trajectories are extremely difficult to detect because of their low probability of occurrence. Previously, researchers had suggested that these exotic trajectories could exist but failed to observe them.”To increase the probability of the occurrence of looped trajectories, the researchers designed a three-slit structure that supports surface plasmons, which the scientists describe as “strongly confined electromagnetic fields that can exist at the surface of metals.” The presence of these electromagnetic fields near the three slits increases the contribution of looped trajectories to the overall interference pattern by almost two orders of magnitude.”We provided a physical explanation that links the probability of these exotic trajectories to the near fields around the slits,” De Leon said. “As such, one can increase the strength of near fields around the slits to increase the probability of photons following looped trajectories.” Superposition principle accounting for looped trajectoriesThe new three-slit experiment with looped trajectories is just one of many variations of the original double-slit experiment, first performed by Thomas Young in 1801. Since then, researchers have been performing versions that use electrons, atoms, or molecules instead of photons.One of the reasons why the double-slit experiment has attracted so much attention is that it represents a physical manifestation of the principle of quantum superposition. The observation that individual particles can create an interference pattern implies that the particles must travel through both slits at the same time. This ability to occupy two places, or states, at once, is the defining feature of quantum superposition. It is when the contribution of the looped trajectories becomes non-negligible that it becomes apparent that the total interference is not simply the superposition of individual wavefunctions of photons with straight trajectories, and so the interference pattern is not correctly described by the usual form of the superposition principle. Magaña-Loaiza explained this apparent deviation in more detail:”The superposition principle is always valid—what is not valid is the inaccurate application of the superposition principle to a system with two or three slits,” he said.”For the past two centuries, scientists have assumed that one cannot observe interference if only one slit is illuminated in a two- or three-slit interferometer, and this is because this scenario represents the usual or typical case. “However, in our paper we demonstrate that this is true only if the probability of photons to follow looped trajectories is negligible. Surprisingly, interference fringes are formed when photons following looped trajectories interfere with photons following straight (direct) trajectories, even when only one of the three slits is illuminated. “The superposition principle can be applied to this surprising scenario by using the sum or ‘superposition’ of two wavefunctions; one describing a straight trajectory and the other describing looped trajectories. Not taking into account looped trajectories would represent an incorrect application of the superposition principle.”To some extent, this effect is strange because scientists know that Thomas Young observed interference when he illuminated both slits and not only one. This is true only if the probability of photons following looped trajectories is negligible.”In addition to impacting physicists’ understanding of the superposition principle as it is applied to these experiments, the results also reveal new properties of light that could have applications for quantum simulators and other technologies that rely on interference effects.”We believe that exotic looped paths can have important implications in the study of decoherence mechanisms in interferometry or to increase the complexity of certain protocols for quantum random walks, quantum simulators, and other algorithms used in quantum computation,” De Leon said. 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.
Month: August 2019 Clawlike nanowires filter bacteria from blood
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. Journal information: Nature Communications While most people are familiar with bacterial infections that appear on or near the skin, there are other types that occur inside of the body. One of the most dangerous situations is when bacteria multiply in the bloodstream—a circumstance that can lead to sepsis. Currently, such infections are treated with antibiotics; if they do not work, the next step is to connect a patient to a dialyser —a machine that filters the blood, removing bacteria. Unfortunately, as the researchers note, current dialysers are not very good at filtering bacteria and patients suffer as a result. In this new effort, the researchers have developed a new type of dialyser that they claim does a far better job.The idea for the new dialyser, the team notes, came from the Venus flytrap—it has tiny hairs that curl and trap prey. To create a dialyser with a similar dynamic, the researchers built a substrate of 3-D carbon foam and implanted a host of flexible polycrystalline nanowires inside of it. Prior research by the team suggested that the nanowires would bend and trap bacteria in a way similar to the hairs on the flytrap. The researchers tested the dialyser by pushing blood through the filter and then noting reductions in blood bacteria levels. They examined the filter to note how many were captured by the nanowires.The researchers report that their filter was 97 percent effective in capturing bacteria in blood samples moving at rates similar to those inside the body. They note that their work is still at the proof-of-concept stage and thus more work is required to make sure that the filter does not cause other problems while filtering bacteria. But they describe their device as a major step forward, and plan further tests to see if it might also be used to filter out other microorganisms, such as cancer cells or viruses. Explore further Genetic study of soil organisms reveals new family of antibiotics A team of researchers from institutions across China has developed a new type of dialyser —one capable of capturing up to 97 percent of bacteria present in a blood sample. In their paper published in the journal Nature Communications, the group explains the origins of their device, how the filter was made and how well it worked during testing.
Month: August 2019 Remembering the maestro
Oxford Bookstore Connaught Place in association with Delhi Diary hosted Remembering Ravi Shankar, an evening dedicated to the legendary musician as Sujit Sanyal presented an audio visual talk show on the life of the extraordinary musician. Pandit Ravi Shankar was one of the best-known exponents of sitar and a composer of Hindustani classical music. He is the recipient of several prestigious awards like Sangeet Natak Akademi Award, Padma Bhushan, Padma Vibhushan and Bharat Ratna. Shankar was born in Varanasi (Kashi) and spent his youth touring Europe and India with the dance group of his brother Uday Shankar. He gave up dancing in 1938 to study sitar playing under court musician Allauddin Khan. After finishing his studies in 1944, Shankar worked as a composer, creating the music for the Apu Trilogy by Satyajit Ray, and was music director of All India Radio. Shankar was born Robindro Shankar on April 7, 1920, in Benares, which is considered the holiest of cities in India. He was the youngest son of a family of Bengali Brahmins, coming from an upper-class background.
Month: August 2019 BJP trying to communalise Bihar atmosphere Nitish
Bihar Chief minister Nitish Kumar today charged the Bharatiya Janata Party (BJP) of trying to communalise the election atmosphere in the state saying the party is in “panic in the face of defeat.” Kumar said the BJP has neither any ‘leader’ nor any ‘policy and intention’ to show the people, and therefore, was trying to communalise the situation.”BJP in panic – without