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Gigantic Lightning Jets Shoot from Clouds to Space.

Postby Qray » Mon Aug 24, 2009 3:32 pm

Gigantic Lightning Jets Shoot from Clouds to Space

By Andrea Thompson.

23 August 2009 01:16 pm ET


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Source: Steven Cummer.

Strokes of lightning flashing down toward the ground are a familiar sight during summer thunderstorms, but scientists have capture an image of a rare lightning bolt shooting out upward from a cloud, almost to the edge of the Earth's atmosphere.

These bolts of upward lightning, one type among a variety of electrical discharges now known to occur above thunderstorms, are called gigantic jets, and were only first discovered in 2001.

Since then, only about 10 gigantic jets have been observed, said Steven Cummer, who was part of the team that photographed this most recent jet. Gigantic jets are essentially the same as cloud-to-ground lightning, only they go the opposite way.

"Gigantic jets are literally lightning that comes out of the thunderclouds, but instead of going down, like most lightning strokes do, these apparently find their way out the tops of thunderclouds, and then keep going and keep going and keep going until they run into something that stops them," Cummer explained.

The something that stops them is the ionosphere, the topmost layer of the Earth's atmosphere (right at the edge of space), which is made up of electrically charged atoms, or ions.

The observations, detailed Sunday in the online issue of the journal Nature Geoscience, confirm that gigantic jets transfer charge from clouds to the highest layers of the Earth's atmosphere, just as their downward cousins transfer it to the ground.

Cummer and his colleagues observed the gigantic jet almost by accident. They were set up to observe sprites and other unusual types of above-cloud lightning associated with Tropical Storm Cristobal on July 21, 2008. Instead, they saw the whopper gigantic jet.

"We knew that there was a slim, slim chance that we would see something interesting, like a gigantic jet, but for sure we got lucky to be able to see that. So we were pretty thrilled," Cummer told LiveScience.

Also lucky where the simultaneous radio observations the team was making, which confirmed that gigantic jets are a conduit to move electric charge from the cloud.

"That's what was telling us that at least in this gigantic jet, and probably in most, there actually is a lot of thundercloud charge that has moved from the thundercloud up to the top of the gigantic jet," Cummer said.

Just as with cloud-to-ground lightning, the conduit travels away from the cloud first, and looks fairly faint. When the stroke hits the conducting surface, whether ground or ionosphere, more charge can flow from the cloud and the lightning explodes with light.

How exactly gigantic jets form and what kinds of storm conditions are necessary to produce them is still unknown.

Electric charge is of course built up in clouds by the motions of water and ice particles. Lightning moves these charges around. But why some lightning goes up and other bolts go down isn't known.

One theory is that high winds at the top of a cloud could nullify a charge layer that would otherwise stop the lightning, thereby allowing it to escape from the top of the cloud. Because nothing else in the atmosphere can stop it until it hits the ionosphere, the lightning can travel about five to 10 times farther than cloud-to-ground lightning, reaching up to about 50 miles (80 km) above Earth's surface.

The thinness of the upper atmosphere also allows gigantic jets to travel much faster than cloud-to-ground lightning.

With every gigantic jet observation made, Cummer and others who study these powerful lightning bolts are hoping to learn more about the conditions that create them and what storms they should be looking for them in.

Researchers in Taiwan have seen gigantic jets sprouting from typhoons (the name for tropical storms in the western Pacific), so these tropical cyclones seem to be good places to look for upward lightning.

Scientific instruments aren't necessary to see gigantic jets. If you're far away enough from a storm so that your view isn't blocked by clouds, they can be seen ricocheting up through the atmosphere.

"They're definitely bright enough and long-enough lasting to see," Cummer said.
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Water Found on the Moon

Postby Qray » Fri Sep 25, 2009 10:44 am

It's Official: Water Found on the Moon

By Andrea Thompson (Senior Writer at Space.com)

23 September 2009


Since man first touched the moon and brought pieces of it back to Earth, scientists have thought that the lunar surface was bone dry. But new observations from three different spacecraft have put this notion to rest with what has been called "unambiguous evidence" of water across the surface of the moon.

The new findings, detailed in the Sept. 25 issue of the journal Science, come in the wake of further evidence of lunar polar water ice by NASA's Lunar Reconnaissance Orbiter and just weeks before the planned lunar impact of NASA's LCROSS satellite, which will hit one of the permanently shadowed craters at the moon's south pole in hope of churning up evidence of water ice deposits in the debris field.

The moon remains drier than any desert on Earth, but the water is said to exist on the moon in very small quantities. One ton of the top layer of the lunar surface would hold about 32 ounces of water, researchers said.

"If the water molecules are as mobile as we think they are — even a fraction of them — they provide a mechanism for getting water to those permanently shadowed craters," said planetary geologist Carle Pieters of Brown University in Rhode Island, who led one of the three studies in Science on the lunar find, in a statement. "This opens a whole new avenue [of lunar research], but we have to understand the physics of it to utilize it."

Finding water on the moon would be a boon to possible future lunar bases, acting as a potential source of drinking water and fuel.

Apollo turns up dry

When Apollo astronauts returned from the moon 40 years ago, they brought back several samples of lunar rocks.

The moon rocks were analyzed for signs of water bound to minerals present in the rocks; while trace amounts of water were detected, these were assumed to be contamination from Earth, because the containers the rocks came back in had leaked.

"The isotopes of oxygen that exist on the moon are the same as those that exist on Earth, so it was difficult if not impossible to tell the difference between water from the moon and water from Earth," said Larry Taylor of the University of Tennessee, Knoxville, who is a member of one of the NASA-built instrument teams for India's Chandrayaan-1 satellite and has studied the moon since the Apollo missions.

While scientists continued to suspect that water ice deposits could be found in the coldest spots of south pole craters that never saw sunlight, the consensus became that the rest of the moon was bone dry.

But new observations of the lunar surface made with Chandrayaan-1, NASA's Cassini spacecraft, and NASA's Deep Impact probe, are calling that consensus into question, with multiple detections of the spectral signal of either water or the hydroxyl group (an oxygen and hydrogen chemically bonded).

Three spacecraft

Chandrayaan-1, India's first-ever moon probe, was aimed at mapping the lunar surface and determining its mineral composition (the orbiter's mission ended 14 months prematurely in August after an abrupt malfunction). While the probe was still active, its NASA-built Moon Mineralogy Mapper (M3) detected wavelengths of light reflected off the surface that indicated the chemical bond between hydrogen and oxygen — the telltale sign of either water or hydroxyl.

Because M3 can only penetrate the top few millimeters of lunar regolith, the newly observed water seems to be at or near the lunar surface. M3's observations also showed that the water signal got stronger toward the polar regions. Pieters is the lead investigator for the M3 instrument on Chandrayaan-1.

Cassini, which passed by the moon in 1999 on its way to Saturn, provides confirmation of this signal with its own slightly stronger detection of the water/hydroxyl signal. The water would have to be absorbed or trapped in the glass and minerals at the lunar surface, wrote Roger Clark of the U.S. Geological Survey in the study detailing Cassini's findings.

The Cassini data shows a global distribution of the water signal, though it also appears stronger near the poles (and low in the lunar maria).

Finally, the Deep Impact spacecraft, as part of its extended EPOXI mission and at the request of the M3 team, made infrared detections of water and hydroxyl as part of a calibration exercise during several close approaches of the Earth-Moon system en route to its planned flyby of comet 103P/Hartley 2 in November 2010.

Deep Impact detected the signal at all latitudes above 10 degrees N, though once again, the poles showed the strongest signals. With its multiple passes, Deep Impact was able to observe the same regions at different times of the lunar day. At noon, when the sun's rays were strongest, the water feature was lowest, while in the morning, the feature was stronger.

"The Deep Impact observations of the Moon not only unequivocally confirm the presence of [water/hydroxyl] on the lunar surface, but also reveal that the entire lunar surface is hydrated during at least some portion of the lunar day," the authors wrote in their study.

The findings of all three spacecraft "provide unambiguous evidence for the presence of hydroxyl or water," said Paul Lucey of the University of Hawaii in an opinion essay accompanying the three studies. Lucey was not involved in any of the missions.

The new data "prompt a critical reexamination of the notion that the moon is dry. It is not," Lucey wrote.

Where the water comes from

Combined, the findings show that not only is the moon hydrated, the process that makes it so is a dynamic one that is driven by the daily changes in solar radiation hitting any given spot on the surface.

The sun might also have something to do with how the water got there.

There are potentially two types of water on the moon: that brought from outside sources, such as water-bearing comets striking the surface, or that that originates on the moon.

This second, endogenic, source is thought to possibly come from the interaction of the solar wind with moon rocks and soils.

The rocks and regolith that make up the lunar surface are about 45 percent oxygen (combined with other elements as mostly silicate minerals). The solar wind — the constant stream of charged particles emitted by the sun — are mostly protons, or positively charged hydrogen atoms.

If the charged hydrogens, which are traveling at one-third the speed of light, hit the lunar surface with enough force, they break apart oxygen bonds in soil materials, Taylor, the M3 team member suspects. Where free oxygen and hydrogen exist, there is a high chance that trace amounts of water will form.

The various study researchers also suggest that the daily dehydration and rehydration of the trace water across the surface could lead to the migration of hydroxyl and hydrogen towards the poles where it can accumulate in the cold traps of the permanently shadowed regions.
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Re: Science News

Postby Golden Knight » Thu Jul 22, 2010 9:50 pm

Scientists invent invisibility cloak made of tiny pieces of glass

But researchers at Michigan Tech University have found a way of capturing infrared light and bending it around an object, making it invisible.
At the moment the science is still based in the lab. But if the same results could be achieved with visible light, the shrouded object would disappear from sight.

Read more: http://www.dailymail.co.uk/sciencetech/article-1296769/Scientists-invent-invisibility-cloak-glass.html
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Re: Science News

Postby Golden Knight » Fri Jul 23, 2010 2:21 pm

This would be good for criminals, trying to get away at night, the night vision, infrared cameras would not be able to see them.
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First glimpse of a planet from another galaxy.

Postby Qray » Sun Nov 21, 2010 6:57 pm

First glimpse of a planet from another galaxy.

WASHINGTON (AFP) – A hot, gaseous and fast-spinning planet has been found orbiting a dying star on the edge of the Milky Way, in the first such discovery of a planet from outside our galaxy, scientists said Thursday.

Slightly larger than the size of Jupiter, the largest in our solar system, the newly discovered exoplanet is orbiting a star 2,000 light years from Earth that has found its way into the Milky Way.

The pair are believed to be part of the Helmi stream, a group of stars that remains after its mini-galaxy was devoured by the Milky Way some six to nine billion years ago, said the study in Science Express.

"This discovery is very exciting," said Rainer Klement of the Max Planck Institute for Astronomy.

"Because of the great distances involved, there are no confirmed detections of planets in other galaxies. But this cosmic merger has brought an extragalactic planet within our reach."

Astronomers were able to locate the planet, coined HIP 13044 b, by focusing on the "tiny telltale wobbles of the star caused by the gravitational tug of an orbiting companion," the study said.

They used a powerful telescope owned by the European Southern Laboratory at La Silla Observatory in Chile, located at an altitude of 2,400 meters (7,800 feet) some 600 kilometers (375 miles) north of the capital, Santiago.

The planet is quite close to the star it is orbiting, and survived a phase in which its host star went through a massive growth after it depleted its core hydrogen fuel supply, a phase known as the "red giant" stage of stellar evolution.

"This discovery is particularly intriguing when we consider the distant future of our own planetary system, as the Sun is also expected to become a red giant in about five billion years," said lead researcher Johny Setiawan of the Max Planck Institute for Astronomy.

The exoplanet is likely to be quite hot because it is orbiting so close to its star, completing each orbit in just over 16 days, and is probably near the end of its life, astronomers said.

The star may have already swallowed other planets in its orbit, making the star spin more quickly and meaning that time is running out for the surviving exoplanet.

Astronomers were mystified as to how the planet might have formed, since the star contained few elements heavier than hydrogen and helium and planets typically form out of a complex cloud of spinning space rubble.

"It is a puzzle for the widely accepted model of planet formation to explain how such a star, which contains hardly any heavy elements at all, could have formed a planet," said Setiawan.

"Planets around stars like this must probably form in a different way."
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Re: Science News

Postby nightlock » Tue Apr 19, 2011 4:12 am

18/02/2011 - Super-Small Transistor Created: Artificial Atom Powered by Single Electrons

A University of Pittsburgh-led team has created a single-electron transistor that provides a building block for new, more powerful computer memories, advanced electronic materials, and the basic components of quantum computers.

The researchers report in Nature Nanotechnology that the transistor's central component -- an island only 1.5 nanometers in diameter -- operates with the addition of only one or two electrons. That capability would make the transistor important to a range of computational applications, from ultradense memories to quantum processors, powerful devices that promise to solve problems so complex that all of the world's computers working together for billions of years could not crack them.

In addition, the tiny central island could be used as an artificial atom for developing new classes of artificial electronic materials, such as exotic superconductors with properties not found in natural materials, explained lead researcher Jeremy Levy, a professor of physics and astronomy in Pitt's School of Arts and Sciences. Levy worked with lead author and Pitt physics and astronomy graduate student Guanglei Cheng, as well as with Pitt physics and astronomy researchers Feng Bi, Daniela Bogorin,and Cheng Cen. The Pitt researchers worked with a team from the University of Wisconsin at Madison led by materials science and engineering professor Chang-Beom Eom, including research associates Chung Wun Bark, Jae-Wan Park, and Chad Folkman. Also part of the team were Gilberto Medeiros-Ribeiro, of HP Labs, and Pablo F. Siles, a doctoral student at the State University of Campinas in Brazil.

Levy and his colleagues named their device SketchSET, or sketch-based single-electron transistor, after a technique developed in Levy's lab in 2008 that works like a microscopic Etch A SketchTM, the drawing toy that inspired the idea. Using the sharp conducting probe of an atomic force microscope, Levy can create such electronic devices as wires and transistors of nanometer dimensions at the interface of a crystal of strontium titanate and a 1.2 nanometer thick layer of lanthanum aluminate. The electronic devices can then be erased and the interface used anew.

The SketchSET -- which is the first single-electron transistor made entirely of oxide-based materials -- consists of an island formation that can house up to two electrons. The number of electrons on the island -- which can be only zero, one, or two -- results in distinct conductive properties. Wires extending from the transistor carry additional electrons across the island.

One virtue of a single-electron transistor is its extreme sensitivity to an electric charge, Levy explained. Another property of these oxide materials is ferroelectricity, which allows the transistor to act as a solid-state memory. The ferroelectric state can, in the absence of external power, control the number of electrons on the island, which in turn can be used to represent the 1 or 0 state of a memory element. A computer memory based on this property would be able to retain information even when the processor itself is powered down, Levy said. The ferroelectric state also is expected to be sensitive to small pressure changes at nanometer scales, making this device potentially useful as a nanoscale charge and force sensor.

The research in Nature Nanotechnology also was supported in part by grants from the U.S. Defense Advanced Research Projects Agency (DARPA), the U.S. Army Research Office, the National Science Foundation, and the Fine Foundation.
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(Anyone mind me hijacking this old thread? I keep track of science news anyway so I might as well share developments that peak my interest.)
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Re: Science News

Postby nightlock » Tue Apr 19, 2011 12:30 pm

16/04/2011 - Could Black Trees Blossom in a World With Two Suns?

A sky with two suns is a favourite image for science fiction films, but how would a binary star system affect life evolving on an orbiting planet? Jack O'Malley-James of the University of St Andrews has studied what plants might be like on an Earth-like planet with two or three suns and found that they may appear black or grey.

He is presenting results at the RAS National Astronomy Meeting in Llandudno on April 19, 2011.

Photosynthesis -- converting sunlight into energy -- is the basis for the majority of life on Earth. It is the energy source for plants and, hence, animals higher up the food chain. With multiple light sources, life may have adapted to use all suns, or different forms may develop that choose to use one specific sun. This may be the more likely option for planets on which parts of the surface are illuminated by only one sun for long periods of time.

"If a planet were found in a system with two or more stars, there would potentially be multiple sources of energy available to drive photosynthesis. The temperature of a star determines its colour and, hence, the colour of light used for photosynthesis. Depending on the colours of their star-light, plants would evolve very differently," said O'Malley-James.

O'Malley-James is working on a PhD, supervised by Dr Jane Greaves at the University of St Andrews, Prof John Raven of the University of Dundee and Prof Charles Cockell of The Open University, to assess the potential for photosynthetic life in multi-star systems with different combinations of Sun-like stars and red dwarfs. Sun-like stars are known to host exoplanets and red dwarfs are the most common type of star in our Galaxy, often found in multi-star systems, and old and stable enough for life to have evolved. Over 25% of Sun-like stars and 50% of red dwarfs are found in multi-star systems. In the team's simulations, the Earth-like planets either orbit two stars close together or orbit one of two widely separated stars. The team has also looked at combinations of these scenarios, with two close stars and one more distant star.

"Our simulations suggest that planets in multi-star systems may host exotic forms of the more familiar plants we see on Earth. Plants with dim red dwarf suns for example, may appear black to our eyes, absorbing across the entire visible wavelength range in order to use as much of the available light as possible. They may also be able to use infrared or ultraviolet radiation to drive photosynthesis. For planets orbiting two stars like our own, harmful radiation from intense stellar flares could lead to plants that develop their own UV-blocking sun-screens, or photosynthesising microorganisms that can move in response to a sudden flare," said O'Malley-James.
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.... And a Major Breakthrough in Quantum Astrology ....

Postby Asp Zelazny » Thu Apr 21, 2011 6:41 pm

Amateur astrologer discovers new constellation
By J Goodbody– January 22, 2011 – (7914 views)
Using her pareidoliascope, Williams was able to observe Aries in a new light The discovery of a new constellation in the night sky has created an upheaval within the astrological community, bringing notoriety to Rockford-area palm reader Debbie Williams.

Unable to determine the ultimate fate of a client during an astrology reading, Williams found that the sign Aries no longer seemed to provide her with any sense of celestial foretelling.

“I always had trouble making out Aries,” said Williams who admits needing to tilt her head in a certain way and squint with one eye in order to see the constellation known as “The Ram”.

According to Williams, Aries is just too small to be considered a constellation and thus can’t reasonably have any real effect on 1/12th of the entire human population. This new revelation left Williams relieved to know that her own difficulties in assigning vague advice to desperate people were not her fault.

“I was thrilled to realize that my recent failures weren’t because of the impossibility to predict future events and personality traits based upon the positions of the planets, the sun and the moon in relation to stars that are trillions of miles away,” Williams said. “It must be because this particular constellation is flawed.”

Seizing an opportunity, Williams first relegated the tiny Aries to merely a dwarf constellation, or constelloid, removing it of its influence over human events.

She then began to construct her own constellation by assigning the stars that once made up Aries and borrowing some others from nearby Pisces. Williams observed that the new cluster of stars looks a lot like her cat, Artemis, and so named the discovery after her dear pet. She is hopeful that her new constellation Artemis will take its rightful place in the daily horoscope.

Astrology is still recovering from the recent controversy brought on by astronomer Parke Kunkle who pointed out that your sign might very well be wrong anyway because of precession of the equinoxes. His competing claim is that a 13th constellation called Ophiuchus should be included in the zodiac calendar. This has left millions concerned and angry that their lives may have been guided in the wrong direction over all these years.

But most astrologers reject Kunkle’s claims, convinced that the science of astronomy, and the methodological naturalism it uses to derive facts from detailed observation and reliable mathematical models, can’t say anything about who should marry whom or what lottery numbers they should play.

“You’re right, we can’t do that,” said each and every astronomer reached for comment. “That’s not the point.”

If Williams’ discovery withstands the rigorous process of peer review –which within the astrological community means that her peers launch a letter writing campaign and press releases to change public sentiment– she may be the first astrologer in millennia to actually change the Zodiac itself.

Since the announcement, hundreds of psychic mediums and astrologers have come forth claiming to have predicted the shakeup. Williams says, now that she thinks about it, her own psychic told her that “big things were going to happen in her personal or professional life, having something to do with the outdoors”.

“She gave me that reading so long ago, I almost forgot about it, but she sure was spot on,” Williams said. “I mean what could be more ‘outdoors’ than the universe, right?”

Using an instrument called a pareidoliascope, astrologers are able to perceive otherwise nonexistent patterns created by stars strewn apart by hundreds of light years. These readings of the constellations can be hugely influential with people because of psychological phenomena such as confirmation bias, apophenia (the tendency to see patterns in otherwise meaningless data) and subjective validation. In fact, Americans spend billions of dollars a year seeking advice on major life decisions.

The astrological community is in full debate over how this new constellation will influence the employment opportunities, stock market trends, and the love-lives of over half a billion people across the world.

In recent years, part-timers seem to be playing a larger role in the field of astrology. According to Dr. Roger Flemming, a professor at the University of Chicago’s Astrology and Astrotherapy Department, it is not uncommon for amateur astrologers to happen upon discoveries that significantly contribute to pseudoscience.

Professional astrologers complain that government and university-supported astrologers are too underfunded and overwhelmed to keep track of the influence of all the celestial bodies.

“It’s great that we have part-time prognosticators contributing to the field of astrology and filling in the gaps,” Flemming said. “You don’t have to be some Zodiacal professor to help people give up personal responsibility for the things that happen in their lives.”

(Reprinted from The Chicago Dope)
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Re: Science News

Postby nightlock » Fri Apr 22, 2011 12:18 am

I'm not sure if I should be offended by the implication this is science or laugh at the sheer brilliance of mocking astrologers like that.
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Re: Science News

Postby Asp Zelazny » Fri Apr 22, 2011 4:14 pm

Just to clarify then ... The Chicago Dope is a satirical newsoutlet, that makes up stuff like this. So, laugh.
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Re: Science News

Postby nightlock » Mon May 02, 2011 5:43 am

29/04/2011 - Physicists Create Quantum Twin Atoms

Objects that are well separated in space but still cannot be understood separately belong to the profoundest mysteries of quantum physics. Pairs of photons are prominent examples of such systems. They allow the teleportation of quantum states or tap-proof data transfer using quantum cryptography. In future, such experiments will not be restricted simply to photons. At the Vienna University of Technology (TU Vienna), a method has been developed to create correlated pairs of atoms using ultracold Bose-Einstein condensates.
The results of the experiments have now been published in the journal Nature Physics.

Separate but Still United

Even Einstein did not like the idea of well-separated particles still being quantum mechanically connected. He called this phenomenon "spooky action at a distance." However, since then, the startling predictions of quantum theory have been verified in countless experiments. Quantum particles can -- even if they are far apart -- still belong together and "share" certain physical properties.

"This does not mean that by manipulating one particle we can at the same time change the other, as if they were connected by an invisible thread," Professor Jörg Schmiedmayer (TU Vienna) says, "but still, we have to treat both particles as one single quantum system -- and that opens the door to fascinating new experiments." Jörg Schmiedmayer's team at the Institute for Atomic and Subatomic Physics, TU Vienna carried out the experiments, while theoretical calculations were done by Ulrich Hohensteiner (Karl Franzens University, Graz, Austria).

Conservation of Energy and Momentum

In order to produce the quantum-correlated atoms, the scientists first create a Bose-Einstein condensate. This exotic state of matter occurs at extremely low temperatures, at less than a millionth of a degree above absolute zero. In a Bose-Einstein condensate, the atoms are in the lowest possible energy state.

"The key to success are our atomchips," Thorsten Schumm (TU Vienna) explains. With perfectly tailored chip structures, atoms can be manipulated with incredible precision. It is possible to deliver single quanta of vibrational energy to the atoms of the ultracold Bose-Einstein condensate. When the atoms return to the lowest energy state, the condensate has to get rid of the surplus energy.

"Because of the sophisticated design of our atomchips, the Bose-Einstein condensate is left with only one single way to dispose of its energy: emitting pairs of atoms. All other possibilities are forbidden by quantum mechanics," Robert Bücker (TU Vienna) explains. According to the law of momentum conservation, the two atoms move in exactly opposite directions. This process is closely related to effects in special optical crystals, in which pairs of photons can be created (so-called "optical parametric oscillators"), but now massive particles can be used instead of light.

Fundamental Research in Vienna

The emitted twin atoms cannot be understood in the same way as classical particles, such as debris scattered into all directions in an explosion. They are quantum mechanical copies of each other and only differ by their direction of motion. They form one common quantum object. One atom cannot be mathematically described without also describing the other.

"We are going to use these atoms for exciting new experiments," Schmiedmayer enthuses. "A fascinating new field of research is opening up which new insights and possible applications will evolve from. This cannot yet be foreseen. It is conceivable that these correlated atom beams will lead to new quantum measurement methods, with a precision far beyond the scope of classical physics."
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Re: Science News

Postby nightlock » Mon May 02, 2011 12:32 pm

02/05/2011 - Single Atom Stores Quantum Information

A data memory can hardly be any smaller: researchers working with Gerhard Rempe at the Max Planck Institute of Quantum Optics in Garching have stored quantum information in a single atom. The researchers wrote the quantum state of single photons, i.e. particles of light, into a rubidium atom and read it out again after a certain storage time. This technique can be used in principle to design powerful quantum computers and to network them with each other across large distances.

Quantum computers will one day be able to cope with computational tasks in no time where current computers would take years. They will take their enormous computing power from their ability to simultaneously process the diverse pieces of information which are stored in the quantum state of microscopic physical systems, such as single atoms and photons. In order to be able to operate, the quantum computers must exchange these pieces of information between their individual components. Photons are particularly suitable for this, as no matter needs to be transported with them. Particles of matter however will be used for the information storage and processing. Researchers are therefore looking for methods whereby quantum information can be exchanged between photons and matter. Although this has already been done with ensembles of many thousands of atoms, physicists at the Max Planck Institute of Quantum Optics in Garching have now proved that quantum information can also be exchanged between single atoms and photons in a controlled way.

Using a single atom as a storage unit has several advantages -- the extreme miniaturization being only one, says Holger Specht from the Garching-based Max Planck Institute, who was involved in the experiment. The stored information can be processed by direct manipulation on the atom, which is important for the execution of logical operations in a quantum computer. "In addition, it offers the chance to check whether the quantum information stored in the photon has been successfully written into the atom without destroying the quantum state," says Specht. It is thus possible to ascertain at an early stage that a computing process must be repeated because of a storage error.

The fact that no one had succeeded until very recently in exchanging quantum information between photons and single atoms was because the interaction between the particles of light and the atoms is very weak. Atom and photon do not take much notice of each other, as it were, like two party guests who hardly talk to each other, and can therefore exchange only a little information. The researchers in Garching have enhanced the interaction with a trick. They placed a rubidium atom between the mirrors of an optical resonator, and then used very weak laser pulses to introduce single photons into the resonator. The mirrors of the resonator reflected the photons to and fro several times, which strongly enhanced the interaction between photons and atom. Figuratively speaking, the party guests thus meet more often and the chance that they talk to each other increases.

The photons carried the quantum information in the form of their polarization. This can be left-handed (the direction of rotation of the electric field is anti-clockwise) or right-handed (clock-wise). The quantum state of the photon can contain both polarizations simultaneously as a so-called superposition state. In the interaction with the photon the rubidium atom is usually excited and then loses the excitation again by means of the probabilistic emission of a further photon. The Garching-based researchers did not want this to happen. On the contrary, the absorption of the photon was to bring the rubidium atom into a definite, stable quantum state. The researchers achieved this with the aid of a further laser beam, the so-called control laser, which they directed onto the rubidium atom at the same time as it interacted with the photon.

The spin orientation of the atom contributes decisively to the stable quantum state generated by control laser and photon. Spin gives the atom a magnetic moment. The stable quantum state, which the researchers use for the storage, is thus determined by the orientation of the magnetic moment. The state is characterized by the fact that it reflects the photon's polarization state: the direction of the magnetic moment corresponds to the rotational direction of the photon's polarization, a mixture of both rotational directions being stored by a corresponding mixture of the magnetic moments.

This state is read out by the reverse process: irradiating the rubidium atom with the control laser again causes it to re-emit the photon which was originally incident. In the vast majority of cases, the quantum information in the read-out photon agrees with the information originally stored, as the physicists in Garching discovered. The quantity that describes this relationship, the so-called fidelity, was more than 90 percent. This is significantly higher than the 67 percent fidelity that can be achieved with classical methods, i.e. those not based on quantum effects. The method developed in Garching is therefore a real quantum memory.

The physicists measured the storage time, i.e. the time the quantum information in the rubidium can be retained, as around 180 microseconds. "This is comparable with the storage times of all previous quantum memories based on ensembles of atoms," says Stephan Ritter, another researcher involved in the experiment. Nevertheless, a significantly longer storage time is necessary for the method to be used in a quantum computer or a quantum network. There is also a further quality characteristic of the single-atom quantum memory from Garching which could be improved: the so-called efficiency. It is a measure of how many of the irradiated photons are stored and then read out again. This was just under 10 percent.

The storage time is mainly limited by magnetic field fluctuations from the laboratory surroundings, says Ritter. "It can therefore be increased by storing the quantum information in quantum states of the atoms which are insensitive to magnetic fields." The efficiency is limited by the fact that the atom does not sit still in the centre of the resonator, but moves. This causes the strength of the interaction between atom and photon to decrease. The researchers can thus also improve the efficiency: by greater cooling of the atom, i.e. by further reducing its kinetic energy.

The researchers at the Max Planck Institute in Garching now want to work on these two improvements. "If this is successful, the prospects for the single-atom quantum memory would be excellent," says Stephan Ritter. The interface between light and individual atoms would make it possible to network more atoms in a quantum computer with each other than would be possible without such an interface; a fact that would make such a computer more powerful. Moreover, the exchange of photons would make it possible to quantum mechanically entangle atoms across large distances. The entanglement is a kind of quantum mechanical link between particles which is necessary to transport quantum information across large distances. The technique now being developed at the Max Planck Institute of Quantum Optics could some day thus become an essential component of a future "quantum Internet."
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