Category Archives: Quantum Physics

In Brief Chinese physicists managed to demonstrate long-distance quantum entanglement in space, breaking previous records. This development, made possible by a novel method, could lead to improved information storage and transfer in the future. Spooky Action Gets to Space

When it comes to weird science stuff, quantum entanglement is probably nearthe top of the list, especially back in the days when Einstein referred to it as that spooky action at a distance. Physicists have since demonstrated the spookyphenomenon to be possible, but now theywant to extend itsreach. A new study shows its possible for quantum entanglement to spanfar longer distances than previously demonstrated.

We have demonstrated the distribution of two entangled photons from a satellite to two ground stations that are 1,203 kilometers [748 miles] apart, lead author Juan Yin, physicist at the Science and Technology University of China in Shanghai, explained in aresearch paper published in the journal Science. The previous record for entanglement distribution reached only 100 kilometers (62 miles).

Yins team used the Micius, the worlds first quantum-enabled satellite which China launched in 2016, to transmit entangled photons to several ground stations separated by long distances. They managed to achieve this feat by using laser beams to prevent the light particles from gettinglost as they traveled.

The result again confirms the nonlocal feature of entanglement and excludes the models of reality that rest on the notions of locality and realism, Yin and his colleagues wrote.

Though quantum entanglement is incredibly complex, its possible to explain itin simple terms. Two or more particles are entangled or linked when a change in ones state or properties instantaneously affects the others. What makes this stranger is that this link works regardless of distance. This phenomenon becomes particularly useful in storing information as in the case of using quantum bits (qubits) in quantum computing.

By proving that quantum entanglement can be maintained in space over such a long distance, this work paves the way for long-distance satellite quantum communication and maybe even realize the possibilities for quantum teleportation. Long-distance entanglement distribution is essential for the testing of quantum physics and quantum networks, Yins team wrote.

Advances in quantum cryptography, which rely heavily on extending entanglement, could change the way information is stored and transferred in the future opening up applications in improved security in communication and even payment systems.

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Physicists Demonstrate Record Breaking Long-Distance Quantum Entanglement in Space - Futurism

China has used a laser on a satellite orbiting 480 kilometres above the earth to produce entangled photons and beam them to stations on the ground. Picture: Cai Yang/Xinhua via ZUMA

IN A bid to build an entirely new kind of internet completely secure and impervious to hackers China has pulled off a major feat in particle physics.

Chinese scientists have set a new distance record for beaming a pair of entangled particles: photons of light that behave like twins and experience the exact same things simultaneously, even though theyre separated by great distances.

The principle is called quantum entanglement and its one of the subatomic worlds weirdest phenomena. And China has smashed the distance record for quantum entanglement.

In a groundbreaking experiment led by Professor Jian-Wei Pan of Hefei University in China, a laser on a satellite orbiting 480 kilometres above the earth produced entangled photons.

They were then transmitted to two different ground-based stations 1200 kilometres apart, without breaking the link between the photons, the researchers said in a report published in the journal Science.

That distance achieved in the experiment is 10 times greater than the previous record for entanglement and is also the first time entangled photons have been generated in space.

Its a huge, major achievement, Thomas Jennewein, physicist at the University of Waterloo in Canada, told Science. They started with this bold idea and managed to do it.

China launched its first quantum satellite in August and if all goes according to plan will send up plenty more to create a system of communication which relies on entanglement.

A COMPLETELY NEW INTERNET

By launching a group of quantum-enabled satellites, China hopes to create a super secure network that uses an encryption technique based on the principles of a field known as quantum communication.

In physics we are trying, and we have demonstrated some encryption techniques that rely on the law of physics rather than the mathematical complexity and we call this quantum key distribution, professor Ping Koy Lam from the ANUs Department of Quantum Science told news.com.au last year, before China launched its first quantum satellite.

For that to work you need to send laser beams that carry certain information, quantum information, and then you need the senders and the receivers to get together to find a protocol to secure the communication.

The reason it cant be hacked is because the information carried in the quantum state of a particle cannot be measured or cloned without destroying the information itself.

We can show that this kind of quantum encryption works in a city radius or at most between two nearby cities, Prof Lam said.

However China believes the atmosphere in space will allow the photons to travel further without disruption because in space theres nothing to attenuate light.

In the latest experiment, both stations which received the photons were in the mountains of Tibet, at a height that reduced the amount of air the fragile photons had to traverse.

The successful characterisation of quantum features under such conditions is a precondition for a global quantum communication network using satellites that would link metropolitan area quantum networks on the ground. Picture: Google, ESASource:Supplied

A NEW SPACE RACE

Chinas ongoing progress will no doubt be watched closely by security agencies around the world.

While the spectre of a communication network enabled via quantum satellites is still a long way off, as China edges closer to the goal it has led to predictions of a new space race.

Quantum technology has been a major focus of Chinas five-year economic development plan, released in March 2016. While other space agencies have been experimenting with the technology, none have seen the level of financial support provided by Beijing.

China has not disclosed how much money it has spent on Quantum research, but funding for basic research which includes quantum physics was $US101 billion in 2015 an absolutely massive increase from the $US1.9 billion the country spent in 2005.

Scientists in the US, Canada, Europe and Japan are also rushing to exploit the power of particle physics to create secure communication systems, but Chinas latest experiment puts the country well ahead of the pack.

With AFP

China launched the world's first quantum satellite on top of a Long March-2D rocket from the Jiuquan Satellite Launch Center in northwest China. Picture: ZumaSource:Supplied

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China sets new record for quantum entanglement en route to build new communication network - NEWS.com.au

A Chinese satellite has split pairs of "entangled photons" and transmitted them to separate ground stations 745 miles (1,200 kilometers) apart, smashing the previous distance record for such a feat and opening new possibilities in quantum communication.

In quantum physics, when particles interact with each other in certain ways they become "entangled." This essentially means they remain connected even when separated by large distances, so that an action performed on one affects the other.

In a new study published online today (June 15) in the journal Science, researchers report the successful distribution of entangled photon pairs to two locations on Earth separated by 747.5 miles (1,203 km). [The 18 Biggest Unsolved Mysteries in Physics]

Quantum entanglement has interesting applications for testing the fundamental laws of physics, but also for creating exceptionally secure communication systems, scientists have said. That's because quantum mechanics states that measuring a quantum system inevitably disturbs it, so any attempt to eavesdrop is impossible to hide.

But, it's hard to distribute entangled particles normally photons over large distances. When traveling through air or over fiber-optic cables, the environment interferes with the particles, so with greater distances, the signal decays and becomes too weak to be useful.

In 2003, Pan Jianwei, a professor of quantum physics at the University of Science and Technology of China, started work on a satellite-based system designed to beam entangled photon pairs down to ground stations. The idea was that because most of the particle's journey would be through the vacuum of space, this system would introduce considerably less environmental interference.

"Many people then thought it [was] a crazy idea, because it was very challenging already doing the sophisticated quantum-optics experiments inside a well-shielded optical table," Pan told Live Science. "So how can you do similar experiments at thousand-kilometers distance scale and with the optical elements vibrating and moving at a speed of 8 kilometers per second [5 miles per second]?"

In the new study, researchers used China's Micius satellite, which was launched last year, to transmit the entangled photon pairs. The satellite features an ultrabright entangled photon source and a high-precision acquiring, pointing and tracking (APT) system that uses beacon lasers on the satellite and at three ground stations to line up the transmitter and receivers.

Once the photons reached the ground stations, the scientists carried out tests and confirmed that the particles were still entangled despite having traveled between 994 miles and 1,490 miles (1,600 and 2,400 km), depending on what stage of its orbit the satellite was positioned at.

Only the lowest 6 miles (10 km) of Earth's atmosphere are thick enough to cause significant interference with the photons, the scientists said. This means the overall efficiency of their link was vastly higher than previous methods for distributing entangled photons via fiber-optic cables, according to the scientists. [Twisted Physics: 7 Mind-Blowing Findings]

"We have already achieved a two-photon entanglement distribution efficiency a trillion times more efficient than using the best telecommunication fibers," Pan said. "We have done something that was absolutely impossible without the satellite."

Apart from carrying out experiments, one of the potential uses for this kind of system is for "quantum key distribution," in which quantum communication systems are used to share an encryption key between two parties that is impossible to intercept without alerting the users. When combined with the correct encryption algorithm, this system is uncrackable even if encrypted messages are sent over normal communication channels, experts have said.

Artur Ekert, a professor of quantum physics at the University of Oxford in the United Kingdom, was the first to describe how entangled photons could be used to transmit an encryption key.

"The Chinese experiment is quite a remarkable technological achievement," Ekert told Live Science. "When I proposed the entangled-based quantum key distribution back in 1991 when I was a student in Oxford, I did not expect it to be elevated to such heights!"

The current satellite is not quite ready for use in practical quantum communication systems, though, according to Pan. For one, its relatively low orbit means each ground station has coverage for only about 5 minutes each day, and the wavelength of photons used means it can only operate at night, he said.

Boosting coverage times and areas will mean launching new satellites with higher orbits, Pan said, but this will require bigger telescopes, more precise tracking and higher link efficiency. Daytime operation will require the use of photons in the telecommunications wavelengths, he added.

But while developing future quantum communication networks will require considerable work, Thomas Jennewein, an associate professor at the University of Waterloo's Institute for Quantum Computing in Canada, said Pan's group has demonstrated one of the key building blocks.

"I have worked in this line of research since 2000 and researched on similar implementations of quantum- entanglement experiments from space, and I can therefore very much attest to the boldness, dedication and skills that this Chinese group has shown," he told Live Science.

Original article on Live Science.

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New Quantum-Entanglement Record Could Spur Hack-Proof Communications - Yahoo News

Quantum mechanics is the body of scientific laws that describe the wacky behavior of photons, electrons and the other particles that make up the universe.

Quantum mechanics is the branch of physics relating to the very small.

It results in what may appear to be some very strange conclusions about the physical world. At the scale of atoms and electrons, many of the equations ofclassical mechanics, which describe how things move at everyday sizes and speeds, cease to be useful. In classical mechanics, objects exist in a specific place at a specific time. However, in quantum mechanics, objects instead exist in a haze of probability; they have a certain chance of being at point A, another chance of being at point B and so on.

Quantum mechanics (QM) developed over many decades, beginning as a set of controversial mathematical explanations of experiments that the math of classical mechanics could not explain. It began at the turn of the 20th century, around the same time that Albert Einstein published histheory of relativity, a separate mathematical revolution in physics that describes the motion of things at high speeds. Unlike relativity, however, the origins of QM cannot be attributed to any one scientist. Rather, multiple scientists contributed to a foundation of three revolutionary principles that gradually gained acceptance and experimental verification between 1900 and 1930. They are:

Quantized properties: Certain properties, such as position, speed and color, can sometimes only occur in specific, set amounts, much like a dial that "clicks" from number to number. This challenged a fundamental assumption of classical mechanics, which said that such properties should exist on a smooth, continuous spectrum. To describe the idea that some properties "clicked" like a dial with specific settings, scientists coined the word "quantized."

Particles of light: Light can sometimes behave as a particle. This was initially met with harsh criticism, as it ran contrary to 200 years of experiments showing that light behaved as a wave; much like ripples on the surface of a calm lake. Light behaves similarly in that it bounces off walls and bends around corners, and that the crests and troughs of the wave can add up or cancel out. Added wave crests result in brighter light, while waves that cancel out produce darkness. A light source can be thought of as a ball on a stick beingrhythmically dipped in the center of a lake. The color emitted corresponds to the distance between the crests, which is determined by the speed of the ball's rhythm.

Waves of matter: Matter can also behave as a wave. This ran counter to the roughly 30 years of experiments showing that matter (such as electrons) exists as particles.

In 1900, German physicist Max Planck sought to explain the distribution of colors emitted over the spectrum in the glow of red-hot and white-hot objects, such as light-bulb filaments. When making physical sense of the equation he had derived to describe this distribution, Planck realized it implied that combinations of only certaincolors(albeit a great number of them) were emitted, specifically those that were whole-number multiples of some base value. Somehow, colors were quantized! This was unexpected because light was understood to act as a wave, meaning that values of color should be a continuous spectrum. What could be forbiddingatomsfrom producing the colors between these whole-number multiples? This seemed so strange that Planck regarded quantization as nothing more than a mathematical trick. According to Helge Kragh in his 2000 article in Physics World magazine, "Max Planck, the Reluctant Revolutionary," "If a revolution occurred in physics in December 1900, nobody seemed to notice it. Planck was no exception "

Planck's equation also contained a number that would later become very important to future development of QM; today, it's known as "Planck's Constant."

Quantization helped to explain other mysteries of physics. In 1907, Einstein used Planck's hypothesis of quantization to explain why the temperature of a solid changed by different amounts if you put the same amount of heat into the material but changed the starting temperature.

Since the early 1800s, the science ofspectroscopyhad shown that different elements emit and absorb specific colors of light called "spectral lines." Though spectroscopy was a reliable method for determining the elements contained in objects such as distant stars, scientists were puzzled aboutwhyeach element gave off those specific lines in the first place. In 1888, Johannes Rydberg derived an equation that described the spectral lines emitted by hydrogen, though nobody could explain why the equation worked. This changed in 1913 whenNiels Bohrapplied Planck's hypothesis of quantization to Ernest Rutherford's 1911 "planetary" model of the atom, which postulated that electrons orbited the nucleus the same way that planets orbit the sun. According toPhysics 2000(a site from the University of Colorado), Bohr proposed that electrons were restricted to "special" orbits around an atom's nucleus. They could "jump" between special orbits, and the energy produced by the jump caused specific colors of light, observed as spectral lines. Though quantized properties were invented as but a mere mathematical trick, they explained so much that they became the founding principle of QM.

In 1905, Einstein published a paper, "Concerning an Heuristic Point of View Toward the Emission and Transformation of Light," in which he envisioned light traveling not as a wave, but as some manner of "energy quanta." This packet of energy, Einstein suggested, could "be absorbed or generated only as a whole," specifically when an atom "jumps" between quantized vibration rates. This would also apply, as would be shown a few years later, when an electron "jumps" between quantized orbits. Under this model, Einstein's "energy quanta" contained the energy difference of the jump; when divided by Plancks constant, that energy difference determined the color of light carried by those quanta.

With this new way to envision light, Einstein offered insights into the behavior of nine different phenomena, including the specific colors that Planck described being emitted from a light-bulb filament. It also explained how certain colors of light could eject electrons off metal surfaces, a phenomenon known as the "photoelectric effect." However, Einstein wasn't wholly justified in taking this leap, said Stephen Klassen, an associate professor of physics at the University of Winnipeg. In a 2008 paper, "The Photoelectric Effect: Rehabilitating the Story for the Physics Classroom," Klassen states that Einstein's energy quanta aren't necessary for explaining all of those nine phenomena. Certain mathematical treatments of light as a wave are still capable of describing both the specific colors that Planck described being emitted from a light-bulb filament and the photoelectric effect. Indeed, in Einstein's controversial winning of the 1921Nobel Prize, the Nobel committee only acknowledged "his discovery of the law of the photoelectric effect," which specifically did not rely on the notion of energy quanta.

Roughly two decades after Einstein's paper, the term "photon" was popularized for describing energy quanta, thanks to the 1923 work of Arthur Compton, who showed that light scattered by an electron beam changed in color. This showed that particles of light (photons) were indeed colliding with particles of matter (electrons), thus confirming Einstein's hypothesis. By now, it was clear that light could behave both as a wave and a particle, placing light's "wave-particle duality" into the foundation of QM.

Since the discovery of the electron in 1896, evidence that all matter existed in the form of particles was slowly building. Still, the demonstration of light's wave-particle duality made scientists question whether matter was limited to actingonlyas particles. Perhaps wave-particle duality could ring true for matter as well? The first scientist to make substantial headway with this reasoning was a French physicist named Louis de Broglie. In 1924, de Broglie used the equations of Einstein'stheory of special relativityto show that particles can exhibit wave-like characteristics, and that waves can exhibit particle-like characteristics. Then in 1925, two scientists, working independently and using separate lines of mathematical thinking, applied de Broglie's reasoning to explain how electrons whizzed around in atoms (a phenomenon that was unexplainable using the equations ofclassical mechanics). In Germany, physicist Werner Heisenberg (teaming with Max Born and Pascual Jordan) accomplished this by developing "matrix mechanics." Austrian physicist ErwinSchrdingerdeveloped a similar theory called "wave mechanics." Schrdinger showed in 1926 that these two approaches were equivalent (though Swiss physicist Wolfgang Pauli sent anunpublished resultto Jordan showing that matrix mechanics was more complete).

The Heisenberg-Schrdinger model of the atom, in which each electron acts as a wave (sometimes referred to as a "cloud") around the nucleus of an atom replaced the Rutherford-Bohr model. One stipulation of the new model was that the ends of the wave that forms an electron must meet. In "Quantum Mechanics in Chemistry, 3rd Ed." (W.A. Benjamin, 1981), Melvin Hanna writes, "The imposition of the boundary conditions has restricted the energy to discrete values." A consequence of this stipulation is that only whole numbers of crests and troughs are allowed, which explains why some properties are quantized. In the Heisenberg-Schrdinger model of the atom, electrons obey a "wave function" and occupy "orbitals" rather than orbits. Unlike the circular orbits of the Rutherford-Bohr model, atomic orbitals have a variety of shapes ranging from spheres to dumbbells to daisies.

In 1927, Walter Heitler and Fritz London further developed wave mechanics to show how atomic orbitals could combine to form molecular orbitals, effectively showing why atoms bond to one another to formmolecules. This was yet another problem that had been unsolvable using the math of classical mechanics. These insights gave rise to the field of "quantum chemistry."

Also in 1927, Heisenberg made another major contribution to quantum physics. He reasoned that since matter acts as waves, some properties, such as an electron's position and speed, are "complementary," meaning there's a limit (related to Planck's constant) to how well the precision of each property can be known. Under what would come to be called "Heisenberg'suncertainty principle," it was reasoned that the more precisely an electron's position is known, the less precisely its speed can be known, and vice versa. This uncertainty principle applies to everyday-size objects as well, but is not noticeable because the lack of precision is extraordinarily tiny. According to Dave Slaven of Morningside College (Sioux City, IA), if a baseball's speed is known to within aprecision of 0.1 mph, the maximum precision to which it is possible to know the ball's position is 0.000000000000000000000000000008 millimeters.

The principles of quantization, wave-particle duality and the uncertainty principle ushered in a new era for QM. In 1927, Paul Dirac applied a quantum understanding of electric and magnetic fields to give rise to the study of "quantum field theory" (QFT), which treated particles (such as photons and electrons) as excited states of an underlying physical field. Work in QFT continued for a decade until scientists hit a roadblock: Many equations in QFT stopped making physical sense because they produced results of infinity. After a decade of stagnation, Hans Bethe made a breakthrough in 1947 using a technique called "renormalization." Here, Bethe realized that all infinite results related to two phenomena (specifically "electron self-energy" and "vacuum polarization") such that the observed values of electron mass and electron charge could be used to make all the infinities disappear.

Since the breakthrough of renormalization, QFT has served as the foundation for developing quantum theories about the four fundamental forces of nature: 1) electromagnetism, 2) the weak nuclear force, 3) the strong nuclear force and 4) gravity. The first insight provided by QFT was a quantum description of electromagnetism through "quantum electrodynamics" (QED), which made strides in the late 1940s and early 1950s. Next was a quantum description of the weak nuclear force, which was unified with electromagnetism to build "electroweak theory" (EWT) throughout the 1960s. Finally came a quantum treatment of the strong nuclear force using "quantum chromodynamics" (QCD) in the 1960s and 1970s. The theories of QED, EWT and QCD together form the basis of theStandard Modelof particle physics. Unfortunately, QFT has yet to produce a quantum theory of gravity. That quest continues today in the studies of string theory and loop quantum gravity.

Robert Coolman is a graduate researcher at the University of Wisconsin-Madison, finishing up his Ph.D. in chemical engineering. He writes about math, science and how they interact with history. Follow Robert@PrimeViridian. Followus@LiveScience,Facebook&Google+.

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What Is Quantum Mechanics? - livescience.com

Quantum physics is an often mind-boggling branch of science filled with strange behavior and bizarre implications. For many people, the mere mention of the term is enough to send us hurtling in the opposite direction, like an electron bouncing off the center of an atom.

But evidence is mounting that the future of technology lies in quantum mechanics, which focuses on how the smallest things in our universe work. And a new breakthrough by scientists in China has just brought the world one very big step closer to this quantum revolution. Hundreds of miles closer, in fact. So its as good a time as any to understand why quantum physics is making such waves.

An Atlas 5 rocket, a national security satellite, launched from California in 2008. Chinese physicists have used a satellite to beat the distance record for quantum entanglement. Gene Blevins/Reuters

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Quantum physics is all about waves. And particles. Together. Sort of.

Mostly, we think of light as something that occurs in waves and matter as distinct particles. But theorist Max Plancks attempt in 1900 to explain observations about colors emitted from hot objects started scientists down a path that transformed our understanding of how life works at the very smallest scale.

The first step was realizing that light behaves like a stream of individual particles, called photons. Albert Einstein came to this conclusion following Plancks work. Each photon contains a discrete amount of energy.

Subsequent research by Niels Bohr and others disrupted what physicists understood about electrons, the negatively charged particles that swirl around the heavy centers of the atoms that make up the elements (gold, silver, potassium, calcium, etc.) that in turn make up matter. That disruption was accentuated by Louis de Broglie, who realized that if light can behave like a particle, then maybe electrons, which physicists had always thought of as particles, could behave like waves. Numerous experiments proved that to be the case. Photons behave like waves and particles. Electrons behavelike waves and particles. The type of measurement you do determines how a photon or an electron behave.

One of the most intriguing effects of quantum physics is something called entanglement. With quantum entanglement, two particles derived from the same source behave the same way, even when they are far apart. The state of either particle cannot be determined until it is measured, and the act of measuring is what determines its state. And the measurement of one particle affects the measurement of the other particle. This thinking is embodied by Erwin Schrdingers thought problem about his famous cat.

If you split photon A into a photon pairB and Cmeasuring B will tell you, with absolute certainty, the measure of C. Paul Kwiat, physicist at the University of Illinois, gives the analogy of flipping a coin. If one flipped coin results in heads, heads, tails, heads, tails, tails, head, then the entangled coin, placed hundreds of miles away, would follow the same sequence. Thats not a behavior you see with coins, says Kwiat. Thats where quantum entanglement is pretty weird. Two things hundreds of miles away behaving as one: Thats quantum entanglement. And its real. Albert Einstein called it spuckhafte ferwirklung, or spooky action at a distance.

For more on the history of quantum physics and the entanglement phenomenon, author Chad Orzel, who teaches physics at Union College in Schenectady, New York, has some excellent videos.

Beyond the weirdness factor, quantum entanglement has broad implications for computing and information sharing. Entanglement distributionfor example, the splitting of a single photon into two linked photonscould be used to create a secure internet connection. The technology, called quantum cryptography, would allow the users to detect any eavesdropper on the channel. The reason you can detect the eavesdropper is that such an intruder would necessarily alter the entangled photons by his or her presence.

The principle allows for a secure communication channel that is unhackable, says Jonathan Dowling, a physicist at Louisiana State University When the Chinese roll out this type of communications nationwide, which is their plan, says Dowling, then no matter how many NSA computers you string together, you are never going to be able to tap into their system.

A new study in Science, by Juan Yin and colleagues at the University of Science and Technology in China and several other institutions there, has brought this future technology within much closer reach. The researchers split a photon on a satellite and sent the two resulting photons in two different directions, aimed at ground stations in China. The ground stations were more than 700 miles apart from one another. The distance from the satellite, which was constantly in motion, to each ground station varied from 300 to 1,200 miles.

The researchers managed to send photon pairs to different ground stations repeatedly and confirmed that the photons were entangled. Using a laser pointer-like source, they made about 6 million photon pairs per second. About one pair per second reached the ground stations. Kwiat says its like throwing a dime into a toll booth bucket while driving at high speed, only youre throwing a much tinier object from much farther awayand at a much faster speed. Measurements confirmed that the photon pairs had the same polarization, proving that they were entangled.

Although previous studies have managed to achieve similar results, never has it been done over such a great distance and from a satellite. (The prior record demonstrated entanglement across two of the Canary Islands, about 89 miles apart.) Its a beautiful experiment, says Kwiat. They demonstrated the persistence of entanglement over a longer distance than any experiment before by roughly a factor of 10.

Dowling says that this achievement proves that the quantum-based technologies many physicists envision are attainable. The long-term goal is to build a quantum internet where future computers around the globe are linked together in an uncrackable network of extraordinary computational power, says Dowling. The satellite will go down in history as the first link in the quantum internet.

The Chinese physicists are not the only team on the quest for this technology. Quantum cryptography systems are commercially available and researchers in several countries, including the U.S., Canada, Italy and Singapore are also forging the way ahead, says Kwiat, who is among them. Google is also working on quantum information science.

Still, the new study is a huge breakthrough because it proves entanglement can be achieved from a satellite and across this large distance. We have done something that was absolutely impossible without the satellite, says senior author Jian-Wei Pan. The next step, he says, is to perform more experiments with light from space, across yet longer distances and at faster speeds, with a goal of controlling quantum states and understanding how gravity affects quantum behavior.

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Cybersecurity Attacks Are a Global Threat. Chinese Scientists Have the Answer: Quantum Mechanics - Newsweek

Chinese scientists have just set a record in quantum physics.

For the first time, pairs of entangled photons have been beamed from a satellite in orbit to two receiving stations almost 1,500 miles away on on Earth.

At the same time, the researchers were able to deliberately separate the entangled photon pairs along a greater distance than has ever been recorded.

The experiment, described Thursday in the journal Science, represents the first measurable proof of an idea that has long been theorized but never tested, experts said.

This is the first time you have a quantum channel between a satellite and the ground that you can actually use, said Norbert Ltkenhaus, a professor at the Institute for Quantum Computing at the University of Waterloo in Canada who was not involved in the new work. People have been talking about doing it for many, many years, but these guys actually did it.

Keep reading to learn what this new work means, and why it matters.

Great question. For starters, a photon is a tiny particle of light. In fact, it's the smallest unit that light can be broken into. It has no mass and no charge.

Entangled photons are a pair of photons whose properties are linked, and remain that way no matter how far apart they get.

If you make a measurement on one of the photons, you get a perfectly correlated outcome on the other member of the pair, Ltkenhaus said.

And that will hold true not matter how many times you look at them.

One measurement alone doesnt tell you they are entangled, you need to repeat it many times, he said. With entangled photons no matter what you measure, or how many times you measure, or which side of the pair you measure, you always get perfect correlation.

Another great question. This one is more difficult to answer.

Scientists have not been able to explain why entanglement occurs. All they know is that it exists.

Einstein referred to the phenomena of entanglement as spooky action at a distance. Others have said it is kind of like the physics version of voodoo.

They built a special satellite to do it.

The spacecraft, nicknamed Micius after a famous 5th century Chinese scientist, launched in August 2016.

It is loaded with a special crystal that can split a single incoming photon into two daughter photons with joint properties. For this experiment, instruments on the satellite separated the entangled photons and sent them to different receiving stations on Earth.

To do this, Micius had to aim at its targets with an amazing degree of precision, said Jian-Wei Pan, a physicist at the University of Science and Technology of China who led the work.

Its the equivalent of clearly seeing a human hair at a distance of 900 feet away, he said.

It is extreme. And, experts say, challenging.

Designing, launching and operating a satellite with this capability is no easy feat, Ltkenhaus said. I see this as a great engineering triumph.

But, as the study demonstrates, using a satellite to send beams of entangled photons to Earth is a better strategy than using optical fibers to distribute them.

The greatest distance scientists have been able to separate entangled photons using optical fibers is 62 miles. By sending the entangled photons through space, Pan and his team were able to separate entangled photons by more than 620 miles.

Not immediately, but eventually, it probably will.

For example, distributing entangled photons over large distances could be used to establish unhackable communications via whats known as quantum cryptography.

This application relies on another strange aspect of quantum mechanics namely that the simple act of observing a photon disturbs it and causes it to change its orientation.

Scientists have already been able to establish secure, quantum channels using fiber optics, but there is a limit to how far those can stretch.

Using the space-based quantum channel, the authors have shown it is possible to significantly extend the distance over which one can perform such a secure communication, said Jrgen Volz, a physicist at the Vienna Center for Quantum Science and Technology who was not involved in the work.

In the time of the Internet, when more and more sensitive information is shared and exchanged via the web, this is of tremendous importance, he said.

But experts say an application like that may still be 10 years away.

Although the experiment was successful, the rate of sending and receiving entangled photons described in the paper was still quite low. Of nearly 6 million entangled photon pairs generated by Micius each second, only one pair was detected at stations here on Earth.

The communication rates here are not yet sufficient for a practical application, said Wenjamin Rosenfeld, a physicist at the Ludwig-Maximilians University in Munich.

However, he added that the mission represents a proof-of-principle demonstration of a quantum communication protocol that could be available in the near future.

Pan put it this way: This is the first baby step for quantum entanglement experiments going into space. It is really new!

deborah.netburn@latimes.com

Do you love science? I do! Follow me @DeborahNetburn and "like" Los Angeles Times Science & Health on Facebook.

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Chinese satellite breaks a quantum physics record, beams entangled photons from space to Earth - Los Angeles Times

June 13, 2017 An artist's rendering of a neural network with two layers. At the top is a real quantum system, like atoms in an optical lattice. Below is a network of hidden neurons that capture their interactions. Credit: E. Edwards/JQI

Machine learning, the field that's driving a revolution in artificial intelligence, has cemented its role in modern technology. Its tools and techniques have led to rapid improvements in everything from self-driving cars and speech recognition to the digital mastery of an ancient board game.

Now, physicists are beginning to use machine learning tools to tackle a different kind of problem, one at the heart of quantum physics. In a paper published recently in Physical Review X, researchers from JQI and the Condensed Matter Theory Center (CMTC) at the University of Maryland showed that certain neural networksabstract webs that pass information from node to node like neurons in the braincan succinctly describe wide swathes of quantum systems .

Dongling Deng, a JQI Postdoctoral Fellow who is a member of CMTC and the paper's first author, says that researchers who use computers to study quantum systems might benefit from the simple descriptions that neural networks provide. "If we want to numerically tackle some quantum problem," Deng says, "we first need to find an efficient representation."

On paper and, more importantly, on computers, physicists have many ways of representing quantum systems. Typically these representations comprise lists of numbers describing the likelihood that a system will be found in different quantum states. But it becomes difficult to extract properties or predictions from a digital description as the number of quantum particles grows, and the prevailing wisdom has been that entanglementan exotic quantum connection between particlesplays a key role in thwarting simple representations.

The neural networks used by Deng and his collaboratorsCMTC Director and JQI Fellow Sankar Das Sarma and Fudan University physicist and former JQI Postdoctoral Fellow Xiaopeng Lican efficiently represent quantum systems that harbor lots of entanglement, a surprising improvement over prior methods.

What's more, the new results go beyond mere representation. "This research is unique in that it does not just provide an efficient representation of highly entangled quantum states," Das Sarma says. "It is a new way of solving intractable, interacting quantum many-body problems that uses machine learning tools to find exact solutions."

Neural networks and their accompanying learning techniques powered AlphaGo, the computer program that beat some of the world's best Go players last year (and the top player this year ). The news excited Deng, an avid fan of the board game. Last year, around the same time as AlphaGo's triumphs, a paper appeared that introduced the idea of using neural networks to represent quantum states , although it gave no indication of exactly how wide the tool's reach might be. "We immediately recognized that this should be a very important paper," Deng says, "so we put all our energy and time into studying the problem more."

The result was a more complete account of the capabilities of certain neural networks to represent quantum states. In particular, the team studied neural networks that use two distinct groups of neurons. The first group, called the visible neurons, represents real quantum particles, like atoms in an optical lattice or ions in a chain. To account for interactions between particles, the researchers employed a second group of neuronsthe hidden neuronswhich link up with visible neurons. These links capture the physical interactions between real particles, and as long as the number of connections stays relatively small, the neural network description remains simple.

Specifying a number for each connection and mathematically forgetting the hidden neurons can produce a compact representation of many interesting quantum states, including states with topological characteristics and some with surprising amounts of entanglement.

Beyond its potential as a tool in numerical simulations, the new framework allowed Deng and collaborators to prove some mathematical facts about the families of quantum states represented by neural networks. For instance, neural networks with only short-range interactionsthose in which each hidden neuron is only connected to a small cluster of visible neuronshave a strict limit on their total entanglement. This technical result, known as an area law, is a research pursuit of many condensed matter physicists.

These neural networks can't capture everything, though. "They are a very restricted regime," Deng says, adding that they don't offer an efficient universal representation. If they did, they could be used to simulate a quantum computer with an ordinary computer, something physicists and computer scientists think is very unlikely. Still, the collection of states that they do represent efficiently, and the overlap of that collection with other representation methods, is an open problem that Deng says is ripe for further exploration.

Explore further: Physicists use quantum memory to demonstrate quantum secure direct communication

More information: Dong-Ling Deng et al. Quantum Entanglement in Neural Network States, Physical Review X (2017). DOI: 10.1103/PhysRevX.7.021021

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Neural networks take on quantum entanglement - Phys.Org

June 9, 2017 by Lisa Zyga feature (Left) False color photomicrograph and (right) simplified circuit diagram of the superconducting quantum circuit for solving 2 2 linear equations. The method uses four qubits, marked Q1 to Q4, with four corresponding readout resonators, marked R1 to R4. Credit: Zheng et al. 2017 American Physical Society

(Phys.org)Physicists have experimentally demonstrated a purely quantum method for solving systems of linear equations that has the potential to work exponentially faster than the best classical methods. The results show that quantum computing may eventually have far-reaching practical applications, since solving linear systems is commonly done throughout science and engineering.

The physicists, led by Haohua Wang at Zhejiang University and Chao-Yang Lu and Xiaobo Zhu at the University of Science and Technology of China, along with their coauthors from various institutions in China, have published their paper on what they refer to as a "quantum linear solver" in a recent issue of Physical Review Letters.

"For the first time, we have demonstrated a quantum algorithm for solving systems of linear equations on a superconducting quantum circuit," Lu told Phys.org. "[This is] one of the best solid-state platforms with excellent scalability and remarkable high fidelity."

The quantum algorithm they implemented is called the Harrow, Hassidim, and Lloyd (HHL) algorithm, which was previously shown to have the ability, in principle, to lead to an exponential quantum speedup over classical algorithms. However, so far this has not been experimentally demonstrated.

In the new study, the scientists showed that a superconducting quantum circuit running the HHL algorithm can solve the simplest type of linear system, which has two equations with two variables. The method uses just four qubits: one ancilla qubit (a universal component of most quantum computing systems), and three qubits that correspond to the input vector b and the two solutions represented by the solution vector x in the standard linear system Ax = b, where A is a 2 x 2 matrix.

By performing a series of rotations, swappings of states, and binary conversions, the HHL algorithm determines the solutions to this system, which can then be read out by a quantum nondemolition measurement. The researchers demonstrated the method using 18 different input vectors and the same matrix, generating different solutions for different inputs. As the researchers explain, it is too soon to tell how much faster this quantum method might work since these problems are easily solved by classical methods.

"The whole calculation process takes about one second," Zhu said. "It is hard to directly compare the current version to the classical methods now. In this work, we showed how to solve the simplest 2 x 2 linear system, which can be solved by classical methods in a very short time. The key power of the HHL quantum algorithm is that, when solving an 's-sparse' system matrix of a very large size, it can gain an exponential speed-up compared to the best classical method. Therefore, it would be much more interesting to show such a comparison when the size of the linear equation is scaled to a very large system."

The researchers expect that, in the future, this quantum circuit could be scaled up to solve larger linear systems. They also plan to further improve the system's performance by making some straightforward adjustments to the device fabrication to reduce some of the error in its implementation. In addition, the researchers want to investigate how the circuit could be used to implement other quantum algorithms for a variety of large-scale applications.

"Our future research will focus on improving the hardware performance, including longer coherence times, higher precision logic gates, larger numbers of qubits, lower crosstalk, better readout fidelity, etc.," Wang said. "Based on the improvement of the hardware, we will demonstrate and optimize more quantum algorithms to really show the power of the superconducting quantum processor."

Explore further: Physicists uncover similarities between classical and quantum machine learning

More information: Yarui Zheng et al. "Solving Systems of Linear Equations with a Superconducting Quantum Processor." Physical Review Letters. DOI: 10.1103/PhysRevLett.118.210504. Also at arXiv:1703.06613 [quant-ph]

2017 Phys.org

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I don't know why people say there are no quantum computers. And this one executes not a niche function like simulated annealing but the highly applicable system of linear equations. It really is a breakthrough.

Interesting but not much advanced beyond analog computers of the 1970s.

Description not clear nor sufficient for analysis without doing some research on the methodology. If this is a superconducting circuit, is it cooled to near absolute zero, or is there some other method? With inductors and capacitors, this implies electron currents, in which case, are we dealing with just one electron? If so, the methodology is even more fuzzy. If these are electronic circuits, as the diagram seems to show, then this is not a QM system. ?????????????????????????????????

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Solving systems of linear equations with quantum mechanics - Phys.Org

June 6, 2017

Scientists all over the world are working towards new methods to realize an unhackable internet, an internet based on quantum entanglement an invisible quantum mechanical connection as networking links. The greatest challenge is scaling to large networks that share entangled links with many particles and network nodes. Researchers in Delft and Oxford have now managed to distil a strong entangled link by combining multiple weaker quantum links into one. This method is essential to realize a trustworthy quantum network between several quantum nodes. This innovative new work has now been published in Science magazine.

Spooky internet

Safe communication is one of today's greatest digital challenges. There is a world-wide scientific effort towards new methods to realize a truly safe internet based on the laws of quantum mechanics. With such networks, secret eavesdropping is fundamentally impossible. However, realizing strong links in a quantum network, based on the powerful but fragile principle of quantum entanglement, is a great scientific challenge.

"Entangled particles behave as one, independent of distance. Any observation of such entangled electrons result in correlated information," Professor Ronald Hanson explains. Measuring one particle therefore instantaneously influences the other, even when they are light-years apart. Albert Einstein did not believe such a connection could exist, but a carefully designed experiment from the group of Professor Hanson in Delft in 2015 reached the world press for showing that this really is the case. They were able to succeed at this long-standing challenge by entangling quantum information over distances of over a kilometre via light particles. Scientists are now working towards ground-breaking technologies based on entanglement. Strong connections via quantum entanglement can be the basis for information sharing. 'The information exists at both places and there is no need for sensitive information to travel in between," Hanson elaborates, "we expect fundamentally safe future networks based on entanglement between quantum nodes: a quantum internet." The power of quantum entanglement is that it is invisible for third parties: the information is impossible to eavesdrop.

Entanglement distillation

The research group of Ronald Hanson at QuTech is famous for realizing networking links based on quantum entanglement. They are now building on this work to construct the first quantum internet. Ronald Hanson: "We are now taking an important step forward. Whereas we first realized entangled information between two electrons in diamonds, we now also are using one of the nuclear spins present in each diamond to temporarily store the entangled information." With the information stored safely, the scientist can entangle the electrons again. Hanson: 'Now we have two entanglement links. By combining these in a smart way, we manage to generate one strongly entangled link using two weaker entangled links, just like distilling whisky out of lower-alcoholic ingredients." In principle, this process of entanglement distillation can be repeated over and over, until high-quality entanglement is obtained."

Extending possibilities

The demonstrated method is an important step towards the quantum internet. Norbert Kalb, one of the leading authors of the paper: "To realize such a network, we need all the ingredients of the current internet: a memory, a processor and networking links. Now we have demonstrated that nuclear spins can be employed as memories that are not disturbed by regenerating entanglement between the electron spins, the processors," says Kalb.

In this publication, Hanson and his team showed that entanglement can be stored in nuclear spins while regenerating entanglement between electron spins. Hanson explains the future possibilities: "We could now entangle electrons in additional quantum nodes such that we can extend the number of networking links towards a first real quantum network. Scientifically, a whole new world opens up." This entanglement distillation is essential for the future quantum internet, which requires multiple networking links of high quality. Hanson thinks the future is within reach: "In five years we will connect four Dutch cities in a rudimentary quantum network."

Explore further: Envisioning a future quantum internet

More information: Entanglement Distillation between Solid-State Quantum Network Nodes. Science, DOI: 10.1126/science.aan0070 , https://arxiv.org/abs/1703.03244

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There's more to hacking than just listening in.

The other thing in the real world is that wiretapping is a small part of listening in, a large part is the backdoor which transmits the data out for 'debugging purposes' which 'accidentally' gets triggered by a hack, sending data to wherever. But its cool stuff nonetheless, just to have it be possible.

Also, quantum cryptography is still vulnerable to man-in-the-middle attacks. I think they're exaggerating with the unCRackable claims.

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One step closer to the quantum internet by distillation - Phys.Org

Hear us out

June 5, 2017 Marielle Wakim Theater

In The Road Not Taken, Robert Frost wrote, Two roads diverged in a yellow wood / And sorry I could not travel both. But what if you could travel both? What if an alternate version of you is traveling the other road right now, except youre wearing cleaner jeans and went with cereal, not eggs, for breakfast? That mind-melting concept is the basis of Constellations, a two-character play opening June 6 at the Geffen Playhouse.

Photograph by Luke Fontana

Playwright Nick Payne conceived his career-launching 2012 drama after stumbling on The Elegant Universe, a documentary by physicist Brian Greene. It turned Payne onto the Quantum Multiverse, the idea that different scenarios play out in endless parallel realities. Constellations zooms in on the infinite loop lived by beekeeper Roland (Downton Abbeys Allen Leech) and cosmologist Marianne (Once Upon a Times Ginnifer Goodwin). Take, for instance, the pairs introduction at a barbecue, a meeting that is repeated a few times over to various ends: In one version, Roland has a girlfriend. In another, hes married. Theres a round in which Marianne wins him over with small talk and another when she doesnt. Over 70 minutes, they break up and stay together, marry and divorce, cheat on and stay true to each other. The effect is engrossing, fueling daydreams about what couldve been if only wed taken the red pill instead of the blue. Chance is our saving grace and our Achilles heel, Payne once wrote. We are both wildly autonomous and utterly powerless.

Goodwin, for whom quantum physics is a pastime (really), calls the plays structure enrapturing. She may be biased, but audiences were smitten when the production ran in London and, three years later, on Broadway, where Jake Gyllenhaal and Ruth Wilson (The Affair) starred. Critics felt the same, if not a little mystified; The New Yorkers John Lahr described it as a singular astonishment but also admitted that he hadnt grasped for certain what it means. Payne is in the same boat. I dont really know what its meaning is, he says. Im very happy not to know and to allow audiences to take from it what they wish. I suspect it might be more about death and love, though, than it is about theoretical physics.

Tags: Allen Leech, Constellations, Downton Abbey, Ginnifer Goodwin, Once Upon A Time, The Geffen Playhouse

This article originally appeared in the June 2017 issue.

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Quantum Physics and Love are Super Weird and Confusing, but This Play Makes Sense of Them Both - LA Magazine