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Scientists discover a 2-D magnet

Scientists discover a 2-D magnet | Amazing Science | Scoop.it

Magnetic materials form the basis of technologies that play increasingly pivotal roles in our lives today, including sensing and hard-disk data storage. But as our innovative dreams conjure wishes for ever-smaller and faster devices, researchers are seeking new magnetic materials that are more compact, more efficient and can be controlled using precise, reliable methods.

 

A team led by the University of Washington and the Massachusetts Institute of Technology has for the first time discovered magnetism in the 2-D world of monolayers, or materials that are formed by a single atomic layer. The findings, published June 8 in the journal Nature, demonstrate that magnetic properties can exist even in the 2-D realm -- opening a world of potential applications.

 

"What we have discovered here is an isolated 2-D material with intrinsic magnetism, and the magnetism in the system is highly robust," said Xiaodong Xu, a UW professor of physics and of materials science and engineering, and member of the UW's Clean Energy Institute. "We envision that new information technologies may emerge based on these new 2-D magnets."

 

Xu and MIT physics professor Pablo Jarillo-Herrero led the international team of scientists who proved that the material -- chromium triiodide, or CrI3 -- has magnetic properties in its monolayer form. Other groups, including co-author Michael McGuire at the Oak Ridge National Laboratory, had previously shown that CrI3 -- in its multilayered, 3-D, bulk crystal form -- is ferromagnetic. In ferromagnetic materials, the "spins" of constituent electrons, analogous to tiny, subatomic magnets, align in the same direction even without an external magnetic field.

 

But no 3-D magnetic substance had previously retained its magnetic properties when thinned down to a single atomic sheet. In fact, monolayer materials can demonstrate unique properties not seen in their multilayered, 3-D forms. "You simply cannot accurately predict what the electric, magnetic, physical or chemical properties of a 2-D monolayer crystal will be based on the behavior of its 3-D bulk counterpart," said co-lead author and UW doctoral student Bevin Huang.

 

Atoms within monolayer materials are considered "functionally" two-dimensional because the electrons can only travel within the atomic sheet, like pieces on a chessboard. To discover the properties of CrI3 in its 2-D form, the team used Scotch tape to shave a monolayer of CrI3 off the larger, 3-D crystal form. "Using Scotch tape to exfoliate a monolayer from its 3-D bulk crystal is surprisingly effective," said co-lead author and UW doctoral student Genevieve Clark. "This simple, low-cost technique was first used to obtain graphene, the 2-D form of graphite, and has been used successfully since then with other materials."

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Gravitational Waves Detected a Third Time

Gravitational Waves Detected a Third Time | Amazing Science | Scoop.it

University of Maryland physicists contribute to identification of third gravitational wave event using data from Advanced LIGO detectors . Gravitational waves carry information about their origins and about the nature of gravity that cannot otherwise be obtained. All three detections of gravitational waves were made by science teams using the Laser Interferometer Gravitational-Wave Observatory (LIGO) detectors located in Livingston, Louisiana, and Hanford, Washington.  The LIGO Scientific Collaboration (LSC) and the Virgo Collaboration observed the third gravitational wave event, named GW170104, on January 4, and published a report describing the discovery and its implications in the journal Physical Review Letters

 

LIGO’s first detection, on September 14, 2015, resulted from a merger of two black holes about 36 and 29 times the mass of the sun. In contrast, the black holes that created the second event were relative flyweights, tipping the scales at 14 and eight times the mass of the sun. 

 

The third and most recent detection lies in the middle, resulting from a merger between two black holes, more than 31 and 19 times the mass of the sun, respectively. The merger produced a single, more massive black hole that is slightly less than 49 times the mass of the sun, and transformed the remaining mass into gravitational energy. 

 

“The observation and interpretation of yet another LIGO signal, GW170104, confirms the success of our theoretical program to model binary black holes,” said Alessandra Buonanno, a UMD College Park Professor of Physics and LSC principal investigator who also has an appointment as Director at the Max Planck Institute for Gravitational Physics in Potsdam, Germany. Buonanno has led the effort to develop highly accurate models of gravitational waves that black holes would generate in the final process of orbiting and colliding with each other.

 

“For the third LIGO signal we could gather some evidence that at least one black hole might be rotating in a direction misaligned with the overall orbital motion—a spin configuration favored by some astrophysical formation scenarios of binary black holes” Buonanno added, noting that her team made substantial improvements to their methodology throughout 2016, in between LIGO’s observing runs.

 

The newly detected merger occurred approximately 3 billion years ago, making it more than twice as old (and more than twice as distant) as the first two events, which occurred 1.3 and 1.4 billion years ago, respectively. Based on the arrival time of the signals—the Hanford detector measured the waves 3 milliseconds before the Livingston detector—researchers can roughly determine the position of the source in the sky.

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Solving linear equations with quantum mechanics

Solving linear equations with quantum mechanics | Amazing Science | Scoop.it

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, swapings of states, and binary conversions, the HHL algorithm determines the solutions to this system, which can then be read out by a quantum non-demolition 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.

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New insights on the spin dynamics of a material candidate for low-power devices

New insights on the spin dynamics of a material candidate for low-power devices | Amazing Science | Scoop.it
Computers process and transfer data through electrical currents passing through tiny circuits and wires. As these currents meet with resistance, they create heat that can undermine the efficiency and even the safety of these devices.

 

To minimize heat loss and optimize performance for low-power technology, researchers are exploring other ways to process information that could be more energy-efficient. One approach that researchers at the U.S. Department of Energy's (DOE) Argonne National Laboratory are exploring involves manipulating the magnetic spin of electrons, a scientific field known as spintronics.

 

"In spintronics, you can think of information as a magnet pointing one way and another magnet pointing in the opposite direction," said Argonne materials scientist Axel Hoffman. "We're interested in how we can use magnetic excitation in applications because processing information this way expends less energy than carrying information through an electrical charge."

 

In a recent report published in Nano Letters, Hoffman and fellow researchers reveal new insights into the properties of a magnetic insulator that is a candidate for low-power device applications; their insights form early stepping-stones towards developing high-speed, low-power electronics that use electron spin rather than charge to carry information. The material they studied, yttrium iron garnet (YIG), is a magnetic insulator that generates and transmits spin current efficiently and dissipates little energy. Because of its low dissipation, YIG has been used in microwave and radar technologies, but recent discoveries of spintronic effects associated with YIG have prompted researchers to explore potential spintronic applications.

 

In their report, Argonne researchers characterize the spin dynamics associated with a small-scale sample of YIG when that material is exposed to an electrical current. "This is the first time for anyone to have measured spin dynamics on a sample size this small," said Benjamin Jungfleisch, an Argonne postdoctoral appointee and lead author of the report. "Understanding the behavior at a small size is crucial because these materials need to be small to ever have the potential to be successfully integrated in low-power devices."

 

Researchers attached the YIG sample to platinum nanowires using electric beam lithography, creating a micrometer-size YIG/platinum structure. They then sent an electrical current through the platinum to excite the YIG and drive spin dynamics. They then took electrical measurements to characterize the magnetization dynamics and measure how these dynamics changed by shrinking the YIG.

 

"When shrinking materials, they can behave in different ways, ways that could present a roadblock to identifying and actualizing potential new applications," Hoffman said. "What we've observed is that, although there are small details that change when YIG is made smaller, there doesn't appear to be a fundamental roadblock that prevents us from using the physical approaches we use for small electrical devices."


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Unveiling the Quantum Necklace

Unveiling the Quantum Necklace | Amazing Science | Scoop.it
Researchers simulate quantum necklace-like structures in superfluids.

 

The quantum world is both elegant and mysterious. It is a sphere of existence where the laws of physics experienced in everyday life are broken—particles can exist in two places at once, they can react to each other over vast distances, and they themselves seem confused over whether they are particles or waves. For those not involved in the field, this world may seem trifling, but recently, researchers from the Okinawa Institute of Science and Technology Graduate University (OIST) have theoretically described two quantum states that are extraordinary in both the physics that define them and their visual appeal: a complex quantum system that simulates classical physics and a spellbinding necklace-like state. Their study is published in the journal Physical Review A.

 

The quest for these states begins with a doughnut, or rather, a doughnut-shaped container housing a rotating superfluid. This superfluid, which is a fluid that moves with no friction, is made of Bose-Einstein condensates (BECs) comprising particles with no charge that are cooled to near-zero degrees kelvin, a temperature so cold, that it does not exist in the universe outside of laboratories. At this temperature, particles begin to exhibit strange properties—they clump together, and eventually become indistinguishable from one another. In effect, they become a single entity and thus move as one.

 

Since this whirling BEC superfluid is operating at a quantum scale, where tiny distances and low temperatures reign, the physical characteristics of its rotation are not those seen in the classical world. Consider a father who is swinging his daughter around in a circle by the arms. Classical physics mandates that the child’s legs will move faster than her hands around the circle, since her legs must travel further to make a complete turn.

 

In the world of quantum physics the relationship is the opposite. “In a superfluid…things which are very far away [from the center] move really slowly, whereas things [that] are close to the center move very fast,” explains OIST Professor Thomas Busch, one of theresearchers involved in the study. This is what is happening in the superfluid doughnut.

 

In addition, the superfluid inside of the doughnut shows a uniform density profile, meaning that it is distributed around the doughnut evenly. This would be the same for most liquids that are rotating via classical or quantum rules. But what happens if another type of BEC is added, one that is made from a different atomic species and that cannot mix with the original BEC? Like oil and water, the two components will separate in a way that minimizes the area in which they are touching and form two semicircles on opposite sides of the doughnut container.

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3D direction-dependent force measurement at the subatomic scale

3D direction-dependent force measurement at the subatomic scale | Amazing Science | Scoop.it

Atomic force microscopy (AFM) is an extremely sensitive technique that allows us to image materials and/or characterize their physical properties on the atomic scale by sensing the force above material surfaces using a precisely controlled tip. However, conventional AFM only provides the surface normal component of the force (the Z direction) and ignores the components parallel to the surface (the X and Y directions).

 

To fully characterize materials used in nanoscale devices, it is necessary to obtain information about parameters with directionality, such as electronic, magnetic, and elastic properties, in more than just the Z direction. That is, it is desirable to measure these parameters in the X and Y directions parallel to the surface of a material as well. Measuring the distribution of such material parameters on the atomic scale will increase our understanding of chemical composition and reactions, surface morphology, molecular manipulation, and nanomachine operation.

 

A research group at Osaka University has recently developed an AFM-based approach called "bimodal AFM" to obtain information about material surfaces in the X, Y, and Z directions (that is, in three dimensions) on the subatomic scale. The researchers measured the total force between an AFM tip and material surface in the X, Y, and Z directions using a germanium (Ge) surface as a substrate. Their collaborative partner, the Institute of Physics of the Slovak Academy of Sciences, contributed computer simulations of the tip-surface interactions. The bimodal AFM approach was recently reported in Nature Physics.

 

"A clean Ge(001) surface has alternately aligned anisotropic dimers, which are rotated by 90° across the step, meaning they show a two-domain structure," explains first author Yoshitaka Naitoh. "We probed the force fields from each domain in the vertical direction by oscillating the AFM tip at the flexural resonance frequency and in the parallel direction by oscillating it at the torsional one."

 

The team first expressed the force components as vectors, providing the vector distribution above the surface at the subatomic scale. The computer simulation supported the experimental results and shed light on the nature of chemical tip termination and morphology and, in particular, helped to clarify the outstanding questions regarding the tip-surface distances in the experiment.

 

"We measured the magnitude and direction of the force between the AFM tip and Ge surface on a subatomic scale in three dimensions," says Naitoh. "Such measurements will aid understanding of the structure and chemical reactions of functionalized surfaces."

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World's largest X-ray laser lights up for the first time

World's largest X-ray laser lights up for the first time | Amazing Science | Scoop.it

In bright news for the scientific world, the world's biggest X-ray laser has generated its first light in Hamburg, Germany. The 3.4 km (2.1 mi) long European X-ray Free Electron Laser (XFEL) produced a pulsing laser light with a wavelength of 0.8 nm at one pulse per second as part of the last major development milestone ahead of its September official opening. When up and running properly, it will generate up to 27,000 pulses per second – a considerable improvement over the previous maximum of 120 per second.

 

A free electron laser operates on the principle of a synchrotron, an atomic accelerator that generates high-intensity electromagnetic radiation by accelerating electrons to relativistic speeds, then directing them through special magnetic structures. Only in this case, the XFEL is a billion times more brilliant than conventional synchrotron light sources and can capture images at atomic resolution.

 

The key component is a 2.1 km (1.3-mi) long superconducting linear accelerator that came online in April. Here electron pulses are accelerated to near the speed of light and to very high energies before entering a photon tunnel containing 210-m (689-ft) of X-ray-generating devices consisting of 17,290 permanent magnets called "undulators" with alternating poles above and below the electron stream. These twist the electrons out of their straight line, and every time they curve they give off energy like an overloaded truck losing its cargo, only this is in the form of extremely short-wavelength X-rays.

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Quantum effects may lead to more powerful battery charging

Quantum effects may lead to more powerful battery charging | Amazing Science | Scoop.it
Physicists have theoretically shown that, when multiple nanoscale batteries are coupled together, they can be charged faster than if each battery was charged individually. The improvement arises from collective quantum phenomena and is rooted in the emerging field of quantum thermodynamics—the study of how quantum effects influence the traditional laws governing energy and work.

The researchers, Francesco Campaioli et al., have published a paper on the fast charging of nanoscale batteries in a recent issue of Physical Review Letters.

Although a great deal of research has shown that quantum phenomena provide advantages in information processing applications, such as computing and secure communication, there have been very few demonstrations of quantum advantages in thermodynamics. In one recent study in this area, researchers showed that quantum entanglement can allow more work to be extracted from a nanoscale energy-storage device, or "quantum battery," than would be possible without entanglement.

In the new study, the researchers build on this result to show that quantum phenomena can also enhance the charging power of quantum batteries. They also found that the process does not necessarily require entanglement, although it does require operations that have the potential to generate entangled states.

"Our work shows how entangling operations—that is, interactions between two or more bodies—are necessary to obtain a quantum advantage for the charging power of many-body batteries, whereas entanglement itself does not constitute a resource," Campaioli, at Monash University in Australia, told Phys.org. "Additionally, we show that for locally coupled batteries the quantum advantage scales with the number of interacting batteries."

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For the first time, physicists have experimentally demonstrated the violation of "bilocal causality"

For the first time, physicists have experimentally demonstrated the violation of "bilocal causality" | Amazing Science | Scoop.it

Physicists have recently been able to experimentally demonstrate the violation of "bilocal causality"—a concept that is related to the more standard local causality, except that it accounts for the precise way in which physical systems are initially generated. The results show that it's possible to violate local causality in an entirely new and more general way, which could lead to a potential new resource for quantum technologies.

 

The physicists, Gonzalo Carvacho et al., from institutions in Italy, Brazil, and Germany, have published a paper on the demonstration of the violation of bilocal causality in a recent issue of Nature Communications.

 

In general, the idea of local causality is usually taken for granted: objects can influence other objects only when they are physically close together, and any correlations between distant objects must have originated in the past when they were closer together. But in the quantum world, distant particles can be correlated in ways that are impossible for classical objects, unless these distant particles can somehow influence each other.

 

To determine whether local causality has been violated, physicists perform Bell tests, which attempt to violate Bell inequalities. If a Bell inequality is violated, then either locality or realism (or simply "local realism") has also been violated. There are dozens of different versions of Bell inequalities, but currently they all make the same assumption: that the correlations between particles all originate from a single common source. In real experiments, however, particles and their correlations can come from many different sources.

 

To address this issue, the new paper considers a new type of Bell inequality that accounts for the fact that the two sources of states used in the experiment are independent, the so-called bilocality assumption. By violating this new type of Bell inequality, the researchers have for the first time violated bilocal causality, indicating the presence of non-bilocal correlations that are completely different than other types of quantum correlations.

 

The researchers also showed that, in certain situations, it's possible to violate bilocal causality but not any other type of local causality. This finding further suggests that this type of violation is truly different than any standard local causality violation.

 

"Our work is an experimental proof-of-principle for network generalizations of Bell's theorem," coauthor Fabio Sciarrino at the Sapienza University of Rome told Phys.org.

 

"We experimentally demonstrated how bilocality can be considered a powerful resource enlarging our current capabilities to process information in a non-classical way."

 
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Time crystals may hold the key to developing quantum computers

Time crystals may hold the key to developing quantum computers | Amazing Science | Scoop.it

Harvard physicists have created a new form of matter - dubbed a time crystal - which could offer important insights into the mysterious behavior of quantum systems.

 

Traditionally speaking, crystals - like salt, sugar or even diamonds - are simply periodic arrangements of atoms in a three-dimensional lattice.

 

Time crystals, on the other hand, take that notion of periodically-arranged atoms and add a fourth dimension, suggesting that - under certain conditions - the atoms that some materials can exhibit periodic structure across time.

 

Led by Professors of Physics Mikhail Lukin and Eugene Demler, a team consisting of post-doctoral fellows Renate Landig and Georg Kucsko, Junior Fellow Vedika Khemani, and Physics Department graduate students Soonwon Choi, Joonhee Choi and Hengyun Zhou built a quantum system using a small piece of diamond embedded with millions of atomic-scale impurities known as nitrogen-vacancy (NV) centers. They then used microwave pulses to "kick" the system out of equilibrium, causing the NV center's spins to flip at precisely-timed intervals - one of the key markers of a time crystal. The work is described in a paper published in Nature in March.

 

But the creation of a time crystal isn't significant merely because it proves the previously-only-theoretical materials can exist, Lukin said, but because they offer physicists a tantalizing window into the behavior of such out-of-equilibrium systems.

 

"There is now broad, ongoing work to understand the physics of non-equilibrium quantum systems," Lukin said. "This is an area that is of interest for many quantum technologies, because a quantum computer is basically a quantum system that's far away from equilibrium. It's very much at the frontier of research...and we are really just scratching the surface."

 

But while understanding such non-equlibrium systems could help lead researchers down the path to quantum computing, the technology behind time crystals may also have more near-term applications as well.

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Physicists search for a decay with a half-life older than the Universe itself

Physicists search for a decay with a half-life older than the Universe itself | Amazing Science | Scoop.it

Many extensions of the Standard Model of particle physics explain the dominance of matter over antimatter in our Universe by neutrinos being their own antiparticles. This would imply the existence of neutrinoless double-β decay, which is an extremely rare lepton-number-violating radioactive decay process whose detection requires the utmost background suppression. Among the programmes that aim to detect this decay, the GERDA Collaboration is searching for neutrinoless double-β decay of 76Ge by operating bare detectors, made of germanium with an enriched 76Ge fraction, in liquid argon.

 

After having completed Phase I of data taking, scientists have recently launched Phase II and report now that in GERDA Phase II that they have achieved a background level of approximately 10−3 counts keV−1kg−1 yr−1. This implies that the experiment is background-free, even when increasing the exposure up to design level. This is achieved by use of an active veto system, superior germanium detector energy resolution and improved background recognition of our new detectors.

 

No signal of neutrinoless double-β decay was found when Phase I and Phase II data were combined, and scientists deduce a lower-limit half-life of 5.3 × 1025 years at the 90 per cent confidence level. The half-life sensitivity of 4.0 × 1025 years is competitive with the best experiments that use a substantially larger isotope mass. The potential of an essentially background-free search for neutrinoless double-β decay will facilitate a larger germanium experiment with sensitivity levels that will bring us closer to clarifying whether neutrinos are their own antiparticles.

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Matter with ‘negative mass’ created at Washington State University

Matter with ‘negative mass’ created at Washington State University | Amazing Science | Scoop.it

Washington State University physicists have created a fluid with negative mass, which is exactly what it sounds like. Push it, and unlike every physical object in the world we know, it doesn’t accelerate in the direction it was pushed. It accelerates backwards.

 

The phenomenon is rarely created in laboratory conditions and can be used to explore some of the more challenging concepts of the cosmos, said Michael Forbes, a WSU assistant professor of physics and astronomy and an affiliate assistant professor at the University of Washington.

 

The research appears today in the journal Physical Review Letters, where it is featured as an “Editor’s Suggestion.”

 

Hypothetically, matter can have negative mass in the same sense that an electric charge can be either negative or positive. People rarely think in these terms, and our everyday world sees only the positive aspects of Isaac Newton’s Second Law of Motion, in which a force is equal to the mass of an object times its acceleration, or F=ma.

 

In other words, if you push an object, it will accelerate in the direction you’re pushing it. Mass will accelerate in the direction of the force. “That’s what most things that we’re used to do,” said Forbes, hinting at the bizarreness to come. “With negative mass, if you push something, it accelerates toward you.”

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Non-localized generation of correlated photon pairs in degenerate down-conversion

Non-localized generation of correlated photon pairs in degenerate down-conversion | Amazing Science | Scoop.it

Researchers at the University of East Anglia (UEA) have shown that when photons – the fundamental particles of light – are created in pairs, they can emerge from different, rather than the same, location. The ground-breaking research could have significant implications for quantum physics, the theoretical basis of modern physics. Until now, the general assumption was that such photon pairs necessarily originate from single points in space.

 

Quantum entanglement – when particles are linked so closely that what affects one directly affects the other - is widely used in labs in numerous processes from quantum cryptography to quantum teleportation. The UEA team were studying a process called spontaneous parametric down-conversion (SPDC), in which photon beams are passed through a crystal to generate entangled pairs of photons.

 

Prof David Andrews in UEA’s School of Chemistry said: “When the emergent pairs equally share the energy of the input, this is known as degenerate down-conversion, or DDC. “Until now, it has been assumed that such paired photons come from the same location. Now, the identification of a new delocalized mechanism shows that each photon pair can be emitted from spatially separated points, introducing a new positional uncertainty of a fundamental quantum origin.”

 

The entanglement of the quantum states in each pair has important applications in quantum computing - theoretical computation systems that could potentially process big data problems at incredible speeds - as well as other areas of quantum physics.

 

The findings are also significant because they place limits on spatial resolution. Prof Andrews said: “Everything has a certain quantum ‘fuzziness’ to it, and photons are not the hard little bullets of light that are popularly imagined.”

 

The study ‘Non-localized generation of correlated photon pairs in degenerate down-conversion’ by Kayn A. Forbes, Jack S. Ford, and David L. Andrews is published in the journal Physical Review Letters.

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Intriguing oscillatory back-and-forth motion of a quantum particle

Intriguing oscillatory back-and-forth motion of a quantum particle | Amazing Science | Scoop.it

In the quantum world, our intuition for the motion of objects is strongly challenged and may sometimes even completely fail. What about imagining a marble falling through water oscillating up and down rather than just moving straight downwards? Sounds strange. Yet, that's what experimental physicist from Innsbruck in collaboration with theorists from Munich, Paris and Cambridge have discovered for a quantum particle. At the heart of this surprising behavior is what physicists call 'quantum interference', the fact that quantum mechanics allows particles to behave like waves, which can add up or cancel each other.

 

To observe the quantum particle oscillating back and forth the team had to cool a gas of Cesium atoms just above absolute zero temperature and to confine it to an arrangement of very thin tubes realized by high-power laser beams. By means of a special trick, the atoms were made to interact strongly with each other. At such extreme conditions the atoms form a quantum fluid whose motion is restricted to the direction of the tubes. The physicists then accelerated an impurity atom, which is an atom in a different spin state, through the gas. As this quantum particle moved, it was observed to scatter off the gas particles and to reflect backwards. This led to an oscillatory motion, in contrast to what a marble would do when falling in water. The experiment demonstrates that Newton's laws cannot be used in the quantum realm.

 

The fact that a quantum-wave may get reflected into certain directions has been known since the early days of the development of the theory of quantum mechanics. For example, electrons reflect at the regular pattern of solid crystals, such as a piece of metal. This effect is termed 'Bragg-scattering'. However, the surprise in the experiment performed in Innsbruck was that no such crystal was present for the impurity to reflect off. Instead, it was the gas of atoms itself that provided a type of hidden order in its arrangement, a property that physicist dub 'correlations'.

 

The Innsbruck work has demonstrated how these correlations in combination with the wave-nature of matter determine the motion of particles in the quantum world and lead to novel and exciting phenomena that counteract the experiences from our daily life.

Understanding the oddity of quantum mechanics may also be relevant in a broader scope, and help to understand and optimize fundamental processes in electronics components, or even transport processes in complex biological systems.

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A stream of superfluid light produced: Room-temperature superfluidity in a polariton condensate

A stream of superfluid light produced: Room-temperature superfluidity in a polariton condensate | Amazing Science | Scoop.it

Scientists have known for centuries that light is composed of waves. The fact that light can also behave as a liquid, rippling and spiraling around obstacles like the current of a river, is a much more recent finding that is still a subject of active research. The "liquid" properties of light emerge under special circumstances, when the photons that form the light wave are able to interact with each other.

 

Researchers from CNR NANOTEC of Lecce in Italy, in collaboration with Polytechnique Montreal in Canada have shown that for light "dressed" with electrons, an even more dramatic effect occurs. Light become superfluid, showing frictionless flow when flowing across an obstacle and reconnecting behind it without any ripples.

Daniele Sanvitto, leading the experimental research group that observed this phenomenon, states that "Superfluidity is an impressive effect, normally observed only at temperatures close to absolute zero (-273 degrees Celsius), such as in liquid Helium and ultracold atomic gasses. The extraordinary observation in our work is that we have demonstrated that superfluidity can also occur at room-temperature, under ambient conditions, using light-matter particles called polaritons."

 

"Superfluidity, which allows a fluid in the absence of viscosity to literally leak out of its container," adds Sanvitto, "is linked to the ability of all the particles to condense in a state called a Bose-Einstein condensate, also known as the fifth state of matter, in which particles behave like a single macroscopic wave, oscillating all at the same frequency.

 

Something similar happens, for example, in superconductors: electrons, in pairs, condense, giving rise to superfluids or super-currents able to conduct electricity without losses."

 

These experiments have shown that it is possible to obtain superfluidity at room-temperature, whereas until now this property was achievable only at temperatures close to absolute zero. This could allow for its use in future photonic devices.

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Destruction of a quantum monopole finally observed

Destruction of a quantum monopole finally observed | Amazing Science | Scoop.it

Scientists at Amherst College and Aalto University have made the first experimental observations of the dynamics of isolated monopoles in quantum matter.

 

The new study provided a surprise: the quantum monopole decays into another analogue of the magnetic monopole. The obtained fundamental understanding of monopole dynamics may help in the future to build even closer analogues of the magnetic monopoles.

 

Unlike usual magnets, magnetic monopoles are elementary particles that have only a south or a north magnetic pole, but not both. They have been theoretically predicted to exist, but no convincing experimental observations have been reported. Thus physicists are busy looking for analogue objects.

 

"In 2014, we experimentally realized a Dirac monopole, that is, Paul Dirac's 80-year-old theory where he originally considered charged quantum particles interacting with a magnetic monopole," says Professor David Hall from Amherst College. And in 2015, we created real quantum monopoles," adds Dr. Mikko Möttönen from Aalto University.

 

Whereas the Dirac monopole experiment simulates the motion of a charged particle in the vicinity of a monopolar magnetic field, the quantum monopole has a point-like structure in its own field resembling that of the magnetic monopole particle itself.

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The World's Most Sensitive Dark Matter Detector Is Now Up and Running

The World's Most Sensitive Dark Matter Detector Is Now Up and Running | Amazing Science | Scoop.it
After three years of construction, the world's most sensitive dark matter experiment is online, and scientists report that the detector is operating as designed.

 

The XENON1T experiment is located deep beneath a mountain at the Gran Sasso National Laboratory in Italy (known by its Italian acronym, LNGS) so it can be shielded from interference caused by cosmic rays and other radiation sources on Earth's surface.

 

XENON1T is looking for the microscopic fireworks created byweakly interacting massive particles (WIMPs) crashing into xenon atoms. WIMPs are hypothetical particles that many scientists think are a primary component of dark matter.

Astronomical observations have confirmed that only about 15 percent of the material universe is composed of "ordinary" (or "baryonic") matter; nearly 85 percent is mysterious dark matter, which cannot be observed directly by telescopes. But dark matter's gravity can be measured indirectly via its effects on galaxy clusters and the rotation rates of galaxies, so we know it's out there.

 

Because WIMPs are so "weakly interacting" — that is, they cannot interact with normal matter via the electromagnetic, strong or weak forces — XENON1T can detect them only by looking out for lucky collisions between WIMPs and atoms in a chamber filled with pure liquid xenon cooled to minus 139 degrees Fahrenheit (minus 95 degrees Celsius).

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Physicists find a way to control charged molecules -- with quantum logic

Physicists find a way to control charged molecules -- with quantum logic | Amazing Science | Scoop.it

National Institute of Standards and Technology (NIST) physicists have solved the seemingly intractable puzzle of how to control the quantum properties of individual charged molecules, or molecular ions. The solution is to use the same kind of "quantum logic" that drives an experimental NIST atomic clock. The new technique achieves an elusive goal, controlling molecules as effectively as laser cooling and other techniques can control atoms. Quantum control of atoms has revolutionized atomic physics, leading to applications such as atomic clocks. But laser cooling and control of molecules is extremely challenging because they are much more complex than atoms.

 

The NIST technique still uses a laser, but only to gently probe the molecule; its quantum state is detected indirectly. This type of control of molecular ions -- several atoms bound together and carrying an electrical charge -- could lead to more sophisticated architectures for quantum information processing, amplify signals in basic physics research such as measuring the "roundness" of the electron's shape, and boost control of chemical reactions.

 

The research is described in the May 11, 2017 issue of Nature and was performed in the NIST Boulder group that demonstrated the first laser cooling of atomic ions in 1978. "We developed methods that are applicable to many types of molecules," NIST physicist James Chinwen Chou said. "Whatever trick you can play with atomic ions is now within reach with molecular ions. Now the molecule will 'listen' to you -- asking, in effect, 'What do you want me to do?'"

 

"This is comparable to when scientists could first laser cool and trap atoms, opening the floodgates to applications in precision metrology and information processing. It's our dream to achieve all these things with molecules," Chou added. Compared to atoms, molecules are more difficult to control because they have more complex structures involving many electronic energy levels, vibrations and rotations. Molecules can consist of many different numbers and combinations of atoms and be as large as DNA strands more than a meter long.

 

The NIST method finds the quantum state (electronic, vibrational, and rotational) of the molecular ion by transferring the information to a second ion, in this case an atomic ion, which can be laser cooled and controlled with previously known techniques. Borrowing ideas from NIST's quantum logic clock, the researchers attempt to manipulate the molecular ion and, if successful, set off a synchronized motion in the pair of ions. The manipulation is chosen such that it can only trigger the motion if the molecule is in a certain state. The "yes" or "no" answer is signaled by the atomic ion. The technique is very gentle, indicating the molecule's quantum states without destroying them.

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Bubble-printed patterning of quantum dots on plasmonic substrates

Bubble-printed patterning of quantum dots on plasmonic substrates | Amazing Science | Scoop.it

The use of quantum dots (QDs) in practical applications relies on the ability to precisely pattern QDs on substrates with desired optical properties. Typical direct-write printing techniques such as inkjet and gravure printing are limited in resolution (micron-scale), structural complexity, and require significant post-processing time.In new work, researchers at the University of Texas at Austin use laser-induced bubble printing to pattern CdSe/CdS QDs on plasmonic substrates with submicron resolution (<700nm line width), high throughput (∼10E4 µm/s) and strong QD-substrate adhesion.Not only is the bubble-mediated immobilization at the submicron scale stable, but the submicron-sized bubble's stability can be maintained over a large area.

 

This technique is also compatible with flexible substrates and can be further integrated with smartphone to realize haptic integration. Finally, the emission characteristics of the QDs in terms of the emission wavelength and lifetime can be modified in real-time to achieve site-sensitive emission.The team, led by Yuebing Zheng, Assistant Professor of Mechanical Engineering and Materials Science & Engineering has been published in ACS Applied Materials & Interfaces ("High-Resolution Bubble Printing of Quantum Dots").

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Physicists achieve direct counterfactual quantum communication

Physicists achieve direct counterfactual quantum communication | Amazing Science | Scoop.it

In the non-intuitive quantum domain, the phenomenon of counterfactuality is defined as the transfer of a quantum state from one site to another without any quantum or classical particle transmitted between them. Counterfactuality requires a quantum channel between sites, which means that there exists a tiny probability that a quantum particle will cross the channel—in that event, the run of the system is discarded and a new one begins. It works because of the wave-particle duality that is fundamental to particle physics: Particles can be described by wave function alone.

 

Well understood as a workable scheme by physicists, theoretical aspects of counterfactual communication have appeared in journals, but until recently, there have been no practical demonstrations of the phenomenon. Now, a collaborative of Chinese scientists has designed and experimentally tested a counterfactual communication system that successfully transferred a monochrome bitmap from one location to another using a nested version of the quantum Zeno effect. They have reported their results in the Proceedings of the National Academy of Sciences.

 

The quantum Zeno effect occurs when an unstable quantum system is subjected to a series of weak measurements. Unstable particles can never decay while they are being measured, and the system is effectively frozen with a very high probability. This is one of the implications of the well known but highly non-intuitive principle that looking at something changes it in the quantum realm.

 

Using this effect, the authors of the new study achieved direct communication between sites without carrier particle transmission. In the setup they designed, two single-photon detectors were placed in the output ports of the last of an array of beam splitters. According to the quantum Zeno effect, it's possible to predict which single-photon detector will "click" when photons are allowed to pass. The system's nested interferometers served to measure the state of the system, thereby preventing it from changing.

 

Alice transfers a single photon to the nested interferometer; it is detected by three single photon detectors, D0, D1 and Df. If D0 or D1 click, Alice concludes a logic result of one or zero. If Df clicks, the result is considered inconclusive, and is discarded in post-processing. After the communication of all bits, the researchers were able to reassemble the image—a monochrome bitmap of a Chinese knot. Black pixels were defined as logic 0, while white pixels were defined as logic 1.

 

The idea came from holography technology. The authors write, "In the 1940s, a new imaging technique—holography—was developed to record not only light intensity but also the phase of light. One may then pose the question: Can the phase of light itself be used for imaging? The answer is yes." In the experiment, the phase of light itself became the carrier of information, and the intensity of the light was irrelevant to the experiment.

 

The authors note that besides applications in quantum communication, the technique could be used for such activities as imaging ancient artifacts that would be damaged by directly shining light.

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Christopher Chilvers's curator insight, May 21, 2:04 AM
A test of quantum communication using photons, the measurement problem and logic gates to send a bitmap without particle transfer. A good indicator of the use of binary code as an enabler.
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CERN: New ALICE results show novel phenomena in proton collisions

CERN: New ALICE results show novel phenomena in proton collisions | Amazing Science | Scoop.it

In a paper published today in Nature Physics(link is external), the ALICE collaboration reports that proton collisions sometimes present similar patterns to those observed in the collisions of heavy nuclei. This behavior was spotted through observation of so-called strange hadrons in certain proton collisions in which a large number of particles are created. Strange hadrons are well-known particles with names such as Kaon, Lambda, Xi and Omega, all containing at least one so-called strange quark. The observed ‘enhanced production of strange particles’ is a familiar feature of quark-gluon plasma, a very hot and dense state of matter that existed just a few millionths of a second after the Big Bang, and is commonly created in collisions of heavy nuclei. But it is the first time ever that such a phenomenon is unambiguously observed in the rare proton collisions in which many particles are created. This result is likely to challenge existing theoretical models that do not predict an increase of strange particles in these events.

 

"We are very excited about this discovery,” said Federico Antinori, Spokesperson of the ALICE collaboration. “We are again learning a lot about this primordial state of matter. Being able to isolate the quark-gluon-plasma-like phenomena in a smaller and simpler system, such as the collision between two protons, opens up an entirely new dimension for the study of the properties of the fundamental state that our universe emerged from.”

 

The study of the quark-gluon plasma provides a way to investigate the properties of strong interaction, one of the four known fundamental forces, while enhanced strangeness production is a manifestation of this state of matter. The quark-gluon plasma is produced at sufficiently high temperature and energy density, when ordinary matter undergoes a transition to a phase in which quarks and gluons become ‘free’ and are thus no longer confined within hadrons. These conditions can be obtained at the Large Hadron Collider by colliding heavy nuclei at high energy. Strange quarks are heavier than the quarks composing normal matter, and typically harder to produce. But this changes in presence of the high energy density of the quark-gluon plasma, which rebalances the creation of strange quarks relative to non-strange ones. This phenomenon may now have been observed within proton collisions as well.

 

In particular, the new results show that the production rate of these strange hadrons increases with the ‘multiplicity’ – the number of particles produced in a given collision – faster than that of other particles generated in the same collision. While the structure of the proton does not include strange quarks, data also show that the higher the number of strange quarks contained in the induced hadron, the stronger is the increase of its production rate. No dependence on the collision energy or the mass of the generated particles is observed, demonstrating that the observed phenomenon is related to the strange quark content of the particles produced. Strangeness production is in practice determined by counting the number of strange particles produced in a given collision, and calculating the ratio of strange to non-strange particles.

 

Enhanced strangeness production had been suggested as a possible consequence of quark-gluon plasma formation since the early eighties, and discovered in collisions of nuclei in the nineties by experiments at CERN[1]’s Super Proton Synchrotron. Another possible consequence of the quark gluon plasma formation is a spatial correlation of the final state particles, causing a distinct preferential alignment with the shape of a ridge. Following its detection in heavy-nuclei collisions, the ridge has also been seen in high-multiplicity proton collisions at the Large Hadron Collider, giving the first indication that proton collisions could present heavy-nuclei-like properties. Studying these processes more precisely will be key to better understand the microscopic mechanisms of the quark-gluon plasma and the collective behaviour of particles in small systems.

 

The ALICE experiment has been designed to study collisions of heavy nuclei. It also studies proton-proton collisions, which primarily provide reference data for the heavy-nuclei collisions. The reported measurements have been performed with 7 TeV proton collision data from LHC run 1.

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Christopher Chilvers's curator insight, May 21, 2:38 AM
Strange quark production from proton collisions and the link to quark gluon plasma after the Big Bang.
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Quantum dots that emit infrared light open new window for biological imaging

Quantum dots that emit infrared light open new window for biological imaging | Amazing Science | Scoop.it
 For certain frequencies of short-wave infrared light, most biological tissues are nearly as transparent as glass. Now, researchers have made tiny particles that can be injected into the body, where they emit those penetrating frequencies. The advance may provide a new way of making detailed images of internal body structures such as fine networks of blood vessels.
 

The key was to develop versions of these quantum dots whose emissions matched the desired short-wave infrared frequencies and were bright enough to then be easily detected through the surrounding skin and muscle tissues. The team succeeded in making particles that are "orders of magnitude better than previous materials, and that allow unprecedented detail in biological imaging," Bruns says. The synthesis of these new particles was initially described in a paper by graduate student Daniel Franke and others from the Bawendi group in Nature Communications last year.

 

The new findings, based on the use of light-emitting particles called quantum dots, is described in a paper in the journal Nature Biomedical Engineering, by MIT research scientist Oliver Bruns, recent graduate Thomas Bischof PhD '15, professor of chemistry Moungi Bawendi, and 21 others.

 

Near-infrared imaging for research on biological tissues, with wavelengths between 700 and 900 nanometers (billionths of a meter), is widely used, but wavelengths of around 1,000 to 2,000 nanometers have the potential to provide even better results, because body tissues are more transparent to that light. "We knew that this imaging mode would be better" than existing methods, Bruns explains, "but we were lacking high-quality emitters"—that is, light-emitting materials that could produce these precise wavelengths.

 

Light-emitting particles have been a specialty of Bawendi, the Lester Wolf Professor of Chemistry, whose lab has over the years developed new ways of making quantum dots. These nanocrystals, made of semiconductor materials, emit light whose frequency can be precisely tuned by controlling the exact size and composition of the particles.

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LHCb finds new hints of possible deviations from the Standard Model

LHCb finds new hints of possible deviations from the Standard Model | Amazing Science | Scoop.it

The LHCb experiment finds intriguing anomalies in the way some particles decay. If confirmed, these would be a sign of new physics phenomena not predicted by the Standard Model of particle physics. 

 

In a recent seminar at CERN, the LHCb collaboration presented new long-awaited results on a particular decay of B0 mesons produced in collisions at the Large Hadron Collider. The Standard Model of particle physics predicts the probability of the many possible decay modes of B0 mesons, and possible discrepancies with the data would signal new physics.

 

In this study, the LHCb collaboration looked at the decays of B0 mesons to an excited kaon and a pair of electrons or muons. The muon is 200 times heavier than the electron, but in the Standard Model its interactions are otherwise identical to those of the electron, a property known as lepton universality. Lepton universality predicts that, up to a small and calculable effect due to the mass difference, electron and muons should be produced with the same probability in this specific B0 decay. LHCb finds instead that the decays involving muons occur less often.

 

While potentially exciting, the discrepancy with the Standard Model occurs at the level of 2.2 to 2.5 sigma, which is not yet sufficient to draw a firm conclusion. However, the result is intriguing because a recent measurement by LHCb involving a related decay exhibited similar behavior.

 

While of great interest, these hints are not enough to come to a conclusive statement. Although of a different nature, there have been many previous measurements supporting the symmetry between electrons and muons. More data and more observations of similar decays are needed in order to clarify whether these hints are just a statistical fluctuation or the first signs for new particles that would extend and complete the Standard Model of particles physics. The measurements discussed were obtained using the entire data sample of the first period of exploitation of the Large Hadron Collider (Run 1). If the new measurements indeed point to physics beyond the Standard Model, the larger data sample collected in Run 2 will be sufficient to confirm these effects.

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Muons’ big moment could fuel the next hunt for new physics

Muons’ big moment could fuel the next hunt for new physics | Amazing Science | Scoop.it
Fermilab experiment to measure muon magnetic moment more precisely might reveal unknown virtual particles.

 

In the search for new physics, experiments based on high-energy collisions inside massive atom smashers are coming up empty-handed. So physicists are putting their faith in more-precise methods: less crash-and-grab and more watching-ways-of-wobbling. Next month, researchers in the United States will turn on one such experiment. It will make a super-accurate measurement of the way that muons, heavy cousins of electrons, behave in a magnetic field. And it could provide evidence of the existence of entirely new particles.

 

The particles hunted by the new experiment, at the Fermi National Laboratory in Batavia, Illinois, comprise part of the virtual soup that surrounds and interacts with all forms of matter. Quantum theory says that short-lived virtual particles constantly ‘blip’ in and out of existence. Physicists already account for the effects of known virtual particles, such as photons and quarks. But the virtual soup might have mysterious, and as yet unidentified, ingredients. And muons could be particularly sensitive to them.

 

The new Muon g−2 experiment will measure this sensitivity with unparalleled precision. And in doing so, it will reanalyze a muon anomaly that has puzzled physicists for more than a decade. If the experiment confirms that the anomaly is real, then the most likely explanation is that it is caused by virtual particles that do not appear in the existing physics playbook — the standard model.

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Electrons Use DNA Like a Wire for Signaling DNA Replication

Electrons Use DNA Like a Wire for Signaling DNA Replication | Amazing Science | Scoop.it

In the early 1990s, Jacqueline Barton, the John G. Kirkwood and Arthur A. Noyes Professor of Chemistry at Caltech, discovered an unexpected property of DNA—that it can act like an electrical wire to transfer electrons quickly across long distances. Later, she and her colleagues showed that cells take advantage of this trait to help locate and repair potentially harmful mutations to DNA.

 

Now, Barton's lab has shown that this wire-like property of DNA is also involved in a different critical cellular function: replicating DNA. When cells divide and replicate themselves in our bodies—for example in the brain, heart, bone marrow, and fingernails—the double-stranded helix of DNA is copied. DNA also copies itself in reproductive cells that are passed on to progeny.

 

The new Caltech-led study, based on work by graduate student Elizabeth O'Brien in collaboration with Walter Chazin's group at Vanderbilt University, shows that a key protein required for replicating DNA depends on electrons traveling through DNA.

 

"Nature is the best chemist and knows exactly how to take advantage of DNA electron-transport chemistry," says Barton, who is also the Norman Davidson Leadership Chair of Caltech's Division of Chemistry and Chemical Engineering.

 

"The electron transfer process in DNA occurs very quickly," says O'Brien, lead author of the study, appearing in the February 24 2017 issue of Science. "It makes sense that the cell would utilize this quick-acting pathway to regulate DNA replication, which necessarily is a very rapid process."

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