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  • richardmitnick 11:19 am on January 15, 2019 Permalink | Reply
    Tags: An effect that Einstein helped discover 100 years ago offers new insight into a puzzling magnetic phenomenon, , ETH Zurich, , , ,   

    From SLAC National Accelerator Lab: “An effect that Einstein helped discover 100 years ago offers new insight into a puzzling magnetic phenomenon” 

    From SLAC National Accelerator Lab

    January 14, 2019
    Ali Sundermier

    1
    At SLAC’s Linac Coherent Light Source, the researchers blasted an iron sample with laser pulses to demagnetize it, then grazed the sample with X-rays, using the patterns formed when the X-rays scattered to uncover details of the process. (Gregory Stewart/SLAC National Accelerator Laboratory)

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    Researchers from ETH Zürich in Switzerland used LCLS to show a link between ultrafast demagnetization and an effect that Einstein helped discover 100 years ago. (Dawn Harmer/SLAC National Accelerator Laboratory)

    Using an X-ray laser, researchers watched atoms rotate on the surface of a material that was demagnetized in millionths of a billionth of a second.

    More than 100 years ago, Albert Einstein and Wander Johannes de Haas discovered that when they used a magnetic field to flip the magnetic state of an iron bar dangling from a thread, the bar began to rotate.

    Now experiments at the Department of Energy’s SLAC National Accelerator Laboratory have seen for the first time what happens when magnetic materials are demagnetized at ultrafast speeds of millionths of a billionth of a second: The atoms on the surface of the material move, much like the iron bar did. The work, done at SLAC’s Linac Coherent Light Source (LCLS) X-ray laser, was published in Nature earlier this month.

    SLAC/LCLS

    Christian Dornes, a scientist at ETH Zürich in Switzerland and one of the lead authors of the report, says this experiment shows how ultrafast demagnetization goes hand in hand with what’s known as the Einstein-de Haas effect, solving a longstanding mystery in the field.

    “I learned about these phenomena in my classes, but to actually see firsthand that the transfer of angular momentum actually makes something move mechanically is really cool,” Dornes says. “Being able to work on the atomic scale like this and see relatively directly what happens would have been a total dream for the great physicists of a hundred years ago.”

    Spinning sea of skaters

    At the atomic scale, a material owes its magnetism to its electrons. In strong magnets, the magnetism comes from a quantum property of electrons called spin. Although electron spin does not involve a literal rotation of the electron, the electron acts in some ways like a tiny spinning ball of charge. When most of the spins point in the same direction, like a sea of ice skaters pirouetting in unison, the material becomes magnetic.

    When the magnetization of the material is reversed with an external magnetic field, the synchronized dance of the skaters turns into a hectic frenzy, with dancers spinning in every direction. Their net angular momentum, which is a measure of their rotational motion, falls to zero as their spins cancel each other out. Since the material’s angular momentum must be conserved, it’s converted into mechanical rotation, as the Einstein-de Haas experiment demonstrated.

    Twist and shout

    In 1996, researchers discovered that zapping a magnetic material with an intense, super-fast laser pulse demagnetizes it nearly instantaneously, on a femtosecond time scale. It has been a challenge to understand what happens to angular momentum when this occurs.

    In this paper, the researchers used a new technique at LCLS combined with measurements done at ETH Zürich to link these two phenomena. They demonstrated that when a laser pulse initiates ultrafast demagnetization in a thin iron film, the change in angular momentum is quickly converted into an initial kick that leads to mechanical rotation of the atoms on the surface of the sample.

    3
    At SLAC’s Linac Coherent Light Source, the researchers blasted an iron sample with laser pulses to demagnetize it, then grazed the sample with X-rays, using the patterns formed when the X-rays scattered to uncover details of the process. (Gregory Stewart/SLAC National Accelerator Laboratory)

    According to Dornes, one important takeaway from this experiment is that even though the effect is only apparent on the surface, it happens throughout the whole sample. As angular momentum is transferred through the material, the atoms in the bulk of the material try to twist but cancel each other out. It’s as if a crowd of people packed onto a train all tried to turn at the same time. Just as only the people on the fringe would have the freedom to move, only the atoms at the surface of the material are able to rotate.

    Scraping the surface

    In their experiment, the researchers blasted the iron film with laser pulses to initiate ultrafast demagnetization, then grazed it with intense X-rays at an angle so shallow that it was nearly parallel to the surface. They used the patterns formed when the X-rays scattered off the film to learn more about where angular momentum goes during this process.

    “Due to the shallow angle of the X-rays, our experiment was incredibly sensitive to movements along the surface of the material,” says Sanghoon Song, one of three SLAC scientists who were involved with the research. “This was key to seeing the mechanical motion.”

    To follow up on these results, the researchers will do further experiments at LCLS with more complicated samples to find out more precisely how quickly and directly the angular momentum escapes into the structure. What they learn will lead to better models of ultrafast demagnetization, which could help in the development of optically controlled devices for data storage.

    Steven Johnson, a scientist and professor at ETH Zürich and the Paul Scherrer Institute in Switzerland who co-led the study, says the group’s expertise in areas outside of magnetism allowed them to approach the problem from a different angle, better positioning them for success.

    “There have been numerous previous attempts by other groups to understand this, but they failed because they didn’t optimize their experiments to look for these tiny effects,” Johnson says. “They were swamped by other much larger effects, such as atomic movement due to laser heat. Our experiment was much more sensitive to the kind of motion that results from the angular momentum transfer.”

    LCLS is a DOE Office of Science user facility. This work was supported by NCCR Molecular Ultrafast Science and Technology, a research instrument of the Swiss National Science Foundation.

    See the full article here .


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    SLAC Campus
    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.

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  • richardmitnick 3:46 pm on October 15, 2018 Permalink | Reply
    Tags: , , ETH Zurich, , , Ultra-light gloves let users 'touch' virtual objects   

    From ETH Zürich: “Ultra-light gloves let users ‘touch’ virtual objects” 

    ETH Zurich bloc

    From ETH Zürich

    15.10.2018

    ETH Zürich
    Media relations
    Phone: +41 44 632 41 41
    mediarelations@hk.ethz.ch

    1
    For now the glove is powered by a very thin electrical cable, but thanks to the low voltage and power required, a very small battery could eventually be used instead. (Photograph: ETH Zürich)

    Scientists from ETH Zürich and EPFL have developed an ultra-light glove – weighing less than 8 grams – that enables users to feel and manipulate virtual objects. Their system provides extremely realistic haptic feedback and could run on a battery, allowing for unparalleled freedom of movement.

    Engineers and software developers around the world are seeking to create technology that lets users touch, grasp and manipulate virtual objects, while feeling like they are actually touching something in the real world. Scientists at ETH Zürich and EPFL have just made a major step toward this goal with their new haptic glove, which is not only lightweight – under 8 grams – but also provides feedback that is extremely realistic. The glove is able to generate up to 40 Newtons of holding force on each finger with just 200 Volts and only a few milliwatts of power. It also has the potential to run on a very small battery. That, together with the glove’s low form factor (only 2 mm thick), translates into an unprecedented level of precision and freedom of movement.

    “We wanted to develop a lightweight device that – unlike existing virtual-reality gloves – doesn’t require a bulky exoskeleton, pumps or very thick cables,” says Herbert Shea, head of EPFL’s Soft Transducers Laboratory (LMTS). The scientists’ glove, called DextrES, has been successfully tested on volunteers in Zürich and will be presented at the upcoming ACM Symposium on User Interface Software and Technology (UIST).

    Fabric, metal strips and electricity

    DextrES is made of cotton with thin elastic metal strips running over the fingers. The strips are separated by a thin insulator. When the user’s fingers come into contact with a virtual object, the controller applies a voltage difference between the metal strips causing them to stick together via electrostatic attraction – this produces a braking force that blocks the finger’s or thumb’s movement. Once the voltage is removed, the metal strips glide smoothly and the user can once again move his fingers freely.

    Tricking your brain

    For now the glove is powered by a very thin electrical cable, but thanks to the low voltage and power required, a very small battery could eventually be used instead. “The system’s low power requirement is due to the fact that it doesn’t create a movement, but blocks one”, explains Shea. The researchers also need to conduct tests to see just how closely they have to simulate real conditions to give users a realistic experience. “The human sensory system is highly developed and highly complex. We have many different kinds of receptors at a very high density in the joints of our fingers and embedded in the skin. As a result, rendering realistic feedback when interacting with virtual objects is a very demanding problem and is currently unsolved. Our work goes one step in this direction, focusing particularly on kinesthetic feedback,” says Otmar Hilliges, head of the Advanced Interactive Technologies Lab at ETH Fabric, metal strips and electricity

    DextrES is made of cotton with thin elastic metal strips running over the fingers. The strips are separated by a thin insulator. When the user’s fingers come into contact with a virtual object, the controller applies a voltage difference between the metal strips causing them to stick together via electrostatic attraction – this produces a braking force that blocks the finger’s or thumb’s movement. Once the voltage is removed, the metal strips glide smoothly and the user can once again move his fingers freely.

    In this joint research project, the hardware was developed by EPFL at its Microcity campus in Neuchâtel, and the virtual reality system was created by ETH Zürich, which also carried out the user tests. “Our partnership with the EPFL lab is a very good match. It allows us to tackle some of the longstanding challenges in virtual reality at a pace and depth that would otherwise not be possible,” adds Hilliges.

    The next step will be to scale up the device and apply it to other parts of the body using conductive fabric. “Gamers are currently the biggest market, but there are many other potential applications – especially in healthcare, such as for training surgeons. The technology could also be applied in augmented reality,” says Shea..

    See the full article here .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    ETH Zurich campus
    ETH Zürich is one of the leading international universities for technology and the natural sciences. It is well known for its excellent education, ground-breaking fundamental research and for implementing its results directly into practice.

    Founded in 1855, ETH Zürich today has more than 18,500 students from over 110 countries, including 4,000 doctoral students. To researchers, it offers an inspiring working environment, to students, a comprehensive education.

    Twenty-one Nobel Laureates have studied, taught or conducted research at ETH Zürich, underlining the excellent reputation of the university.

     
  • richardmitnick 9:18 pm on October 1, 2018 Permalink | Reply
    Tags: 3D-printing for carbon fibre cores, , At the ETH in Zürich the composite materials of the future are being developed, CRP’s-carbon fibre-reinforced polymers, ETH Zurich, Futuristic car components, , Optimizing the core elements of sandwich structures, Semi-active elements – so-called mechanical switches – are embedded in the material, Structural efficiency, The cores of these composite materials contain a truss construction of carbon fibre rods, These materials are particularly interesting for aerospace application   

    From ETH Zürich: “Materials of the future” 

    ETH Zurich bloc

    From ETH Zürich

    01.10.2018
    Oliver Morsch

    In Paolo Ermanni’s laboratory at the ETH in Zürich, the composite materials of the future are developed. By optimizing the core elements of sandwich structures, the researchers create materials that are extremely light, robust and adaptable at once – and thus ideal for aerospace applications.

    1
    Lightweight sandwich structures. The cores of these composite materials contain a truss construction of carbon fibre rods. By optimizing the arrangement of the rods, the material can be tailored to specific applications. (Photograph: ETH Zürich / Christoph Karl, CMASLab)

    Materials that are light and robust, inherently stable and still easily adjustable, and which can also be produced sustainably and in a resource-friendly way – what may appear as impossible as squaring the circle becomes a reality day after day in Paolo Ermanni’s lab at the ETH in Zürich. “It is our philosophy to develop modern composite materials for adaptive systems and, while doing so, to optimize their structural efficiency – that is, obtaining the same performance with fewer resources or better functionality with the same amount of material”, says Paolo Ermanni, professor for Composite Materials and Adaptive Structures at ETH. At the same time, he and his collaborators investigate appropriate production processes that make the new materials interesting for practical applications.

    Truss structures in sandwiches

    Ermanni’s PhD student Christoph Karl takes care of the “structural efficiency” aspect. “As they feature a large stiffness and stability whilst also being very light, sandwich structures are often used for lightweight construction”, he explains. Sandwich structures typically consist of two thin and stiff cover layers and a low-density core material. “In our research we develop high-performance sandwich composites made of carbon fibre-reinforced polymers, also known as CRP’s or simply carbon fibre. In this approach, the core consists of a truss structure of carbon fibre rods”, says Karl. The good mechanical properties of carbon fibre mean that such core structures can have a larger stiffness and stability than conventional foam or honeycomb cores.

    According to Karl, another significant advantage of the truss cores is the possibility of a load-optimized design: “The mechanical properties of the sandwich composite depend strongly on the core topology – in other words, on the arrangement and orientation of the rods inside the core. With the help of numerical optimizations, we can tailor the orientation of the rods to specific external loads and thus maximize the structural efficiency for a particular application.”

    Applications in aerospace engineering

    The core of a sandwich material constructed and optimized in this way weighs less than 30 kilograms per cubic metre (a cubic metre of steel, for comparison, weighs in at almost 8000 kilograms). “This makes ours materials particularly interesting for aerospace application, where structural efficiency is of crucial importance,” says Karl. “Moreover, it is possible to integrate additional features, such as vibration damping, directly into the core structure.” In the framework of the EU project ALTAIR led by the French aerospace lab Onera, real-life applications of the new sandwich structures are investigated. Within that project, Ermanni’s research group is involved in the development of load-bearing structures of new deployment systems for small satellites.

    Futuristic car components

    Flexible and adaptive structures, on the other hand, are the specialty of PhD student Oleg Testoni. Within the Strategic Focus Area “Advanced Manufacturing” of the ETH board, he develops techniques that allow one to adapt sandwich structures flexibly and dynamically. Those techniques could be used, for instance, to build futuristic spoilers or wheelhouses for sports cars that can be deformed while the vehicle is in motion in order to accurately optimize its aerodynamics for a particular velocity or wheel position when cornering.


    Oleg Testoni explains his research in the field of adaptive structures. (Video: ETH Zürich / Industry Relations)

    Switches in the material

    To achieve such a degree of flexibility whilst maintaining the robustness of the material, semi-active elements – so-called mechanical switches – are embedded in the material. “With such switches, the rods inside the core can be temporarily loosened in order to adapt the shape. After that, they are locked in place again so that the material regains its original stiffness”, Testoni explains.

    Mechanical switches can be built using “intelligent materials” such as shape memory alloys. A component made of such an alloy can take on two different shapes depending on temperature. Above a certain critical temperature, its shape changes, but when cooled down it goes back to its exact original shape. By fitting many of those mechanical switches inside the rods of a sandwich structure, one can change the shape of the entire material.

    3D-printing for carbon fibre cores

    Ermanni and his co-workers do not just carry out basic research on new materials, however. The spin-off company 9T Labs, co-founded by Ermanni’s PhD student Martin Eichenhofer, develops a 3D-printing technology that can be used to produce high-quality carbon fibre components such as the rods for sandwich structure cores in a robust and flexible manner. “First and foremost, this is about expanding the range of application of such materials through novel production techniques, which will enable smaller companies to use them as well. This ‹democratizes› lightweight construction technologies, as it were,” says Eichenhofer. The first products for 3D-printing are supposed to hit the market as early as 2019. “This procedure also opens up the possibility of integrating active elements directly into the printing process in the future, thus realizing 4D-printing,” Ermanni adds.

    See the full article here .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    ETH Zurich campus
    ETH Zürich is one of the leading international universities for technology and the natural sciences. It is well known for its excellent education, ground-breaking fundamental research and for implementing its results directly into practice.

    Founded in 1855, ETH Zürich today has more than 18,500 students from over 110 countries, including 4,000 doctoral students. To researchers, it offers an inspiring working environment, to students, a comprehensive education.

    Twenty-one Nobel Laureates have studied, taught or conducted research at ETH Zürich, underlining the excellent reputation of the university.

     
  • richardmitnick 9:05 am on May 28, 2018 Permalink | Reply
    Tags: Astronomers Just Found 6 Bizarre Galaxies That Appear to Be 'Empty' of Stars, , , , , ETH Zurich   

    From ETH Zürich via Science Alert: “Astronomers Just Found 6 Bizarre Galaxies That Appear to Be ‘Empty’ of Stars” 

    ETH Zurich bloc

    From ETH Zürich

    1

    Science Alert

    28 MAY 2018
    MICHELLE STARR

    2
    (Marino et al./The Astrophysical Journal)

    When you think of galaxies, you first think of glorious pinwheels filled with stars. But now astrophysicists have found something deeply peculiar: what seem to be galaxies in the early Universe with few stars – if they even have any stars at all.

    It’s thought that these star-less galaxies, also known as dark galaxies, might be a very early stage of galactic formation. According to some theoretical models they may have been more common in the early Universe, when galaxies might have had more difficulty forming stars.

    However, because dark galaxies don’t contain stars, just matter and gas, they emit little visible light – making them very difficult to detect and study. Just a few candidates have ever been detected.

    So the discovery of six new candidates could really help to unravel what dark galaxies are, and their place in the formation of galaxies.

    It was through a combination of an old technique and new technology that enabled a team of researchers led by physicists at ETH Zurich to make the discovery.

    The technique relies on the presence of quasars, which are some of the brightest objects in the Universe, powered by supermassive black holes in the centres of galaxies. The light doesn’t come from the black hole itself, but the incredible friction in the accretion disc around the black hole as it falls into it.

    They give off intense ultraviolet light, which fluoresces nearby hydrogen atoms. This emission is known as the Lyman-alpha line.

    If a dark galaxy, full of hydrogen, is near a galaxy with a quasar at the centre, it will act as a sort of cosmic flashlight, and this line will show up in its spectrum.

    This technique has been used before – most notably to identify a number of dark galaxy candidates in the early Universe in 2012, using the European Southern Observatory’s Very Large Telescope.

    ESO VLT Platform at Cerro Paranal elevation 2,635 m (8,645 ft)

    But in 2014, a new instrument was added to the telescope, the Multi Unit Spectroscopic Explorer, or MUSE. this allowed the team to peer farther than previous instrumentation had been able to reach, identifying earlier dark galaxies than had been spotted previously.

    ESO MUSE on the VLT

    The researchers pointed MUSE at six quasar fields, studying each for a total of 10 hours of observation time.

    They acquired full spectral information for each of the dark galaxy candidates, and were able to distinguish them from around 200 or so Lyman-alpha emitters as unlikely to be normal, star-forming galaxies.

    We still don’t have solid proof that these candidates are dark galaxies, but they’re looking a lot more like it than anything else that we know of. Which means, as predicted in 2012, MUSE could be a powerful tool for hunting out these mysterious objects.

    “Every quasar field observed with MUSE will … offer the potential to discover new Dark Galaxy candidates and provide crucial information on the early and dark phases of galaxy formation,” the researchers wrote in their paper.

    The paper has been published under open access in The Astrophysical Journal.

    See the full article here .


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    Please help promote STEM in your local schools.
    stem
    Stem Education Coalition

    ETH Zurich campus
    ETH Zürich is one of the leading international universities for technology and the natural sciences. It is well known for its excellent education, ground-breaking fundamental research and for implementing its results directly into practice.

    Founded in 1855, ETH Zürich today has more than 18,500 students from over 110 countries, including 4,000 doctoral students. To researchers, it offers an inspiring working environment, to students, a comprehensive education.

    Twenty-one Nobel Laureates have studied, taught or conducted research at ETH Zürich, underlining the excellent reputation of the university.

     
  • richardmitnick 9:32 am on May 24, 2018 Permalink | Reply
    Tags: , , , , ETH Zurich, Guantum cascade laser,   

    From ETH Zürich: “From a quantum laboratory to the stratosphere” 

    ETH Zurich bloc

    From ETH Zürich

    23.05.2018
    Felix Würsten

    ETH physicists have developed a quantum cascade laser that can be used to visualise weak infrared signals from space. It is now being put to use on a flight of the world’s largest airborne observatory.

    1
    SOFIA enables special astronomic measurements in the infrared range. The open cavity where the 2.5-meter telescope is housed can be seen in the rear of the plane. (Photograph: NASA/USRA)

    Lorenzo Bosco, doctoral student with Jérôme Faist, a professor at the Institute for Quantum Electronics, is taking an unusual flight: he travels to the stratosphere in a special NASA aircraft, a converted Boeing 747SP, to contribute to astrophysical measurements. The crew of the Stratospheric Observatory for Infrared Astronomy (SOFIA), as the aircraft is officially named, measured infrared signals from cooling gases. The astrophysicists hope to thereby gain new insights into how stars form in our galaxy.

    Additional device makes signals visible

    Although Faist’s research is focused on futuristic quantum-optical systems rather than stars, his involvement in the astrophysics mission is for a good reason: together with his team, he has developed a special laser that makes these measurements possible in the first place. The infrared signals that will be measured on this flight are so weak that they can only be measured using a trick.

    The frequency of the incident light is changed using a local oscillator, so that it can be better distinguished from the background noise. This principle is also used in fields such as telecommunications, to improve the reception of radio broadcasts. Since the astrophysicists wanted to measure signals in the far infrared range on this flight, they needed to use a laser that provides a corresponding additional signal in the terahertz region as a local oscillator.

    Practical application for an innovative device

    This is just what the quantum cascade lasers that Faist and his group have been developing for several years are able to do. Although the principle of these lasers was first implemented in the 1990s, those operating in the terahertz range have so far hardly been applied. One reason for this is that they have to be cooled down to very low temperatures during operation.

    For the current SOFIA mission, Faist and his team developed a quantum cascade laser specifically tailored to the astrophysicists’ requirements. “The challenge was to develop a device that provides a precise and powerful signal with a clearly definable frequency,” explains Faist. He is very satisfied that this laser concept now has a practical application after so many years of development.

    The ETH professor hopes that the mission will also provide indications of how they can continue to improve the laser so that the astrophysicists can conduct further infrared measurements with higher resolutions on their flights.

    See the full article here .


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    Please help promote STEM in your local schools.
    stem
    Stem Education Coalition

    ETH Zurich campus
    ETH Zürich is one of the leading international universities for technology and the natural sciences. It is well known for its excellent education, ground-breaking fundamental research and for implementing its results directly into practice.

    Founded in 1855, ETH Zürich today has more than 18,500 students from over 110 countries, including 4,000 doctoral students. To researchers, it offers an inspiring working environment, to students, a comprehensive education.

    Twenty-one Nobel Laureates have studied, taught or conducted research at ETH Zürich, underlining the excellent reputation of the university.

     
  • richardmitnick 7:31 am on February 27, 2018 Permalink | Reply
    Tags: , ETH Zurich, ,   

    From ETH Zürich: “Teaching quantum physics to a computer” 

    ETH Zurich bloc

    ETH Zürich

    26.02.2018
    Oliver Morsch

    An international collaboration led by ETH physicists has used machine learning to teach a computer how to predict the outcomes of quantum experiments. The results could prove to be essential for testing future quantum computers.

    1
    Using neural networks, physicists taught a computer to predict the results of quantum experiments. (Graphic: http://www.colourbox.com)

    Physics students spend many years learning to master the often counterintuitive laws and effects of quantum mechanics. For instance, the quantum state of a physical system may be undetermined until a measurement is made, and a measurement on one part of the system can influence the state of a distant part without any exchange of information. It is enough to make the mind boggle. Once the students graduate and start doing research, the problems continue: to exactly determine the state of some quantum system in an experiment, one has to carefully prepare it and make lots of measurements, over and over again.

    Very often, what one is actually interested in cannot even be measured directly. An international team of researchers led by Giuseppe Carleo, a lecturer at the Institute for Theoretical Physics of ETH Zürich, has now developed machine learning software that enables a computer to “learn” the quantum state of a complex physical system based on experimental observations and to predict the outcomes of hypothetical measurements. In the future, their software could be used to test the accuracy of quantum computers.

    Quantum physics and handwriting

    The principle of his approach, Carleo explains, is rather simple. He uses an intuitive analogy that avoids the complications of quantum physics: “What we do, in a nutshell, is like teaching the computer to imitate my handwriting. We will show it a bunch of written samples, and step by step it then learns to replicate all my a’s, l’s and so forth.”

    The way the computer does this is by looking at the ways, for instance, in which an “l” is written when it follows an “a”. These may not always be the same, so the computer will calculate a probability distribution that expresses mathematically how often a letter is written in a certain way when it is preceded by some other letter. “Once the computer has figured out that distribution, it could then reproduce something that looks very much like my handwriting”, Carleo says.

    2
    A neural network (top) “learns” the quantum state of a spin system from measurement data by trying different possibilities of the spin directions (bottom) and correcting itself step by step. (Graphic: ETH Zürich / G. Carleo)

    Quantum physics is, of course, much more complicated than a person’s handwriting. Still, the principle that Carleo (who recently moved to the Flatiron Institute in New York), together with Matthias Troyer, Guglielmo Mazzola (both at ETH) and Giacomo Torlai from the University of Waterloo as well as colleagues at the Perimeter Institute and the company D-Wave in Canada have used for their machine learning algorithm is quite similar.

    The quantum state of the physical system is encoded in a so-called neural network, and learning is achieved in small steps by translating the current state of the network into predicted measurement probabilities. Those probabilities are then compared to the actually measured data, and adjustments are made to the network in order to make them match better in the next round. Once this training period is finished, one can then use the quantum state stored in the neural network for “virtual” experiments without actually performing them in the laboratory.

    Faster tomography for quantum states

    “Using machine learning to extract a quantum state from measurements has a number of advantages”, Carleo explains. He cites one striking example, in which the quantum state of a collection of just eight quantum objects (trapped ions) had to be experimentally determined. Using a standard approached called quantum tomography, around one million measurements were needed to achieve the desired accuracy. With the new method, a much smaller number of measurements could do the same job, and substantially larger systems, previously inaccessible, could be studied.

    This is encouraging, since common wisdom has it that the number of calculations necessary to simulate a complex quantum system on a classical computer grows exponentially with the number of quantum objects in the system. This is mainly because of a phenomenon called entanglement, which causes distant parts of the quantum system to be intimately connected although they do not exchange information. The approach used by Carleo and his collaborators takes this into account by using a layer of “hidden” neurons, which allow the computer to encode the correct quantum state in a much more compact fashion.

    Testing quantum computers

    Being able to study quantum systems with a large number of components – or “qubits”, as they are often called – also has important implications for future quantum technologies, as Carleo points out: “If we want to test quantum computers with more than a handful of qubits, that won’t be possible with conventional means because of the exponential scaling. Our machine learning approach, however, should put us in a position to test quantum computers with as many as 100 qubits.”

    Also, the machine learning software can help experimental physicists by allowing them to perform virtual measurements that would be hard to do in the laboratory, such as measuring the degree of entanglement of a system composed of many interacting qubits. So far, the method has only been tested on artificially generated data, but the researchers plan to use it for analysing real quantum experiments very soon.

    Science paper:
    Torlai G, Mazzola G, Carrasquilla J, Troyer M, Melko R, Carleo G: Neural-network quantum state tomography. Nature Physics.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    ETH Zurich campus
    ETH Zürich is one of the leading international universities for technology and the natural sciences. It is well known for its excellent education, ground-breaking fundamental research and for implementing its results directly into practice.

    Founded in 1855, ETH Zürich today has more than 18,500 students from over 110 countries, including 4,000 doctoral students. To researchers, it offers an inspiring working environment, to students, a comprehensive education.

    Twenty-one Nobel Laureates have studied, taught or conducted research at ETH Zürich, underlining the excellent reputation of the university.

     
  • richardmitnick 3:41 pm on January 15, 2018 Permalink | Reply
    Tags: , ETH Zurich, , Quantum physics turned into tangible reality   

    From ETH Zürich: “Quantum physics turned into tangible reality” 

    ETH Zurich bloc

    ETH Zürich

    15.01.2018
    Felix Würsten

    ETH physicists have developed a silicon wafer that behaves like a topological insulator when stimulated using ultrasound. They have thereby succeeded in turning an abstract theoretical concept into a macroscopic product.

    1
    When the silicon wafer is stimulated at a single point using ultrasound, it begins to vibrate – but only at the corners. (Visualisation: ETH Zürich).

    The usual procedure goes like this: you have a complex physical system and attempt to explain its behaviour through as simple a model as possible. Sebastian Huber, Assistant Professor at the Institute for Theoretical Physics, has shown that this procedure also works in reverse: he develops macroscopic systems that exhibit exactly the same properties predicted by theory, but which have not yet been observed at this level.

    He succeeded in creating an illustrative example two and a half years ago. Together with his team, he built a mechanical device made of 270 pendulums connected by springs in such a way that the installation behaves like a topological insulator. This means that the pendulum and springs are positioned so that a vibrational excitation from the outside only moves the pendulums at the edges of the installation, but not the ones in the middle (as ETH News reported).

    Vibration only in the corners

    The new project, which will be published this week in the journal Nature, is also focused on a macroscopic system. This time, however, he created no large mechanical device, but a much more manageably-sized object. With his team, Huber created a 10 x 10 centimetre silicon wafer that consists of 100 small plates connected to each other via thin beams. The key aspect is that when the wafer is stimulated using ultrasound, only the plates in the corners vibrate; the other plates remain still, despite their connections.

    Huber drew his inspiration for the new material from a work published around a year ago by groups from Urbana-Champaign and Princeton; the researchers presented a new theoretical approach for a second-order topological insulator. “In a conventional topological insulator, the vibrations only spread across the surface, but not inside,” explains Huber. “The phenomenon is reduced by one dimension.” In the case of the pendulum installation, this means that the two-dimensional arrangement led to a one-dimensional vibration pattern along the edges.

    In a second-order topological insulator, however, the phenomenon is reduced by two dimensions. Accordingly, with a two-dimensional silicon wafer, the vibration no longer occurs along the edges, but only in the corners, at a zero-dimensional point. “We are the first to succeed in experimentally creating the predicted higher-order topological insulator,” says Huber.

    A new theoretical concept

    Huber has again created something that behaves in exactly the way predicted by the theory. To solve this “inverse problem”, he used a systematic process that he developed together with the group led by Chiara Daraio, now a professor at Caltech, and which he has published this week in the journal Nature Materials. Broadly speaking, Huber shows how a theoretically predicted functionality can be turned into concrete geometry. “In our example, we tested it using mechanical vibrations, by coupling elements with clearly defined modes of vibration using weak links,” says Huber. “But the process can also be transferred to other applications, such as to optical or electrical systems.”

    Expansion to the third dimension

    Huber already has clear plans for how to proceed: he wants to achieve a three-dimensional second-order topological insulator, in which the vibrations can be transmitted one-dimensionally. He recently received a Consolidator Grant from the European Research Council (ERC) for this project. Huber explains the basic idea: “We stack a number of these two-dimensional structures on top of each other, so that a three-dimensional form emerges. In this form, information or energy can be conducted from point A to point B through a one-dimensional channel.”

    Huber can think of a few possible applications. For example, such new topological insulators could be used to build robust and precise waveguides for communications networks. They could also be of use in the energy sector, for example for energy harvesting, in which energy from a diffuse surrounding source is focused for technological use.

    Also of interest to theoreticians

    Huber’s results will not only be of interest to engineers and materials researchers, but also theoretical physicists. “The key finding from a theoretical viewpoint is that certain second-order topological insulators cannot be mathematically described as a dipole, as conventional topological insulators are, but as quadrupoles, which are far more complex,” explains Huber. “The fact that we have been able to implement this experimentally in a macroscopic structure for the first time is therefore also a breakthrough for theoreticians.”

    See the full article here .

    Please help promote STEM in your local schools.

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    ETH Zurich campus
    ETH Zürich is one of the leading international universities for technology and the natural sciences. It is well known for its excellent education, ground-breaking fundamental research and for implementing its results directly into practice.

    Founded in 1855, ETH Zürich today has more than 18,500 students from over 110 countries, including 4,000 doctoral students. To researchers, it offers an inspiring working environment, to students, a comprehensive education.

    Twenty-one Nobel Laureates have studied, taught or conducted research at ETH Zürich, underlining the excellent reputation of the university.

     
  • richardmitnick 10:49 am on January 11, 2018 Permalink | Reply
    Tags: , Carbon cycle, , ETH Zurich, , Japan Trench, Radiocarbon dating   

    From ETH Zürich: “Earthquakes as a driver for the deep-ocean carbon cycle” 

    ETH Zurich bloc

    ETH Zürich

    09.01.2018
    Samuel Schlaefli

    An international team led by geologist Michael Strasser has used novel methods to analyse sediment deposits in the Japan Trench in order to gain new insights into the carbon cycle.

    1
    The research vessel RV Sonne, aboard which the sediment samples in the Japan Trench were taken in 2012. (Image: RF Forschungsschiffahrt Bremen/Germany)

    In a paper recently published in Nature Communications, geologist Michael Strasser presented the initial findings of a month-long research expedition off the coast of Japan. The research initiative had been organised in March 2012 by MARUM – Center for Marine Environmental Sciences. Strasser, who until 2015 was Assistant Professor for Sediment Dynamics at ETH Zürich and is now a Full Professor for Sediment Geology at the University of Innsbruck, took an international team there to study dynamic sediment remobilisation processes triggered by seismic activity.

    At a depth of 7,542 metres below sea level, the team took a core sample from the Japan Trench, an 800-km-long oceanic trench in the northwestern part of the Pacific Ocean. The trench, which is seismically active, was the epicentre of the Tohoku earthquake in 2011, which made headlines when it caused the nuclear meltdown at Fukushima. Such earthquakes wash enormous amounts of organic matter from the shallows down into deeper waters. The resulting sediment layers can thus be used later to glean information about the history of earthquakes and the carbon cycle in the deep ocean.

    New dating methods in the deep ocean

    The current study provided the researchers with a breakthrough. They analysed the carbon-rich sediments using radiocarbon dating. This method – measuring the amount of organic carbon as well as radioactive carbon (14C) in mineralised compounds – has long been a means of determining the age of individual sediment layers. Until now, however, it has not been possible to analyse samples from deeper than 5,000 metres below the surface, because the mineralised compounds dissolve under increased water pressure.

    Strasser and his team therefore had to use new methods for their analysis. One of these was what is known as the online gas radiocarbon method, developed by ETH doctoral student Rui Bao and the Biogeoscience Group at ETH Zürich. This greatly increases efficiency, since it takes just a single core sample to make more than one hundred 14C age measurements directly on the organic matter contained within the sediment.

    In addition, the researchers applied the Ramped PyrOx measurement method (pyrolysis) for the first time in the dating of deep-ocean sediment layers. This was done in cooperation with the Woods Hole Oceanographic Institute (U.S.), which developed the method. The process involves burning organic matter at different temperatures. Because older organic matter contains stronger chemical bonds, it requires higher temperatures to burn. What makes this method novel is that the relative age variation of the individual temperature fractions between two samples very precisely distinguishes the age difference between sediment levels in the deep sea.

    Dating earthquakes to increase forecast accuracy

    Thanks to these two innovative methods, the researchers could determine the relative age of organic matter in individual sediment layers with a high degree of precision. The core sample they tested contained older organic matter in three places, as well as higher rates of carbon export to the deep ocean. These places correspond to three historically documented yet hitherto partially imprecisely dated seismic events in the Japan Trench: the Tohoku earthquake in 2011, an unnamed earthquake in 1454, and the Sanriku earthquake in 869.

    At the moment, Strasser is working on a large-scale geological map of the origin and frequency of sediments in deep-ocean trenches. To do so, he is analysing multiple core samples taken during a follow-up expedition to the Japan Trench in 2016. “The identification and dating of tectonically triggered sediment deposits is also important for future forecasts about the likelihood of earthquakes,” Strasser says. “With our new methods, we can predict the recurrence of earthquakes with much more accuracy.”

    2
    Michael Strasser (right), then assistant professor at ETH Zürich, and expedition head Gerold Wefer, professor at MARUM and Bremen University, make recommendations about the core sample on board the RV Sonne. Source/Copyright: V. Diekamp, MARUM, Bremen University.

    Science team:
    Bao R, Strasser M, McNichol A, Haghipour N, McIntyre C Wefer G, Eglinton T.

    See the full article here .

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    ETH Zurich campus
    ETH Zürich is one of the leading international universities for technology and the natural sciences. It is well known for its excellent education, ground-breaking fundamental research and for implementing its results directly into practice.

    Founded in 1855, ETH Zürich today has more than 18,500 students from over 110 countries, including 4,000 doctoral students. To researchers, it offers an inspiring working environment, to students, a comprehensive education.

    Twenty-one Nobel Laureates have studied, taught or conducted research at ETH Zürich, underlining the excellent reputation of the university.

     
  • richardmitnick 10:30 am on January 11, 2018 Permalink | Reply
    Tags: , , ETH Zurich, Extremely bright and fast light emission, , ,   

    From ETH: “Extremely bright and fast light emission” 

    ETH Zürich bloc

    ETH Zürich

    11.01.2018
    Fabio Bergamin

    A type of quantum dot that has been intensively studied in recent years can reproduce light in every colour and is very bright. An international research team that includes scientists from ETH Zürich has now discovered why this is the case. The quantum dots could someday be used in light-emitting diodes.

    1
    A caesium lead bromide nanocrystal under the electron microscope (crystal width: 14 nanometres). Individual atoms are visible as points. (Photograph: ETH Zürich / Empa / Maksym Kovalenko)

    An international team of researchers from ETH Zürich, IBM Research Zürich, Empa and four American research institutions have found the explanation for why a class of nanocrystals that has been intensively studied in recent years shines in such incredibly bright colours. The nanocrystals contain caesium lead halide compounds that are arranged in a perovskite lattice structure.

    Three years ago, Maksym Kovalenko, a professor at ETH Zürich and Empa, succeeded in creating nanocrystals – or quantum dots, as they are also known – from this semiconductor material. “These tiny crystals have proved to be extremely bright and fast emitting light sources, brighter and faster than any other type of quantum dot studied so far,” says Kovalenko. By varying the composition of the chemical elements and the size of the nanoparticles, he also succeeded in producing a variety of nanocrystals that light up in the colours of the whole visible spectrum. These quantum dots are thus also being treated as components for future light-emitting diodes and displays.

    In a study published in the most recent edition of the scientific journal Nature, the international research team examined these nanocrystals individually and in great detail. The scientists were able to confirm that the nanocrystals emit light extremely quickly. Previously-studied quantum dots typically emit light around 20 nanoseconds after being excited when at room temperature, which is already very quick. “However, caesium lead halide quantum dots emit light at room temperature after just one nanosecond,” explains Michael Becker, first author of the study. He is a doctoral student at ETH Zürich and is carrying out his doctoral project at IBM Research.

    2
    A sample with several green glowing perovskite quantum dots excited by a blue laser. (Photograph: IBM Research / Thilo Stöferle)

    Electron-hole pair in an excited energy state

    Understanding why caesium lead halide quantum dots are not only fast but also very bright entails diving into the world of individual atoms, light particles (photons) and electrons. “You can use a photon to excite semiconductor nanocrystals so that an electron leaves its original place in the crystal lattice, leaving behind a hole,” explains David Norris, Professor of Materials Engineering at ETH Zürich. The result is an electron-hole pair in an excited energy state. If the electron-hole pair reverts to its energy ground state, light is emitted.

    Under certain conditions, different excited energy states are possible; in many materials, the most likely of these states is called a dark one. “In such a dark state, the electron hole pair cannot revert to its energy ground state immediately and therefore the light emission is suppressed and occurs delayed. This limits the brightness”, says Rainer Mahrt, a scientist at IBM Research.

    No dark state

    The researchers were able to show that the caesium lead halide quantum dots differ from other quantum dots: their most likely excited energy state is not a dark state. Excited electron-hole pairs are much more likely to find themselves in a state in which they can emit light immediately. “This is the reason that they shine so brightly,” says Norris.

    The researchers came to this conclusion using their new experimental data and with the help of theoretical work led by Alexander Efros, a theoretical physicist at the Naval Research Laboratory in Washington. He is a pioneer in quantum dot research and, 35 years ago, was among the first scientists to explain how traditional semiconductor quantum dots function.

    Great news for data transmission

    As the examined caesium lead halide quantum dots are not only bright but also inexpensive to produce they could be applied in television displays, with efforts being undertaken by several companies, in Switzerland and world-wide. “Also, as these quantum dots can rapidly emit photons, they are of particular interest for use in optical communication within data centres and supercomputers, where fast, small and efficient components are central,” says Mahrt. Another future application could be the optical simulation of quantum systems which is of great importance to fundamental research and materials science.

    ETH professor Norris is also interested in using the new knowledge for the development of new materials. “As we now understand why these quantum dots are so bright, we can also think about engineering other materials with similar or even better properties,” he says.

    Science team:
    Becker MA, Vaxenburg R, Nedelcu G, Sercel PC, Shabaev A, Mehl MJ, Michopoulos JG, Lambrakos SG, Bernstein N, Lyons JL, Stöferle T, Mahrt RF, Kovalenko MV, Norris DJ, Rainò G, Efros AL.

    See the full article here .

    Please help promote STEM in your local schools.

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    ETH Zürich campus
    ETH Zürich is one of the leading international universities for technology and the natural sciences. It is well known for its excellent education, ground-breaking fundamental research and for implementing its results directly into practice.

    Founded in 1855, ETH Zürich today has more than 18,500 students from over 110 countries, including 4,000 doctoral students. To researchers, it offers an inspiring working environment, to students, a comprehensive education.

    Twenty-one Nobel Laureates have studied, taught or conducted research at ETH Zürich, underlining the excellent reputation of the university.

     
  • richardmitnick 10:26 am on September 17, 2017 Permalink | Reply
    Tags: , , ETH Zurich, ,   

    From ETH Zürich: Women in STEM- “At home in the world of cold atoms” Physicist Laura Corman 

    ETH Zurich bloc

    ETH Zürich

    16.09.2017
    Isabelle Herold

    1
    Laura Corman plunges into the world of cold atoms (Image: Annick Ramp/ETH Zürich)

    Physicist Laura Corman is fascinated by the behaviour of electrons in solids. But this up and coming researcher’s other interests give her plenty of opportunities to get out of the lab.

    For most people, the world of cold atoms is likely to be somewhat of an enigma. In contrast, Laura Corman (a postdoctoral researcher at the Institute for Quantum Electronics) can’t hide her enthusiasm when she explains how atoms suddenly become visible and gather into clouds. For her, this is a unique visual experience – almost magical. The cooling of atoms to near absolute zero allows scientists to draw conclusions about the behaviour of electrons in solids.

    Laura Corman enjoys popularising science and succeeded in taking her complex subject through to the finals of the competition “Ma thèse en 180 secondes” (My thesis in 180 seconds). Here, she compared atoms to the spectators in the hall: If they have time, they occupy an even spread of seats. If you stop them abruptly, however, there are gaps here and collisions there. “After that, even my grandmother understood what my work is about,” the 29-year-old says.

    Corman discovered her passion for science as a ten-year-old when she visited an amateur observatory during the summer holidays in Provence. She is enormously grateful to her parents – her father is an engineer in the automobile industry, her mother a teacher – for giving her and her younger brother the opportunity to discover different worlds from an early age.

    When she went to university, she moved from the northernmost tip of France to Paris. There, whole new horizons once again opened up before her: “As I experimented with my own projects, I increasingly understood how things were connected.” In her spare time, she became involved in an association helping socially disadvantaged children to learn mathematics and physics.

    In the minority

    When it came to studying for her Master’s in physics, she toyed with the idea of an exchange in the USA. Then some colleagues brought ETH to her attention, and she applied immediately. The interest was mutual: ETH offered Corman an Excellence Scholarship, and her move to Switzerland was settled. To round off her year, she received the Willi Studer Prize for her outstanding mark in her final Master’s examination.

    As a woman, she has always been in a minority within her subject. As far as she is concerned, though, this has hardly made any difference – or rather, just once. This was when Corman felt that she was getting less interesting work to do than her male colleagues during an industrial internship. Being a direct person, she refused to accept that. In hindsight, she wondered to what extent the problem really had to do with the fact she is a woman, or whether perhaps prejudices were distorting her perception. “Men probably never ask themselves questions like that,” Corman acknowledges thoughtfully.

    2
    Laura Corman, Postdoctoral researcher at the Institute for Quantum Electronics

    When Professor of Quantum Optics Tilman Esslinger invited her to return to his laboratory at ETH after her doctorate in Paris, she did not hesitate for a moment. The team is fantastic, the infrastructure and support superb, says Corman. She is now receiving support from the ETH fellowship programme for promising postdoctoral researchers, although she still finds it a huge challenge to give lectures in German. In order to improve their language skills and make some contacts, she and her partner play handball at the ASVZ. “Whether it’s handball or German, we are total beginners in both,” she laughs.

    Corman is adamant that she would continue to pursue her career, even if she were to become a mother someday. In France that’s the norm, she explains, although the conditions there are somewhat different: a single income is not usually enough to get by, but then day care places are affordable and in sufficient supply. Corman gets annoyed that it is often only women who are confronted with the issue of reconciling work and family life. Nowadays that’s just as much a matter for men, and it’s mainly a question of organisation.

    Where her career path will one day lead her still remains to be seen: “It would be fantastic to establish my own group at a university. But exciting possibilities might be lying in wait in other places too – everything is left to play for.”

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    ETH Zurich campus
    ETH Zurich is one of the leading international universities for technology and the natural sciences. It is well known for its excellent education, ground-breaking fundamental research and for implementing its results directly into practice.

    Founded in 1855, ETH Zurich today has more than 18,500 students from over 110 countries, including 4,000 doctoral students. To researchers, it offers an inspiring working environment, to students, a comprehensive education.

    Twenty-one Nobel Laureates have studied, taught or conducted research at ETH Zurich, underlining the excellent reputation of the university.

     
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