From Niels Bohr Institute: “Quantum Alchemy: Researchers use laser light to transform metal into magnet”

University of Copenhagen

From Niels Bohr Institute

16 September 2019

Mark Spencer Rudner
Associate Professor
Condensed Matter Physics
Niels Bohr Institutet
rudner@nbi.ku.dk

Maria Hornbek
Journalist
The Faculty of Science
maho@science.ku.dk
+45 22 95 42 83

CONDENSED MATTER PHYSICS: Pioneering physicists from the University of Copenhagen and Nanyang Technological University in Singapore have discovered a way to get non-magnetic materials to make themselves magnetic by way of laser light. The phenomenon may also be used to endow many other materials with new properties.

Mark Rudner, Niels Bohr Institute, University of Copenhagen

Asst Prof Justin Song Chien Wen

The intrinsic properties of materials arise from their chemistry — from the types of atoms that are present and the way that they are arranged. These factors determine, for example, how well a material may conduct electricity or whether or not it is magnetic. Therefore, the traditional route for changing or achieving new material properties has been through chemistry.

Now, a pair of researchers from the University of Copenhagen and Nanyang Technological University in Singapore have discovered a new physical route to the transformation of material properties: when stimulated by laser light, a metal can transform itself from within and suddenly acquire new properties.

“For several years, we have been looking into how to transform the properties of a matter by irradiating it with certain types of light. What’s new is that not only can we change the properties using light, we can trigger the material to change itself, from the inside out, and emerge into a new phase with completely new properties. For instance, a non-magnetic metal can suddenly transform into a magnet,” explains Associate Professor Mark Rudner, a researcher at the University of Copenhagen’s Niels Bohr Institute.

He and colleague Justin Song of Nanyang Technological University in Singapore made the discovery that is now published in Nature Physics. The idea of using light to transform the properties of a material is not novel in itself. But up to now, researchers have only been capable of manipulating the properties already found in a material. Giving a metal its own ‘separate life’, allowing it to generate its own new properties, has never been seen before.

By way of theoretical analysis, the researchers have succeeded in proving that when a non-magnetic metallic disk is irradiated with linearly polarized light, circulating electric currents and hence magnetism can spontaneously emerge in the disk.

Researchers use so-called plasmons (a type of electron wave) found in the material to change its intrinsic properties. When the material is irradiated with laser light, plasmons in the metal disk begin to rotate in either a clockwise or counterclockwise direction. However, these plasmons change the quantum electronic structure of a material, which simultaneously alters their own behavior, catalyzing a feedback loop. Feedback from the plasmons’ internal electric fields eventually causes the plasmons to break the intrinsic symmetry of the material and trigger an instability toward self-rotation that causes the metal to become magnetic.

Technique can produce properties ‘on demand’

According to Mark Rudner, the new theory pries open an entire new mindset and most likely, a wide range of applications:

“It is an example of how the interaction between light and material can be used to produce certain properties in a material ‘on demand’. It also paves the way for a multitude of uses, because the principle is quite general and can work on many types of materials. We have demonstrated that we can transform a material into a magnet. We might also be able to change it into a superconductor or something entirely different,” says Rudner. He adds:

“You could call it 21st century alchemy. In the Middle Ages, people were fascinated by the prospect of transforming lead into gold. Today, we aim to get one material to behave like another by stimulating it with a laser.”

Among the possibilities, Rudner suggests that the principle could be useful in situations where one needs a material to alternate between behaving magnetically and not. It could also prove useful in opto-electronics – where, for example, light and electronics are combined for fiber-internet and sensor development.

The researchers’ next steps are to expand the catalog of properties that can be altered in analogous ways, and to help stimulate their experimental investigation and utilization.

See the full article here .

five-ways-keep-your-child-safe-school-shootings

Stem Education Coalition

Niels Bohr Institute (Danish: Niels Bohr Institutet) is a research institute of the University of Copenhagen. The research of the institute spans astronomy, geophysics, nanotechnology, particle physics, quantum mechanics and biophysics.

The Institute was founded in 1921, as the Institute for Theoretical Physics of the University of Copenhagen, by the Danish theoretical physicist Niels Bohr, who had been on the staff of the University of Copenhagen since 1914, and who had been lobbying for its creation since his appointment as professor in 1916. On the 80th anniversary of Niels Bohr’s birth – October 7, 1965 – the Institute officially became The Niels Bohr Institute.[1] Much of its original funding came from the charitable foundation of the Carlsberg brewery, and later from the Rockefeller Foundation.[2]

During the 1920s, and 1930s, the Institute was the center of the developing disciplines of atomic physics and quantum physics. Physicists from across Europe (and sometimes further abroad) often visited the Institute to confer with Bohr on new theories and discoveries. The Copenhagen interpretation of quantum mechanics is named after work done at the Institute during this time.

On January 1, 1993 the institute was fused with the Astronomic Observatory, the Ørsted Laboratory and the Geophysical Institute. The new resulting institute retained the name Niels Bohr Institute.

The University of Copenhagen (UCPH) (Danish: Københavns Universitet) is the oldest university and research institution in Denmark. Founded in 1479 as a studium generale, it is the second oldest institution for higher education in Scandinavia after Uppsala University (1477). The university has 23,473 undergraduate students, 17,398 postgraduate students, 2,968 doctoral students and over 9,000 employees. The university has four campuses located in and around Copenhagen, with the headquarters located in central Copenhagen. Most courses are taught in Danish; however, many courses are also offered in English and a few in German. The university has several thousands of foreign students, about half of whom come from Nordic countries.

The university is a member of the International Alliance of Research Universities (IARU), along with University of Cambridge, Yale University, The Australian National University, and UC Berkeley, amongst others. The 2016 Academic Ranking of World Universities ranks the University of Copenhagen as the best university in Scandinavia and 30th in the world, the 2016-2017 Times Higher Education World University Rankings as 120th in the world, and the 2016-2017 QS World University Rankings as 68th in the world. The university has had 9 alumni become Nobel laureates and has produced one Turing Award recipient

From Niels Bohr Institute: “Probing the beginning of the Universe can soon be done more accurately”

University of Copenhagen

From Niels Bohr Institute

Measurement of the Cosmic Microwave Background radiation:

In the Karoo desert in South Africa, scientists from all over the world plan to set up a huge array of telescopes – the Square Kilometer Array (SKA).

SKA South Africa

As many as 200 telescopes will be erected in the next decade, in order to achieve the highest possible precision in measuring radiation from the Universe.

Photograph of the SKA-MPG telescope for which the study was performed. The primary dish has a diameter of 15 meters and can receive signals between 1.7 and 3.5 Gigahertz. It is currently being installed in the South African Karoo desert. © South African Radio Astronomy Observatory (SARAO)

Among the many scientific goals of the SKA are tests of Einstein’s relativity theory, probing the nature of Dark Energy, and studying the properties of our Galaxy, to name just a few. A team of researchers, amongst them Sebastian von Hausegger, who just finished as a PhD fellow in the Theoretical Particle Physics and Cosmology group of the Niels Bohr Institute, University of Copenhagen, has developed a plan to utilize the very first prototype, the SKA-MPG telescope, in the Karoo in a different way in the near future: the additional knowledge about our Galaxy which this telescope will bring can be used immediately for the study of the Cosmic Microwave Background (CMB), the earliest picture of our Universe. In a detailed study, they investigate the scientific potential of the SKA-MPG telescope – the prototype for those dishes which eventually should be built into the array is built by the German Max Planck Society – and demonstrate the huge advantage already this single dish will have for cosmology. This forecast was led by Aritra Basu from Bielefeld University and is now published in Monthly Notices of the Royal Astronomical Society.

Separating the foreground from the background

The Cosmic Microwave Background radiation (CMB) is the afterglow of the forming of our Universe.

CMB per ESA/Planck

ESA/Planck 2009 to 2013

In this respect, it carries the fingerprint of how everything we know and are came to be. If analyzed correctly, it will tell us about the very early universe, perhaps including stories about gravitational waves generated by a process called inflation, the currently leading theory of the Universe’s beginning – obviously, we want to be able to study it as closely and accurately as possible.

Inflation

Alan Guth, from Highland Park High School and M.I.T., who first proposed cosmic inflation

HPHS Owls

Lambda-Cold Dark Matter, Accelerated Expansion of the Universe, Big Bang-Inflation (timeline of the universe) Date 2010 Credit: Alex MittelmannColdcreation

Alan Guth’s notes:

Alan Guth’s original notes on inflation

However, all measurements we attempt to take of the CMB are disturbed by the radiation emitted by our own Galaxy. This radiation is called `foreground emission’ in the CMB community, to distinguish it from the sought-for cosmic `background’. To reliably remove thisforeground, we must understand exactly what it is, and what is causing it. This is where telescopes like the one shown come into play.

Sebastian von Hausegger’s work as a PhD student dealt with the problem of foreground separation. “Essentially, you take a picture of the sky at different frequencies, and by tracing the differences of those pictures, you understand what sort of foreground emission they contain. Once that is done properly, the real work with interpreting the background can begin”, Sebastian explains. “The more frequencies you take pictures at – the better your understanding gets of the physical processes, the structure, and the composition of the Milky Way!” The SKA-MPG telescope is able to measure at 2048 different frequencies between 1.7 and 3.5 GHz – many more than previously possible.

Bringing the radio astronomy and the CMB community together

Sebastian continues, “The radio emission of our Galaxy is mainly caused by electrons, zooming around in the Galactic disk, and they can do crazy things. As a part of my PhD, I visited the Astroparticle Physics and Cosmology group at Bielefeld University, Germany. The group includes experts on galactic radio emission – the emission we call foreground radiation. I visited them as a representative from the CMB research community, so to say. Our own Galaxy is not that interesting in the grand scale of things, but the insight gained from measurements of its emission can sure help us learn about this grand scale! In this collaboration,we tried to bring the two communities closer together.”

Motivated by the properties of the telescope, the authors of this study consider a much more ambitious model for the radio-foregrounds than was done in previous efforts. Even considering the impact of the SKA-MPG prototype alone, the level of achievable detail is much higher than with current data and the inferred prospects for CMB analyses are highly promising.

An array of up to 200 telescopes is the goal

The ambition of the Square Kilometer Array is to finally place 200 telescopes in the South African desert. The reason for choosing a remote area like a desert for performing their measurements the restriction of radio emission in the surroundings(the Karoo desert has been made a so-called Radio Quiet Zone). The large number of telescopes will give the SKA unprecedented precision. “As we speak, the prototype telescope is being built, and is expected to be completed in the autumn. It will be very interesting to see what the data will tell us, once it is up – not to mention the future data of the entire array”, says Sebastian.

See the full article here .

five-ways-keep-your-child-safe-school-shootings

Stem Education Coalition

Niels Bohr Institute (Danish: Niels Bohr Institutet) is a research institute of the University of Copenhagen. The research of the institute spans astronomy, geophysics, nanotechnology, particle physics, quantum mechanics and biophysics.

The Institute was founded in 1921, as the Institute for Theoretical Physics of the University of Copenhagen, by the Danish theoretical physicist Niels Bohr, who had been on the staff of the University of Copenhagen since 1914, and who had been lobbying for its creation since his appointment as professor in 1916. On the 80th anniversary of Niels Bohr’s birth – October 7, 1965 – the Institute officially became The Niels Bohr Institute.[1] Much of its original funding came from the charitable foundation of the Carlsberg brewery, and later from the Rockefeller Foundation.[2]

During the 1920s, and 1930s, the Institute was the center of the developing disciplines of atomic physics and quantum physics. Physicists from across Europe (and sometimes further abroad) often visited the Institute to confer with Bohr on new theories and discoveries. The Copenhagen interpretation of quantum mechanics is named after work done at the Institute during this time.

On January 1, 1993 the institute was fused with the Astronomic Observatory, the Ørsted Laboratory and the Geophysical Institute. The new resulting institute retained the name Niels Bohr Institute.

The University of Copenhagen (UCPH) (Danish: Københavns Universitet) is the oldest university and research institution in Denmark. Founded in 1479 as a studium generale, it is the second oldest institution for higher education in Scandinavia after Uppsala University (1477). The university has 23,473 undergraduate students, 17,398 postgraduate students, 2,968 doctoral students and over 9,000 employees. The university has four campuses located in and around Copenhagen, with the headquarters located in central Copenhagen. Most courses are taught in Danish; however, many courses are also offered in English and a few in German. The university has several thousands of foreign students, about half of whom come from Nordic countries.

The university is a member of the International Alliance of Research Universities (IARU), along with University of Cambridge, Yale University, The Australian National University, and UC Berkeley, amongst others. The 2016 Academic Ranking of World Universities ranks the University of Copenhagen as the best university in Scandinavia and 30th in the world, the 2016-2017 Times Higher Education World University Rankings as 120th in the world, and the 2016-2017 QS World University Rankings as 68th in the world. The university has had 9 alumni become Nobel laureates and has produced one Turing Award recipient

From U Wisconsin IceCube Collaboration: A Flock of Articles on NSF Grant to Upgrade IceCube

U Wisconsin ICECUBE neutrino detector at the South Pole

From From U Wisconsin IceCube Collaboration

From U Wisconsin: “UW lab gears up for another Antarctic drilling campaign”

With news that the National Science Foundation (NSF) and international partners will support an upgrade to the IceCube neutrino detector at the South Pole, the UW–Madison lab that built the novel drill used to bore mile-deep holes in the Antarctic ice is gearing up for another drilling campaign.

The UW’s Physical Sciences Laboratory (PSL), which specializes in making customized equipment for UW–Madison researchers, will once again lead drilling operations. The $37 million upgrade announced this week (July 16, 2019) will expand the IceCube detector by adding seven new strings of 108 optical modules each to study the basic properties of neutrinos, phantom-like particles that emanate from black holes and exploding stars, but that also cascade through Earth’s atmosphere as a result of colliding subatomic particles.

“It takes a crew of 30 people to run this 24/7. It’s the people that make it work,” says Bob Paulos, director of the Physical Sciences Lab. Photo: Bryce Richter

See the full article here .

From U Wisconsin: “IceCube: Antarctic neutrino detector to get $37 million upgrade”

The IceCube Neutrino Observatory is located at NSF’s Amundsen-Scott South Pole Station. Management and operation of the observatory is through the Wisconsin IceCube Particle Astrophysics Center at UW–Madison. Raffaela Busse, IceCube / NSF

IceCube, the Antarctic neutrino detector that in July of 2018 helped unravel one of the oldest riddles in physics and astronomy — the origin of high-energy neutrinos and cosmic rays — is getting an upgrade.

This month, the National Science Foundation (NSF) approved $23 million in funding to expand the detector and its scientific capabilities. Seven new strings of optical modules will be added to the 86 existing strings, adding more than 700 new, enhanced optical modules to the 5,160 sensors already embedded in the ice beneath the geographic South Pole.

The upgrade, to be installed during the 2022–23 polar season, will receive additional support from international partners in Japan and Germany as well as from Michigan State University and the University of Wisconsin–Madison. Total new investment in the detector will be about $37 million.

See the full article here .

From Niels Bohr Institute: “A new Upgrade for the IceCube detector”

Illustration of the IceCube laboratory under the South Pole. The sensors detecting neutrinos are attached to the strings lowered into the ice. The upgrade will take place in the Deep Core area. Illustration: IceCube/NSF

Neutrino Research:

The IceCube Neutrino Observatory in Antarctica is about to get a significant upgrade. This huge detector consists of 5,160 sensors embedded in a 1x1x1 km volume of glacial ice deep beneath the geographic South Pole. The purpose of the installation is to detect neutrinos, the “ghost particles” of the Universe. The IceCube Upgrade will add more than 700 new and enhanced optical sensors in the deepest, purest ice, greatly improving the observatory’s ability to measure low-energy neutrinos produced in the Earth’s atmosphere. The research in neutrinos at the Niels Bohr Institute, University of Copenhagen is led by Associate Professor Jason Koskinen

See the full article here .

From Michigan State University: “Upgrade for neutrino detector, thanks to NSF grant”

The IceCube Neutrino Observatory, the Antarctic detector that identified the first likely source of high-energy neutrinos and cosmic rays, is getting an upgrade. Courtesy of IceCube

The IceCube Neutrino Observatory, the Antarctic detector that identified the first likely source of high-energy neutrinos and cosmic rays, is getting an upgrade.

The National Science Foundation is upgrading the IceCube detector, extending its scientific capabilities to lower energies, and bridging IceCube to smaller neutrino detectors worldwide. The upgrade will insert seven strings of optical modules at the bottom center of the 86 existing strings, adding more than 700 new, enhanced optical modules to the 5,160 sensors already embedded in the ice beneath the geographic South Pole.

The upgrade will include two new types of sensor modules, which will be tested for a ten-times-larger future extension of IceCube – IceCube-Gen2. The modules to be deployed in this first extension will be two to three times more sensitive than the ones that make up the current detector. This is an important benefit for neutrino studies, but it becomes even more relevant for planning the larger IceCube-Gen2.

The $37 million extension, to be deployed during the 2022-23 polar field season, has now secured $23 million in NSF funding. Last fall, the upgrade office was set up, thanks to initial funding from NSF and additional support from international partners in Japan and Germany as well as from Michigan State University and the University of Wisconsin-Madison.

See the full article here .

From U Wisconsin IceCube: “The IceCube Upgrade: An international effort”

The IceCube Upgrade project is an international collaboration made possible not only by support from the National Science Foundation but also thanks to significant contributions from partner institutions in the U.S. and around the world. Our national and international collaborators play a huge role in manufacturing new sensors, developing firmware, and much more. Learn more about a few of our partner institutions below.

The Chiba University group poses with one of the new D-Egg optical detectors. Credit: Chiba University

Chiba University is responsible for the new D-Egg optical detectors, 300 of which will be deployed on the new Upgrade strings. A D-Egg is 30 percent smaller than the original IceCube DOM, but its photon detection effective area is twice as large thanks to two 8-inch PMTs in the specially designed egg-shaped vessel made of UV-transparent glass. Its up-down symmetric detection efficiency is expected to improve our precision for measuring Cherenkov light from neutrino interactions. The newly designed flasher devices in the D-Egg will also give a better understanding of optical characteristics in glacial ice to improve the resolution of arrival directions of cosmic neutrinos.

See the full article here .

From DESY: “Neutrino observatory IceCube receives significant upgrade”

Deep down in the perpetual ice of Antarctica IceCube watches out for a faint bluish glow that indicates a rare collision of a cosmic neutrino within the ice. Artist’s concept: DESY, Science Communication Lab

Particle detector at the South Pole will be expanded to comprise a neutrino laboratory

The international neutrino observatory IceCube at the South Pole will be considerably expanded in the coming years. In addition to the existing 5160 sensors, a further 700 optical modules will be installed in the perpetual ice of Antarctica. The National Science Foundation in the USA has approved 23 million US dollars for the expansion. The Helmholtz Centres DESY and Karlsruhe Institute of Technology (KIT) are supporting the construction of 430 new optical modules with a total of 5.7 million euros (6.4 million US dollars), which will turn the observatory into a neutrino laboratory. IceCube, for which Germany with a total of nine participating universities and the two Helmholtz Centres is the most important partner after the USA, had published convincing indications last year of a first source of high-energy neutrinos from the cosmos.

See the full article here .

See the full articles above .

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Please help promote STEM in your local schools.

Stem Education Coalition
IceCube is a particle detector at the South Pole that records the interactions of a nearly massless sub-atomic particle called the neutrino. IceCube searches for neutrinos from the most violent astrophysical sources: events like exploding stars, gamma ray bursts, and cataclysmic phenomena involving black holes and neutron stars. The IceCube telescope is a powerful tool to search for dark matter, and could reveal the new physical processes associated with the enigmatic origin of the highest energy particles in nature. In addition, exploring the background of neutrinos produced in the atmosphere, IceCube studies the neutrinos themselves; their energies far exceed those produced by accelerator beams. IceCube is the world’s largest neutrino detector, encompassing a cubic kilometer of ice.

IceCube employs more than 5000 detectors lowered on 86 strings into almost 100 holes in the Antarctic ice NSF B. Gudbjartsson, IceCube Collaboration

Lunar Icecube

IceCube DeepCore annotated

IceCube PINGU annotated

DM-Ice II at IceCube annotated

From Niels Bohr Institute at University of Copenhagen: “Greenland Telescope to image black holes by moving onto the Greenland ice sheet”

University of Copenhagen

From Niels Bohr Institute

10 April 2019

Marianne Vestergaard
Associate Professor, DARK, Niels Bohr Institute, University of Copenhagen
mvester@nbi.ku.dk
Phone: +45 35 32 59 09

Scientists from the Niels Bohr Institute, University of Copenhagen, will soon be able to participate in the “Event Horizon Telescope” (EHT) with the Greenland Telescope (GLT). The GLT will become part of a global network of radio telescopes designed to get the first images of black holes.

NRAO/CfA Greenland Telescope will be moved to the Summit of the ice sheet during the summer of 2021, reaching an altitude of approx. 3000 meters above sea level, where the clear, dry and cold climate will offer better observing conditions. Photo: Greenlandtelescope.dk

How do you take a picture of something that emits no light?

It’s hard to get an image of a black hole. They are the darkest objects in the universe because their gravity is so intense that no light can escape them, and their tremendous density makes them very small in spite of their enormous mass. To overcome these problems, the experiment is targeting much larger black holes than normal, namely so-called supermassive black holes, millions or billions of times more massive than the sun, as well as distributing the network of telescopes across the Globe to maximise the resolution of the image. It is possible to detect the black hole because the EHT can image the “shadow” of the black hole against a bright background of hot material near it.

While black holes have been theoretically expected for the best part of a century, the first conclusive evidence for the existence of black holes was only obtained in 2015, when gravitational waves from a merger of two (smaller) black holes were detected. However, so far, no one has ever managed to get an image of a black hole because they are so small and so dark. In the center of almost every galaxy in the Universe there is a compact and supermassive object that astronomers believe to be supermassive black holes, vastly more massive than the merging black holes detected in 2015. But the final evidence is still lacking that these concentrations of mass in the hearts of galaxies are actually black holes. By detecting and creating an image of the black hole, viewed in contrast against the powerful radiation from the gas being drawn into the hole, researchers can confirm that the compact object doesn’t have a surface to reflect any light, and that light behaves in the warped way that we expect from the theory of general relativity near a black hole and its strong gravitational field.

[Supermassive black hole at Messier 87 was successfully imaged by the Event Horizon Telescope in 2107

In April of 2017, all 8 of the telescopes/telescope arrays associated with the Event Horizon Telescope pointed at Messier 87. This is what a supermassive black hole looks like, where the event horizon is clearly visible. Event Horizon Telescope collaboration et al.]

Danish access to the data EHT will be producing

A press conference was held at DTU Space on Wednesday 10. April, where the first results from the EHT consortium were presented. With the addition of the Greenland Telescope, the precision and sensitivity of the images will substantially increase, and at the same time, Danish researchers will gain access to the EHT.

“ It is fascinating to know that our generation is not only the first to learn, via detections of gravitational waves, that black holes really exist. We will also be the first to see what they look like!” says Marianne Vestergaard, associate professor at DARK, the Niels Bohr Institute and she continues: “We, the researchers, are thrilled. These excellent results from the Event Horizon Telescope show us the remarkable things that a dedicated, global collaboration can achieve, and it reveals the great potential there is for exploring the complex parts of our universe of which black holes are a manifest. It is particularly enjoyable that we, the Danish researchers, will be able to contribute to this new type of telescope on the front line.

The Summit of the icecap will be the new home for the Greenland Telescope

Greenland Telescope will be moved to the Summit of the ice sheet, reaching an altitude of approx. 3000 meters above sea level. The air is much drier, and the clear, dry and cold climate will offer better observing conditions compared to the humid air along the coast. The complicated task of moving the telescope across the ice is planned to take place during the summer of 2021. Researchers from the Niels Bohr Institute’s Physics of Ice, Climate and Earth section are assisting in that operation.

See the full article here .

five-ways-keep-your-child-safe-school-shootings

Stem Education Coalition

Niels Bohr Institute (Danish: Niels Bohr Institutet) is a research institute of the University of Copenhagen. The research of the institute spans astronomy, geophysics, nanotechnology, particle physics, quantum mechanics and biophysics.

The Institute was founded in 1921, as the Institute for Theoretical Physics of the University of Copenhagen, by the Danish theoretical physicist Niels Bohr, who had been on the staff of the University of Copenhagen since 1914, and who had been lobbying for its creation since his appointment as professor in 1916. On the 80th anniversary of Niels Bohr’s birth – October 7, 1965 – the Institute officially became The Niels Bohr Institute.[1] Much of its original funding came from the charitable foundation of the Carlsberg brewery, and later from the Rockefeller Foundation.[2]

During the 1920s, and 1930s, the Institute was the center of the developing disciplines of atomic physics and quantum physics. Physicists from across Europe (and sometimes further abroad) often visited the Institute to confer with Bohr on new theories and discoveries. The Copenhagen interpretation of quantum mechanics is named after work done at the Institute during this time.

On January 1, 1993 the institute was fused with the Astronomic Observatory, the Ørsted Laboratory and the Geophysical Institute. The new resulting institute retained the name Niels Bohr Institute.

The University of Copenhagen (UCPH) (Danish: Københavns Universitet) is the oldest university and research institution in Denmark. Founded in 1479 as a studium generale, it is the second oldest institution for higher education in Scandinavia after Uppsala University (1477). The university has 23,473 undergraduate students, 17,398 postgraduate students, 2,968 doctoral students and over 9,000 employees. The university has four campuses located in and around Copenhagen, with the headquarters located in central Copenhagen. Most courses are taught in Danish; however, many courses are also offered in English and a few in German. The university has several thousands of foreign students, about half of whom come from Nordic countries.

The university is a member of the International Alliance of Research Universities (IARU), along with University of Cambridge, Yale University, The Australian National University, and UC Berkeley, amongst others. The 2016 Academic Ranking of World Universities ranks the University of Copenhagen as the best university in Scandinavia and 30th in the world, the 2016-2017 Times Higher Education World University Rankings as 120th in the world, and the 2016-2017 QS World University Rankings as 68th in the world. The university has had 9 alumni become Nobel laureates and has produced one Turing Award recipient

From Niels Bohr Institute: “Long-distance quantum information exchange – success at the nanoscale”

University of Copenhagen

From Niels Bohr Institute

At the Niels Bohr Institute, University of Copenhagen, researchers have realized the swap of electron spins between distant quantum dots. The discovery brings us a step closer to future applications of quantum information, as the tiny dots have to leave enough room on the microchip for delicate control electrodes. The distance between the dots has now become big enough for integration with traditional microelectronics and perhaps, a future quantum computer. The result is achieved via a multinational collaboration with Purdue University and the University of Sydney, Australia, now published in Nature Communications.

Size matters in quantum information exchange even on the nanometer scale.

Quantum information can be stored and exchanged using electron spin states. The electrons’ charge can be manipulated by gate-voltage pulses, which also controls their spin. It was believed that this method can only be practical if quantum dots touch each other; if squeezed too close together the spins will react too violently, if placed too far apart the spins will interact far too slowly. This creates a dilemma, because if a quantum computer is ever going to see the light of day, we need both, fast spin exchange and enough room around quantum dots to accommodate the pulsed gate electrodes.

Normally, the left and right dots in the linear array of quantum dots (Illustration 1) are too far apart to exchange quantum information with each other. Frederico Martins, postdoc at UNSW, Sydney, Australia, explains: “We encode quantum information in the electrons’ spin states, which have the desirable property that they don’t interact much with the noisy environment, making them useful as robust and long-lived quantum memories. But when you want to actively process quantum information, the lack of interaction is counterproductive – because now you want the spins to interact!” What to do? You can’t have both long lived information and information exchange – or so it seems. “We discovered that by placing a large, elongated quantum dot between the left dots and right dots, it can mediate a coherent swap of spin states, within a billionth of a second, without ever moving electrons out of their dots. In other words, we now have both fast interaction and the necessary space for the pulsed gate electrodes ”, says Ferdinand Kuemmeth, associate professor at the Niels Bohr Institute.

Researchers at the Niels Bohr Institute cooled a chip containing a large array of spin qubits below -273 Celsius. To manipulate individual electrons within the quantum-dot array, they applied fast voltage pulses to metallic gate electrodes located on the surface of the gallium-arsenide crystal (see scanning electron micrograph). Because each electron also carries a quantum spin, this allows quantum information processing based on the array’s spin states (the arrows on the graphic illustration). During the mediated spin exchange, which only took a billionth of a second, two correlated electron pairs were coherently superposed and entangled over five quantum dots, constituting a new world record within the community.

Collaborations are an absolute necessity, both internally and externally.

The collaboration between researchers with diverse expertise was key to success. Internal collaborations constantly advance the reliability of nanofabrication processes and the sophistication of low-temperature techniques. In fact, at the Center for Quantum Devices, major contenders for the implementation of solid-state quantum computers are currently intensely studied, namely semiconducting spin qubits, superconducting gatemon qubits, and topological Majorana qubits.

All of them are voltage-controlled qubits, allowing researchers to share tricks and solve technical challenges together. But Kuemmeth is quick to add that “all of this would be futile if we didn’t have access to extremely clean semiconducting crystals in the first place”. Michael Manfra, Professor of Materials Engineering, agrees: “Purdue has put a lot of work into understanding the mechanisms that lead to quiet and stable quantum dots. It is fantastic to see this work yield benefits for Copenhagen’s novel qubits”.

The theoretical framework of the discovery is provided by the University of Sydney, Australia. Stephen Bartlett, a professor of quantum physics at the University of Sydney, said: “What I find exciting about this result as a theorist, is that it frees us from the constraining geometry of a qubit only relying on its nearest neighbours”. His team performed detailed calculations, providing the quantum mechanical explanation for the counterintuitive discovery.

Overall, the demonstration of fast spin exchange constitutes not only a remarkable scientific and technical achievement, but may have profound implications for the architecture of solid-state quantum computers. The reason is the distance: “If spins between non-neighboring qubits can be controllably exchanged, this will allow the realization of networks in which the increased qubit-qubit connectivity translates into a significantly increased computational quantum volume”, predicts Kuemmeth.

See the full article here .

five-ways-keep-your-child-safe-school-shootings

Stem Education Coalition

Niels Bohr Institute (Danish: Niels Bohr Institutet) is a research institute of the University of Copenhagen. The research of the institute spans astronomy, geophysics, nanotechnology, particle physics, quantum mechanics and biophysics.

The Institute was founded in 1921, as the Institute for Theoretical Physics of the University of Copenhagen, by the Danish theoretical physicist Niels Bohr, who had been on the staff of the University of Copenhagen since 1914, and who had been lobbying for its creation since his appointment as professor in 1916. On the 80th anniversary of Niels Bohr’s birth – October 7, 1965 – the Institute officially became The Niels Bohr Institute.[1] Much of its original funding came from the charitable foundation of the Carlsberg brewery, and later from the Rockefeller Foundation.[2]

During the 1920s, and 1930s, the Institute was the center of the developing disciplines of atomic physics and quantum physics. Physicists from across Europe (and sometimes further abroad) often visited the Institute to confer with Bohr on new theories and discoveries. The Copenhagen interpretation of quantum mechanics is named after work done at the Institute during this time.

On January 1, 1993 the institute was fused with the Astronomic Observatory, the Ørsted Laboratory and the Geophysical Institute. The new resulting institute retained the name Niels Bohr Institute.

The University of Copenhagen (UCPH) (Danish: Københavns Universitet) is the oldest university and research institution in Denmark. Founded in 1479 as a studium generale, it is the second oldest institution for higher education in Scandinavia after Uppsala University (1477). The university has 23,473 undergraduate students, 17,398 postgraduate students, 2,968 doctoral students and over 9,000 employees. The university has four campuses located in and around Copenhagen, with the headquarters located in central Copenhagen. Most courses are taught in Danish; however, many courses are also offered in English and a few in German. The university has several thousands of foreign students, about half of whom come from Nordic countries.

The university is a member of the International Alliance of Research Universities (IARU), along with University of Cambridge, Yale University, The Australian National University, and UC Berkeley, amongst others. The 2016 Academic Ranking of World Universities ranks the University of Copenhagen as the best university in Scandinavia and 30th in the world, the 2016-2017 Times Higher Education World University Rankings as 120th in the world, and the 2016-2017 QS World University Rankings as 68th in the world. The university has had 9 alumni become Nobel laureates and has produced one Turing Award recipient

From Niels Bohr Institute: “Catching a glimpse of the gamma-ray burst engine”

University of Copenhagen

From Niels Bohr Institute

16 January 2019

A gamma-ray burst registered in December of 2017 turns out to be “one of the closets GRBs ever observed”. The discovery is featured in Nature [co-authors are: Jonathan Selsing, Johan Fynbo, Jens Hjorth and Daniele Malesani from the Niels Bohr Institute, Giorgos Leloudas from the Technical University of Denmark and Kasper Heintz from University of Iceland] – and it has yielded valuable information about the formation of the most luminous phenomenon in the universe. Scientists from the Niels Bohr Institute at the University of Copenhagen helped carrying out the analysis.

Jonatan Selsing frequently receives text messages from a certain sender regarding events in space. It happens all around the clock, and when his cell phone goes ‘beep’ he knows that yet another gamma-ray burst (GRB) notification has arrived. Which, routinely, raises the question: Does this information – originating from the death of a massive star way back, millions if not billions of years ago – merit further investigation?

The development in a dying star until the gamma ray burst forms. Attribution: National Science Foundation

Gamma ray bursts – bright signals from space

“GRBs represent the brightest phenomenon known to science – the luminous intensity of a single GRB may in fact exceed that of all stars combined! And at the same time GRBs – which typically last just a couple of seconds – represent one of the best sources available, when it comes to gleaning information about the initial stages of our universe”, explains Jonatan Selsing.

He is astronomer and postdoc at Cosmic Dawn Center at the Niels Bohr Institute in Copenhagen. And he is one of roughly 100 astronomers in a global network set up to ensure that all observational resources needed can be instantaneously mobilized when the GRB-alarm goes off.

Quick action must be taken when a gamma ray burst is registered

The alarm sits on board the international Swift-telescope which was launched in 2004 – and has orbited Earth ever since with the mission of registering GRBs.

NASA Neil Gehrels Swift Observatory

Swift is capable of constantly observing one third of the night sky, and when the telescope registers a GRB – which on average happens a couple of times per week – it will immediately text the 100 astronomers. The message will tell where in space the GRB has been observed – whereupon the astronomer on duty must make a here-and-now decision:

Is there reason to assume that this specific GRB is of such importance that we should ask the VLT-telescope in Chile to immediately take a closer look at it?

ESO VLT at Cerro Paranal in the Atacama Desert, •ANTU (UT1; The Sun ),
•KUEYEN (UT2; The Moon ),
•MELIPAL (UT3; The Southern Cross ), and
•YEPUN (UT4; Venus – as evening star).
elevation 2,635 m (8,645 ft) from above Credit J.L. Dauvergne & G. Hüdepohl atacama photo,

Or should we consider the information from Swift sheer routine, and leave it at that?

On December 5th 2017 – just around 09 o’clock in the morning Copenhagen time – the GRB-alarm went off. Luca Izzo, Italian astronomer, was on duty – and Izzo did not harbor the slightest doubt: He right away alerted VLT – the Very Large Telescope in Chile – which is run by 11 European countries, including Germany, Great Britain, Italy, France, Sweden and Denmark.

At that time it was early in the morning in Chile – 05 o’clock – and dawn was rapidly approaching, tells Jonatan Selsing: “For VLT to take a closer look at the GRB, action had to be taken immediately – since the telescope is only capable of working against a background of the night sky. And fortunately this was exactly what happened, when Izzo contacted VLT”.

This is also why Luca Izzo is listed as first author of the scientific article describing this GRB – an article which has just been published in Nature, one of the world’s most influential scientific journals. The article is based on analyses of the VLT-recordings, and the recordings reveal that this GRB in more than one respect can be described as unusual, says Jonatan Selsing:

“Not least because this is one of the closest GRBs ever observed. GRB171205A – which has since become the official name of this gamma-ray burst – originated a mere 500 million years ago, and has ever since traveled through space at the speed of light, i.e. at 300.000 kilometer per second”. Working closely with a number of his colleagues at the Niels Bohr Institute, Jonatan Selsing contributed to the Nature-article with an analysis which – put simply – represents “a glimpse” of the very engine behind a gamma-ray burst.

Gamma ray bursts are the results of violent events in space

When a massive star – rotating at very high speed – dies, its core may collapse, thus creating a so-called black hole.

This computer-simulated image of a supermassive black hole at the core of a galaxy. Credit NASA, ESA, and D. Coe, J. Anderson

A massive star may weigh up to 300 times more than the Sun, and due to combustion the star is transforming light elements to heavier elements. This process, which takes place in the core, is the source of energy not only in massive stars, but in all stars.

Ashes – the by-product of combustion – may over time become such a heavy load that a massive star can no longer carry its own weight, which is why it finally collapses. When that happens, the outer layers will gradually fall towards the core – towards the black hole – at which point a disc is formed.

Due to the star’s rotation, the disc will function as a dynamo creating a gigantic magnetic field – which will emit two jets, both going away from the black hole at a velocity close to the speed of light. During this process, the dying star is also releasing – spewing – matter, which lightens up with extreme intensity.
This light is the very gamma-ray burst – the GRB itself. And the matter which is released from the center of the star is set free in the form of a so-called jet cocoon.

The gamma ray burst confirms our assumptions about the elements stars produce

“One of the unique features of GRB171205A is that it proved possible to determine which elements this gamma-ray burst released via the jet cocoon 500 million years ago. That was measured here at the Niels Bohr Institute, and that is our contribution to the Nature-article. These measurements were carried out via X-shooter – an extremely sensitive piece of equipment mounted on the VLT-telescope”, says Jonatan Selsing.

X-shooter analyzed the VLT-footage of the gamma-ray burst – and this analysis led to the conclusion that the jet cocoon from GRB171205A contained iron, cobalt and nickel which had formed in the center of the star, explains Jonatan Selsing:

“This corresponds with our theoretical expectations – and therefore also corroborates our model for a star-collapse of this magnitude. Being able to establish that it actually did happen in this way is, however, really special. That’s when you get a glimpse of the very engine behind a gamma-ray burst”.

ESO X-shooter on VLT on UT2 at Cerro Paranal, Chile

ESO X-shooter on VLT on UT2 at Cerro Paranal, Chile

See the full article here .

five-ways-keep-your-child-safe-school-shootings

Stem Education Coalition

The Niels Bohr Institute (Danish: Niels Bohr Institutet) is a research institute of the University of Copenhagen. The research of the institute spans astronomy, geophysics, nanotechnology, particle physics, quantum mechanics and biophysics.

The Institute was founded in 1921, as the Institute for Theoretical Physics of the University of Copenhagen, by the Danish theoretical physicist Niels Bohr, who had been on the staff of the University of Copenhagen since 1914, and who had been lobbying for its creation since his appointment as professor in 1916. On the 80th anniversary of Niels Bohr’s birth – October 7, 1965 – the Institute officially became The Niels Bohr Institute.[1] Much of its original funding came from the charitable foundation of the Carlsberg brewery, and later from the Rockefeller Foundation.[2]

During the 1920s, and 1930s, the Institute was the center of the developing disciplines of atomic physics and quantum physics. Physicists from across Europe (and sometimes further abroad) often visited the Institute to confer with Bohr on new theories and discoveries. The Copenhagen interpretation of quantum mechanics is named after work done at the Institute during this time.

On January 1, 1993 the institute was fused with the Astronomic Observatory, the Ørsted Laboratory and the Geophysical Institute. The new resulting institute retained the name Niels Bohr Institute.

The University of Copenhagen (UCPH) (Danish: Københavns Universitet) is the oldest university and research institution in Denmark. Founded in 1479 as a studium generale, it is the second oldest institution for higher education in Scandinavia after Uppsala University (1477). The university has 23,473 undergraduate students, 17,398 postgraduate students, 2,968 doctoral students and over 9,000 employees. The university has four campuses located in and around Copenhagen, with the headquarters located in central Copenhagen. Most courses are taught in Danish; however, many courses are also offered in English and a few in German. The university has several thousands of foreign students, about half of whom come from Nordic countries.

The university is a member of the International Alliance of Research Universities (IARU), along with University of Cambridge, Yale University, The Australian National University, and UC Berkeley, amongst others. The 2016 Academic Ranking of World Universities ranks the University of Copenhagen as the best university in Scandinavia and 30th in the world, the 2016-2017 Times Higher Education World University Rankings as 120th in the world, and the 2016-2017 QS World University Rankings as 68th in the world. The university has had 9 alumni become Nobel laureates and has produced one Turing Award recipient

From Niels Bohr Institute: “The state of the Early Universe: The beginning was fluid”

University of Copenhagen

From Niels Bohr Institute

04 October 2018

You Zhou, Postdoc
Experimental Particle Physics
Niels Bohr Institute, University of Copenhagen
Email: you.zhou@nbi.ku.dk
Phone: +45 35 33 12 82

Scientists from the Niels Bohr Institute, University of Copenhagen, and their colleagues from the international ALICE collaboration recently collided Xenon nuclei, in order to gain new insights into the properties of the Quark-Gluon Plasma (the QGP) – the matter that the universe consisted of up to a microsecond after the Big Bang.

The QGP, as the name suggests, is a special state consisting of the fundamental particles, the quarks, and the particles that bind the quarks together, the gluons. The result was obtained using the ALICE experiment at the 27 km long superconducting Large Hadron Collider (LHC) at CERN. The result is now published in Physics Letters B.

Fig. 1 [Left] An event from the first Xenon-Xenon collision at the Large Hadron Collider at the top energy of the Large Hadron Collider (5.44 TeV ) registered by ALICE [credit: ALICE]. Every colored track (The blue lines) corresponds to the trajectory of a charged particle produced in a single collision; [Right] formation of anisotropic flow in relativistic heavy-ion collisions due to the geometry of the hot and dense overlap zone (shown in red color).

The beginning was a liquid state of affairs

The particle physicists at the Niels Bohr Institute have obtained new results, working with the LHC, replacing the lead-ions, usually used for collisions, with Xenon-ions. Xenon is a “smaller” atom with fewer nucleons in its nucleus. When colliding ions, the scientists create a fireball that recreates the initial conditions of the universe at temperatures in excess of several thousand billion degrees. In contrast to the Universe, the lifetime of the droplets of QGP produced in the laboratory is ultra short, a fraction of a second (In technical terms, only about 10-22 seconds). Under these conditions the density of quarks and gluons is very large and a special state of matter is formed in which quarks and gluons are quasi-free (dubbed the strongly interacting QGP). The experiments reveal that the primordial matter, the instant before atoms formed, behaves like a liquid that can be described in terms of hydrodynamics.

How to approach “the moment of creation”

“One of the challenges we are facing is that, in heavy ion collisions, only the information of the final state of the many particles which are detected by the experiments are directly available – but we want to know what happened in the beginning of the collision and first few moments afterwards”, You Zhou, Postdoc in the research group Experimental Subatomic Physics at the Niels Bohr Institute, explains. “We have developed new and powerful tools to investigate the properties of the small droplet of QGP (early universe) that we create in the experiments”. They rely on studying the spatial distribution of the many thousands of particles that emerge from the collisions when the quarks and gluons have been trapped into the particles that the Universe consists of today. This reflects not only the initial geometry of the collision, but is sensitive to the properties of the QGP. It can be viewed as a hydrodynamical flow.” The transport properties of the Quark-Gluon Plasma will determine the final shape of the cloud of produced particles, after the collision, so this is our way of approaching the moment of QGP creation itself”, You Zhou says.

Two main ingredients in the soup: Geometry and viscosity

The degree of anisotropic particle distribution – the fact that there are more particles in certain directions – reflects three main pieces of information: The first is, as mentioned, the initial geometry of the collision. The second is the conditions prevailing inside the colliding nucleons. The third is the shear viscosity of the Quark-Gluon Plasma itself. Shear viscosity expresses the liquid’s resistance to flow, a key physical property of the matter created. “It is one of the most important parameters to define the properties of the Quark-Gluon Plasma”, You Zhou explains, “ because it tells us how strongly the gluons bind the quarks together “.

The Xenon experiments yield vital information to challenge theories and models

“With the new Xenon collisions, we have put very tight constraints on the theoretical models that describe the outcome. No matter the initial conditions, Lead or Xenon, the theory must be able to describe them simultaneously. If certain properties of the viscosity of the quark gluon plasma are claimed, the model has to describe both sets of data at the same time, says You Zhou. The possibilities of gaining more insight into the actual properties of the “primordial soup” are thus enhanced significantly with the new experiments. The team plans to collide other nuclear systems to further constrain the physics, but this will require significant development of new LHC beams.

Science is not a lonesome affair, far from it

“This is a collaborative effort within the large international ALICE Collaboration, consisting of more than 1800 researchers from 41 countries and 178 institutes”. You Zhou emphasised.

See the full article here .

five-ways-keep-your-child-safe-school-shootings

Stem Education Coalition

The Niels Bohr Institute (Danish: Niels Bohr Institutet) is a research institute of the University of Copenhagen. The research of the institute spans astronomy, geophysics, nanotechnology, particle physics, quantum mechanics and biophysics.

The Institute was founded in 1921, as the Institute for Theoretical Physics of the University of Copenhagen, by the Danish theoretical physicist Niels Bohr, who had been on the staff of the University of Copenhagen since 1914, and who had been lobbying for its creation since his appointment as professor in 1916. On the 80th anniversary of Niels Bohr’s birth – October 7, 1965 – the Institute officially became The Niels Bohr Institute.[1] Much of its original funding came from the charitable foundation of the Carlsberg brewery, and later from the Rockefeller Foundation.[2]

During the 1920s, and 1930s, the Institute was the center of the developing disciplines of atomic physics and quantum physics. Physicists from across Europe (and sometimes further abroad) often visited the Institute to confer with Bohr on new theories and discoveries. The Copenhagen interpretation of quantum mechanics is named after work done at the Institute during this time.

On January 1, 1993 the institute was fused with the Astronomic Observatory, the Ørsted Laboratory and the Geophysical Institute. The new resulting institute retained the name Niels Bohr Institute.

The University of Copenhagen (UCPH) (Danish: Københavns Universitet) is the oldest university and research institution in Denmark. Founded in 1479 as a studium generale, it is the second oldest institution for higher education in Scandinavia after Uppsala University (1477). The university has 23,473 undergraduate students, 17,398 postgraduate students, 2,968 doctoral students and over 9,000 employees. The university has four campuses located in and around Copenhagen, with the headquarters located in central Copenhagen. Most courses are taught in Danish; however, many courses are also offered in English and a few in German. The university has several thousands of foreign students, about half of whom come from Nordic countries.

The university is a member of the International Alliance of Research Universities (IARU), along with University of Cambridge, Yale University, The Australian National University, and UC Berkeley, amongst others. The 2016 Academic Ranking of World Universities ranks the University of Copenhagen as the best university in Scandinavia and 30th in the world, the 2016-2017 Times Higher Education World University Rankings as 120th in the world, and the 2016-2017 QS World University Rankings as 68th in the world. The university has had 9 alumni become Nobel laureates and has produced one Turing Award recipient

From Niels Bohr Institute: “Boosting gravitational wave detectors with quantum tricks”

University of Copenhagen

From Niels Bohr Institute

03 September 2018
Eugene Polzik, professor and head of the Center for Quantum Optics, Quantop at the Niels Bohr Institute, University of Copenhagen
Phone: +45 2338 2045
Email: polzik@nbi.dk

Gravitational wave detectors: Niels Bohr Institute scientists are convinced they can expand space surveillance using a small glass cell filled with caesium atoms.

Eugene Polzik and Farid Khalili from LIGO collaboration and Moscow State University, have recently published in the scientific journal Physical Review Letters how they can improve gravitational wave detectors. Photo: Ola J. Joensen

A group of scientists from the Niels Bohr Institute (NBI) at the University of Copenhagen will soon start developing a new line of technical equipment in order to dramatically improve gravitational wave detectors.

Gravitational wave detectors are extremely sensitive and can e.g. register colliding neutron stars in space. Yet even higher sensitivity is sought for in order to expand our knowledge about the Universe, and the NBI-scientists are convinced that their equipment can improve the detectors, says Professor Eugene Polzik: “And we should be able to show proof of concept within approximately three years”.

If the NBI-scientists are able to improve the gravitational wave detectors as much as they “realistically expect can be done”, the detectors will be able to monitor and carry out measurements in an eight times bigger volume of space than what is currently possible, explains Eugene Polzik: “This will represent a truly significant extension”.

Polzik is head of Quantum Optics (Quantop) at NBI and he will spearhead the development of the tailor made equipment for gravitational wave detectors. The research – which is supported by the EU, the Eureka Network Projects and the US-based John Templeton Foundation with grants totaling DKK 10 million – will be carried out in Eugene Polzik’s lab at NBI.

A collision well noticed

News media all over the world shifted into overdrive in October of 2017 when it was confirmed that a large international team of scientists had indeed measured the collision of two neutron stars; an event which took place 140 million light years from Earth and resulted in the formation of a kilonova.

The international team of scientists – which also included experts from NBI – was able to confirm the collision by measuring gravitational waves from space – waves in the fabric of spacetime itself, moving at the speed of light. The waves were registered by three gravitational wave detectors: the two US-based LIGO-detectors and the European Virgo-detector in Italy.

VIRGO Gravitational Wave interferometer, near Pisa, Italy

Caltech/MIT Advanced aLigo Hanford, WA, USA installation

Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA

Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project

Gravitational waves. Credit: MPI for Gravitational Physics/W.Benger-Zib

ESA/eLISA the future of gravitational wave research

Skymap showing how adding Virgo to LIGO helps in reducing the size of the source-likely region in the sky. (Credit: Giuseppe Greco (Virgo Urbino group)

See also https://sciencesprings.wordpress.com/2017/10/16/from-ucsc-a-uc-santa-cruz-special-report-neutron-stars-gravitational-waves-and-all-the-gold-in-the-universe/

Caesium atoms contained in a spin-protecting cell are expected to enhance the sensitivity of Gravitational Waves Detectors. Photo: Ola J. Joensen

“These gravitational wave detectors represent by far the most sensitive measuring equipment man has yet manufactured – still the detectors are not as accurate as they could possibly be. And this is what we intend to improve”, says Professor Eugene Polzik.

How this can be done is outlined in an article which Eugene Polzik and a colleague, Farid Khalili from LIGO collaboration and Moscow State University, have recently published in the scientific journal Physical Review Letters. And this is not merely a theoretical proposal, says Eugene Polzik:

“We are convinced this will work as intended. Our calculations show that we ought to be able to improve the precision of measurements carried out by the gravitational wave detectors by a factor of two. And if we succeed, this will result in an increase by a factor of eight of the volume in space which gravitational wave detectors are able to examine at present”.

A small glass cell

In July of last year Eugene Polzik and his team at Quantop published a highly noticed article in Nature – and this work is actually the very foundation of their upcoming attempt to improve the gravitational wave detectors.

If laser light used to measure motion of a vibrating membrane (left) is first transmitted through an atom cloud (center) the measurement sensitivity can be better than standard quantum limits envisioned by Bohr and Heisenberg. Photo: Bastian Leonhardt Strube and Mads Vadsholt

The article in Nature centered on ‘fooling’ Heisenberg’s Uncertainty Principle, which basically says that you cannot simultaneously know the exact position and the exact speed of an object.

This has to do with the fact that observations conducted by shining light on an object inevitably will lead to the object being ‘kicked’ in random directions by photons, particles of light. This phenomenon is known as Quantum Back Action (QBA) and these random movements put a limit to the accuracy with which measurements can be carried out at the quantum level.

The article in Nature in the summer of 2017 made headlines because Eugene Polzik and his team were able to show that it is – to a large extent – actually possible to neutralize QBA.

And QBA is the very reason why gravitational wave detectors – that also operate with light, namely laser light – “are not as accurate as they could possibly be”, as professor Polzik says.

Put simply, it is possible to neutralize QBA if the light used to observe an object is initially sent through a ‘filter’. This was what the article in Nature described – and the ‘filter’ which the NBI-scientists at Quantop had developed and described consisted of a cloud of 100 million caesium atoms locked-up in a hermetically closed glass cell just one centimeter long, 1/3 of a millimeter high and 1/3 of a millimeter wide.

The principle behind this ‘filter’ is exactly what Polzik and his team are aiming to incorporate in gravitational wave detectors.

PhD student Tulio Brasil, postdoctoral fellow Michael Zugenmaier and Professor Eugene Polzik in front of the future site of the experiment. Foto: Ola J. Joensen

In theory one can optimize measurements of gravitational waves by switching to stronger laser light than the detectors in both Europe and USA are operating with. However, according to quantum mechanics, that is not an option, says Eugene Polzik:

“Switching to stronger laser light will just make a set of mirrors in the detectors shake more because Quantum Back Action will be caused by more photons. These mirrors are absolutely crucial, and if they start shaking, it will in fact increase inaccuracy”.

Instead, the NBI-scientists have come up with a plan based on the atomic ‘filter’ which they demonstrated in the Nature article: They will send the laser light by which the gravitational wave detectors operate through a tailor made version of the cell with the locked-up atoms, says Eugene Polzik: “And we hope that it will do the job”.

See the full article here .

five-ways-keep-your-child-safe-school-shootings

Stem Education Coalition

The Niels Bohr Institute (Danish: Niels Bohr Institutet) is a research institute of the University of Copenhagen. The research of the institute spans astronomy, geophysics, nanotechnology, particle physics, quantum mechanics and biophysics.

The Institute was founded in 1921, as the Institute for Theoretical Physics of the University of Copenhagen, by the Danish theoretical physicist Niels Bohr, who had been on the staff of the University of Copenhagen since 1914, and who had been lobbying for its creation since his appointment as professor in 1916. On the 80th anniversary of Niels Bohr’s birth – October 7, 1965 – the Institute officially became The Niels Bohr Institute.[1] Much of its original funding came from the charitable foundation of the Carlsberg brewery, and later from the Rockefeller Foundation.[2]

During the 1920s, and 1930s, the Institute was the center of the developing disciplines of atomic physics and quantum physics. Physicists from across Europe (and sometimes further abroad) often visited the Institute to confer with Bohr on new theories and discoveries. The Copenhagen interpretation of quantum mechanics is named after work done at the Institute during this time.

On January 1, 1993 the institute was fused with the Astronomic Observatory, the Ørsted Laboratory and the Geophysical Institute. The new resulting institute retained the name Niels Bohr Institute.

The University of Copenhagen (UCPH) (Danish: Københavns Universitet) is the oldest university and research institution in Denmark. Founded in 1479 as a studium generale, it is the second oldest institution for higher education in Scandinavia after Uppsala University (1477). The university has 23,473 undergraduate students, 17,398 postgraduate students, 2,968 doctoral students and over 9,000 employees. The university has four campuses located in and around Copenhagen, with the headquarters located in central Copenhagen. Most courses are taught in Danish; however, many courses are also offered in English and a few in German. The university has several thousands of foreign students, about half of whom come from Nordic countries.

The university is a member of the International Alliance of Research Universities (IARU), along with University of Cambridge, Yale University, The Australian National University, and UC Berkeley, amongst others. The 2016 Academic Ranking of World Universities ranks the University of Copenhagen as the best university in Scandinavia and 30th in the world, the 2016-2017 Times Higher Education World University Rankings as 120th in the world, and the 2016-2017 QS World University Rankings as 68th in the world. The university has had 9 alumni become Nobel laureates and has produced one Turing Award recipient

From Niels Bohr Institute: “New observations link gigantic star collisions to homeless short duration gamma ray bursts”

From Niels Bohr Institute

Neutron star collision:

Scientists from the Niels Bohr Institute, University of Copenhagen, have been involved in detecting a beam of light that provides a link between neutron star mergers and short duration gamma ray bursts. The result is now published in Nature Astronomy.

Artist’s impression of jets of material from first confirmed neutron star merger – Image copyright Mark Garlick/University of Warwick

Neutron stars are small, but extremely dense objects, only tens of kilometers across, but with the mass of a star. When they collide or merge, they produce enormous amounts of energy. It has been believed for some time that they are responsible for short bursts of gamma rays, a celestial phenomenon first discovered in the 1960s by cold war nuclear monitoring satellites. This new finding establishes that link much more clearly, and opens the way to use the hundreds of known short gamma ray bursts to study the mergers of neutron stars – so far, very rare phenomena.

What exactly is a “short duration gamma ray burst”?

Gamma ray bursts, we know now, are the signatures of extremely violent merger of two neutron stars. A quick burst of gamma rays is emitted milliseconds after the collision, and the bursts are observable from Earth. Hundreds of bursts have been detected to date, but it hasn’t been possible to conclusively link the observations to a source. The present study has used a now famous celestial event in 2017, to link such a burst to the merger of a neutron star. It made headlines when the gravitational wave event of 17 August 2017 – hence the name GW170817 – became the first gravitational waves to be positively identified with an astrophysical source — a neutron star merger. In ongoing investigations of the event, a team of scientists, including members from the Niels Bohr Institute, continued to monitor the source, and were rewarded with the first, confirmed sighting of a jet of material, the afterglow, still streaming out from the event.

Gravitational waves. Credit: MPI for Gravitational Physics/Werner Benger

The traces of a massive collision

The gravitational wave detection provides a wealth of unprecedented data: the masses of the merging objects, how they spin, the final mass of the merged remnant. However, light emitted at different frequencies from the event is also critical to understanding the merger. And there are two different sources of light, each of which provides unique information. The first is the prompt emission of high energy radiation lasting only milliseconds, which comes out immediately – in this case 1.7 seconds after the gravitational wave signal – the gamma ray burst. The second, the kilonova, emerges in the subsequent days, and has a much slower emission of optical and infrared light, which rises, and then fades. Currently, this is believed to be a radioactive fireball of ejected matter from the neutron star merger. GW170817 produced a gamma ray burst believed by some to have been dim because the earth was off the main axis. This study shows that the merger did indeed launch a jet, which we observed off-axis, and which was distinguishable from the optical light from the kilonova. This was done by detecting visible light from the afterglow months after the merger, characteristic of jet emission rather than kilonova emission. This provides the link between the jet-driven short gamma ray bursts and a neutron star merger. So now, the framework for understanding both GW170817 and hundreds of formerly “homeless” observations of short duration gamma ray bursts is far better established.

The bigger picture

Of particular interest is the question of the origin of the heaviest elements, which is still a matter of serious debate among scientists, with many now believing that the rare earth elements, as well gold and platinum, are created in these mergers and scattered into the universe. While the signature of such elements has yet to be clearly identified, as a result of this study, it may now be possible to get a better census of the number of neutron star mergers happening in the universe by using short gamma-ray bursts. Statistics for this much larger group of events may make it possible to work backwards and perhaps establish the properties of neutron star mergers as a whole.

Jens Hjorth, Johan Fynbo, Christa Gall, Bo Milvang-Jensen, and Darach Watson of the Niels Bohr Institute were involved in the publication, and their work supported by the Villum Foundation and the Carlsberg Foundation.

See the full article here .

five-ways-keep-your-child-safe-school-shootings

Stem Education Coalition

The Niels Bohr Institute (Danish: Niels Bohr Institutet) is a research institute of the University of Copenhagen. The research of the institute spans astronomy, geophysics, nanotechnology, particle physics, quantum mechanics and biophysics.

The Institute was founded in 1921, as the Institute for Theoretical Physics of the University of Copenhagen, by the Danish theoretical physicist Niels Bohr, who had been on the staff of the University of Copenhagen since 1914, and who had been lobbying for its creation since his appointment as professor in 1916. On the 80th anniversary of Niels Bohr’s birth – October 7, 1965 – the Institute officially became The Niels Bohr Institute.[1] Much of its original funding came from the charitable foundation of the Carlsberg brewery, and later from the Rockefeller Foundation.[2]

During the 1920s, and 1930s, the Institute was the center of the developing disciplines of atomic physics and quantum physics. Physicists from across Europe (and sometimes further abroad) often visited the Institute to confer with Bohr on new theories and discoveries. The Copenhagen interpretation of quantum mechanics is named after work done at the Institute during this time.

On January 1, 1993 the institute was fused with the Astronomic Observatory, the Ørsted Laboratory and the Geophysical Institute. The new resulting institute retained the name Niels Bohr Institute.

From Niels Bohr Institute: “One more spin makes the whole difference. Success with complex quantum states at the Niels Bohr Institute”

From Niels Bohr Institute

23 July 2018
Kasper Grove-Rasmussen, Associate professor
Niels Bohr Institute, University of Copenhagen
Email: k_grove@nbi.ku.dk
Phone: +45 21 32 86 15

Gorm Ole Steffensen, Ph.d. student
Niels Bohr Institute, University of Copenhagen
Email: gorm.steffensen@nbi.ku.dk
Phone: +45 35 33 38 04

Publication:
Scientists from the Niels Bohr Institute at the University of Copenhagen have, for the first time, succeeded in producing, controlling and understanding complex quantum states based on two electron spins connected to a superconductor. The result has been published in Nature Communications, and has come about in a collaboration between the scientists of the Niels Bohr Institute, a scientist from abroad and last, but not least, a Master’s thesis student.

Scanning electron microscope micrograph of a semiconductor nanowire, made from Indium Arsenide, connected electrically to a superconductor and a normal metal. The location on the nanowire of the two spins – the microscopic magnets – are illustrated by the arrows. In this case the microscopic magnets are created by electron spins.

Quantum technology is based on understanding and controlling quantum states in e.g. nanoelectronic devices with components at the nanoscale. The control could be via electrical signals, like in the components of a computer. The devices are just significantly more complex, when we are dealing with quantum components at nanoscale, and the scientists are still examining and attempting to understand the phenomena that arise on this tiny scale. In this case it is about the quantum states in nanoelectronic devices made from semiconductor nanowires and superconducting material. This requires understanding two fundamental phenomena in modern physics, magnetism and superconductivity.

Accumulating new knowledge is like playing with building blocks

The scientists have defined microscopic magnets electrically along a semiconductor nanowire. This is done by placing an electron spin close to a superconductor and then observing how it changes the quantum states. By placing two microscopic magnets rather than one, as has been done before, the possibilities for observing new quantum states arise. In this way the scientists accumulate knowledge by adding more and more complexity to the systems. “It is a bit like playing with building blocks. Initially we control one single electron spin, then we expand to two, we can modify the coupling between them, tune the magnetic properties etc. Somewhat like building a house with each additional brick increasing our knowledge of these quantum states.”, says Kasper Grove-Rasmussen, who has been in charge of the experimental part of the work.

Quantum theory from 1960 revitalized in nano devices

It is all about categorizing the different quantum states and their relations to one another, in order to achieve an overview of how the individual parts interact. During the 1960s, the theoretical foundation for this work was done, as three physicists, L. Yu, H. Shiba and A.I. Rusinov published three independent theoretical works on how magnetic impurities on the surface of the superconductor can cause new types of quantum states. The states, now achieved experimentally by the scientists at the Niels Bohr Institute, are named after the physicists: Yu-Shiba-Rusinov states. But they are significantly more complex than the Yu-Shiba-Rusinov states with a single spin previously achieved. This could be a step on the way to more complex structures that would enhance our understanding of potential quantum computer components, based on semiconductor-superconductor materials. Kasper Grove-Rasmussen emphasizes that what they are doing now is basic research.

3D model of the Yu-Shiba-Rusinov device. Two electron spins are defined along the nanowire, by placing appropriate voltages on the tiny electrodes under the nanowire. By coupling the spins to the superconductor Yu-Shiba-Rusinov states can be realized. Observation of these states are achieved by analyzing the current through the device from the normal metal to the superconductor.

Theoretical basis provided by a Master’s thesis student

Gorm Steffensen, now a PhD student at the Niels Bohr Institute, was writing his Master’s thesis at the time of the article, and has played an important role for the result. He was studying theoretical physics and has collaborated with his supervisor, Jens Paaske, on describing the quantum phenomena theoretically. So the article also demonstrates that collaboration on a scientific result at the Niels Bohr Institute can include the students. The task for Gorm Steffensen was to develop a theoretical model that encompassed all the phenomena in the experiments in collaboration with his supervisor and the Slovenian scientist, Rok Žitko, on. The nanowires in the experiment were developed by PhD students in the research group of Professor Jesper Nygaard. It is a common modus operandi for scientists at the Niels Bohr Institute to work together, applying many different competences across all scientific levels, from student to professor.

The Scientific publication: “Yu–Shiba–Rusinov screening of spins in double quantum dots” https://www.nature.com/articles/s41467-018-04683-x

See the full article here .

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The Niels Bohr Institute (Danish: Niels Bohr Institutet) is a research institute of the University of Copenhagen. The research of the institute spans astronomy, geophysics, nanotechnology, particle physics, quantum mechanics and biophysics.

The Institute was founded in 1921, as the Institute for Theoretical Physics of the University of Copenhagen, by the Danish theoretical physicist Niels Bohr, who had been on the staff of the University of Copenhagen since 1914, and who had been lobbying for its creation since his appointment as professor in 1916. On the 80th anniversary of Niels Bohr’s birth – October 7, 1965 – the Institute officially became The Niels Bohr Institute.[1] Much of its original funding came from the charitable foundation of the Carlsberg brewery, and later from the Rockefeller Foundation.[2]

During the 1920s, and 1930s, the Institute was the center of the developing disciplines of atomic physics and quantum physics. Physicists from across Europe (and sometimes further abroad) often visited the Institute to confer with Bohr on new theories and discoveries. The Copenhagen interpretation of quantum mechanics is named after work done at the Institute during this time.

On January 1, 1993 the institute was fused with the Astronomic Observatory, the Ørsted Laboratory and the Geophysical Institute. The new resulting institute retained the name Niels Bohr Institute.