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

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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 .

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: “Milky Way type dust particles discovered in a galaxy 11 billion light years from Earth”

From Niels Bohr Institute

7.3.18
Professor Johan Peter Uldall Fynbo
Dark Cosmology Centre
Juliane Maries Vej 30, 2100 København Ø.
jfynbo@nbi.ku.dk
Phone: +45 35 32 59 83
Mobile: +45 28 75 59 83

An international research team, with participation from the Niels Bohr Institute at the University of Copenhagen, has found the same type of interstellar dust that we know from the Milky Way in a distant galaxy 11 billion light years from Earth. This type of dust has been found to be rare in other galaxies and the new discovery plays an important role in understanding what it takes for this particular type of interstellar dust to be formed.

The discovery of the afterglow. To the left is an image from the so-called Pan-STARRS telescope in Hawaii taken before the explosion. To the right is an image of the same part of the sky taken with the Nordic Optical Telescope a few minutes after the explosion was registered by the Swift satellite.

Pann-STARSR1 Telescope, U Hawaii, Mauna Kea, Hawaii, USA, Altitude 3,052 m (10,013 ft)

Nordic Optical telescope, at Roque de los Muchachos Observatory, La Palma in the Canary Islands, Spain, Altitude 2,396 m (7,861 ft)

NASA Neil Gehrels Swift Observatory

Dust in galaxies

Galaxies are complex structures comprised of many individual parts, such as stars, gas, dust and dark matter. Even though the dust only represents a small part of the total amount of matter in a galaxy, it plays a major role in how stars are formed and how the light from the stars escapes the galaxies. Dust grains can both absorb and scatter light. Dust particles also play a decisive role in the formation of planets and thus also for the understanding of our own existence on Earth.

How do you measure dust 11 billion light years away?

The dust in galaxies consists of small grains of carbon, silicon, iron, aluminium and other heavier elements. The Milky Way has a very high content of carbonaceous dust, which has been shown to be very rare in other galaxies. But now a similar type of dust has been found in a few, very distant galaxies that researchers have been able to investigate using light from gamma-ray bursts. Gamma-ray bursts come from massive stars that explode when the when the fuel in its core is exhausted. The explosion causes the dying stars to emit powerful bursts of light that astronomers can use to analyse what the galaxies are comprised of. Specifically, they can measure the elemental content and analyse their way forward to the properties of the dust properties by examining the light that escapes from the galaxies.

Spectra of the afterglow from GRB 180325A taken with the NOT and the ESO/VLT X-shooter. The dust bump is seen as the downward bulge, which is in the spectrum around 7000 Å. For comparison, you can see the Milky Way dust bump in the small inset to the left. Credit: Tayyaba Zafar (AAO) et al.

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

ESO X-shooter on VLT at Cerro Paranal, Chile

Article in The Astrophysical Journal Letters

The carbonaceous dust is registered in the measurements as a “dust bump”, that is, a high value of dust with the said composition. This ultraviolet dust bump has now been detected in a gamma-ray burst, which has been named GRB180325A and the result has just been accepted for publication in the journal The Astrophysical Journal Letters. The lead author is Tayyaba Zafar who completed her PhD studies at the Niels Bohr Institute in Copenhagen and is now working at the Angle Australian Observatory in Australia. Several other researchers from NBI are co-authors of the article.

Collaboration between observatories

GRB180325A was detected by Neil Gehrel’s Swift Observatory (NASA) on 28 March 2018. Swift is a satellite mission that detects gamma rays from the dying stars. When such a detection from the satellite hits the astronomers, a hectic period begins. The astronomers try to observe that part of the sky as quickly as possible in order to secure the crucial information that allows them to study the interior of the galaxy the explosion originated from. In this case Kasper Heintz, who did his master’s thesis at the Niels Bohr Institute and is now a PhD student at the University of Iceland, was on duty. He activated the Nordic Optical Telescope (NOT) at La Palma, where Professor Johan Fynbo from the Niels Bohr Institute was observing for another project. The first observations of the light from the gamma-ray burst were secured only a few minutes after the discovery by Swift.

The observations from NOT showed that the star had exploded in a galaxy with a red shift of 2.25, which means that the light has travelled approximately 11 billion light years. The observations immediately showed that the dust bump, known from the Milky Way, was present in this galaxy. The team then observed the gamma-ray burst with the X-shooter spectrograph on ESO’s Very Large Telescope (European Southern Observatory) on the Cerro Paranal in Chile. All in all, four spectra of the afterglow from the gamma-ray burst were secured – all with a clear detection of the dust bump.

“It is a beautiful example of how observations in space and around the world can work together and create breakthroughs in research. The work also gives cause to express great thanks to the Carlsberg Foundation, without which Danish astronomy would neither have access to the Very Large Telescope nor NOT,” says Professor Johan Fynbo.

“Our spectra show that the presence of atomic carbon seems to be a requirement for the dust that causes the dust bump to be formed,” says Kasper Heintz.

The dust bump has previously been seen in observations of four other gamma-ray bursts, the last of which was detected 10 years ago.

“Further observations of this type will allow us to find more galaxies with this dust bump and thus conduct a more systematic study of similarities and differences in dust composition throughout the history of the Universe and in galaxies with different properties,” says Dr. Tayyaba Zafar.

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: “Here is what it looks like, when a massive black hole devours a star”

From Niels Bohr Institute

29 May 2018
Lixin Dai, Assistant professor, Dark Cosmology Centre and NBIA, Niels Bohr Institute, University of Copenhagen,
lixin.dai@nbi.ku.dk
+45 35 33 29 33

New computer model:

Dr. Jane Lixin Dai, theoretical astrophysicist and assistant professor and Prof. Enrico Ramirez-Ruiz, both from the DARK Cosmology Center at the Niels Bohr Institute, University of Copenhagen, have recently provided the scientific community with a much-needed computer model. It is necessary for the investigation of Tidal Disruption Events – rare, but extremely forceful events taking place in the center of galaxies.

In the figure we see a cross section of what happens when the material from the disrupted star is devoured by the black hole. An accretion disk is formed (disk) by the material. There is too much material for it to pass into the black hole at once. It is heated up in the process and emits vast amounts of light and radiation, visible from Earth (Double arrow). Dr. Jane Dai’s computer model takes the difference in viewing angle from Earth into account, which means we are now able to categorize the variations in observations correctly. This means we can study the properties of the black hole, and learn about a celestial body we would otherwise not be able to see.

Tidal disruption events

In the center of every big galaxy, there is a supermassive black hole, millions to billions times heavier than the Sun. However, it is difficult to observe the majority of them, as they don’t emit any light or radiation. This only happens, when some form of material is pulled into the extremely strong gravitational field of the black hole. On rare occasions, actually as rare as once in every 10.000 years for one galaxy, a star passes very close by the supermassive black hole, and the gravity of the black hole tears it apart. This type of fatal event is called a tidal disruption event.

When a tidal disruption event happens, the black hole will be “overfed” with stellar debris for a while. “It is interesting to see how materials get their way into the black hole under such extreme conditions,” says Dr. Jane Dai who has led the study [The breakthrough study, published in Astrophysical Journal Letters, provides a new theoretical perspective for a fast-growing research field.Thank you Tim Stephans at UCSC for providing this information, left completely out of the Niels Bohr Institute article] . “As the black hole is eating the stellar gas, a vast amount of radiation is emitted. The radiation is what we can observe, and using it we can understand the physics and calculate the black hole properties. This makes it extremely interesting to go hunting for tidal disruption events.”

A unification model

While the same physics is expected to happen in all tidal disruption events, the observed properties of these events have shown great variation: Some emitting mostly X-ray emissions, while others mainly emitting visible light and UV. It has been in high demand to understand this diversity and assemble these very different pieces of the puzzle. In the model, it is the viewing angle of the observer that has set the difference. Astronomers observe everything from Earth, but the galaxies are oriented randomly across the universe. “It is like there is a veil that covers part of a beast. From some angles we see an exposed beast, but from other angles we see a covered beast. The beast is the same, but our perceptions are different,” said Prof. Enrico Ramirez-Ruiz, a co-author on the study.

Jane Lixin Dai, theoretical astrophysicist at DARK Cosmology Centre and Niels Bohr International Academy at the Niels Bohr Institute, University of Copenhagen, has long wanted a computer model that makes it possible to calculate black hole properties.

Collaboration and perspectives

This work has been made possible by the collaboration between Dr. Jane Dai from the DARK Cosmology Centre at the Niels Bohr Institute (NBI), Prof. Enrico Ramirez-Ruiz from both NBI and the University of California at Santa Cruz (UCSC), as well as researchers from the University of Maryland: Prof. Jonathan McKinney, Dr. Nathaniel Roth, and Prof. Cole Miller.

In particular, state-of-the-art computational tools were employed to solve the puzzle. These simulations were carried out by Dr. Dai and Dr. Roth, on the recently acquired large computer cluster made possible by the Villum Grant from Professor Jens Hjorth, head of DARK Cosmology Centre, as well as clusters funded by NSF and NASA.

This breakthrough has provided a new perspective to the fast-growing research field. “Only in the last decade or so have we been able to distinguish TDEs from other galactic phenomena, and the model by Dr. Dai will provide us with the basic framework for understanding these rare events”, says Prof. Enrico Ramirez-Ruiz.

In coming years, the Young Supernova Experiment (YSE) transient survey, led by DARK and UCSC, together with other telescopes such as the Large Synoptic Survey Telescopes being built in Chile, will give us access to much more data, and help greatly to expand this field of research.

LSST telescope, currently under construction at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes.

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: “Neutron scattering brings us a step closer to the quantum computer”

Niels Bohr Institute

29 March 2018

Mikkel Agerbæk Sørensen,
Ph.D.-student, Department of Chemistry, University of Copenhagen
mikkel.agerbaek@chem.ku.dk
http://www.ki.ku.dk

Ursula Bengård Hansen,
Postdoc, X-ray and Neutron Science
Niels Bohr Institute, University of Copenhagen
uhansen@nbi.ku.dk
+45 60 47 86 15

Kim Lefmann,
Lektor, X-ray and Neutron Science
Niels Bohr Institute, University of Copenhagen
lefmann@nbi.ku.dk
+45 29 25 04 76

Jesper Bendix,
Professor, Kemisk Institut, University of Copenhagen
bendix@kiku.dk
+45 35 32 01 01

Quantum computers:

A major challenge for future quantum computers is that you have to keep the quantum information long enough to make calculations on it – but the information only has a very short lifespan, often less than a microsecond. Now researchers at the Niels Bohr Institute and the Department of Chemistry at the University of Copenhagen, in collaboration with a team of international researchers, have come closer to a solution. The results are published in the renowned journal Nature Communications.

PhD student Mikkel Agerbæk Sørensen from the Department of Chemistry and Postdoc Ursula Bengård Hansen from the research group X-ray and Neutron Science at the Niels Bohr Institute shows a 3D model of the studied molecule. By making small changes in the form of the molecule, the tunnelling can be suppressed. In the background Associate Professor Kim Lefmann and Professor Jesper Bendix. Photo: Ola J. Joensen.

In order to build the quantum computer of the future, you need to be able to store the quantum information – what we call “quantum bits” or “qubits” – (which corresponds to bits and bytes in a traditional computer). Several research groups are experimenting with different ideas for how this can be done in practice.

A team of chemists and physicists from the Niels Bohr Institute and the Department of Chemistry at the University of Copenhagen, as well as collaborators from Germany, France, Switzerland, Spain and the United States, have studied the possibility of producing qubits from organometallic molecules with a single magnetic ion in each molecule.

In these “nanomagnets” there is the particular challenge that random movements in the outside world can interfere with the magnetic ions, so that the quantum information is lost before you can manage to perform calculations with it. Even at ultra-low temperatures just above absolute zero (0.05 Kelvin), where all motion “normally” stops, the system can still be subjected to quantum mechanical disturbances, also known as “tunnelling”.

Mikkel Agerbæk Sørensen, who is the first author of the study, explains that suppressing the tunnelling is considered one of the greatest challenges in the production of new nanomagnets with actual application possibilities: “there are several theoretical models for how to suppress the tunnelling in such molecule-based magnets. With this study, we are the first to have been able to prove the leading model experimentally.”

Changes in the form of the molecule are part of the solution

There is still a long way to go to be able to use these nanomagnets in a practical quantum computer, but the researchers have now discovered another “control lever”, namely the geometric form of the molecule that can be used to get closer to the goal. With the construction of the largest neutron facility (ESS) in Lund, Sweden, researchers will have better opportunities to measure and understand tunnelling, thus getting closer to controlling it – and ultimately pave the way for quantum computing.

In order to understand the quantum behavior of a molecule-based magnet, it is necessary to measure the energy levels of the molecule very accurately. This is best done with the so-called inelastic neutron scattering. Such experiments can only be done using instruments located at major international research facilities. With the performance of ESS, researchers at the University of Copenhagen will have even better opportunities to conduct such studies. Here Mikkel Agerbæk Sørensen at the entrance of the instrument IN6 at the Institute Laue-Langevin in Grenoble.

See the full article here .

Please help promote STEM in your local schools.

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: “New ’building material’ points toward quantum computers”

Niels Bohr Institute

28 September 2017
Fabrizio Nichele
fnichele@nbi.ku.dk

A Danish-American research team has shown that it is possible to produce ‘Majorana particles’ in a new ‘building material’. The research, led by scientists from Niels Bohr institute, University of Copenhagen, paves the road for new types of experiments – and at the same time represents an important contribution to the construction of the information circuits of tomorrow.

Fabrizio Nichele in the lab at Center for Quantum Devices. The scientists keep their samples in the transparent ‘cabinet’ – in an oxygen-free environment. Photo: Ola Jakup Joensen

Ever since Ettore Majorana – legendary and mythical Italian physicist – back in 1937 suggested the existence of a particle that is also its own anti-particle, scientists have been searching for the ‘Majorana particle’, as it is has come to be known.

This far the search has been to no avail

A team of scientists from Center for Quantum Devices at Niels Bohr Institute (NBI) and from Purdue University, USA, have – however – recently contributed to the advancement of Majorana research.

The blue part of the structure – one half of a wafer – is where the scientists start building the nano wire. Photo: Ola Jakup Joensen

Not by finding the elusive particle itself, but by figuring out how to produce a material in which electrons behave in accordance with the theoretical predictions for Majorana particles.

The results of the research project are published in this week issue of the scientific journal Physical Review Letters.

No charge

An anti-particle is an elementary particle – identical to its ‘counterpart’, but with opposite electrical charge. As seen in the relationship between negatively charged electrons and positively charged positrons.

If a particle is also its own anti-particle – which, given it does indeed exist, will be the case with a Majorana particle – it will therefore have no charge at all.

The properties that, according to Ettore Majorana´s calculations, will characterize a Majorana particle do for a number of reasons fascinate scientists. Obviously because such properties ‘packaged’ in one particle will represent new experimental possibilities. But also because Majorana-properties are thought to be useful when scientists are e.g. attempting to construct quantum computers – i.e. the information circuits of tomorrow that will have the capacity to process data loads far, far heavier than those dealt with by our present super computers.

The nano wire is embedded in spider shaped structures. These structures are here seen through the lense of an optical microscope. The structures sit in rows, two in each row. Photo: Ola Jakup Joensen

All over the world scientists are trying to design quantum computers.

It’s a race – Center for Quantum Devices at NBI is one of the contestants – and assistant professor Fabrizio Nichele and professor Charles Marcus, both representing the NBI-center, have been in charge of the Danish-American research project.

“The condensed version is that it is possible to produce a material in which electrons behave like Majorana particles, as our experiments suggest – and that it is possible to produce this material by means of techniques rather similar to those used today when manufacturing computer circuits. On top of that we have shown how this material enables us to measure properties of Majorana particles never measured before – and carry out these measurements with great precision”, explains Fabrizio Nichele.

Laptop design

Two ultra thin sheets – combined in a ‘sandwich’ – are at the center of the Danish-American discovery, and it all has to do with producing a material based on this ‘sandwich’.

One of the optical microscopes available to the NBI-scientists. Photo: Ola Jakup Jensen

The bottom layer of the ‘sandwich’ is made out of indium arsenide, a semiconductor, and the top layer is made out of aluminium, a superconductor. And the ‘sandwich’ sits on top of a so called wafer, one of the building blocks used in modern computer technology.

If you carve out a nano wire from this ‘sandwich’-layer it is possible to create a state where electrons inside the wire display Majorana-properties – and the theory behind this approach has in part been known since 2010, says Fabrizio Nichele:

“However, until now there has been a major problem because it was necessary to ‘grow’ the nano wire in special machines in a lab – and the wire was, literally, only available in the form of minute ‘hair-like’ straws. In order to build e.g. a chip based on this material, you therefore had to assemble an almost unfathomable number of single straws – which made it really difficult and very challenging to construct circuits this way”.

And this is exactly where the Danish-American discovery comes in very handily, explains Fabrizio Nichele: “We are now able to design the nano wire on a laptop – and include the details we go for. Further down the road production capacity will no doubt increase – which will allow us to use this technique in order to construct computers of significant size”.

Signature of a Majorana particle, shown on a screen. “The horizontal stripe in the center of the figure shows that a zero energy particle appears in a magnetic field in our devices – as expected for a Majorana particle”, explains Fabrizio Nichele.

Faster road to Majorana

At Center for Quantum Devices at NBI, focus is very much on the construction of a quantum computer. Still it is a long haul – the quantum computer is by no means just around the corner, says Fabrizio

One of the nanowires central to the NBI-scientist’s research. The wire is made out of aluminum. It is approx. 1/1.000 millimeter long, and 1/20.000 wide. Illustration: NBI

Nichele: “Materials with Majorana-properties obviously have a number of relevant qualities in this context – which is why we try to investigate this field through various experiments”.

Some of these experiments are carried out at temperatures just above absolute zero (-273,15 C), explains Fabrizio Nichele: “When you do that – which naturally requires equipment tailored for experiments of this kind – you are able to study details related to quantum properties in various materials. When it comes to constructing a quantum computer, Majorana-particles do, however, represent just one of a number of possible and promising options. This field is very complex – and when, some day, a quantum computer has indeed been constructed and is up and running, it may very well be based on some form of integration of a number of different techniques and different materials, whereof some may be based on our research”, says Fabrizio Nichele.

Fabrizio Nichele. Photo: Ola Jakup Joensen

Scientists working with Ettore Majoranas equations for entirely other reasons than the desire to build a quantum computer, can also benefit from the Danish-American research, explains Fabrizio Nichele:

“Our technique makes it possible to conduct experiments that have up till now not been doable – which will also facilitate the understanding of the Majorana particle itself”.

The research project has been funded by the Danish National Research Foundation, the Villum Foundation, Deutsche Forschungsgemeinschaft (DFG) and – representing the commercial donor side – Microsoft; the latter joining the project as part of a well established cooperation with NBI.

In addition to cooperating with colleagues from Purdue University, the NBI-researchers have also recently studied Majorana properties working together with scientists from University of California, Santa Barbara, USA. The results of this project are published in a separate article in Physical Review Letters.

See the full article here .

Please help promote STEM in your local schools.

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 U Copenhagen Niels Bohr Institute: “Smart atomic cloud solves Heisenberg’s observation problem”

University of Copenhagen

Niels Bohr Institute

13 July 2017
Eugene Polzik
polzik@nbi.dk
+45 2338 2045

Quantum physics: Scientists at the Niels Bohr Institute, University of Copenhagen have been instrumental in developing a ‘hands-on’ answer to a challenge intricately linked to a very fundamental principle in physics: Heisenberg’s Uncertainty Principle. The NBI-researchers used laser light to link caesium atoms and a vibrating membrane. The research, the first of its kind, points to sensors capable of measuring movement with unseen precision.

From the left: Phd student Rodrigo Thomas, Professor Eugene Polzik and PhD student Christoffer Møller in front of the experiment demonstrating quantum measurement of motion. Photo: Ola J. Joensen.

Our lives are packed with sensors gathering all sorts of information – and some of the sensors are integrated in our cell phones which e.g. enables us to measure the distances we cover when we go for a walk – and thereby also calculate how many calories we have burned thanks to the exercise. And this to most people seems rather straight forward.

When measuring atom structures or light emissions at the quantum level by means of advanced microscopes or other forms of special equipment, things do, however, get a little more complicated due to a problem which during the 1920’s had the full attention of Niels Bohr as well as Werner Heisenberg. And this problem – this has to do with the fact that in-accuracies inevitably taint certain measurements conducted at quantum level – is described in Heisenberg’s Uncertainty Principle.

In a scientific report published in this week’s issue of Nature, NBI-researchers – based on a number of experiments – demonstrate that Heisenberg’s Uncertainty Principle to some degree can be neutralized. This has never been shown before, and the results may spark development of new measuring equipment as well as new and better sensors.

Professor Eugene Polzik, head of Quantum Optics (QUANTOP) at the Niels Bohr Institute, has been in charge of the research – which has included the construction of a vibrating membrane and an advanced atomic cloud locked up in a small glass cage.

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.

Light ‘kicks’ object

Heisenberg’s Uncertainty Principle basically says that you cannot simultaneously know the exact position and the exact speed of an object.

Which has to do with the fact that observations conducted via a microscope operating with laser light inevitably will lead to the object being ‘kicked’. This happens because light is a stream of photons which when reflected off the object give it random ‘kicks’ – and as a result of those kicks the object begins to move in a random way.

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 quantum level.

To conduct the experiments at NBI professor Polzik and his team of “young, enthusiastic and very skilled NBI-researchers” used a ‘tailor-made’ membrane as the object observed at quantum level. The membrane was built by Ph.D. Students Christoffer Møller and Yegishe Tsaturyan, whereas Rodrigo Thomas and Georgios Vasikalis – Ph.D. Student and researcher, respectively – were in charge of the atomic aspects. Furthermore Polzik relied on other NBI-employees, assistant professor Mikhail Balabas, who built the minute glass cage for the atoms, researcher Emil Zeuthen and professor Albert Schliesser who – collaborating with German colleagues – were in charge of the substantial number of mathematical calculations needed before the project was ready for publication in Nature.

The atomic part of the hybrid experiment. The atoms are contained in a micro-cell inside the magnetic shield seen in the middle. Photo: Ola J. Joensen.

Over the last decades scientists have tried to find ways of ‘fooling’ Heisenberg’s Uncertainty Principle. Eugene Polzik and his colleagues came up with the idea of implementing the advanced atomic cloud a few years ago – and the cloud consists of 100 million caesium-atoms locked up in a hermetically closed cage, a glass cell, explains the professor:

“The cell is just 1 centimeter long, 1/3 of a millimeter high and 1/3 of a millimeter wide, and in order to make the atoms work as intended, the inner cell walls have been coated with paraffin. The membrane – whose movements we were following at quantum level – measures 0,5 millimeter, which actually is a considerable size in a quantum perspective”.

The idea behind the glass cell is to deliberately send the laser light used to study the membrane-movements on quantum level through the encapsulated atomic cloud BEFORE the light reaches the membrane, explains Eugene Polzik: “This results in the laser light-photons ‘kicking’ the object – i.e. the membrane – as well as the atomic cloud, and these ‘kicks’ so to speak cancel out. This means that there is no longer any Quantum Back Action – and therefore no limitations as to how accurately measurements can be carried out at quantum level”.

The optomechanical part of the hybrid experiment. The cryostat seen in the middle houses the vibrating membrane whose quantum motion is measured. Photo: Ola J. Joensen.

How can this be utilized?

“For instance when developing new and much more advanced types of sensors for various analyses of movements than the types we know today from cell phones, GPS and geological surveys”, says professor Eugene Polzik: “Generally speaking sensors operating at the quantum level are receiving a lot of attention these days. One example is the Quantum Technologies Flagship, an extensive EU program which also supports this type of research”.

The fact that it is indeed possible to ‘fool’ Heisenberg’s Uncertainty Principle may also prove significant in relation to better understanding gravitational waves – waves in the fabric of space-time itself of light.

In September of 2015 the American LIGO-experiment was able to publish the first direct registrations and measurements of gravitational waves stemming from a collision between two very large black holes.

However, the equipment used by LIGO is influenced by Quantum Back Action, and the new research from NBI may prove capable of eliminating that problem, says Eugene Polzik.

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.

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