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Enhancing the quantum sensing capabilities of diamond: Shooting electrons at diamonds can introduce quantum sensors into them

22/11/2017

Researchers have discovered that dense ensembles of quantum spins can be created in diamond with high resolution using an electron microscopes, paving the way for enhanced sensors and resources for quantum technologies.

Diamonds are made of carbon atoms in a crystalline structure, but if a carbon atom is replaced with another type of atom, this will result in a lattice defect. One such defect is the Nitrogen-Vacancy (NV), where one carbon atom is replaced by a nitrogen atom, and its neighbor is missing (an empty space remains in its place).

If this defect is illuminated with a green laser, in response it will emit red light (fluoresce) with an interesting feature: its intensity varies depending on the magnetic properties in the environment. This unique feature makes the NV center particularly useful for measuring magnetic fields, magnetic imaging (MRI), and quantum computing and information.

In order to produce optimal magnetic detectors, the density of these defects should be increased without increasing environmental noise and damaging the diamond properties.

Now, scientists from the research group of Nir Bar-Gill at the Hebrew University of Jerusalem’s Racah Institute of Physics and Department of Applied Physics, in cooperation with Prof. Eyal Buks of the Technion – Israel Institute of Technology, have shown that ultra-high densities of NV centers can be obtained by a simple process of using electron beams to kick carbon atoms out of the lattice.

This work, published in the scientific journal Applied Physics Letters, is a continuation of previous work in the field, and demonstrates an improvement in the densities of NV centers in a variety of diamond types. The irradiation is performed using an electron beam microscope (Transmission Electron Microscope or TEM), which has been specifically converted for this purpose. The availability of this device in nanotechnology centers in many universities in Israel and around the world enables this process with high spatial accuracy, quickly and simply.

The enhanced densities of the NV color centers obtained, while maintaining their unique quantum properties, foreshadow future improvements in the sensitivity of diamond magnetic measurements, as well as promising directions in the study of solid state physics and quantum information theory.

Nitrogen Vacancy (NV) color centers exhibit remarkable and unique properties, including long coherence times at room temperature (~ ms), optical initialization and readout, and coherent microwave control.

“This work is an important stepping stone toward utilizing NV centers in diamond as resources for quantum technologies, such as enhanced sensing, quantum simulation and potentially quantum information processing”, said Bar-Gill, an Assistant Professor in the Dept. of Applied Physics and Racah Institute of Physics at the Hebrew University, where he founded the Quantum Information, Simulation and Sensing lab.

"What is special about our approach is that it's very simple and straightforward," said Hebrew University researcher Dima Farfurnik. "You get sufficiently high NV concentrations that are appropriate for many applications with a simple procedure that can be done in-house."

CITATION: Farfurnik, D., et al. Enhanced concentrations of nitrogen-vacancy centers in diamond through TEM irradiationAppl. Phys. Lett. 111, 123101 (2017). Publisher's Version

SUPPORT: This work was supported in part by the Minerva ARCHES award, the CIFAR-Azrieli global scholars program, the Israel Science Foundation (Grant No. 750/14), the Ministry of Science and Technology, Israel, the Technion security research foundation, and the CAMBR fellowship for Nanoscience and Nanotechnology.

PHOTO 1: http://media.huji.ac.il/new/photos/hu171114_bar-gill.jpg - Diamond sample illuminated by green light in our home-built microscope. Sample is placed on a special mount, within a printed circuit board, used to deliver microwaves which allow quantum manipulations and magnetic sensing with the NVs. (Credit: Yoav Romach)

PHOTO 2: http://media.huji.ac.il/new/photos/hu171114_bar-gill-cryo.jpg - Cryogenic sample chamber, with diamond sample mounted on copper cold plate. (Credit: Yoav Romach)

PHOTO 3: https://drive.google.com/file/d/1TsGTAKrw1l_dw2X2tUDlbBluwnP_LoGf/view - Hebrew University researchers Nir Bar-Gill and Dima Farfurnik with a diamond magnetic microscope. (Credit: Nir Bar-Gill)

Enhancing the quantum sensing capabilities of diamond: Shooting electrons at diamonds can introduce quantum sensors into them
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Novel technique reveals the intricate beauty of a cracked glass

31/10/2017

Physics, math and special gels explain the formation of fracture patterns in brittle materials

Researchers have long pondered the origin of delicate criss-cross facetted patterns that are commonly found on the surfaces of broken material. Typical crack speeds in glass easily surpass a kilometer per second, and broken surface features may be well smaller than a millimeter. Since the formation of surface structure lasts a tiny fraction of a second, the processes generating these patterns have been largely a mystery.

Now there is a way around this problem. Replacing hard glass with soft but brittle gels makes it possible to slow down the cracks that precipitate fracture to mere meters per second. This novel technique has enabled researchers Itamar Kolvin, Gil Cohen and Prof. Jay Fineberg, at the Hebrew University of Jerusalem’s Racah Institute of Physics, to unravel the complex physical processes that take place during fracture in microscopic detail and in real time.

Their work sheds new light on how broken surface patterns are formed. Surface facets bounded by steps are formed due to a special “topological” arrangement of the crack that cannot easily be undone, much as a knot along a string cannot be unraveled without pulling the whole length of the string through it.

These “crack knots” increase the surface formed by a crack, thereby creating a new venue for dissipating the energy required for material failure, and thereby making materials harder to break. 

“The complex surfaces that are commonly formed on any fractured object have never been entirely understood,” said Prof. Jay Fineberg. “While a crack could form perfectly flat, mirror-like fracture surfaces (and sometimes does), generally complex facetted surfaces are the rule, even though they require much more energy to form. This study illuminates both how such beautiful and intricate patterns emerge in the fracture process, and why the crack cannot divest itself of them once they are formed.”

This physically important process provides an aesthetic example of how physics and mathematics intertwine to create intricate and often unexpected beauty. The research appears in Nature Materials.

The Hebrew University of Jerusalem is Israel’s leading university and premier research institution. Founded in 1918 by innovative thinkers including Albert Einstein, the Hebrew University is a pluralistic institution that advances science and knowledge for the benefit of humankind. For more information, please visit http://new.huji.ac.il/en.

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FUNDING: Fineberg and Kolvin acknowledge the support of the Israel Science Foundation (grant no.1523/15), as well as the US-Israel Bi-national Science Foundation (grant no. 2016950).

CITATION: Itamar Kolvin, Gil Cohen, Jay Fineberg. Topological defects govern crack front motion and facet formation on broken surfaces. Nature Materials, Advance Online Publication October 16, 2017. doi:10.1038/nmat5008. Link: http://dx.doi.org/10.1038/nmat5008

Novel technique reveals the intricate beauty of a cracked glass
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LIGO Confirms 1989 Hebrew University Prediction About Neutron Star Mergers Producing Gamma Ray Bursts

16/10/2017

Prof. Tsvi Piran at Hebrew University's Racah Institute of Physics led a team that published an accurate prediction in 'Nature' that met with skepticism for years

Watch video at https://youtu.be/KhfGqK6st_A 

Two years ago, the LIGO gravitational wave detector stunned the world with the discovery of a merger of two black holes. This past August, LIGO did it again: with the help of a second detector called VIRGO, it discovered a new source of gravitational radiation. Seconds later, NASA’s Fermi satellite detected a gamma-ray burst from the same direction. Several hours later, a telescope in Chile identified the source at a Galaxy located 120 million light years away. While this is an enormous distance for us, on a cosmological scale it is relatively close. 

Since these initial discoveries, most of the telescopes in the world, including the Hubble Space Telescope, have observed this galactic event. The results, which have been kept secret until now (despite a partial leak), are reported today in several scientific papers published in the prestigious journals Physical Review LettersNature, Science and the Astrophysical Journal.

These observations confirm a longstanding prediction made almost thirty years ago by a team headed by Prof. Tsvi Piran at the Hebrew University of Jerusalem. Piran is the Schwartzman Chair for Theoretical Physics at the Hebrew University's Racah Institute of Physics. The prediction, published in Nature in 1989 ("Nucleosynthesis, neutrino bursts and γ-rays from coalescing neutron stars"), suggests that when two neutron star merger they emit, in addition to gravitational waves, a burst of gamma-rays. They also synthesize and eject to outer space rare heavy elements, like gold plutonium and uranium. The merged neutron stars form a black hole in this process.

Neutron stars are rare types of stars that are produced in supernova explosions when a regular star dies. Unlike regular matter that is composed from 50% neutron and 50% protons, neutron stars are made just from neutrons. Due to their strange composition, they are extremely dense: a teaspoon of neutron star matter weights about 100 million tons, and a neutron star of 10 km (smaller than the width of Jerusalem) weights about a million times the mass of Earth. 

The first neutron star was discovered in 1967 by Antony Hewish, who received the 1974 Nobel Prize in Physics. Later a binary pair of neutron stars rotating around each other was discovered by Hulse and Taylor, who were awarded the 1993 Nobel Prize in Physics. (And on October 3, LIGO’s three leading champions were awarded the 2017 Nobel Prize in Physics: Barry Barish and Kip Thorne of Caltech and Rainer Weiss of MIT.)

Shortly after the discovery of a binary neutron star pair in 1975, researchers realized that that such a pair would emit gravitational radiation and eventually merge. The question that Piran and colleagues asked in 1989 was: in addition to the gravitational radiation, what else will be emitted as a result of this merger? They suggested that the merger will produce a burst of gamma-rays — which have the smallest wavelengths and the most energy of any other wave in the electromagnetic spectrum — and at the same time will synthesize and eject into outer space freshly synthesized heavy elements like gold, plutonium and uranium. The ultimate result will be a black hole. This prediction, which Piran and colleagues published in Nature, was met with skepticism and initially ignored. However, Piran continued to work on it, and indirect evidence in its favor mounted over the years. These last observations confirm it without any doubt.

“I am exhilarated by this confirmation of a prediction we made nearly thirty years ago,” said Prof. Tsvi Piran following today’s announcement confirming his prediction. “I also remember how difficult it was to convince the scientific community of our idea: at the time it was against the standard model that was published even in freshman textbooks on astronomy. When we made this prediction in 1989, we did not expect it to be confirmed within our lifetimes. But with continued curiosity and the development of new technologies, we are able learn ever deeper truths about the nature of our Universe."

LIGO’s observations confirmed that the event involved a binary neutron star merger, and the formation of a black hole. The Fermi satellite detected the predicted gamma-rays, and the optical observation confirmed the nucleosynthesis of heavy elements. All of this is published today in multiple research papers, with Piran’s participation in several papers published in the journals Nature, Science and The Astrophysical Journal. These observations solve several puzzles that have bothered astronomers over the years, and open new ways to understand the nature of our Universe.

The Hebrew University of Jerusalem is Israel’s leading university and premier research institution. Founded in 1918 by innovative thinkers including Albert Einstein, the Hebrew University is a pluralistic institution that advances science and knowledge for the benefit of humankind. For more information, please visit http://new.huji.ac.il/en.

A related video can be seen at https://youtu.be/KhfGqK6st_A.

 LIGO Confirms 1989 Hebrew University Prediction About Neutron Star Mergers Producing Gamma Ray Bursts
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