First T2K measurement of antineutrino identity-shifting behaviour announced

The Super-Kamiokande detector in Japan

Antineutrinos have been observed changing their identities in the same way as their normal neutrino counterparts by the T2K experiment.

The latest results from the T2K experiment in Japan were announced this week by a team of researchers including physicists from Imperial College London.

Differences between the identity-shifting behaviour of neutrinos and antineutrinos could explain why the universe is made up of normal matter, and was not obliterated by antimatter shortly after the Big Bang.

It’s a small step but we’ve already achieved world-best sensitivity. – Dr Morgan Wascko

Every type of particle that makes up the universe has an antimatter counterpart – an identical particle with the opposite charge. Physicists predict that during the Big Bang, the creation of the universe, equal amounts of matter and antimatter should have been created.

However, matter and antimatter annihilate each other, so the persistence of matter making up our universe is a mystery. Small differences in the way matter and antimatter behave could explain why one survived at the expense of the other.

Differences found so far between matter and antimatter particles have been too small to account for the makeup of the universe as we know it, but the strange behaviour of neutrinos may hold the answer.

DIFFERENT FLAVOURS

Neutrinos have the smallest mass of any known particle, and are created in several ways, including during radioactive decay, nuclear reactions and when cosmic rays from the Sun hit the Earth’s atmosphere. Through interactions with other matter, neutrinos are known to come in three types, or 'flavours,' – one paired with the electron (called the electron neutrino), and two more paired with the electron's heavier cousins, the muon and tau leptons (called the muon and tau neutrinos).

The fact that neutrino masses and flavours do not exactly overlap each other means that the three different flavours of neutrinos can spontaneously change into each other as they travel, a phenomenon called neutrino oscillation. Scientists have previously observed all three flavours changing into each other, and measured the degree of change in each type of identity shift.

To explore the neutrinos’ oscillations, the T2K experiment fired a beam of neutrinos from the J-PARC laboratory at Tokai Village on the eastern coast of Japan, and detected them at the Super-Kamiokande neutrino detector, 295 km away in the mountains of the north-western part of the country. Here, the scientists looked to see if the neutrinos at the end of the beam matched those emitted at the start.

Now, they have measured the degree of change for the first of the antineutrino identity shifts: muon antineutrinos oscillating into tau antineutrinos. When comparing these to their results for the muon to tau neutrino shift, there appears to be no difference in their behaviour.

WEIRDNESS WANTED

The Standard Model of Physics predicts the consistency in behaviour, but deviations from the expected answers are what the team wants in order to try and explain the difference between matter and antimatter. “We want the weird stuff,” said Dr Asher Kaboth, a Post-Doctoral researcher from the Department of Physics who announced the results at a meeting earlier this week.

The new measurements are not as precise as those for normal neutrinos, and the team will collect more data, but they are reasonably confident in their result. “Even this small amount of data is a promising result,” said T2K scientist Dr Yoshi Uchida from the Department of Physics at Imperial.

“It’s a small step but we’ve already achieved world-best sensitivity,” added International Co-Spokesperson of T2K and Imperial physicist Dr Morgan Wascko. In 2011 the team saw the first hints of the as-yet unobserved shift between muon neutrinos and electron neutrinos, which they later confirmed in 2013 with more data.

Read more about the latest results on the T2K website.

http://www3.imperial.ac.uk/newsandeventspggrp/imperialcollege/newssummary/news_22-5-2015-16-30-53

The monopoly of Aluminium is broken

©TUDelft/Tremani

Discovering Majorana’s was only the first step, but utilizing it as a quantum bit (qubit) still remains a major challenge. An important step towards this goal has just been taken, as shown by researchers from TU Delft in today’s issue of Nature Physics. It is an almost thirty years old scientific problem that has just been resolved: demonstrating the difference between the even and odd occupation of a superconductor in high magnetic fields. Thus far, this was only possible in aluminium which is however incompatible with Majorana’s. This result enables the read out and manipulation of quantum states encoded in prospective Majorana qubits.

Qubit

Qubits store information similarly to normal (digital) bits. While a bit represents either 0 or 1, a qubit utilizes the laws of quantum mechanics, making it possible to be in the state of 0 and 1 at the same time. This enables solving several mathematical problems much faster than the most capable supercomputers ever built. Several research groups and companies around the globe pursue the development and prototyping of such a powerful quantum computer, including QuTech at the Delft University of Technology.

Majorana’s

A qubit encoded by Majorana’s is a promising building block for a practical quantum computer. However, until now, it was a major challenge to read out such a Majorana qubit. In order to do so, one needs to determine whether the number of the electrons is even or odd, or, in other words, what the parity state is.  The measurement of the parity of superconductors has been performed for the last thirty years, however, successful experiments were exclusively done on aluminium while all attempts addressing different superconducting materials, such as vanadium or niobium, have failed. This is a major issue for Majorana research as superconductivity is required to survive up to high magnetic fields, at which aluminium ceases to be a superconductor.

An alternative of aluminium

The research group at TU Delft has succeeded in determining the parity in a different superconductor: niobium titanium nitride (NbTiN). Most importantly, this material remains superconducting at high magnetic fields, which is an essential property to create Majorana’s. “The most beautiful outcome is that not only can we distinguish between the even and odd number of electrons, but a prepared, say, even state remains the same for more than one minute” as David van Woerkom from QuTech explains. “Since we typically work with timescales of micro- or even nanoseconds, one minute is essentially an eternity”.

Quasiparticles

Majorana’s are a special kind of so-called (quasi-)particles: all measurable properties of Majorana’s are zero, meaning that this particle is its own antiparticle. A pair of Majorana’s are insensitive to local perturbations and is therefore a very promising candidate to become the building block of quantum computation. Majorana’s were first postulated in the 1930’s by the young Italian scientist Ettore Majorana, who disappeared under mysterious circumstances not more than one year after his groundbreaking work. The first experimental evidence of the Majorana particle was reported in 2012 by the group of Leo Kouwenhoven in Delft.

The Quantum Technology Institute

QuTech, founded by TU Delft and TNO is an institute developing quantum computers. The current research reported today in Nature Physics has been performed in collaboration by QuTech and Microsoft Corporation Station Q. QuTech became a ‘Nation Icon’ of the Dutch government in 2014.

Source link: http://www.tudelft.nl/en/current/latest-news/article/detail/wetenschappers-doorbreken-monopolie-aluminium/

DNA Double Helix Does Double Duty in Assembling Arrays of Nanoparticles

A combination cryo-electron microscopy image of an octahedral frame with one gold nanoparticle bound to each of the six vertices, shown from three different angles

Synthetic pieces of biological molecule form framework and glue for making nanoparticle clusters and arrays

In a new twist on the use of DNA in nanoscale construction, scientists at the U.S. Department of Energy's (DOE) Brookhaven National Laboratory and collaborators put synthetic strands of the biological material to work in two ways: They used ropelike configurations of the DNA double helix to form a rigid geometrical framework, and added dangling pieces of single-stranded DNA to glue nanoparticles in place. 

The method, described in the journal Nature Nanotechnology, produced predictable clusters and arrays of nanoparticles—an important step toward the design of materials with tailored structures and functions for applications in energy, optics, and medicine.

"These arrays of nanoparticles with predictable geometric configurations are somewhat analogous to molecules made of atoms," said Brookhaven physicist Oleg Gang, who led the project at the Lab's Center for Functional Nanomaterials (CFN), a DOE Office of Science User Facility. "While atoms form molecules based on the nature of their chemical bonds, there has been no easy way to impose such a specific spatial binding scheme on nanoparticles. This is exactly the problem that our method addresses." 

Using the new method, the scientists say they can potentially orchestrate the arrangements of different types of nanoparticles to take advantage of collective or synergistic effects. Examples could include materials that regulate energy flow, rotate light, or deliver biomolecules. 

"We may be able to design materials that mimic nature's machinery to harvest solar energy, or manipulate light for telecommunications applications, or design novel catalysts for speeding up a variety of chemical reactions," Gang said.

Scientists built octahedrons using ropelike structures made of bundles 
of DNA double-helix molecules to form the frames (a). Single strands of 
DNA attached at the vertices (numbered in red) can be used to attach 
nanoparticles coated with complementary strands. This approach can 
yield a variety of structures, including ones with the same type of particle 
at each vertex (b), arrangements with particles placed only on certain 
vertices (c), and structures with different particles placed strategically 
on different vertices (d).

"We may be able to design materials that harvest solar energy, manipulate light, or speed up a variety of chemical reactions." — Brookhaven physicist Oleg Gang

The scientists demonstrated the technique to engineer nanoparticle architectures using an octahedral scaffold with particles positioned in precise locations on the scaffold according to the specificity of DNA coding. The designs included two different arrangements of the same set of particles, where each configuration had different optical characteristics. They also used the geometrical clusters as building blocks for larger arrays, including linear chains and two-dimensional planar sheets.

"Our work demonstrates the versatility of this approach and opens up numerous exciting opportunities for high-yield precision assembly of tailored 3D building blocks in which multiple nanoparticles of different structures and functions can be integrated," said CFN scientist Ye Tian, one of the lead authors on the paper.

Details of assembly

This nanoscale construction approach takes advantage of two key characteristics of the DNA molecule: the twisted-ladder double helix shape, and the natural tendency of strands with complementary bases (the A, T, G, and C letters of the genetic code) to pair up in a precise way. 

First, the scientists created bundles of six double-helix molecules, then put four of these bundles together to make a stable, somewhat rigid building material—similar to the way individual fibrous strands are woven together to make a very strong rope. The scientists then used these ropelike girders to form the frame of three-dimensional octahedrons, "stapling" the linear DNA chains together with hundreds of short complementary DNA strands.

"We refer to these as DNA origami octahedrons," Gang said.

To make it possible to "glue" nanoparticles to the 3D frames, the scientists engineered each of the original six-helix bundles to have one helix with an extra single-stranded piece of DNA sticking out from both ends. When assembled into the 3D octahedrons, each vertex of the frame had a few of these "sticky end" tethers available for binding with objects coated with complementary DNA strands.

"When nanoparticles coated with single strand tethers are mixed with the DNA origami octahedrons, the 'free' pieces of DNA find one another so the bases can pair up according to the rules of the DNA complementarity code. Thus the specifically DNA-encoded particles can find their correspondingly designed place on the octahedron vertices" Gang said.

The scientists can change what binds to each vertex by changing the DNA sequences encoded on the tethers. In one experiment, they encoded the same sequence on all the octahedron's tethers, and attached strands with a complementary sequence to gold nanoparticles. The result: One gold nanoparticle attached to each of octahedron's six vertices. 

In additional experiments the scientists changed the sequence of some vertices and used complementary strands on different kinds of particles, illustrating that they could direct the assembly and arrangement of the particles in a very precise way. In one case they made two different arrangements of the same three pairs of particles of different sizes, producing products with different optical properties. They were even able to use DNA tethers on selected vertices to link octahedrons end to end, forming chains, and in 2D arrays, forming sheets.

Visualization of arrays

By strategically placing tethers on particular vertices, the scientists
used the octahedrons to link nanoparticles into one-dimensional
chainlike arrays (left) and two-dimensional square sheets (right). 

Confirming the particle arrangements and structures was a major challenge because the nanoparticles and the DNA molecules making up the frames have very different densities. Certain microscopy techniques would reveal only the particles, while others would distort the 3D structures. 

To see both the particles and origami frames, the scientists used cryo-electron microscopy (cryo-EM), led by Brookhaven Lab and Stony Brook University biologist Huilin Li, an expert in this technique, and Tong Wang, the paper's other lead co-author, who works in Brookhaven's Biosciences department with Li. They had to subtract information from the images to "see" the different density components separately, then combine the information using single particle 3D reconstruction and tomography to produce the final images. 

"Cryo-EM preserves samples in their near-native states and provides close to nanometer resolution," Wang said. "We show that cryo-EM can be successfully applied to probe the 3D structure of DNA-nanoparticle clusters."

These images confirm that this approach to direct the placement of nanoparticles on DNA-encoded vertices of molecular frames could be a successful strategy for fabricating novel nanomaterials.

This research was supported by the DOE Office of Science.

Brookhaven National Laboratory is supported by the Office of Science of the U.S. Department of Energy.  The Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time.  For more information, please visit science.energy.gov.

Source link: http://www.bnl.gov/newsroom/news.php?a=11728

Fundamental science effort aims to reveal maximum information contained in photons to guide development of future imaging technologies 

Conventional optical imaging systems today largely limit themselves to the measurement of light intensity, providing two-dimensional renderings of three-dimensional scenes and ignoring significant amounts of additional information that may be carried by captured light. For example, many photons traverse complex paths punctuated by multiple bounces prior to entering the aperture of a camera or other imager—a process through which these photons pick up information about their surroundings. Beyond such directional variability, light enjoys other aspects or degrees of freedom—including variations in propagation time, polarization state and spectral content, as well as wave-related properties such as coherence, diffraction and interference—all of which provide potential mechanisms by which light can acquire and convey information. Most of this information remains untapped today.

DARPA’s Revolutionary Enhancement of Visibility by Exploiting Active Light-fields (REVEAL) program seeks to unlock information in photons that current imaging systems discard. The REVEAL program aims to develop a comprehensive theoretical framework to enable maximum information extraction from complex scenes by using all the photon pathways of captured light and leveraging light’s multiple degrees of freedom. The goal is for this framework to guide the development of new imaging hardware and software technologies. Furthermore, the program will test the bounds of the developed framework and the functionality of the new imaging technologies via a challenge problem that calls for full 3D scene reconstruction from a single viewpoint. By contrast, current light-capturing methods require multiple viewpoints for rendering a scene in 3D.

“There are some current limited efforts attempting to exploit some of light’s multiple degrees of freedom, but REVEAL aims to make a revolutionary leap forward by simultaneously addressing all aspects of light,” said Predrag Milojkovic, program manager in DARPA’s Defense Sciences Office. “In effect, we want to use mathematical methods to coax from photons a little more of a story about where they’ve been and what they’ve seen.”

An ability to interpret the information that light may be carrying in degraded form could enhance situational awareness for troops—potentially allowing them to reconstruct, from a single vantage point, a complex scene including objects or people not visible by line-of-sight viewing. Imagine, for example, squad members patrolling a street in a deployed urban environment, and an armed assailant crouching behind a car or a concrete barrier. Without the benefit of different vantage points (from the air, for example), the squad could be blind to the hidden threat. If by chance a glass storefront window were behind the assailant, the squad might spot the assailant’s reflection in the window. But if the backdrop were a brick wall, there would be no visible reflection. By exploiting currently untapped aspects of light and the varied paths of photons bouncing off the brick wall, troops using hardware based on the theoretical foundations provided by REVEAL might someday be able to detect the otherwise hidden assailant.

Another potential application could be determining an unknown material’s composition and other properties from a safe distance, avoiding the potential danger associated with close proximity and physical examination. Based on information carried by the photons interacting with the material, it may be possible for troops in the future to identify radioactive, biological or chemical threats and camouflaged targets from much farther away than currently possible.

“Ultimately, collecting all pertinent information about a scene could enable computational generation of arbitrarily located virtual viewpoints and effectively allow ‘flying through the scene’ without changing one’s physical location,” Milojkovic said.

The REVEAL program is structured in two 24-month phases. The first phase seeks to determine fundamental limits of single-viewpoint scene reconstruction through laboratory experimentation to validate critical concepts and approaches. Phase 2 intends to test and evaluate full 3D scene reconstruction under realistic illumination conditions and develop a general theoretical framework for exploiting light’s multiple degrees of freedom. As a basic research effort, REVEAL will not develop fieldable hardware, software or imaging systems.

A REVEAL Proposers Day webcast is scheduled for May 27, 2015, 3:00 – 4:30 p.m. EDT. Advance registration is required. For more information, visit http://go.usa.gov/38JC4. 

The REVEAL Broad Agency Announcement solicitation is available here:http://go.usa.gov/39jfA 

Source: http://www.darpa.mil/NewsEvents/Releases/2015/05/22.aspx

Visualizing How Radiation Bombardment Boosts Superconductivity

High-energy gold ions impact the crystal surface from above at the sites indicated schematically by dashed circles. Measurement of the strength of superconductivity in this same field of view, as shown on the lower panel, reveals how the impact sites are the regions where the superconductivity is also annihilated. In additional studies, the scientists discovered that it is in these same regions that the strongest pinning of quantized vortices occurs, followed at higher magnetic fields by pinning at the single atom crystal damage sites. Pinning the vortices allows high current superconductivity to flow unimpeded through the rest of the sample.

Atomic-level flyovers show how impact sites of high-energy ions pin potentially disruptive vortices to keep high-current superconductivity flowing

In a paper published May 22, 2015, in Science Advances, researchers from the U.S. Department of Energy's (DOE) Brookhaven and Argonne national laboratories describe atomic-level "flyovers" of the pockmarked landscape of an iron-based superconductor after bombardment with heavy ion radiation. The surface-scanning images show how certain types of damage can pin potentially disruptive magnetic vortices in place, preventing them from interfering with superconductivity. 

Sometimes a little damage can do a lot of good—at least in the case of iron-based high-temperature superconductors. Bombarding these materials with high-energy heavy ions introduces nanometer-scale damage tracks that can enhance the materials' ability to carry high current with no energy loss—and without lowering the critical operating temperature. Such high-current, high-temperature superconductors could one day find application in zero-energy-loss power transmission lines or energy-generating turbines. But before that can happen, scientists would like to understand quantitatively and in detail how the damage helps—and use that knowledge to strategically engineer superconductors with the best characteristics for a given application.

The work is a product of the Center for Emergent Superconductivity, a DOE Energy Frontier Research Center established at Brookhaven in partnership with Argonne and the University of Illinois to foster collaboration and maximize the impact of this research. 

"This study opens a new way forward for designing and understanding high-current, high-performing superconductors," said study co-author J.C. Séamus Davis, a physicist at Brookhaven Lab and Cornell University. "We demonstrated a procedure whereby you can irradiate a sample with heavy ions, visualize what the ions do to the crystal at the atomic scale, and simultaneously see what happens to the superconductivity in precisely the same field of view."

"Quantum vortices are like eddies in a river moving across or counter to the direction of flow. They are the enemy of superconductivity." — Brookhaven Lab and Cornell University physicist Séamus Davis

Argonne physicist Wai-Kwong Kwok led the effort on heavy ion bombardment. "Heavy ions such as gold can create nearly continuous or discontinuous column shaped damage tracks penetrating through the crystal. As the very high-energy ions traverse the material, they melt the crystal at the atomic scale and destroy the crystal structure over a diameter of a few nanometers. It's important to understand the details of how these atomic-scale defects affect local electronic properties and the macroscopic current carrying capacity of the bulk material," he said.

The scientists were particularly interested in how the nanoscale defects interact with microscopic magnetic vortices that form when iron-based superconductors are placed in a strong magnetic field—the type that would be present in turbines and other energy applications.

"These quantum vortices are like eddies in a river moving across or counter to the direction of flow," Davis said. "They are the enemy of superconductivity. You can't prevent them from forming, but scientists as long ago as the 1970s found you can sometimes prevent them from moving around by shooting some high-energy ions into the material to form atomic-scale damage tracks that trap the vortices." 

But random bombardment is, literally, hit-or-miss. Scientists developing materials for energy applications would like to take a more strategic approach by developing a quantitative and predictive theory for how to engineer these materials. 

"If a company comes to us and says we are developing these superconductors and we want them to have this current at a certain temperature in this type of magnetic field, we'd like to be able to tell them exactly what type of defects to introduce," Kwok said. To do that they needed a way to map out the defects, map out the superconductivity, and map out the locations of the vortices—and a quantitative theoretical model that describes how those variables relate to one another and the material's bulk superconductivity.

A precision spectroscopic-imaging scanning tunneling microscope (SI-STM) developed by Davis is the first tool that can map out those three characteristics on the same material. Under Davis' guidance, Brookhaven Lab postdoctoral fellow Freek Massee (now at University Paris-Sud in France) and Cornell University graduate student Peter Sprau—the two lead co-authors on the paper—used the instrument's fine electron-tunneling tip to scan over the material's surface, imaging the atomic structure of the landscape below and the properties of its electrons, atom by atom. The precision allows the scientists to scan the same atoms repeatedly under different external conditions—such as changes in temperature and ramped up magnetic fields—to study the formation, movement, and effects of quantum vortices.

Their atomic-scale imaging studies reveal that vortex pinning—the ability to keep those disruptive eddies in place—depends on the shape of the high-energy ion damage tracks (specifically whether they are point-like or elongated), and also on a form of "collateral damage" discovered by the researchers far from the primary route traversed by each ion. Collaborating theorists at the University of Illinois are now using the experimental results to develop a descriptive framework the scientists can use to predict and test new approaches for materials design.

"These studies will really help us solve at which temperature which type of defects will be best for carrying a particular current," Kwok said. "The ability to achieve critical current by design is one of the ultimate goals of the Center for Emergent Superconductivity."

This work was supported by the DOE Office of Science through the Center for Emergent Superconductivity at Brookhaven National Laboratory.

Brookhaven National Laboratory and Argonne National Laboratory are supported by the Office of Science of the U.S. Department of Energy.  The Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time.  For more information, please visit science.energy.gov.

Source: http://www.bnl.gov/newsroom/news.php?a=11727