From DOE’s Oak Ridge National Laboratory (US): “Giant leap toward quantum internet realized with Bell state analyzer”

From DOE’s Oak Ridge National Laboratory (US)

March 4, 2022
Scott Jones
jonesg@ornl.gov
865.241.6491

ORNL’s Joseph Lukens runs experiments in an optics lab. Credit: Jason Richards/ORNL, U.S. Dept. of Energy.

Scientists’ increasing mastery of quantum mechanics is heralding a new age of innovation. Technologies that harness the power of nature’s most minute scale show enormous potential across the scientific spectrum, from computers exponentially more powerful than today’s leading systems, sensors capable of detecting elusive dark matter, and a virtually unhackable quantum internet.

Researchers at the Department of Energy’s Oak Ridge National Laboratory, Freedom Photonics and Purdue University have made strides toward a fully quantum internet by designing and demonstrating the first ever Bell state analyzer for frequency bin coding.

Their findings were published in Optica.

Before information can be sent over a quantum network, it must first be encoded into a quantum state. This information is contained in qubits, or the quantum version of classical computing “bits” used to store information, that become entangled, meaning they reside in a state in which they cannot be described independently of one another.

Entanglement between two qubits is considered maximized when the qubits are said to be in “Bell states.”

Measuring these Bell states is critical to performing many of the protocols necessary to perform quantum communication and distribute entanglement across a quantum network. And while these measurements have been done for many years, the team’s method represents the first Bell state analyzer developed specifically for frequency bin coding, a quantum communications method that harnesses single photons residing in two different frequencies simultaneously.

“Measuring these Bell states is fundamental to quantum communications,” said ORNL research scientist, Wigner Fellow and team member Joseph Lukens. “To achieve things such as teleportation and entanglement swapping, you need a Bell state analyzer.”

Teleportation is the act of sending information from one party to another across a significant physical distance, and entanglement swapping refers to the ability to entangle previously unentangled qubit pairs.

“Imagine you have two quantum computers that are connected through a fiber-optic network,” Lukens said. “Because of their spatial separation, they can’t interact with each other on their own.

“However, suppose they can each be entangled with a single photon locally. By sending these two photons down optical fiber and then performing a Bell state measurement on them where they meet, the end result will be that the two distant quantum computers are now entangled — even though they never interacted. This so-called entanglement swapping is a critical capability for building complex quantum networks.”

While there are four total Bell states, the analyzer can only distinguish between two at any given time. But that’s fine, as measuring the other two states would require adding immense complexity that is so far unnecessary.

The analyzer was designed with simulations and has demonstrated 98% fidelity; the remaining two percent error rate is the result of unavoidable noise from the random preparation of the test photons, and not the analyzer itself, said Lukens. This incredible accuracy enables the fundamental communication protocols necessary for frequency bins, a previous focus of Lukens’ research.

In the fall of 2020, Lukens and colleagues at Purdue first showed how single frequency-bin qubits can be fully controlled as needed to transfer information over a quantum network.

Using a technology developed at ORNL known as a quantum frequency processor, the researchers demonstrated widely applicable quantum gates, or the logical operations necessary for performing quantum communications protocols. In these protocols, researchers need to be able to manipulate photons in a user-defined way, often in response to measurements performed on particles elsewhere in the network.

Whereas the traditional operations used in classical computers and communications technologies, such as AND/OR, operate on digital zeros and ones individually, quantum gates operate on simultaneous superpositions of zeros and ones, keeping the quantum information protected as it passes through, a phenomenon required to realize true quantum networking.

While frequency encoding and entanglement appear in many systems and are naturally compatible with fiber optics, using these phenomena to perform data manipulation and processing operations has traditionally proven difficult.

With the Bell state analyzer completed, Lukens and colleagues are looking to expand to a complete entanglement swapping experiment, which would be the first of its kind in frequency encoding. This work is planned as part of ORNL’s Quantum-Accelerated Internet Testbed project, recently awarded by DOE.

This work was funded in part by the DOE’s Office of Science through the Early Career Research Program.

See the full article here .

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Please help promote STEM in your local schools.

Stem Education Coalition

Established in 1942, DOE’s Oak Ridge National Laboratory (US) is the largest science and energy national laboratory in the Department of Energy system (by size) and third largest by annual budget. It is located in the Roane County section of Oak Ridge, Tennessee. Its scientific programs focus on materials, neutron science, energy, high-performance computing, systems biology and national security, sometimes in partnership with the state of Tennessee, universities and other industries.

ORNL has several of the world’s top supercomputers, including Summit, ranked by the TOP500 as Earth’s second-most powerful.

ORNL OLCF IBM Q AC922 SUMMIT supercomputer, was No.1 on the TOP500..

The lab is a leading neutron and nuclear power research facility that includes the Spallation Neutron Source and High Flux Isotope Reactor.

ORNL Spallation Neutron Source annotated.

It hosts the Center for Nanophase Materials Sciences, the BioEnergy Science Center, and the Consortium for Advanced Simulation of Light Water Nuclear Reactors.

ORNL is managed by UT-Battelle for the Department of Energy’s Office of Science. DOE’s 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.

Areas of research

ORNL conducts research and development activities that span a wide range of scientific disciplines. Many research areas have a significant overlap with each other; researchers often work in two or more of the fields listed here. The laboratory’s major research areas are described briefly below.

Chemical sciences – ORNL conducts both fundamental and applied research in a number of areas, including catalysis, surface science and interfacial chemistry; molecular transformations and fuel chemistry; heavy element chemistry and radioactive materials characterization; aqueous solution chemistry and geochemistry; mass spectrometry and laser spectroscopy; separations chemistry; materials chemistry including synthesis and characterization of polymers and other soft materials; chemical biosciences; and neutron science.
Electron microscopy – ORNL’s electron microscopy program investigates key issues in condensed matter, materials, chemical and nanosciences.
Nuclear medicine – The laboratory’s nuclear medicine research is focused on the development of improved reactor production and processing methods to provide medical radioisotopes, the development of new radionuclide generator systems, the design and evaluation of new radiopharmaceuticals for applications in nuclear medicine and oncology.
Physics – Physics research at ORNL is focused primarily on studies of the fundamental properties of matter at the atomic, nuclear, and subnuclear levels and the development of experimental devices in support of these studies.
Population – ORNL provides federal, state and international organizations with a gridded population database, called Landscan, for estimating ambient population. LandScan is a raster image, or grid, of population counts, which provides human population estimates every 30 x 30 arc seconds, which translates roughly to population estimates for 1 kilometer square windows or grid cells at the equator, with cell width decreasing at higher latitudes. Though many population datasets exist, LandScan is the best spatial population dataset, which also covers the globe. Updated annually (although data releases are generally one year behind the current year) offers continuous, updated values of population, based on the most recent information. Landscan data are accessible through GIS applications and a USAID public domain application called Population Explorer.

From The DOE’s Oak Ridge National Laboratory (US) and The DOE’s Oak Ridge Leadership Computing Facility (US) : “Summit study spins up new insights into correlated electron systems”

From The DOE’s Oak Ridge National Laboratory (US)

and

The DOE’s Oak Ridge Leadership Computing Facility (US)

February 18, 2022

Scott Jones
jonesg@ornl.gov
865.241.6491

An international team of researchers used Summit to model spin, charge and pair-density waves in cuprates, a type of copper alloy, to explore the materials’ superconducting properties. The results revealed new insights into the relationships between these dynamics as superconductivity develops. Credit: Jason Smith/ORNL

A study led by researchers at the U.S. Department of Energy’s Oak Ridge National Laboratory used the nation’s fastest supercomputer to close in on the answer to a central question of modern physics that could help conduct development of the next generation of energy technologies.

“This is mostly about solving what’s now a decades-old problem,” said Thomas Maier, an ORNL physicist who led the study with researchers from the University of Tennessee and The Swiss Federal Institute of Technology ETH Zürich [Eidgenössische Technische Hochschule Zürich)](CH). “If we can answer the question of what’s the mechanism for superconductivity in certain correlated electron systems and understand the reasons for that behavior, then we can design materials to make the most of that behavior.”

Findings appeared in the PNAS.

The study used Summit, the Oak Ridge Leadership Computing Facility’s 200-petaflop IBM AC922 supercomputing system [below], to simulate interactions among a system of electrons within a solid. The simulations applied the Hubbard model [Nature Physics], the most straightforward model of a system of interacting electrons in various dimensions, to explore how a class of copper alloys known as cuprates act as superconductors that transmit electricity with no loss of energy.

Cuprates can be used in power transmission and generation, high-speed magnetic levitation, or maglev, trains and medical applications, but generally display their full superconducting properties under extreme cold — typically hundreds of degrees below freezing. Explaining this superconductivity could crack the code to deliver superconductivity at room temperature and provide cheap, speedy and sustainable energy.

The Hubbard model, developed nearly 60 years ago and named for British physicist John Hubbard, posits a system of electrons within a 2D lattice. Each electron has a spin — either up or down, similar to the positive and negative poles of a magnet — and no two electrons of the same spin can occupy the same site. The first term of the model describes kinetic energy. In this term, the electrons move or “hop” back and forth between adjacent sites in the lattice and diagonally between their next nearest neighbors. The second term describes interaction energy and the energy increase if two electrons of opposite spin try to occupy a single site.

Hubbard didn’t design the model to explain electron behavior in superconductors like cuprates. Researchers have experimented with layers of copper and oxygen in search of a room-temperature superconductor and adjusted or “doped” the Hubbard model over the years to try to understand superconducting properties.

The doped models remove electrons, leaving “holes” that encourage the remaining electrons to form pairs that easily conduct electricity. Under the right conditions, the holes fall in line to form stripes, believed by scientists to compete with superconductivity, and the electrons form a wave pattern, known as a charge and spin density wave.

But those models so far fail to reliably explain or predict superconductivity in enough detail for practical use.

“The approaches we have to solve this problem are not exact, and the model in theory would be infinite in size with many distinct phases, which requires extremely large, complex calculations,” Maier said. “Energy differences can be tiny — less than a millielectron volt. We can try to approximate all this in a finite-sized lattice, but that approach neglects too many aspects and we end up with a lattice too small to draw the kind of robust conclusions we’re looking for. We need a simple model that describes all the physics and consistently produces the same results.”

Maier’s team received an allocation grant of 900,000 node hours on Summit via the DOE’s Innovative and Novel Computational Impact on Theory and Experiment, or INCITE, program to explore the model in depth. The results revealed new insights into the relationships between electron spin and charge stripes, including when stripes form as superconductivity develops.

“These were some really heavy computations that couldn’t be done anywhere but on Summit,” Maier said. “We kind of took a chance, but it paid off because we finally had a machine that could support computations for a system large enough to see the stripes. This method allowed us to show that when the stripes show up in charge and spin, the superconducting correlations form a similar wave-like pattern known as a pair-density wave. The results could set a new standard for understanding this model.”

The simulations don’t spell out the secret to raising the temperature for superconductivity. But the lessons learned point to targets for further study as researchers zero in on how superconducting occurs.

“We know more each year than we did the last,” Maier said. “Now we need to explore other methods for solving the model and replicate the results. We’re closer now than ever before, and we want to get even closer.”

Support for this research came from the DOE Office of Science’s INCITE program and Scientific Discovery through Advanced Computing program. The OLCF is an Office of Science user facility at ORNL.

See the full article here .

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Please help promote STEM in your local schools.

Stem Education Coalition

The Oak Ridge Leadership Computing Facility (OLCF) was established at Oak Ridge National Laboratory in 2004 with the mission of accelerating scientific discovery and engineering progress by providing outstanding computing and data management resources to high-priority research and development projects.

ORNL’s supercomputing program has grown from humble beginnings to deliver some of the most powerful systems in the world. On the way, it has helped researchers deliver practical breakthroughs and new scientific knowledge in climate, materials, nuclear science, and a wide range of other disciplines.

The OLCF delivered on that original promise in 2008, when its Cray XT “Jaguar” system ran the first scientific applications to exceed 1,000 trillion calculations a second (1 petaflop). Since then, the OLCF has continued to expand the limits of computing power, unveiling Titan in 2013, which was capable of 27 petaflops.

ORNL Cray XK7 Titan Supercomputer once No 1 in the world

Titan was one of the first hybrid architecture systems—a combination of graphics processing units (GPUs), and the more conventional central processing units (CPUs) that have served as number crunchers in computers for decades. The parallel structure of GPUs makes them uniquely suited to process an enormous number of simple computations quickly, while CPUs are capable of tackling more sophisticated computational algorithms. The complimentary combination of CPUs and GPUs allow Titan to reach its peak performance.

The OLCF gives the world’s most advanced computational researchers an opportunity to tackle problems that would be unthinkable on other systems. The facility welcomes investigators from universities, government agencies, and industry who are prepared to perform breakthrough research in climate, materials, alternative energy sources and energy storage, chemistry, nuclear physics, astrophysics, quantum mechanics, and the gamut of scientific inquiry. Because it is a unique resource, the OLCF focuses on the most ambitious research projects—projects that provide important new knowledge or enable important new technologies.

Established in 1942, DOE’s Oak Ridge National Laboratory (US) is the largest science and energy national laboratory in the Department of Energy system (by size) and third largest by annual budget. It is located in the Roane County section of Oak Ridge, Tennessee. Its scientific programs focus on materials, neutron science, energy, high-performance computing, systems biology and national security, sometimes in partnership with the state of Tennessee, universities and other industries.

ORNL has several of the world’s top supercomputers, including Summit, ranked by the TOP500 as Earth’s second-most powerful.

ORNL OLCF IBM AC922 SUMMIT supercomputer, was No.1 on the TOP500..

With a peak performance of 200,000 trillion calculations per second—or 200 petaflops, Summit will be eight times more powerful than ORNL’s previous top-ranked system, Titan. For certain scientific applications, Summit will also be capable of more than three billion billion mixed precision calculations per second, or 3.3 exaops. Summit will provide unprecedented computing power for research in energy, advanced materials and artificial intelligence (AI), among other domains, enabling scientific discoveries that were previously impractical or impossible.

The lab is a leading neutron and nuclear power research facility that includes the Spallation Neutron Source and High Flux Isotope Reactor.

ORNL Spallation Neutron Source annotated.

It hosts the Center for Nanophase Materials Sciences, the BioEnergy Science Center, and the Consortium for Advanced Simulation of Light Water Nuclear Reactors.

ORNL is managed by UT-Battelle for the Department of Energy’s Office of Science. DOE’s 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.

Areas of research

ORNL conducts research and development activities that span a wide range of scientific disciplines. Many research areas have a significant overlap with each other; researchers often work in two or more of the fields listed here. The laboratory’s major research areas are described briefly below.

Chemical sciences – ORNL conducts both fundamental and applied research in a number of areas, including catalysis, surface science and interfacial chemistry; molecular transformations and fuel chemistry; heavy element chemistry and radioactive materials characterization; aqueous solution chemistry and geochemistry; mass spectrometry and laser spectroscopy; separations chemistry; materials chemistry including synthesis and characterization of polymers and other soft materials; chemical biosciences; and neutron science.
Electron microscopy – ORNL’s electron microscopy program investigates key issues in condensed matter, materials, chemical and nanosciences.
Nuclear medicine – The laboratory’s nuclear medicine research is focused on the development of improved reactor production and processing methods to provide medical radioisotopes, the development of new radionuclide generator systems, the design and evaluation of new radiopharmaceuticals for applications in nuclear medicine and oncology.
Physics – Physics research at ORNL is focused primarily on studies of the fundamental properties of matter at the atomic, nuclear, and subnuclear levels and the development of experimental devices in support of these studies.
Population – ORNL provides federal, state and international organizations with a gridded population database, called Landscan, for estimating ambient population. LandScan is a raster image, or grid, of population counts, which provides human population estimates every 30 x 30 arc seconds, which translates roughly to population estimates for 1 kilometer square windows or grid cells at the equator, with cell width decreasing at higher latitudes. Though many population datasets exist, LandScan is the best spatial population dataset, which also covers the globe. Updated annually (although data releases are generally one year behind the current year) offers continuous, updated values of population, based on the most recent information. Landscan data are accessible through GIS applications and a USAID public domain application called Population Explorer.

From DOE’s Oak Ridge National Laboratory (US): “Updated exascale system for Earth simulations delivers twice the speed”

From DOE’s Oak Ridge National Laboratory (US)

January 20, 2022

Kimberly A Askey
askeyka@ornl.gov
865.576.2841

The Energy Exascale Earth System Model project reliably simulates aspects of earth system variability and projects decadal changes that will critically impact the U.S. energy sector in the future. A new version of the model delivers twice the performance of its predecessor. Credit: E3SM, Dept. of Energy.

A new version of the Energy Exascale Earth System Model, or E3SM, is two times faster than an earlier version released in 2018.

Earth system models have weather-scale resolution and use advanced computers to simulate aspects of Earth’s variability and anticipate decadal changes that will critically impact the U.S. energy sector in coming years.

Scientists at the Department of Energy’s Oak Ridge National Laboratory are part of the team that developed version 2 of the model — E3SMv2 — which was released to the scientific community in September 2021.

“E3SMv2 delivered twice the performance over E3SMv1 when using identical computational resources,” said ORNL computational scientist Sarat Sreepathi, who co-leads the E3SM Performance Group. “This is a significant achievement as the performance boost is reflected while running the fully integrated Earth system model and not just confined to smaller model components.”

The Earth, with its myriad interactions of atmosphere, oceans, land and ice components, presents an extraordinarily complex system for investigation. Earth system simulation involves solving approximations of physical, chemical and biological governing equations on spatial grids at resolutions that are as fine in scale as computing resources will allow.

“Even with the addition of new features in E3SMv2 to the atmosphere model and how it represents precipitation and clouds, we still doubled the model throughput,” Sreepathi said. “To put it another way, we cut the computational run time or time-to-solution in half.”

“E3SMv2 allows us to more realistically simulate the present, which gives us more confidence to simulate the future,” said David Bader, Lawrence Livermore National Laboratory scientist and lead of the E3SM project. “The increase in computing power allows us to add more detail to processes and interactions that results in more accurate and useful simulations than the previous version.”

Achieving these improvements required collaboration across the national laboratory system. Sreepathi, along with ORNL’s Gaurab KC and Youngsung Kim, accelerated the effort by creating a comprehensive monitoring framework called PACE, or Performance Analytics for Computational Experiments. The PACE web portal provided both an automatic data collection system and a streamlined interface for scientists to evaluate the performance of E3SM experiments executed on DOE supercomputers. These data facilitated feedback-driven E3SMv2 model development and allowed researchers to optimize their experiments.

“Using the PACE web portal helped the multi-laboratory team understand how new model features were impacting computational performance,” said Sreepathi. “We were able to accurately track the evolution of the model’s performance.”

The E3SM project reliably simulates aspects of Earth system variability, including regional air and water temperatures, which can strain energy grids; water availability, which affects power plant operations; extreme water-cycle events, such as floods and droughts, which impact infrastructure and bioenergy resources; and sea-level rise and coastal flooding, which threaten coastal infrastructure.

In addition, the resolution has been refined due to more powerful computers. There are now two fully coupled configurations: 100-kilometer, or km, globally uniform resolution atmosphere model and a regionally refined model, or RRM, with a resolution with 25 km over North America and 100 km elsewhere. The refined mesh configuration is particularly well suited for DOE applications.

“Thanks to the performance improvements, the RRM configuration of E3SMv2 runs as fast as E3SMv1 did in its standard resolution configuration (100 km) a few years ago. We are essentially getting the much higher resolution for ‘free,’” said LLNL atmospheric scientist Chris Golaz.

The team is now conducting the simulation campaign with E3SMv2. Team members have already simulated several thousand years, and are planning to run several thousand more.

The project includes more than 100 scientists and software engineers at multiple DOE laboratories as well as several universities; the DOE laboratories include DOE’s Argonne National Laboratory(US), DOE’s Brookhaven National Laboratory(US), DOE’s Lawrence Livermore National Laboratory(US), DOE’s Lawrence Berkeley National Laboratory (US), DOE’s Los Alamos National Lab (US), Oak Ridge, DOE’s Pacific Northwest National Laboratory (US) and DOE’s Sandia National Laboratory (US). In recognition of unifying the DOE earth system modeling community to perform high-resolution coupled simulations, the E3SM executive committee was awarded the Secretary of Energy’s Achievement Award in 2015.

In addition, the E3SM project benefits from DOE programmatic collaborations, including The Exascale Computing Project and research efforts in Scientific Discovery Through Advanced Computing, Climate Model Development and Validation, Atmospheric Radiation Measurement, Program for Climate Model Diagnosis and Intercomparison, International Land Model Benchmarking Project, Community Earth System Model and Next Generation Ecosystem Experiments for the Arctic and the Tropics.

The E3SM project is supported by the Biological and Environmental Research program in DOE’s Office of Science.

See the full article here .

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

Please help promote STEM in your local schools.

Stem Education Coalition

Established in 1942, DOE’s Oak Ridge National Laboratory (US) is the largest science and energy national laboratory in the Department of Energy system (by size) and third largest by annual budget. It is located in the Roane County section of Oak Ridge, Tennessee. Its scientific programs focus on materials, neutron science, energy, high-performance computing, systems biology and national security, sometimes in partnership with the state of Tennessee, universities and other industries.

ORNL has several of the world’s top supercomputers, including Summit, ranked by the TOP500 as Earth’s second-most powerful.

ORNL OLCF IBM AC922 SUMMIT supercomputer, was No.1 on the TOP500..

The lab is a leading neutron and nuclear power research facility that includes the Spallation Neutron Source and High Flux Isotope Reactor.

ORNL Spallation Neutron Source annotated.

It hosts the Center for Nanophase Materials Sciences, the BioEnergy Science Center, and the Consortium for Advanced Simulation of Light Water Nuclear Reactors.

ORNL is managed by UT-Battelle for the Department of Energy’s Office of Science. DOE’s 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.

Areas of research

ORNL conducts research and development activities that span a wide range of scientific disciplines. Many research areas have a significant overlap with each other; researchers often work in two or more of the fields listed here. The laboratory’s major research areas are described briefly below.

Chemical sciences – ORNL conducts both fundamental and applied research in a number of areas, including catalysis, surface science and interfacial chemistry; molecular transformations and fuel chemistry; heavy element chemistry and radioactive materials characterization; aqueous solution chemistry and geochemistry; mass spectrometry and laser spectroscopy; separations chemistry; materials chemistry including synthesis and characterization of polymers and other soft materials; chemical biosciences; and neutron science.
Electron microscopy – ORNL’s electron microscopy program investigates key issues in condensed matter, materials, chemical and nanosciences.
Nuclear medicine – The laboratory’s nuclear medicine research is focused on the development of improved reactor production and processing methods to provide medical radioisotopes, the development of new radionuclide generator systems, the design and evaluation of new radiopharmaceuticals for applications in nuclear medicine and oncology.
Physics – Physics research at ORNL is focused primarily on studies of the fundamental properties of matter at the atomic, nuclear, and subnuclear levels and the development of experimental devices in support of these studies.
Population – ORNL provides federal, state and international organizations with a gridded population database, called Landscan, for estimating ambient population. LandScan is a raster image, or grid, of population counts, which provides human population estimates every 30 x 30 arc seconds, which translates roughly to population estimates for 1 kilometer square windows or grid cells at the equator, with cell width decreasing at higher latitudes. Though many population datasets exist, LandScan is the best spatial population dataset, which also covers the globe. Updated annually (although data releases are generally one year behind the current year) offers continuous, updated values of population, based on the most recent information. Landscan data are accessible through GIS applications and a USAID public domain application called Population Explorer.

From The DOE’s Oak Ridge National Laboratory (US) : “Key witness helps scientists detect ‘spooky’ quantum entanglement in solid materials”

From The DOE’s Oak Ridge National Laboratory (US)

November 8, 2021

Scott Jones
jonesg@ornl.gov
865.241.6491

A material’s spins, depicted as red spheres, are probed by scattered neutrons. Applying an entanglement witness, such as the QFI calculation pictured, causes the neutrons to form a kind of quantum gauge. This gauge allows the researchers to distinguish between classical and quantum spin fluctuations. Credit: Nathan Armistead/ORNL, Department of Energy (US).

Quantum entanglement occurs when two particles appear to communicate without a physical connection, a phenomenon Albert Einstein famously called “spooky action at a distance.” Nearly 90 years later, a team led by the U.S. Department of Energy’s Oak Ridge National Laboratory demonstrated the viability of a “quantum entanglement witness” capable of proving the presence of entanglement between magnetic particles, or spins, in a quantum material.

The team – including researchers from ORNL, Helmholtz Center Berlin for Materials and Energy [Helmholtz-Zentrum für Materialien und Energie] (HZB) (DE) , The Technical University of Berlin [Technische Universität Berlin](DE) , Laue – Langevin Institute [Institut Laue-Langevin (ILL)](FR), The University of Oxford (UK) and Adam Mickiewicz University [[Uniwersytet im. Adama Mickiewicza w Poznaniu](PL) – tested three entanglement witnesses using a combination of neutron scattering experiments and computational simulations. Entanglement witnesses are techniques that act as data analysis tools to determine which spins cross the threshold between the classical and quantum realms.

First introduced by John Stewart Bell in the 1960s, entanglement witnesses confirmed that the quantum theory questioned by other scientists had been correct. Bell’s technique relied on detecting one pair of particles at a time, but this approach is not useful for studying solid materials composed of trillions and trillions of particles. By targeting and detecting large collections of entangled spins using new entanglement witnesses, the team extended this concept to characterize solid materials and study exotic behavior in superconductors and quantum magnets.

To ensure that the witnesses could be trusted, the team applied all three of them to a material they knew to be entangled because of a previous spin dynamics study. Two of the witnesses, which are based on Bell’s approach, adequately indicated the presence of entanglement in this one-dimensional spin chain – a straight line of adjacent spins that communicate with their neighbors while disregarding other particles – but the third, which is based on quantum information theory, fared exceptionally well at the same task.

“The quantum Fisher information, or QFI, witness showed a close overlap between theory and experiment, which makes it a robust and reliable way to quantify entanglement,” said Allen Scheie, a postdoctoral research associate at ORNL and a lead author of the team’s proof-of-concept paper published in Physical Review B.

Because fluctuations in a material that appear to be quantum in nature can be caused by random thermal motion, which only vanishes at absolute zero on the temperature scale, most modern methods cannot distinguish between these false alarms and actual quantum activity. The team not only confirmed the theoretical prediction that entanglement increases as temperature decreases but also successfully differentiated between classical and quantum activity as part of the most comprehensive QFI demonstration since the technique was proposed in 2016.

“The most interesting materials are full of quantum entanglement but those are precisely the ones that are the most difficult to calculate,” said ORNL neutron scattering scientist Alan Tennant, who leads a project focused on quantum magnets for the Quantum Science Center, or QSC, a DOE National Quantum Information Science Research Center headquartered at ORNL.

Previously, the challenge of quickly identifying quantum materials presented a significant roadblock to the center’s mission, which involves exploiting entanglement to develop novel devices and sensors while advancing the field of quantum information science. Streamlining this process with QFI allows QSC researchers to focus on harnessing the power of substances such as rare phases of matter called quantum spin liquids and materials that do not resist electricity called superconductors for data storage and computing applications.

“The power of QFI comes from its connection to quantum metrology in which scientists entangle multiple quasiparticles to shrink uncertainty and obtain extremely precise measurements,” Scheie said. “The QFI witness reverses this approach by using the precision of an existing measurement to determine the minimum number of particles each spin is entangled with. This is a powerful way to reveal quantum interactions, which means that QFI is really applicable to any quantum magnetic material.”

Having established that QFI could correctly categorize materials, the team tested a second one-dimensional spin chain, a more complex material featuring anisotropy, which is a property that causes spins to lie in a plane rather than rotating at random. The researchers applied a magnetic field to the spin chain and observed an entanglement transition, in which the amount of entanglement fell to zero before reappearing. They published this finding in Physical Review Letters.

To achieve these results, the researchers studied both spin chains using neutron scattering and then analyzed legacy data from experiments conducted decades ago at the ISIS Neutron Source in England and The Langevin Institute [Institut Laue-Langevin (ILL)](FR) along with new data from the Wide Angular-Range Chopper Spectrometer located at the Spallation Neutron Source [below], a DOE Office of Science user facility operated by ORNL.

STFC ISIS Neutron and Muon source

They also ran complementary simulations to validate the results against idealized theoretical data.

Neutrons, which Tennant describes as “beautifully simple,” are an ideal tool for probing the properties of a material because of their neutral charge and nondestructive nature.

“By studying the distribution of neutrons that scatter off of a sample, which transfers energy, we were able to use neutrons as a gauge to measure quantum entanglement without relying on theories and without the need for massive quantum computers that don’t exist yet,” Tennant said.

According to the team, this combination of advanced computational and experimental resources provided answers about the nature of quantum entanglement originally asked by the founders of quantum mechanics. Scheie expects that QFI calculations are likely to become part of the standard procedure for neutron scattering experiments that could eventually characterize even the most mysterious quantum materials.

The researchers received support from the DOE Office of Science, DOE’s Scientific Discovery through Advanced Computing program, the QSC, ORNL’s Laboratory Directed Research and Development program, the Center for Nanophase Materials Sciences – a DOE Office of Science user facility located at ORNL – and the European Research Council under the European Union Horizon 2020 Research and Innovation Programme.

See the full article here .

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

Please help promote STEM in your local schools.

Stem Education Coalition

Established in 1942, DOE’s Oak Ridge National Laboratory (US) is the largest science and energy national laboratory in the Department of Energy system (by size) and third largest by annual budget. It is located in the Roane County section of Oak Ridge, Tennessee. Its scientific programs focus on materials, neutron science, energy, high-performance computing, systems biology and national security, sometimes in partnership with the state of Tennessee, universities and other industries.

ORNL has several of the world’s top supercomputers, including Summit, ranked by the TOP500 as Earth’s second-most powerful.

IBM AC922 SUMMIT supercomputer, was No.1 on the TOP500.

The lab is a leading neutron and nuclear power research facility that includes the Spallation Neutron Source and High Flux Isotope Reactor.

ORNL Spallation Neutron Source annotated.

It hosts the Center for Nanophase Materials Sciences, the BioEnergy Science Center, and the Consortium for Advanced Simulation of Light Water Nuclear Reactors.

ORNL is managed by UT-Battelle for the Department of Energy’s Office of Science. DOE’s 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.

Areas of research

ORNL conducts research and development activities that span a wide range of scientific disciplines. Many research areas have a significant overlap with each other; researchers often work in two or more of the fields listed here. The laboratory’s major research areas are described briefly below.

Chemical sciences – ORNL conducts both fundamental and applied research in a number of areas, including catalysis, surface science and interfacial chemistry; molecular transformations and fuel chemistry; heavy element chemistry and radioactive materials characterization; aqueous solution chemistry and geochemistry; mass spectrometry and laser spectroscopy; separations chemistry; materials chemistry including synthesis and characterization of polymers and other soft materials; chemical biosciences; and neutron science.
Electron microscopy – ORNL’s electron microscopy program investigates key issues in condensed matter, materials, chemical and nanosciences.
Nuclear medicine – The laboratory’s nuclear medicine research is focused on the development of improved reactor production and processing methods to provide medical radioisotopes, the development of new radionuclide generator systems, the design and evaluation of new radiopharmaceuticals for applications in nuclear medicine and oncology.
Physics – Physics research at ORNL is focused primarily on studies of the fundamental properties of matter at the atomic, nuclear, and subnuclear levels and the development of experimental devices in support of these studies.
Population – ORNL provides federal, state and international organizations with a gridded population database, called Landscan, for estimating ambient population. LandScan is a raster image, or grid, of population counts, which provides human population estimates every 30 x 30 arc seconds, which translates roughly to population estimates for 1 kilometer square windows or grid cells at the equator, with cell width decreasing at higher latitudes. Though many population datasets exist, LandScan is the best spatial population dataset, which also covers the globe. Updated annually (although data releases are generally one year behind the current year) offers continuous, updated values of population, based on the most recent information. Landscan data are accessible through GIS applications and a USAID public domain application called Population Explorer.