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Primeur weekly 2019-03-11

Focus

Interview with EuroHPC JU interim executive director Gustav Kalbe ...

Quantum computing

9,1 million euro for trinational quantum research ...

IBM achieves highest quantum volume to date and establishes roadmap for reaching quantum advantage ...

Microsoft Quantum Team is announcing the Microsoft Quantum Network ...

Los Alamos National Laboratory upgrades to D-Wave 2000Q quantum computer ...

New hurdle cleared in race toward quantum computing ...

Focus on Europe

Hyperion Research invites submissions for HPC Innovation Excellence Awards ...

Optalysys launches world's first commercial optical processing system, the FT:X 2000 ...

SDSC's Research Data Services to host first U.S. GO FAIR Office ...

Intel to support the Irish Centre for High End Computing on new collaborative quantum computing project ...

New simulation methods to visualise quantum effects in superfluid fermions ...

Middleware

International team to organize 2019 survey of MPI usages ...

Energy Laboratory chooses Qumulo's file storage for its computational science centre ...

Hardware

Mellanox showcases live system demonstrations of LinkX 200G & 400G cables and transceivers at OFC 2019 ...

Alan D. George named Interim Director of the Pittsburgh Supercomputing Center ...

ScaleMP and AMD announce strategic collaboration for scale-up EPYC servers ...

NVIDIA to acquire Mellanox for $6,9 billion ...

Air Force Research Laboratory introduces new sharable supercomputing capability for classified research ...

Applications

High CO2 levels can destabilize marine layer clouds ...

Using supercomputers to checkmate cancer ...

Revealing the role of neutron stars in gravitational wave discoveries ...

UC San Diego scientists computationally model chemical realities of water ...

TACC assists in massive data collection effort in lung development to help premature babies ...

New AI tool revolutionizes process for matching cancer patients with clinical trials ...

Raph Hix models the inner workings of supernovae on the world’s most powerful supercomputers ...

EPFL researchers simulate the process of adhesive wear ...

The Cloud

Oracle participates in National Science Foundation Cloud for scientific research project ...

New simulation methods to visualise quantum effects in superfluid fermions


Schematic structure of a neutron star. Image: Watts A. et al., Rev. Mod. Phys. 88, 021001.
4 Mar 2019 Lugano - What exactly happens inside neutron stars - the final stage of a giant star - is subject to speculation. In terms of physics, the interiors of neutron stars, cold atomic gasses and nuclear systems all have one thing in common: they are gaseous systems made up of highly interactive, superfluid fermions. Researchers fed the supercomputer "Piz Daint" with a new simulation method, and the results are finally offering insight into unknown processes of such systems.
The shapes represent the various vortices that the researchers discovered forming in a spin-imbalanced atomic cloud. Image: Gabriel Wlazlowski.

Neutron stars, cold atomic gasses and nuclear systems are all gaseous systems made up of highly interactive, superfluid fermions, i.e. systems whose matter is made up of particles with half-integer spin - intrinsic angular momentum. The category of fermions includes electrons, protons and neutrons. At very low temperatures, these systems are described as superfluid, meaning that the particles in them do not generate any internal friction whatsoever and possess the property of almost perfect thermal conductivity.

These superfluid Fermi gases do not behave according to the laws of classical physics, but rather can be better described using the laws of quantum mechanics. Gabriel Wlazlowski, an assistant professor at Warsaw University of Technology and the University of Washington in Seattle, and his team have recently developed a new method based on density functional theory (DFT). With the help of the supercomputer "Piz Daint", they are aiming to create a highly precise description of these superfluid fermion systems and their dynamics. In other words, they will describe how vortices form and decay in this "atomic cloud". The results were published inPhysical Review Letters.

In superfluid Fermi gases, individual fermions and correlated fermions occur alongside each other. From correlations between particles with opposite spins, superconducting properties of materials emerge. Correlated fermions, like electrons in superconductors, exist in pairs as a condensate and are called Cooper pairs. Each pair can move through the system without energy loss. However, for many years it has been investigated what happens in spin-imbalanced cases, because not every particle can find a partner with opposite spin to form the Cooper pair. "The situation is similar to a folk dance party, where the numbers of men and women are imbalanced, someone would be frustrated as he/she cannot form a pair", stated Gabriel Wlazlowski. What do unpaired atoms do? This is exactly what the researchers have been studying.

An accurate description of superfluid Fermi gases, especially of spin-imbalanced systems, has previously been very difficult. Spin imbalance occurs when a system is affected by a magnetic field, Gabriel Wlazlowski said. The target of the researcher now is to apply DFT formalism to neutron stars as well as to magnetars - neutron stars with a strong magnetic field - for predicting what happens inside. "Clearly, there is no way to probe explicitly interiors of stars. Thus, we need to rely on simulations, for which we need reliable tools", Gabriel Wlazlowski stated. Therefore, researchers were searching for a terrestrial system that shares a lot of similarities with the target system. "It turns out that strongly interacting ultra-cold atomic gases are very similar to neutron matter."

For their numerical experiments, the researchers used the most complete quantum theoretical description currently available for many-body systems to describe this type of system. This enabled them to produce a more in-depth DFT theory for superfluid systems. They also combined it with a special time-dependent superfluid local density approximation for a unitary spin-imbalanced Fermi gas. "Without approximation, superconducting DFT will lead to integro-differentional equations that are beyond reach even for exascale supercomputers", Gabriel Wlazlowski stated. With their current study, the researchers are now able to demonstrate that this approximation is working very well in the considered systems.

"By creating a visualisation of the calculations and comparing these images with photos from experiments, we were able to observe these quantum mechanical systems directly", stated Gabriel Wlazlowski. "Comparing the theoretical and experimental results yielded excellent correlations." This allowed the researchers to offer up proof that their new method for calculating the behaviour of such systems works. The next step will be for them to apply the method to processes that will never be visible to the naked eye, such as those inside neutron stars.

Another important finding came from the researchers’ observations of three different vortex decay patterns in the superfluids. According to the researchers, the various decay patterns depend on the spin polarization of the particles of the system. They also say that the polarization is caused by the sucking effect of the unpaired particles in the superfluid gas. In other words: nature tries to collect unpaired particles in regions, where they do not hinder the flow. Cores of quantized vortices are such places, and polarization of the different vortices should then prevent them from bonding again, or so the researchers predict. They therefore assume that polarization effects have a considerable influence on quantum phenomena and will lead to new, yet-to-be-discovered areas of physics. "However, just to show that we reproduce some data is not enough - can we predict something completely new?", Gabriel Wlazlowski asked himself. For him, the next important barrier to overcome will be to find out if the method has predictive power.

This kind of highly complex problem requires enormous computing power. Technically, the researchers solve hundreds of thousands of time-dependent nonlinear coupled 3D Partial Differential Equations (PDEs). For this reason, the authors of the study submitted a request for computing time to the Partnership for Advanced Computing in Europe (PRACE) and were granted access to use Piz Daint at CSCS, because, according to the authors, in Europe only Piz Daint can handle this type of calculations.

Wlazlowski G., Sekizawa K., Marchwiany M., and Magierski P. are the authors of the paper titled " Suppressed solitonic cascade in spin-imbalanced superfluid Fermi gas ", published inPhysical Review Letters(2018), 120, 253002 - DOI 10.1103/PhysRevLett.120.253002.

Source: Swiss National Supercomputing Centre - CSCS

Back to Table of contents

Primeur weekly 2019-03-11

Focus

Interview with EuroHPC JU interim executive director Gustav Kalbe ...

Quantum computing

9,1 million euro for trinational quantum research ...

IBM achieves highest quantum volume to date and establishes roadmap for reaching quantum advantage ...

Microsoft Quantum Team is announcing the Microsoft Quantum Network ...

Los Alamos National Laboratory upgrades to D-Wave 2000Q quantum computer ...

New hurdle cleared in race toward quantum computing ...

Focus on Europe

Hyperion Research invites submissions for HPC Innovation Excellence Awards ...

Optalysys launches world's first commercial optical processing system, the FT:X 2000 ...

SDSC's Research Data Services to host first U.S. GO FAIR Office ...

Intel to support the Irish Centre for High End Computing on new collaborative quantum computing project ...

New simulation methods to visualise quantum effects in superfluid fermions ...

Middleware

International team to organize 2019 survey of MPI usages ...

Energy Laboratory chooses Qumulo's file storage for its computational science centre ...

Hardware

Mellanox showcases live system demonstrations of LinkX 200G & 400G cables and transceivers at OFC 2019 ...

Alan D. George named Interim Director of the Pittsburgh Supercomputing Center ...

ScaleMP and AMD announce strategic collaboration for scale-up EPYC servers ...

NVIDIA to acquire Mellanox for $6,9 billion ...

Air Force Research Laboratory introduces new sharable supercomputing capability for classified research ...

Applications

High CO2 levels can destabilize marine layer clouds ...

Using supercomputers to checkmate cancer ...

Revealing the role of neutron stars in gravitational wave discoveries ...

UC San Diego scientists computationally model chemical realities of water ...

TACC assists in massive data collection effort in lung development to help premature babies ...

New AI tool revolutionizes process for matching cancer patients with clinical trials ...

Raph Hix models the inner workings of supernovae on the world’s most powerful supercomputers ...

EPFL researchers simulate the process of adhesive wear ...

The Cloud

Oracle participates in National Science Foundation Cloud for scientific research project ...