Lifeboat Foundation

What happens to information after it has passed beyond the event horizon of a black hole? There have been suggestions that the geometry of wormholes might help us solve this vexing problem – but the math has been tricky, to say the least.

In a new paper, an international team of physicists has found a workaround for better understanding how a collapsing black hole can avoid breaking the fundamental laws of quantum physics (more on that in a bit).

Although highly theoretical, the work suggests there are likely things we are missing in the quest to resolve general relativity with quantum mechanics.

Superconductors—metals in which electricity flows without resistance—hold promise as the defining material of the near future, according to physicist Brad Ramshaw, and are already used in medical imaging machines, drug discovery research and quantum computers being built by Google and IBM.

However, the super-low temperatures conventional superconductors need to function—a few degrees above absolute zero—make them too expensive for wide use.

In their quest to find more useful superconductors, Ramshaw, the Dick & Dale Reis Johnson Assistant Professor of physics in the College of Arts and Sciences (A&S), and colleagues have discovered that magnetism is key to understanding the behavior of electrons in “high-temperature” superconductors. With this finding, they’ve solved a 30-year-old mystery surrounding this class of superconductors, which function at much higher temperatures, greater than 100 degrees above absolute zero. Their paper, “Fermi Surface Transformation at the Pseudogap Critical Point of a Cuprate Superconductor,” published in Nature Physics March 10.

Scientists from the Max Planck Institute for Polymer Research, Paderborn University, and the University of Konstanz have succeeded in achieving a rare quantum state. They are the first to have demonstrated Wannier-Stark localization in a polycrystalline substance. Predicted around 80 years ago, the effect has only recently been proven — in a monocrystal. Until now, researchers assumed this localization to be possible only in such monocrystalline substances which are very complicated to produce. The new findings represent a breakthrough in the field of physics and could in future give rise to new optical modulators, for example, that can be used in information technologies based on light, among other things. The physicists have published their findings in the well-respected technical journal, Nature Communications.

Stronger and faster than lightning

The atoms of a crystal are arranged in a three-dimensional grid, held together by chemical bonds. These bonds can, however, be dissolved by very strong electric fields which displace atoms, even going so far as to introduce so much energy into the crystal that it is destroyed. This is what happens when lightning strikes and materials liquefy, vaporize or combust, for example. To demonstrate Wannier-Stark localization, the scientists’ experiments involved setting up electric fields of several million volts per centimeter, much stronger than the fields involved in lightning strikes. During this process, the electronic system of a solid — in this case, a polycrystal — is forced far from a state of equilibrium for a very short time. Wannier-Stark localization involves virtually shutting down some of the chemical bonds temporarily. This state can only be maintained for less than a picosecond — one millionth of one millionth of a second — without destroying the substance.

A new review paper on magnetic topological materials introduces a theoretical concept that interweaves magnetism and topology. It identifies and surveys potential new magnetic topological materials and suggests possible future applications in spin and quantum electronics and as materials for efficient energy conversion.

Magnetic topological materials represent a class of compounds whose properties are strongly influenced by the topology of the electronic wavefunctions coupled with their spin configuration. Topology is a simple concept dealing with the surfaces of objects. The topology of a mathematical structure is identical if it is preserved under continuous deformation. A pancake has the same topology as a cube, a donut as a coffee cup, and a pretzel as a board with three holes. Adding spin offers additional structure—a new degree of freedom—for the realization of new states of matter that are not known in non-magnetic materials. Magnetic topological materials can support chiral channels of electrons and spins, and can be used for an array of applications including information storage, control of dissipationless spin and charge transport, and giant responses under external stimuli such as temperature and light.

The review summarizes the theoretical and experimental progress achieved in the field of magnetic topological materials beginning with the theoretical prediction of the quantum anomalous Hall effect without Landau levels, leading to recent discoveries of magnetic Weyl semimetals and antiferromagnetic topological insulators. It also outlines recent tabulations of all magnetic symmetry group representations and topology. As a result, all known magnetic materials—including future discoveries—can be fully characterized by their topological properties. The identification of materials for a specific technological application (e.g., quantum anomalous Hall) is straightforward.

Do two promising structural materials corrode at very high temperatures when in contact with “liquid metal fuel breeders” in fusion reactors? Researchers of Tokyo Institute of Technology (Tokyo Tech), National Institutes for Quantum Science and Technology (QST), and Yokohama National University (YNU) now have the answer. This high-temperature compatibility of reactor structural materials with the liquid breeder—a lining around the reactor core that absorbs and traps the high energy neutrons produced in the plasma inside the reactor—is key to the success of a fusion reactor design.

Fusion reactors could be a powerful means of generating clean electricity, and currently, several potential designs are being explored. In a fusion reactor, the fusion of two nuclei releases massive amounts of energy. This energy is trapped as heat in a “breeding blanket” (BB), typically a liquid lithium alloy, surrounding the reactor core. This heat is then used to run a turbine and generate electricity. The BB also has an essential function of fusion fuel breeding, creating a closed fuel cycle for the endless operation of the reactors without fuel depletion.

The operation of a BB at extremely high temperatures over 1,173 K serves the attractive function of producing hydrogen from water, which is a promising technology for realizing a carbon-neutral society. This is possible because the BB heats up to over 1,173 K by absorbing the energy from the fusion reaction. At such temperatures, there is the risk of structural materials in contact with the BB becoming corroded, compromising the safety and stability of the reactors. It is thus necessary to find structural materials that are chemically compatible with the BB material at these temperatures.

Both quantum computing and machine learning have been touted as the next big computer revolution for a fair while now.

However, experts have pointed out that these techniques aren’t generalized tools – they will only be the great leap forward in computer power for very specialized algorithms, and even more rarely will they be able to work on the same problem.

Continue reading “What’s Inside a Black Hole? Quantum Computers May Be Able to Simulate It” »

Our new US2QC program aims to determine if an underexplored approach to quantum computing is capable of achieving operation much faster than conventional predictions. https://ow.ly/ABgY50I1qEq

Researchers at the National Institute of Standards and Technology (NIST) have constructed and tested a system that allows commercial electronic components—such as microprocessors on circuit boards—to operate in close proximity with ultra-cold devices employed in quantum information processing. That design allows four times as much data to be output for the same number of connected wires.

In the rising excitement about quantum computing, it can be easy to overlook the physical fact that the data produced by manipulation of quantum bits (qubits) at cryogenic temperatures a few thousandths of a degree above absolute zero still has to be initiated, read out, and stored using conventional electronics, which presently work only at room temperature, several meters away from the qubits. This separation has obstructed development of quantum computing devices that outperform their classical counterparts.

That extra distance between the quantum computing elements and the external electronics requires extra time for signals to travel, which also causes signals to degrade. In addition, each (comparatively very hot) wire needed to connect the electronics to the cryogenic components adds heat, making it hard to maintain the ultracold temperature required for the quantum devices to work.