Industrial Physics Forum 2013: Frontiers in physics

The second session of this year’s Industrial Physics Forum, Frontiers in Physics, explored a variety of topics ranging from the smallest building blocks of matter to the oldest galaxies in the universe. Five speakers presented the histories of and future outlooks for their fields.

More to come on the Higgs

In July, particle physicists sifting data collected by the Large Hadron Collider made a groundbreaking announcement. Pairs of photons spotted by LHC’s detectors supported the existence of a Higgs boson with a mass about 133 times that of a proton, and a Higgs field that grants mass to other particles.

That preliminary finding, just shy of the 5-sigma standard for claiming discovery, has now strengthened to a 7.4-sigma result with the inclusion of more data, said Michael Tuts of Columbia University and the LHC’s ATLAS detector team. A search for another hallmark of the Higgs, pairs of electrons and muons, provided corroborating evidence at the 6.6-sigma level.

Now shut down for repairs and upgrades , the LHC hasn’t yet finished its work on the Higgs. The particle should also decay into fermions such as tau leptons and bottom quarks, which hasn’t yet been shown.

‘The errors bars are large enough right now that we can’t say anything too definitive about that right now,’ said Tuts.

The spin of the particle is also still uncertain. After analyzing more than half of the data collected so far, CERN scientists favor a spin of zero, consistent with the simplest Higgs predicted by the standard model of particle physics. But there’s still a 10% chance that the particle has a spin of two, consistent with it being a graviton. Looking at the rest of the data collected to date could improve the statistics by a factor of the square root of two, but a 5-sigma result for spin may have to wait for the “bigger, badder” LHC due to start up again in two years, said Tuts.

Entangled magnetism

More than half a century ago, physicist Louis Néel described antiferromagnetism as a static, ordered state in which ions inside a cooled material line up such that their spins point in opposite directions. Experiments with neutrons then confirmed this depiction for some antiferromagnetic materials.

Now Collin Broholm of the National Institute of Standards and Technology and other scientists have found a stranger process at work in antiferromagnets rooted in the quantum phenomenon of entanglement. Frustrated materials with charges that never settle down neatly, even at extremely low temperatures, seem to host excitations that can be thought of as entangled quasiparticles.

Neutrons fired into these materials scatter in ways consistent with the presence of multiple quasiparticles linked over large distances. One-dimensional geometries can give rise to entangled spin states, as can two-dimensional networks of triangles and hexagons called Kagome lattices .

In an upcoming issue of Nature Communications, Broholm will report new work revealing entangled magnetism in three-dimensional tetrahedral structures. Those quantum interconnections may some day be useful for magnetic cooling, he said, or for building quantum computers.

Surveying the field in quantum computing

IBM’s Matthias Steffen also discussed quantum computers , bringing audience members up to date on their development and emphasizing that such devices would be large, expensive, and unsuitable for everyday use. Instead, quantum computers would specialize in factoring large numbers, searching piles of information, and other tasks that take advantage of the massive parallelism possible in the quantum world.

But even those applications face a host of unknowns, said Steffen. Open questions include how many bits will be needed, how much each bit will cost, and whether the clock speed of quantum computers will actually be faster than those of traditional computers.

‘The million dollar question is, will a quantum computer actually run faster?’ said Steffen.

No single technology has yet fulfilled all of the requirements for quantum computing; each comes with trade-offs. Quantum dots may be hard to scale up, for instance, because they require a network of wires that quickly becomes unmanageable. Josephson junctions, made of superconducting metal, have the advantage of being compatible with existing manufacturing technologies used in the semiconductor industry, but can only store quantum information for short periods of time.

Giant Magellan Telescope

Daniel Fabricant of Harvard University scaled the session from particles and atoms to galaxies. He studies the how galaxies form, a field limited by the ability of telescopes to spot old, faint, far-away galaxies.

‘At present we have very little information about the early generation of galaxies,’ said Fabricant.

The Giant Magellan Telescope , destined for Las Campanas Mountain in Chile’s Atacama Desert, could help. Sporting seven mirrors, each 8.4 m across, it will collect more light than any other on the planet today and thus provide sharper images of distant galaxies. Spectra that would require 16 hours to measure with an 8-m telescope will take an hour with the GMT.

The first mirror is done and is, according to Fabricant, ‘neigh perfect,’ with an accuracy of 19 nm. A second awaits polishing, and a third will soon be cast.

Like all ground-based telescopes, GMT will contend with several sources of blurriness. Its housing must resist vibrations caused by the wind. Atmospheric turbulence also tends to blur images, distorting light from distant objects and limiting the telescope’s view to a few hundred milliarcseconds.

Adaptive optics can compensate by projecting a laser into the sky and measuring its distortion moment-to-moment. Secondary mirrors that deform a thousand times per second will correct for aberrations in the light gathered by the telescope’s massive primary mirrors, potential providing an even clearer look at the heavens than NASA’s planned James Webb Space Telescope , said Fabricant.

Carbon’s many histories

MIT’s Mildred Dresselhaus wrapped up the session with a topic that has a long history—longer than many researchers working in the field realize.

Carbon nanotubes became popularized in 1991, when Sumio Iijima reported a new way to make them. But Japanese researchers had already discussed the structures during a closed conference in 1977 conducted entirely in Japanese. A 1952 paper published in Russian had also described a fabrication method.

‘The history of this field could have been very different,’ said Dresselhaus. ‘Discovery doesn’t turn out to be everything. Follow-up is very important.’

Her own interest started in 1990, during a public discussion about carbon balls called fullerenes. Her imagination caught fire when an audience member asked her if there was any connection between those balls and carbon tubes. Working with Japanese researchers, she published a theoretical paper in 1992 demonstrating that carbon nanotubes with different geometries can be either metallic or semiconducting.

Now a world leader in the field, Dresselhaus said that carbon nanotubes have more surprises in store. For one thing, the angle of the hexagons that make up the tubes’ walls seems to affect their properties. Double- and triple-walled nanotubes, made by sliding one tube into another, have also become an active area of research, as has the interface between carbon nanotubes and their flat carbon cousin, graphene.

Devin Powell is a freelance science writer based in Washington, DC. His stories have appeared in Science News, Wired, US News & World Report, and other outlets.