In this issue: Is it Quantum Computing?, Matter Adds Twist to Cosmic Microwave Background, Planetary Waves that Connect the Climate Network, Accelerating Electrons with Light
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Is it Quantum Computing?
Scientists at D-Wave, the Canadian company that claims to have built the first commercial quantum computer, report they have used their hardware to solve a famously difficult problem in mathematics.
The heart of the device used by the D-Wave team is an array of 84 tiny superconducting loops, each representing one bit in the form of a current that can flow clockwise, counterclockwise, or in a quantum “superposition” of the two states. As a proof of principle, the researchers ran an algorithm on their hardware to solve the Ramsey problem - an optimization challenge similar in flavor to the traveling salesman problem (finding the optimal route that connects a number of cities) - for a few simple cases where the solutions were already known. A Viewpoint commentary appearing in Physics September 25provides a critical analysis of the report and explains what further experiments are needed to be sure the researchers have performed a truly “quantum” computation that could outperform what classical hardware can do.
* Z Bian, Frank Gaitan (contact author) et al, “Experimental determination of Ramsey numbers”, Physical Review Letters (expected publication date: Sep 25)
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Matter Adds Twist to Cosmic Microwave Background
A microwave telescope at the South Pole has captured a signal in the cosmic microwave background that arises from gravitational lensing by intervening matter.
The cosmic microwave background (CMB) provides us with a snapshot of the early Universe of 13.7 billion years ago. But this ancient photography has been slightly distorted: as CMB light rays propagated through the Universe, the matter they encountered on their path deflected them through the effect called “gravitational lensing”. Some aspects of this lensing have been observed before, but now a team of researchers at the South Pole Telescope (SPT) has detected for the first time a subtle twisting in the polarization of the CMB due to gravitational lensing. Collecting these signals could help scientists map the distribution of matter in the Universe, including the invisible dark matter, and may be used to detect primordial gravitational waves.
* The SPTpol Collaboration (contact author: Duncan Hanson), “Detection of B-mode polarization in the cosmic microwave background with data from the South Pole Telescope”, Physical Review Letters (expected publication date: Sep 30)
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Planetary Waves that Connect the Climate Network
(Image credit: NASA/GSFC)
A new study suggests that giant, high-altitude air waves have a profound effect on how energy is transported within the climate system.
Rossby waves are planetary-scale meanders in the high-altitude winds that flow about 10 km above ground. They arise because of the temperature difference between polar air and tropical air, together with variation of the Coriolis force with latitude. Meteorologists know them well, as they determine low-pressure systems that have a major influence on the weather. But according to simulations by a research team in Israel, such waves may determine more than whether it will rain or shine in the short term: they redistribute energy on planetary scales, connecting remote regions and thereby affecting the longer-term dynamics of the climate system. The finding may help improve the accuracy of global climate models.
* Yang Wang (contact author) et al, “Dominant imprint of Rossby waves in the climate network”, Physical Review Letters (published Sep 24)
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Accelerating Electrons with Light
Researchers at the Max Planck Institute of Quantum Optics have demonstrated that, in the vicinity of finely patterned substrates, laser pulses can accelerate electrons more efficiently than large-scale accelerator facilities. The principle may lead to compact, laboratory-size accelerators or to versatile light and x-ray sources.
* J Breuer, Peter Hommelhoff (contact author), “Laser-based acceleration of nonrelativistic electrons at a dielectric structure”, Physical Review Letters (expected publication date: Sep 27)
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Journal articles and preprints are available to journalists on request.
Matteo Rini, PhD
Deputy Editor, Physics
