Quantum split: Particle this way, properties that way - physics-math - 23 July 2014 - New Scientist

Quantum split: Particle this way, properties that way - physics-math - 23 July 2014 - New Scientist: In Grenoble, the Vienna team used a feeble magnetic field and a weakly interacting neutron absorber to make the weak measurements. They found that when they put the absorber in one path of the interferometer (say left), there was a discernible effect at the output. But when they put it in the right path, it had no such effect. The neutrons were travelling in one path only.

Next, the experimenters introduced a weak magnetic field near each arm of the interferometer, to interact with the spin of the neutrons. When they did this in the left path, there was no change in the interferometer's output. If they introduced the magnetic field in the right path, though, there was a change: the magnetic field had interacted with the spin. In other words, they had confirmed that the spin had chosen the path not taken by the parent neutron...

Tractor Beam Created Using Water Waves� — The Physics arXiv Blog — Medium

Tractor Beam Created Using Water Waves� — The Physics arXiv Blog — Medium: This fluid jet carries any floating particles along with the waves...

But as the waves get bigger, they become unstable and their behaviour changes dramatically...

Punzmann and co say the interaction between the waves in this non-linear regime changes the direction of the jet at the centre of the wave maker. “It now pushes floaters inward, towards the wave maker and against the wave propagation,” they say. Any floaters caught in this jet, are therefore pulled.

To test this idea, Punzmann and co have recreated exactly this situation in a wave tank with an elongated wave maker. They place a ping-pong ball on the water and then measure its movement as well as the shape of the water surface and the fluid flow on the surface.

Sure enough, when the amplitude of the waves is small, the ping-pong ball moves in the same direction as the waves. But as the waves become larger, the ping-pong ball reverses direction and moves back towards the wave maker...

Tiny waves could build livers on a 'liquid template' - tech - 04 July 2014 - New Scientist

Tiny waves could build livers on a 'liquid template' - tech - 04 July 2014 - New Scientist: After adding a handful of starter pieces, such as silicon chips or small plastic beads, the researchers tuned the generator to various frequencies to create waves in the solution. Depending on their surface chemistry, the added particles spontaneously collected in either the crests or the valleys. Retuning the generator let the team switch between multiple patterns...

He and his colleagues cultured mouse cells and put them in the liquid template. The cells collected into little spheres that became the building blocks of larger geometric patterns. Adding blood clotting proteins to the saline solution locked the cells in place, an approach that the team is now investigating for growing liver tissue.

Quantum Method Closes in on Gravitational Constant - Scientific American

Quantum Method Closes in on Gravitational Constant - Scientific American; Researchers have been unable to identify the source of errors causing the disagreement in the conventional measurements. The set-up of the latest measurement is unlikely to contain the same errors as the torque method...

In the experiment described by Tino’s team, pulses of laser light tickle a cloud of rubidium atoms cooled to nearly absolute zero, driving the atoms to rise and fall like a fountain under the influence of gravity. The pulses split the 'matter wave' associated with each atom into a superposition of two energy states, each of which has a different velocity and reaches a different height — 60 or 90 centimeters — before falling back. The matter wave that rises farthest has a greater separation from the tungsten cylinders, and thus senses a slightly different gravitational pull. The difference in force imparts a measurable shift in the final state of the two matter waves when they recombine, creating an interference pattern.

Could wireless replace wearables? | MIT News Office

Could wireless replace wearables? | MIT News Office: As described in an earlier MIT News story, the system works by transmitting a low-power wireless signal and using its reflections to track moving humans. It can do so even if the humans are in closed rooms or hiding behind a wall.

As the signal is transmitted at a wall, a portion of the signal penetrates through, reflecting off a person on the other side. However, due to all the signal interference from other objects, the team had to create technology to cancel out irrelevant reflections.

In order to monitor breathing, the technology needed to be precise: The researchers created a complex metric that approximates the subject’s volume, and then observed and amplified its changes to distinguish the breathing.

Researchers design a new structure that absorbs all sound

Researchers design a new structure that absorbs all sound: In their work, the researchers have demonstrated how the designed structure achieves extraordinary sound absorption using an apparently contradictory strategy: the sound attenuation increases when the quantity of absorbent material is reduced. This way, a totally reflective surface becomes a perfect absorbent despite the fact that, for the most part, there is no material that absorbs sound.

Unbelievable Display Technology Uses Levitating Particles as Pixels

Unbelievable Display Technology Uses Levitating Particles as Pixels: Researchers actually figured out how to levitate objects using nothing but sound years ago, but to date it's really only been with single particles. This new research, from Yoichi Ochiai, Takayuki Hoshi, and Jun Rekimoto, presented at the annual Siggraph conference, involves hundreds of tiny specks, all strategically arranged in real-time to form images, and even moving animations.

A Tractor Beam Made Of Sound Waves | Popular Science

A Tractor Beam Made Of Sound Waves | Popular Science: The device consists of about a thousand ultrasound emitters, placed underwater. When turned on, scientists used it to tug along centimeter-sized objects (roughly half and inch), such as a small hollow triangular shape. Normally the effect of sending acoustic beams at something would tend to push it away. But the scientists found that by precisely controlling the angle of sound waves, they can create a low pressure zone in front of the object, thus pulling it closer.

Whoa: Watch Scientists Use Sound Waves to Make Things Levitate | Wired Design | Wired.com

Whoa: Watch Scientists Use Sound Waves to Make Things Levitate | Wired Design | Wired.com: ...scientists have been experimenting with acoustic levitation for decades, using sound waves to suspend materials in mid-air. What’s new here, though, is the ability to move those materials in three dimensions.

That’s made possible by the unique arrangement of the speakers themselves. Where former setups bounced sound waves off a solid plate, the Tokyo researchers instead use four panels of speakers, all facing each other. These walls combine to create an “ultrasonic focal point,” which can be moved—along with the object trapped in it—by adjusting the output from each speaker array.

Researchers slow light to a crawl in liquid crystal matrix

Researchers slow light to a crawl in liquid crystal matrix: The new approach... uses little power, does not require an external electrical field, and operates at room temperature, making it more practical than many other slow light experiments...


The key to achieving a significant drop-off in speed is to take advantage of the fact that when light travels as a pulse it is really a collection of waves, each having a slightly different frequency, says Bortolozzo. However, all the waves in the pulse must travel together. Scientists can design materials to be like obstacles courses that "trip up" some of the waves more than others. In order to exit the material together, the pulse must wait until it can reconstitute itself...


They added a chemical component that twisted the liquid crystal molecules into a helical shape and then added dye molecules that nestled in the helical structures. The dye molecules change their shape when irradiated by light, altering the optical properties of the material and hence changing the relative velocities of the different wave components of the light pulse as it travelled through. In addition, the helical structure of the liquid crystal matrix ensures a long lifetime of the shape-shifted dyes, which makes it possible to "store" a light pulse in the medium and later release it on demand...

Redesigned Window Stops Sound But Not Air, Say Materials Scientists | MIT Technology Review

Redesigned Window Stops Sound But Not Air, Say Materials Scientists | MIT Technology Review: Their resonance chamber is actually very simple—it consists of two parallel plates of transparent acrylic plastic about 150 millimetres square and separated by 40 millimetres, rather like a section of double-glazing about the size of a paperback book.

This chamber is designed to ensure that any sound resonating inside it acts against the way the same sound compresses the chamber. When this happens the bulk modulus of the entire chamber is negative.

...To maximise this efficiency, they drill a 50 millimetre hole through each piece of acrylic. This acts as a diffraction element causing any sound that hits the chamber to diffract strongly into it.

Superheated Bose-Einstein condensate exists above critical temperature

Superheated Bose-Einstein condensate exists above critical temperature: In BECs and distilled water, the inhibition of a phase transition at the critical temperature occurs for different reasons. In general, there are two types of phase transitions. The boiling of water is a first-order phase transition, and it can be inhibited in clean water because, in the absence of impurities, there is in an energy barrier that "protects" the liquid from boiling away. On the other hand, boiling a BEC is a second-order phase transition. In this case, superheating occurs because the BEC component and the remaining thermal (non-condensed) component decouple and evolve as two separate equilibrium systems...


Here, the researchers demonstrated that in an optically trapped potassium-39 gas the strength of interactions can be reduced just enough so that the two components remain at the same temperature, but the particle flow between them is slowed down and their chemical potentials decouple. This condition makes it possible for the BEC to maintain a higher chemical potential than the surrounding thermal component, and thus survive far above its equilibrium transition temperature...



In the new study, the physicists experimentally demonstrated that a BEC could persist in the superheated regime... for more than a minute.

Peaceful matter-antimatter pairing looks more real

Peaceful matter-antimatter pairing looks more real: The first signs of these Majorana fermions came last year in the form of a current that appeared at zero voltage in a nano-size wire...
They created a similar set-up but this time ramped the voltage up and down and shortened the wire. The plan was to cause the quantum waves associated with each fermion to overlap and constructively interfere, creating two extra peaks in current. Sure enough, the team saw two more blips...

‘Metascreen’ forms ultra-thin invisibility cloak

‘Metascreen’ forms ultra-thin invisibility cloak: The trick: a new, ultrathin layer called a “metascreen,” made by attaching strips of 66-micron-thick copper tape to a 100-micron-thick, flexible polycarbonate film in a fishnet design. It was used to cloak (hide) an 18 cm cylindrical rod from microwaves...

Previous cloaking studies have used metamaterials to refract (bend) the incoming waves around an object. The new “mantle cloaking” method uses instead an ultrathin metallic metascreen to cancel out the waves as they are scattered off the cloaked object...

New Type of Clock Keeps Time by Weighing Atoms

New Type of Clock Keeps Time by Weighing Atoms: The researchers start with a puff of cesium atoms that falls through space toward a detector. Along the way, the atoms encounter pulses of two opposing lasers with slightly different frequencies that gently nudge the atoms without making their inner structure change. The pulses split the cloud in two, and one half of the cloud falls as normal. The other gets pushed up away from the first half and then gets pushed back toward it to catch up.

Here's where the relativity enters. From the perspective of the un-nudged half of the cloud, the second half moves away and then moves back. Because that second half is moving at a few centimeters per second, its time should appear to slow down just a bit thanks to the weird time dilation predicted by Einstein's theory of special relativity. So the quantum wave for that half of the cloud oscillates slightly slower than the one for the first half of the cloud.

When the clouds recombine, that difference in oscillations affects how they overlap and "interfere." If the researchers tune the difference in the two lasers' frequency just right, the recombining waves will interfere "constructively" so that the cloud falls into the detector...

The real value of the approach may come in redefining the kilogram...

Seafloor Platform 'Cloaks' Big Ocean Waves : Discovery News

Seafloor Platform 'Cloaks' Big Ocean Waves : Discovery News: Alam found that if he used a rippled sheet of material, one that had a specific set of heights and lengths, and put it on the ocean floor, the energy from deep water would make the internal waves in the thermocline more energetic, but cancel out surface waves. That makes for calm water on the surface.

Nanoscale Device Makes Light Travel Infinitely Fast - ScienceNOW

Nanoscale Device Makes Light Travel Infinitely Fast - ScienceNOW: They've developed a tiny device in which the index of refraction for visible light is zero—so that light waves of a particular wavelength move infinitely fast.

The device consists of a rectangular bar of insulating silicon dioxide 85 nanometers thick and 2000 nanometers long surrounded by conducing silver, which light generally doesn't penetrate. The result is a light-conveying chamber called a waveguide. Researchers fashioned different devices in which the width of the silicon dioxide ranged from 120 to 400 nanometers...

Right at the cutoff wavelength, things get interesting. Instead of producing a banded pattern, the whole waveguide lights up. That means that instead of acting as waves with equally spaced peaks, or "phase fronts," the wave behaves as if its peaks are moving infinitely fast and are everywhere at once. So the light oscillates in synchrony along the length of the waveguide.

Tractor beam built from rings of laser light - New Scientist - New Scientist

Tractor beam built from rings of laser light: David Ruffner and David Grier of New York University instead projected two Bessel beams side by side and used a lens to angle them so that they overlapped, creating a pattern of alternating bright and dark regions along the length of the beam. Fine-tuning the beam causes photons in the bright regions, initially flowing past a chosen particle in the beam, to scatter backwards. When these photons hit the particle, they knock it to the next bright region. The particle is thus constantly pushed close to the beam's source.

Weird waves help model tsunamis' destructive potential

Weird waves help model tsunamis' destructive potential: Once thought to be extremely rare, X- and Y-shaped waves with unusually high peaks regularly appear in ankle-deep water under certain conditions...


Linear interaction between ocean waves creates a peak that cannot be greater than the sum of the individual wave heights. But X- and Y-shaped waves are created when two waves hit each other at an angle, causing a non-linear interaction. That means their combined height can be more than the sum of the original peaks...

"People thought you might see them once every few years. The surprise is that they occur every day..."

Logic blooms with new 11-set Venn diagram - physics-math - 10 August 2012 - New Scientist

Logic blooms with new 11-set Venn diagram: To find the rose-like diagram, the pair had to comb through myriad potential diagrams, represented as lists of numbers corresponding to the way the curves cross. Sifting through all of the possibilities for an 11-set diagram would be an impossible task even for the combined might of Earth's computers, so the researchers narrowed the options by restricting the search to diagrams with a property called crosscut symmetry, meaning that a segment of each set crosses all the other sets exactly once.