architizer:

“Three Cubes Colliding,” an experimental kite made of carbon fiber, aerospace fabric and 3D-printed connectors that challenges notions of airborne architecture.

First Observation Of 8 Entangled Photons Smashes Entanglement Record

Entanglement is the strange quantum phenomenon in which objects become so closely linked that they share the same existence. In the language of physics, they are described by the same wavefunction.

Entangling things isn’t so difficult really. Most interactions involve entanglement of one sort or another.

The trouble is pinning it down. Entanglement is a fragile and fleeting phenomenon. Blink and it leaks into the environment. That’s why it’s so difficult to preserve, to observe and ultimately so difficult for physicists to play with.

In recent years, physicists have learnt how to entangle all kinds of objects in pairs—photons, electrons, atoms and so on. In 1999, they created a qutrit by entangling three photons. Last year, they even entangled 6 photons.

Today, however, Xing-Can Yao and buddies at the University of Science and Technology of China in Hefei, say they’ve smashed this record by entangling 8 photons, then manipulating and observing them all simultaneously.

That’s no easy feat. Getting eight photons exactly where you want them at the same time is the quantum mechanical equivalent of herding cats (clearly of the Schrodinger variety).

(via Technology Review, h/t to outofcontextscience)

 ’We’ve all been taught that this doesn’t happen’

A dramatic and surprising magnetic effect of light discovered by University of Michigan researchers could lead to solar power without traditional semiconductor-based solar cells.

The researchers found a way to make an “optical battery,” said Stephen Rand, a professor in the departments of Electrical Engineering and Computer Science, Physics and Applied Physics.

In the process, they overturned a century-old tenet of physics.

“You could stare at the equations of motion all day and you will not see this possibility. We’ve all been taught that this doesn’t happen,” said Rand, an author of a paper on the work published in the Journal of Applied Physics. “It’s a very odd interaction. That’s why it’s been overlooked for more than 100 years.”

Light has electric and magnetic components. Until now, scientists thought the effects of the magnetic field were so weak that they could be ignored. Rand and his colleagues found that at the right intensity, when light is traveling through a material that does not conduct electricity, the light field can generate magnetic effects that are 100 million times stronger than previously expected. Under these circumstances, the magnetic effects develop strength equivalent to a strong electric effect.

“This could lead to a new kind of solar cell without semiconductors and without absorption to produce charge separation,” Rand said. “In solar cells, the light goes into a material, gets absorbed and creates heat. Here, we expect to have a very low heat load. Instead of the light being absorbed, energy is stored in the magnetic moment. Intense magnetization can be induced by intense light and then it is ultimately capable of providing a capacitive power source.”

What makes this possible is a previously undetected brand of “optical rectification,” says William Fisher, a doctoral student in applied physics. In traditional optical rectification, light’s electric field causes a charge separation, or a pulling apart of the positive and negative charges in a material. This sets up a voltage, similar to that in a battery. This electric effect had previously been detected only in crystalline materials that possessed a certain symmetry.

(via Michigan Today)

GRIN plasmonics: A practical path to superfast computing, invisibility carpet-cloaking devices

Berkeley Lab researchers have carried out the first experimental demonstration of GRIN plasmonics, a hybrid technology that opens the door to a wide range of exotic applications in optics, including superfast photonic computers, ultra-powerful optical microscopes and “invisibility” carpet-cloaking devices.

They said it could be done and now they’ve done it. What’s more, they did it with a GRIN. A team of researchers with the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California, Berkeley, have carried out the first experimental demonstration of GRIN – for gradient index – plasmonics, a hybrid technology that opens the door to a wide range of exotic optics, including superfast computers based on light rather than electronic signals, ultra-powerful optical microscopes able to resolve DNA molecules with visible light, and “invisibility” carpet-cloaking devices.

Working with composites featuring a dielectric (non-conducting) material on a metal substrate, and “grey-scale” electron beam lithography, a standard method in the computer chip industry for patterning 3-D surface topographies, the researchers have fabricated highly efficient plasmonic versions of Luneburg and Eaton lenses. A Luneburg lens focuses light from all directions equally well, and an Eaton lens bends light 90 degrees from all incoming directions.

“This past year, we used computer simulations to demonstrate that with only moderate modifications of an isotropic dielectric material in a dielectric-metal composite, it would be possible to achieve practical transformation optics results,” says Xiang Zhang, who led this research. “Our GRIN plasmonics technique provides a practical way for routing light at very small scales and producing efficient functional plasmonic devices.”

GRIN plasmonics combines methodologies from transformation optics and plasmonics, two rising new fields of science that could revolutionize what we are able to do with light. In transformation optics, the physical space through which light travels is warped to control the light’s trajectory, similar to the way in which outer space is warped by a massive object under Einstein’s relativity theory. In plasmonics, light is confined in dimensions smaller than the wavelength of photons in free space, making it possible to match the different length-scales associated with photonics and electronics in a single nanoscale device. 

SpaceX Dragon reaches orbit atop a Falcon with a fiery tail

Until recently, there have been two classes of people playing with rockets: those of us who enjoy playing with small (and not so small) toy models in our backyards and open fields, and the governments, who get the big boy toys to do some serious rocketry. Recently, private companies have been getting into the act and showing what can be done.

A few years ago, Scaled Composites’ SpaceShipOne completed the unprecedented act of putting a human into space (the edge of space, mind you) and returning him safely to Earth. Yesterday, the Space Exploration Technologies corporation one-upped them by becoming the first nongovernmental entity to put a vehicle into low Earth orbit.

Image credit: Thomas Scheidl, et al. and Google Earth, ©2008 Google, Map Data ©Tele Atlas.

Physicists close two loopholes while violating local realism

Physicists performed a Bell experiment between the islands of La Palma and Tenerife at an altitude of 2,400 m. Starting with an entangled pair of photons, one photon was sent 6 km away to Alice, and the other photon was sent 144 km away to Bob. The physicists took several steps to simultaneously close the locality loophole and freedom-of-choice loophole. 

The physicists, who belong to the group of Rupert Ursin and Anton Zeilinger and were all at either the Austrian Academy of Sciences in Vienna or the University of Vienna when performing the experiments in 2008, have published their study on the new Bell test in the early edition of PNAS. As they explain in their study, local realism consists of both realism – the view that reality exists with definite properties even when not being observed – and locality – the view that an object can only be influenced by its immediate surroundings. If a Bell test shows that a measurement of one object can influence the state of a second, distant object, then local realism has been violated.

“The question of whether nature can be understood in terms of classical concepts and explained by local realism is one of the deepest in physics,” coauthor Johannes Kofler told PhysOrg.com. “Getting Bell tests as loophole-free as possible and confirming quantum mechanics is therefore an extremely important task. From a technological perspective, certain protocols of quantum cryptography (which is entering the market at the moment) are based on entanglement and violation of Bell’s inequality. This so-called ‘unconditional security’ must in practice take care of the loopholes in Bell tests.”

The physicists explained that, in experimental tests, there are three loopholes that allow observed violations of local realism to still be explained by local realistic theories. These three loopholes can involve locality (if there is not a large enough distance separating the two objects at the time of measurement), the freedom to choose any measurement settings (so measurement settings may be influenced by hidden variables, or vice versa), and fair sampling (a small fraction of observed objects may not accurately represent all objects due to detection inefficiencies).

Previous experiments have closed the first loophole, which was done by ensuring a large spatial separation between the two objects (in this case, two quantum mechanically entangled photons) so that measurements of the objects could not be influenced by each other. Special relativity then ensures that the objects cannot influence each other, since no physical signals can travel faster than the speed of light. In these experiments, classically unexplainable correlations were still observed between the objects, indicating a violation of local realism. (The fair sampling loophole was closed in another earlier experiment using ions, where large detection efficiencies can be reached.) 

In the current experiment, the physicists simultaneously ruled out both the locality loophole and the freedom-of-choice loophole. They performed a Bell test between the Canary Islands of La Palma and Tenerife, located 144 km apart. On La Palma, they generated pairs of entangled photons using a laser diode. Then they locally delayed one photon in a 6-km-long optical fiber (29.6-microsecond traveling time) and sent it to one measurement station (Alice), and sent the other photon 144 km away (479-microsecond traveling time) through open space to the other measurement station (Bob) on Tenerife.

The scientists took several steps to close both loopholes. For ruling out the possibility of local influence, they added a delay in the optical fiber to Alice to ensure that the measurement events there were space-like separated from those on Tenerife such that no physical signal could be interchanged. Also, the measurement settings were randomly determined by quantum random number generators.

To close the freedom-of-choice loophole, the scientists spatially separated the setting choice and the photon emission, which ensured that the setting choice and photon emission occurred at distant locations and nearly simultaneously (within 0.5 microseconds of each other). The scientists also added a delay to Bob’s random setting choice. These combined measures eliminated the possibility of the setting choice or photon emission events influencing each other. But again, despite these measures, the scientists still detected correlations between the separated photons that can only be explained by quantum mechanics, violating local realism.

More information: Thomas Scheidl, et al. “Violation of local realism with freedom of choice.” 19708-19713, PNAS, November 16, 2010, vol. 107, no. 46. DOI:10.1073/pnas.1002780107

“In this video, the BBC’s Jem Stansfield test fires a vortex cannon that uses an acetylene and oxygen fueled explosion to fire an extremely powerful blast of air across a lake. Stansfield attacks three targets: houses of straw, sticks and bricks, with some spectacular results.”

Another Win for Quantum Mechanics: Passing the Triple-Slit Test | 80beats | Discover Magazine

To test the basics of quantum theory, physicists recently pulled out an antique. In a paper published today in Science, they confirmed a staple of quantum mechanics, using a test derived from a classic nineteenth century light experiment.

In particular, the researchers questioned how particles move through three slits, something previously too difficult to measure. They found that the particles behaved just like quantum theory–or more specifically the Born Rule–would have predicted.

As physicist Chad Orzel describes in his blog, that’s bad news for theorists hoping to tweak this rule to solve Nobel Prize-worthy problems related to quantum gravity or Grand Unifying Theories.

[The study is good news if] you’re the ghost of Max Born, or the author of an introductory quantum book…. This was disappointing news for some theorists, though, as there are a number of ways to approach problems … that would require some modification of the Born rule. [Uncertain Principles]

Laminar Flow Reversibility: Why does the Blob Rewind? | Unruled Notebook