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‘Nanofishnet’ Could Be the First Metamaterial to Impossibly Bend Light in the Visible Spectrum
By Clay DillowPosted 04.30.2012 at 2:09 pm
Metamaterials hold the elusive promise of the true invisibility cloak, one that bends light right around objects to make them invisible to viewers. But most metamaterials with any kind of potential can only be fabricated in very small sizes, and even the ones that work well–and there are a few–generally don’t work in the visible spectrum. But researchers from Spain and the UK have reported that they have constructed what may be the first practical metamaterial that works in the visible range.
The material was designed with optical switching in mind–sub-picosecond pulsing of light in fiber optics networks or in highly tuned pulsing lasers–but the researchers themselves are convinced that its layered structure could be scaled up into usable, practically-sized objects. Everyone in the materials science community isn’t so optimistic, but the fact that it works at all in the visible range marks something of a breakthrough in the field.
Visible light has been a particularly tough nut to crack when it comes to metamaterials, which essentially bend light unnaturally to achieve a desired effect. Light waves in the visible spectrum tend to degrade to nothing after passing through materials just a fraction of a wavelength thick, so it’s tough to make a metamaterial that can bend light in a predetermined way without also losing the visible light wave altogether.
The UK/Spanish team (from King’s College London and the Valencia Nanophotonics Technology Center, respectively) overcame this through a novel layered construction of silver and hydrogen silsesquioxane (a type of glass). Using a focused ion beam, they punched tiny holes through the layers to create a structure they refer to as a “nanofishnet.” This combination of materials, layering, and nanofishnet structure allows the material to create the necessary negative magnetic permeability (a necessary ingredient for metamaterials that you can learn more abouthere) in the red and near-infrared parts of the spectrum.
By varying the size of the holes in the nanofishnet the team was able to adjust the materials index of refraction, giving them some degree of freedom when it comes to “programming” the material for different kinds of light. So while the team hasn’t created the wundermaterial that will enable our invisibility-cloaked future, they have created a metamaterial that works in one sliver of the spectrum and that could perhaps be cajoled into working in other slivers as well. Click through toIEEE Spectrum for a much more detailed explanation of this.
Water drop at 10.000 fps
In New Quantum Experiment, Effect Happens Before Cause
A real-world demonstration of a thought experiment conducted at the University of Vienna, has produced a result that is somewhat befuddling to people with what the lead researcher calls a “naïve classical world view.” Two pairs of particles are either quantum-entangled or not. One person makes the decision as to whether to entangle them or not, and another pair of people measure the particles to see whether they’re entangled or not.
The head-scratcher is: the measurement is made before the decision is made, and it is accurate. “Classical correlations can be decided after they are measured,” says Xiao-song Ma, the writer of the study. Entanglement can be created “after the entangled particles have been measured and may no longer exist.”
The finding can be integrated into potential quantum computers, one hopes. Causality, clearly, is a quaint, irrelevant concept.
[Nature]
For the First Time, Electrons are Observed Splitting into Smaller Quasi-Particles
By Clay Dillow Posted 04.19.2012 at 1:34 pm
We generally think of electrons as fundamental building blocks of atoms, elementary subatomic particles with no smaller components to speak of. But according to Swiss and German researchers reporting in Nature this week, we are wrong to think so. For the first time, the researchers have recorded an observation of an electron splitting into two different quasi-particles, each taking different characteristics of the original electron with it.
Using samples of the copper-oxide compound Sr2CuO3, the researchers lifted some of the electrons belonging to the copper atoms out of their orbits and placed them into higher orbits by manipulating them with X-rays. Upon placing them in these higher–and higher-velocity–orbits, the electrons split into two parts, one called a spinon that carried the electron’s spin with it, and another called an obitron that carried the electron’s orbital momentum with it.
Spin and orbit are–at least as our basic understanding goes–attached to each particular electron. So the fact that they have been separated is pretty significant. And while researchers have thought for a while that this kind of separation could be theoretically achieved, they’ve had a hard time proving it empirically until now. It’s a reminder that at the quantum level there are still things that more or less mystify us.
But that’s not all it is. This particular observation of an electron splitting could have big-time implications in the field of high-temperature superconductivity. Understanding the way electrons can decay into quasi-particles could improve our overall understanding of the electron and how it moves, and thus help us figure out new ways of moving electrons–or electricity–around in bulk without losing large amounts of it as waste.
[PhysOrg]
Holometer experiment to test if the universe is a hologram
October 28, 2010 by Lisa Zyga 
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A conceptual design of Fermilab’s holometer. Image credit: symmetry magazine
(PhysOrg.com) — Many ideas in theoretical physics involve extra dimensions, but the possibility that the universe has only two dimensions could also have surprising implications. The idea is that space on the ultra-small Planck scale is two-dimensional, and the third dimension is inextricably linked with time. If this is the case, then our three-dimensional universe is nothing more than a hologram of a two-dimensional universe.
This idea of the holographic universe is not new, but physicists at Fermilab are now designing an experiment to test the idea. Fermilab particle astrophysicist Craig Hogan and others are building a holographic interferometer, or “holometer,” in an attempt to detect the noise inherent in spacetime, which would reveal the ultimate maximum frequency limit imposed by nature.
As Hogan explains in a recent issue of Fermilab’s symmetry magazine, the holometer will be “the most sensitive measurement ever made of spacetime itself.” Hogan and others have already built a one-meter-long prototype of the instrument. They have just begun building the entire 40-meter-long holometer and plan to start collecting data next year.
The holometer consists of two completely separate interferometers positioned on top of one other. In each interferometer, a light beam is split into two different parts that travel in different directions. After bouncing off a mirror, the light beams are brought back together where the difference in their phases is measured. Even the smallest vibration will interfere with the light’s frequency during its travels and cause the two light beams to be out of sync.
While interferometers have been used for more than 100 years, the key to the holometer is achieving extreme precision at high frequencies. The scientists say that the holometer will be seven orders of magnitude more precise than any atomic clock in existence over very short time intervals. By having two interferometers, the researchers can compare them to confirm measurements. In addition, the scientists are making sure that any vibration that is detected isn’t coming from the holometer itself. They will arrange sensors outside the holometer to detect normal vibrations, and then cancel these vibrations by shaking the mirrors at the same frequency.
After taking these precautions, any detected high-frequency noise could be the jitter of spacetime itself, or “holographic noise.” The noise is expected to have a frequency of a million cycles per second, which is a thousand times higher than what the human ear can hear, noted Fermilab experimental physicist Aaron Chou. If the experiment does find this holographic noise, it would be the first glimpse beyond our three-dimensional illusion and into the universe’s true two-dimensional nature at the Planck scale.
http://www.physorg.com/news/2010-10-holometer-universe-hologram.html
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