Using natural crystals, two independent research teams have designed “carpet cloaks” that can abracadabra 3-D objects as big as an ant or a grain of sand seemingly into nothing. Up to now, making things invisible has relied on tiny structures called metamaterials. These fabrications are often a mix of stacks and crisscrosses of nano-sized metals and other materials that can guide electromagnetic rays, such as microwaves or infrared and visible light, around objects. If researchers tweak metamaterials just right, they can make tiny things disappear — at certain light wavelengths and from certain angles, at least.

But now two teams, including an MIT group that published its results in Physical Review Letters in January and another from England and Denmark that published Tuesday in Nature Communications, didn’t bother with metamaterials. They adopted calcite prisms, a type of naturally occurring crystal, to build carpet cloaks. Carpet cloaks aren’t true now-you-see-them-now-you-don’t apparatuses. The bottom of the cloaking device is notched with a small triangle that looks like a bent mirror. Thanks to the optical properties of metamaterials or, in this case, calcite, the bent mirror can look like a flat plane when viewed from some angles. Anything hiding in the notch vanishes.

This low-tech design sidesteps some of the limitations of metamaterial invisibility cloaks, says Ulf Leonhardt, a physicist at the University of St. Andrews in Scotland who was not involved in either study. His landmark 2006 paper in Science helped to launch invisibility research. Because metamaterials require intricate sculpting by lasers or other tools, scientists can make them only so big. Harry Potter would need to be more than paper-thin to hide under early carpet cloaks. The calcite shields, on the other hand, can disappear objects 1 to 2 millimeters tall. Metamaterial designs “liberated the imaginations,” he says. “Now, it’s time to come back to reality.”

But with such tricky optical sleight of hand, reality may seem like a misnomer. With the right type of light, calcite prisms can bend laser beams in different directions based on the crystal’s orientation. Light enters the cloak — a triangle or trapezoid made of two prisms glued together — and bounces off the bent mirror at the bottom into the second prism, then out. By the time the beams leave the cloak, they look like they changed direction only once, says George Barbastathis of MIT, coauthor of the Physical Review Letters article. His team used the cloak to hide a small metal wedge. “Putting calcite on top of the wedge, the light goes back into the same direction that it would have with a flat mirror,” he says. But it’s not just the same direction — the light looks exactly like it bounced off a flat mirror. The metal wedge vanishes.

“It’s not a Harry Potter cloak,” says Shuang Zhang, a physicist at the University of Birmingham in England and one of the Nature Communications study coauthors. The cloak works only under one light polarization. And while it works at all angles, it’s not three-dimensional. It only cloaks when Zhang aims the light source dead-on at the crystals. But, he says, scaling up to 3-D isn’t too big of a leap from 2-D. Zhang imagines similar technology one day concealing submarines on the sea floor.

When you shine light on a substance, part of the light is reflected, part is transmitted and part is absorbed. If you choose the color of light and the substance sensibly, you can arrange things so that all the light is absorbed. Nothing special about that, right? OK, but what if you could shine a second light on the substance and make it transparent for the first light field? That would be a bit strange, wouldn’t it?

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Electromagnetically induced transparency (EIT), as it is called, is a bizarre phenomenon all by itself. But there is nothing like taking the bizarre and making it even more so. A group of researchers has shown that, under the right conditions, this second light field doesn’t have to hit the substance to make EIT work—it only has to have the potential to be there. My response: OMFG, that is too cool to be true.

Warning: here there be quantum mechanics

EIT occurs due to an interaction between two light fields that is mediated via an atom. Atoms absorb light in discrete chunks. Normally, an atom would be sitting in a single ground state, but some atoms have two states that are at about the same energy and are about as stable. In this case, we can think of the atom as having two ground states. Through careful preparation, we can generate a group of these atoms so that they are all in just one of the two ground states. If I turn on a light field (called the probe light) with the right color, it will be absorbed by the atoms, putting them into an excited state.

A light field, called the control light field, that is tuned to match the energy required to move the atom from the other ground state to an excited state, however, will not be absorbed; there are no atoms in that ground state to act as an absorber. But the presence of the control light still sets the electrons around the atom in motion. Provided this motion remains coherent, it changes the energy levels of the atoms slightly. More specifically, the excited state splits into two excited states: one at a slightly higher energy, and one at a slightly lower frequency.

If we turn on the probe light while the control light is on, neither will be absorbed. That’s because the control light has shifted the excited state of the atoms, so that the probe light no longer matches that expectation. Indeed, one can turn off the control light while the probe light is on and trap some of the probe light in the atoms. Turn the probe light off and the control light back on, and the atoms emit a pulse of probe light as if nothing had happened.

An important point is that, when the control field is applied, the energy level of the excited state always splits into two, with one moving up in energy and one moving down in energy. But the distance that they move depends on how bright the control field is. So, if the control field is off, there is no splitting and EIT won’t work, right?
EIT without any control

Not so, according to results published in Science. What we have overlooked is that, when atoms absorb and emit light, they do so from what are called modes. And, because photons are bosons, they like to get together. What this means is that if a mode has a photon in it already, an atom is more likely to emit into the mode of that photon in preference to all the others. Normally, we don’t observe this because atoms are surrounded by empty space—there are a near infinite number of modes and none of them have photons in them.

But we can change that. By putting the atoms between two mirrors, we create an optical cavity. This cavity severely restricts the number of modes available to the atom. Combine that with the fact that the atom is most likely to emit a photon with a particular energy, and it will find that it has just one mode available to it.

How do modes relate to EIT? To explain, let’s jump back to the experiment. The researchers put their cloud of atoms between two very highly reflective mirrors and prodded them until they were all in the first ground state. The probe light field is shone through the sample from the side—this light field doesn’t go anywhere near the mirrors, but it does pass through the atoms. That light is absorbed, and all seems to be lost.

But, once excited, the atoms have a choice: decay back to the first ground state, or decay to the second ground state and emit a photon into the optical cavity. Most respond to the existing light field and decay back to their original ground state.

But a few don’t. These atoms emit photons at the frequency of the control light field. And, thanks to the cavity, these few photons pass back and forth through those atoms a large number of times, making the atoms respond as if it were in a much stronger light field.* As with the normal EIT, once this field is established, the excited state energy level splits, and the cloud of atoms becomes transparent to the probe light. Even though we’ve never exposed the sample to the control light, it ends up behaving as if it were present.

That is pretty cool. But I suspect the pragmatists among you will be asking, “Where’s the application?” To be honest, I doubt if this will ever be directly applied. EIT has the potential to be very useful in terms of light being used to switch light—think optical computers. But no one really wants a cloud of atoms and optical cavities and all that sort of stuff hanging around in their computers: if you think dust is a problem now, imagine getting dust in this system.

The glimmer of utility on the horizon are things called quantum dots. These are little packages of material that behave like artificial atoms. With the right physical structure, EIT should be possible with quantum dots. These could then be combined with integrated optical devices to create optical switches, without needing the vacuum and vast array of instruments. Unfortunately, even with this development, switching times will likely be slower than electronic devices, and individual gates will be much larger than current electronic gates. So, in the end, this is for the pure joy of discovery.

* This is technically incorrect. The light field in the cavity is actually that strong, but if the photons were not bouncing back and forth in a cavity, the light field would be very weak, and that is the comparison I want to make.

This outstanding image was taken by Stephane Vetter and it has won The World at Night’s 2011 International Earth and Sky Photo Contest. Taken at Jökulsárlón lake, the image merges six different exposures to capture two wild green auroral rings, caused by a massive coronal mass ejection back on February

Another electric motorcycle startup is jumping into the e-moto arena with a pair of machines it promises will deliver the performance of a 250cc dirt bike.

The RedShift MX motocrosser and RedShift SM supermoto are the first machines from San Francisco startup BRD, a company started by, and for, guys who like to ride.

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“We just want to make faster motorcycles,” says CEO Marc Fenigstein. “We’re a team of riders and racers with high-performance gas machines in the garage. We’re building the bikes we’d rather be riding.”

The BRD RedShift MX is good for 40 horsepower and weighs 240 pounds without lights, specs that put it on par with the KTM 250 SX-F. With a 5.2 kilowatt-hour battery pack, the electric motorcycle should be capable of one if not two full motos of anywhere from 10 to 20 miles apiece.

It’s not often that multibillion-dollar tech companies take to the internet to throw elbows at each other, at least without hiring outside PR to do it on the sly. Watching it unfold in public is a little like watching a big family meltdown at a restaurant: Harsh words turn from whispers to shouts, secrets are dredged up, and eventually the teenager storms out the door, stopping only to let everyone know how much she hates them for doing this to her and that she’ll be walking home alone.

That’s pretty much what happened with Google yesterday — only the big fighting family included Microsoft, Apple, Oracle and Samsung. The fight was over software patents, not dinner, and the declaration of independence in miniature didn’t come from an angry teenager, but an angry lawyer:

Android’s success has yielded … a hostile, organized campaign against Android by Microsoft, Oracle, Apple and other companies, waged through bogus patents….

Instead of competing by building new features or devices, they are fighting through litigation…. Unless we act, consumers could face rising costs for Android devices — and fewer choices for their next phone.

Google’s chief legal officer David Drummond is angry. He’s angry that Google lost its bid for Nortel’s patent portfolio. He’s angry that winners of the $4.5 billion bid, a consortium of tech companies including mobile rivals like Microsoft, Apple and RIM, will probably use Android’s real or apparent infringement patents as leverage in lawsuits against or licensing settlements with Google and Android device makers.

He’s angry that Microsoft makes more money straight-up for Android’s OS than Google does; he’s angry that companies like Oracle, who once stood against software patents in principle and claimed to use them only defensively, have aligned with other companies who aren’t, and don’t, and even sued Google for infringement; and he’s angry that Google, even after buying up patents from IBM and elsewhere, doesn’t have much intellectual property leverage of its own.

The semi-official response to Google’s attack from Microsoft general counsel Brad Smith was so simple, it fit on Twitter: “Google says we bought Novell patents to keep them from Google. Really? We asked them to bid jointly with us. They said no.”

Named after the mythical Roman goddess and wife of Jupiter, Juno will take about five years to reach the gas giant and slip into orbit. It packs a suite of scientific instruments to study Jupiter, in addition to some Lego figurines.

Once there, NASA expects the spacecraft to spend a year making at least 32 pole-to-pole orbits before intense radiation bakes its circuits.

“From Juno we’re going to go learn about Jupiter so we can start to put together the pieces of how the solar system was made,” said planetary scientist and mission leader Scott Bolton of the Southwest Research Institute in a video. “Jupiter’s got the first clues for us.”

Jupiter orbits about 400 million miles away from Earth and is thought to be one of the first planets that formed in the solar system some 4.6 billion years ago.

If nothing goes awry during the spacecraft’s trip, Juno will be the 10th spacecraft to visit the gas giant, but only the second to stick around for more than a flyby. The Galileo is currently the sole spacecraft to have orbited Jupiter.

Those missions racked up some serious knowledge of Jupiter, but brought up perhaps more questions than they answered. In this gallery are six mysteries Juno may resolve before its radiation-induced death

The debate about whether or not computers are making us dumber, largely speculative to this point, has recently gotten a healthy dose of scientific data. Last week scientists at Columbia University published a report showing that our dependency on Google for information has changed how we think.

The study involved a series of experiments that tested how much people rely on readily-available information in lieu of committing it to memory. In the first experiment students were given true-or-false statements after which they were presented a series of colored words for which they had to match each word to its color. Typically reaction times for this task are slower if the word relates to what the person is thinking–if the question involves an ostrich, matching “bird” to its color would take longer than matching “ladder” to its color, for example. Interestingly, they found that reaction times for words related to the Internet, such as “Google” or “Yahoo,” got slower reactions times, indicating that the students were thinking about looking the answers up online. When presented with any factual question, to Google is now a human instinct.

The next set of experiments showed that the students’ memory suffered if they were told that whatever they learned would be saved on the computer, as if they resisted “saving” the data to their own memory if it was already being saved in the computer’s. But then something interesting happened. Even though they couldn’t recall the facts, they recalled very well the specific computer folders into which the facts had been saved. Betsy Sparrow, lead author in the study, summed it up by saying that the students “were better at remembering where information was stored than the information itself.”

Finally Android tablets are going to be able to live up to their names. At the recent Google I/O conference, Colin Angle of iRobot announced that the Boston based company would be teaming up with the search engine to get Android apps on the new AVA robot this year. AVA is a pedestal shaped bot on wheels which can autonomously navigate itself through a crowd without breaking anyone’s ankles. While containing a great deal of its own functionality, AVA’s head is a tablet computer. Any tablet computer. iPad2, Galaxy, you name it – iRobot claims they want AVA to be “head agnostic”. Yet with the latest announcement, AVA is poised to be tested with Android applications first, and that’s sure to make a big difference in the way it’s adopted and developed. Check out AVA as it wheels around Google I/O in the videos below. Could this tablet-headed bot be the platform that finally brings personal robotics into the home on a grand scale?

Since they started showing off AVA at CES earlier this year, iRobot has gone out of its way to highlight how the bot’s navigation skills make it people-friendly and human environment ready. In the following clip taken at Google I/O 2011, you’ll see it move fairly quickly in a crowded environment. Top speed for AVA is supposedly two meters per second. Not bad at all. While all of this running around is head-independent (the processing is done in AVA’s own body) it’s unclear to me how much of this navigation is happening in real time thanks to its two Kinect sensors, and how much relies upon preprogrammed maps of the area.

The King of Pop would have been proud. As a man who pushed the boundaries of technology himself, from his backyard Never Land, to sleeping in a hyperbaric chamber (is that actually true?), to his cryogenic chamber (is that actually true?), to showing us the versatility of plastic surgery, Michael Jackson was one of those multi-billionaires who liked to spend money on really neat things.

Well, some other really neat things have taken notice. The video below is a compilation of robots dancing–or appearing to dance–to Jackson’s “Thriller.” I recognize the Nao Robots performing their eight minute dance at the 2010 Shanghai World Expo. The original score was not Michael Jackson, but who cares, this is a fun YouTube video and listening to “Thriller” never gets old. And while you’re bobbing your head at your cubicle instead of taking care of that thing your boss needs pronto, you get to check out some pretty nifty moves from these robots of all shapes and sizes. The complexity and smoothness of some of the dances are impressive. I have to admit the synchrony at that part–you know, when MJ and all the zombies line up and they start marching towards the girl and he’s got some really big contact lenses in–yeah, the synchrony of the robots at that part is way better than in the original video.

Seeing as how Michael Jackson probably grew up doing the robot a lot, I think it’s poetic that now robots get to do the Michael Jackson–without the soul for getting down!