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Quantum computers would leverage the unique properties of the quantum world to solve huge computing problems--problems our best and biggest classical supercomputers can’t cope with. But first we have to gain precise control over those particles, turning them into quantum analogs for our classical computer bits.

Ions are a good candidate for those quantum bits, or “qubits”--the basic building blocks of the quantum computing scheme. And the ability to manipulate ions with microwaves to achieve quantum entanglement--a phenomenon in which the properties of two separated ions become linked (and a central pillar of information storage and transfer in the quantum scheme)--is huge.

Microwaves are already used to carry wireless communications. The technology used to generate and control them is well understood, ubiquitous, and therefore relatively inexpensive. And while there is still a need for an ultraviolet laser to cool and measure the ions in a microwave entanglement setup, it’s a low-power laser that could feasibly be scaled down to the size of those lasers used in portable optical readers like CD or DVD players.

The rest of the technology also packs significantly less bulk. The entire layout described by the NIST researchers in an upcoming issue of the journal Nature is tabletop-size, or roughly one-tenth as big as the usual room-sized “laser park” needed to generate controlled ion entanglement with light. As the technology develops, the team thinks they could scale a microwave device down to the size of a desktop computer, and perhaps someday even a tablet or smartphone device (for a more detailed, technical explanation of how this technology works, click through). Microwaves also demonstrate other quantum computing advantages, like the ability to reduce errors caused by instabilities in laser beams.

But there’s still a long way to go before microwave technology unseats laser tech in the pursuit of practical quantum computing. The NIST team could only achieve entanglement with microwaves about 76 percent of the time. The best laser schemes miss less than one percent of the time.

For those that need a primer, entanglement is that strange quantum phenomenon that links two particles across distances such that any any measurements carried out on one particle immediately changes the properties of the other--even if they are separated by the entire universe. Einstein called it “spooky action at a distance.” And indeed it is weird.

Nicolas Gisin at U. of Geneva noted that Italian physicists had previously done an interesting thing with entangled photons. Rather than entangling just a few as experimenters usually do, the Italian team had entangled a pair of photons and then amplified one of them to create a photon shower containing thousands of particles, all linked to the single other photon from the original pair. That is, there was one “microscopic” photon, and a shower of “macroscopic” photons, all tied together at the quantum level.

Gisin realized that while the naked eye can’t see a single photon, it can certainly see thousands. So he used a setup similar to the Italians’, but rather than putting a photon detector in front of the macroscopic photons he put himself and his colleagues there. The beam of photons produced by the amplifier would appear in one of two positions in their darkened room, depending on the polarization state given to their microscopic single photon. Time after time, when the human results were tested against photon detectors, they got a positive result.

It may sounds like a bunch of scientists sitting in a dark room looking at blinking lights, but it represents the first time quantum entanglement has been directly observed with the naked eye.

Sort of. The Swiss team also found that what they were looking at wasn’t necessarily macro-micro entanglement. Even when they deliberately broke the quantum link between micro and macro and then ran their “human detector” experiment, they still got a positive result. This is due to the imperfection of detectors (even human ones) and a loophole in what’s known as the Bell Test (which, in a nutshell, is used to measure entanglement) that’s negligible in small quantities of photons but grows along with their quantity. This introduces a degree of uncertainty (for a better explanation of this, click through the Nature link below).

What the Swiss team does know is this: when they started, they had two entangled photons. Even though flaws may have been introduced in the amplification process, they could still “see” the effects of entanglement. A new method is being devised by the original Italian researchers (who also detected this flaw in their research) to verify micro-macro entanglement with lasers. Unfortunately, humans can’t be used as detectors for these experiments, as the highly focused beams of light would be the last thing those humans would see.

[Nature]

For those that need a primer, entanglement is that strange quantum phenomenon that links two particles across distances such that any any measurements carried out on one particle immediately changes the properties of the other--even if they are separated by the entire universe. Einstein called it “spooky action at a distance.” And indeed it is weird.

Nicolas Gisin at U. of Geneva noted that Italian physicists had previously done an interesting thing with entangled photons. Rather than entangling just a few as experimenters usually do, the Italian team had entangled a pair of photons and then amplified one of them to create a photon shower containing thousands of particles, all linked to the single other photon from the original pair. That is, there was one “microscopic” photon, and a shower of “macroscopic” photons, all tied together at the quantum level.

Gisin realized that while the naked eye can’t see a single photon, it can certainly see thousands. So he used a setup similar to the Italians’, but rather than putting a photon detector in front of the macroscopic photons he put himself and his colleagues there. The beam of photons produced by the amplifier would appear in one of two positions in their darkened room, depending on the polarization state given to their microscopic single photon. Time after time, when the human results were tested against photon detectors, they got a positive result.

It may sounds like a bunch of scientists sitting in a dark room looking at blinking lights, but it represents the first time quantum entanglement has been directly observed with the naked eye.

Sort of. The Swiss team also found that what they were looking at wasn’t necessarily macro-micro entanglement. Even when they deliberately broke the quantum link between micro and macro and then ran their “human detector” experiment, they still got a positive result. This is due to the imperfection of detectors (even human ones) and a loophole in what’s known as the Bell Test (which, in a nutshell, is used to measure entanglement) that’s negligible in small quantities of photons but grows along with their quantity. This introduces a degree of uncertainty (for a better explanation of this, click through the Nature link below).

What the Swiss team does know is this: when they started, they had two entangled photons. Even though flaws may have been introduced in the amplification process, they could still “see” the effects of entanglement. A new method is being devised by the original Italian researchers (who also detected this flaw in their research) to verify micro-macro entanglement with lasers. Unfortunately, humans can’t be used as detectors for these experiments, as the highly focused beams of light would be the last thing those humans would see.

[Nature]

Scientists led by Mikkel F. Andersen at the University of Otago in New Zealand used lasers to slow down the frenetic movement of a group of rubidium-85 atoms, and then capture them inside optical tweezers. The method could catch and isolate atoms 83 percent of the time. Using the optical tweezers — really two lasers acting as a kind of tractor beam — Andersen’s team was able to hold a single rubidium atom in front of a camera designed for use in space, and snap its picture.

The process could simplify the process of building quantum-logic computers, which use small groups of atoms as information processors. Unlike binary computers, quantum processors could perform many difficult calculations at once, crunching data much more quickly. They could also (maybe) break secret codes that would otherwise be too hard to hack.

Andersen said his method would allow computer engineers to grasp 10 or so atoms at a time. The next step is to entangle the atoms so they can share information, he said.

Meanwhile, last Friday, IBM researchers published a study in the journal Science that also used advanced imaging to record individual atoms. Their measurements could help scientists see an atom’s electronic and magnetic properties, and it could help them engineer the spin of individual atoms to create spintronic devices.

IBM’s study used a scanning tunneling microscope to watch the behavior of individual iron atoms at a speed about a million times faster than previously possible. It worked like a high-speed camera freezing the motion of a hummingbird’s wings, as IBM Research explains.

Typically, scanning tunneling microscopes work relatively slowly, so scientists can’t watch atomic action in real time. But the new technique let them capture atomic motion to study atoms’ magnetic orientation. They found the speed at which atoms change their magnetic orientation depends on the magnetic field they’re in. This could help scientists engineer atoms’ magnetic lifetime, according to IBM.

Learn more about it in this video.

String theory elegantly reconciles the otherwise competing rules of quantum mechanics and general relativity. It’s the most widely accepted unified field theory, but it remains controversial. It basically posits that electrons and quarks are not objects, but one-dimensional strings, whose oscillation gives them their observed qualities. The most fun element of string theory is the requirement that the universe has about a dozen dimensions, rather than the usual four (length, width, height and time).

M-theory, the dominant version of string theory, holds that the universe is made up of unfathomably small slices of a 2-dimensional membrane, wriggling in 11-dimensional space.

These bizarre ideas are widely accepted by many theoretical physicists, but the problem is that they can’t be tested — how do you examine an 11th dimension? The field has suffered a backlash in recent years partly for this reason, as some scientists say a theory is not a theory if its predictions can’t be studied in a lab.

Well, now they can, according to professor Mike Duff of the theoretical physics department at Imperial College London. He is lead author of a paper to be published tomorrow in Physical Review Letters, which explains how string theory math can be used to predict quantum entanglement.

Duff said he was at a conference in Tasmania when a colleague presented some mathematical formulas describing entanglement of multiple quantum bits. The equations looked familiar. Upon returning home, Duff checked his notebooks from a few years earlier, and realized the formulas were the same as those he developed to use string theory to describe black holes.

This is completely unexpected, he said. There is no obvious reason why the insanely complex mathematics underlying string theory can also be used to predict the behavior of entangled quantum systems.

“This may be telling us something very deep about the world we live in, or it may be no more than a quirky coincidence,” he said.

Either way, it’s useful, he added. Using string theory math, Duff predicted the pattern that would occur when four quantum bits are entangled with each other. This can be measured in a lab, and the results will demonstrate whether string theory actually works.

Right now, the best hope for string theory tests comes from CERN’s Large Hadron Collider, which is designed to find the tiniest elementary particles that make up matter. It’s theoretically possible that LHC experiments will uncover supersymmetric particles — one element of string theory — or bounce a graviton into a higher dimension, which could help prove M-theory. But testing the fuzzy math that predicts these behaviors will be much easier.

Postselection is one of the notions that makes quantum computing simultaneously so exciting and perplexing; the idea that for a super-complex problem riddled with variables, you solve by letting the variables take any value at random and postselect for the one combination that makes the problem true. Put another way, rather than solving all the possible combinations to the problem one at a time, you run all possible combinations simultaneously and extract the set of variables that make the problem true.

Quantum mechanics seems to allow for such simultaneous computations of all possible outcomes theoretically, though actually making it happen is another issue altogether (such quantum computing would blow conventional computing methods out of the water). But combined with quantum teleportation – using quantum entanglement to reproduce a quantum state in space that previously existed at another point in space – MIT’s Seth Lloyd and colleagues say you can theoretically teleport a particle back in time.

This form of theoretical time travel solves two major problems associated with the feat. For one, it doesn’t require the bending of spacetime as most time travel theories do. Considering the conditions necessary to bend the fabric of spacetime might only exist in black holes, that’s a good thing. But further, due to the probabilistic laws of quantum mechanics, anything this method of time travel allows to happen already had a finite chance of happening anyhow. That means a particle can’t really go back and accidentally destroy itself.

Of course, the physicists didn’t demonstrate their theory in hopes of going back in time to ensure their parents end up getting married or some such. They’re hoping that by demonstrating these properties they will help push quantum thought toward a theory of gravity. But the idea of moving backward along the timeline without bending the fabric of the universe – or altering ones own future existence – is pretty amazing. If your interest is piqued, you can check out the entire paper here.

[Tech Review's Physics ArXiv Blog]

It's hard to prove, but it would be a potentially explosive finding, as Technology Review explains.

In quantum entanglement, two objects are connected by an invisible wave, like an umbilical cord, that allows them to essentially share the same existence. When something happens to one object, it immediately happens to the other, no matter how far apart they are.

Elisabeth Rieper and colleagues at the National University of Singapore say this entanglement might prevent the DNA double helix from shaking itself apart.

Technology Review's blog provides a nice description of some complex physics. Here's a breakdown:

Rieper and colleagues used a theoretical model of DNA in which each nucleotide consists of electrons orbiting a positively charged nucleus. The movement of the negative cloud is a harmonic oscillator.

When the nucleotides bond to form a base pair, the clouds must oscillate in opposite directions or the structure won't be stable. Rieper and colleagues asked what would happen to those oscillations when the base pairs are stacked in a double helix.

The helix should vibrate and fall apart, but it doesn't. Rieper and co. say this is because the oscillations occur as a superposition of states -- meaning they oscillate in all possible states at once. That effectively holds it all together.

The question is how to prove all this, as Tech Review notes. Rieper and co. say that in a standard analysis, there's not enough energy to hold DNA together, but their quantum theory makes it work. Still, that's not enough experimental evidence to prove that biology, too, is really just physics.

[Technology Review]