Toshiba invention brings quantum computing closer

路透社Ben Hirschler

LONDON (Reuters) – Superfast quantum computing, one of the holy grails of science, could be a step closer following the invention of a new device capable of producing so-called "entangled" light on demand.

Scientists at Toshiba Corp'sresearch center in Cambridge, England, said on Wednesday their Entangled Light Emitting Diode (ELED) opened a path to ultra-powerful semiconductor chips.

Quantum computers would in theory try out many possible solutions to a problem at once and should solve in seconds problems that take today's fastest machines years to crack.

But harnessing the weird powers of quantum physics -- which looks at the universe at the level of atoms, photons and other particles -- is easier said than done.

Now, though, Andrew Shields of Toshiba and colleagues believe they have a key tool for the job in the form of a simple-to-make device, which can be hooked up to a battery to produce entangled light as and when required.

"It's a big step because it means you can now start to integrate lots of devices on a single chip," Shields said.

So far, the Toshiba team haven't got to the stage of doing calculations, but Shields thinks basic quantum computing circuits using the technology could be ready in five years.

Quantum computers based on optical processes need a large number of entangled photons, where light particles are linked so that they exist in two possible states simultaneously -- something Albert Einstein described as "spooky."

Until now, making entangled light has only been possible using bulky lasers. But Toshiba's new ELED uses standard semiconductor technology and is made of gallium arsenide, a common material in optical electronics.

It is similar to conventional light emitting diodes used in consumer electronics and modern household lighting, except it contains a tiny region, called a quantum dot, which converts electrical current into entangled light.

The Toshiba team, working with the University of Cambridge's Cavendish Laboratory, described their invention in a paper in the journal Nature.

Other researchers are using atoms or electrons, rather than photons, as quantum computing building blocks. But Shields said the ELED marked a big step forward for the optical approach.

Quantum computers are likely to be used initially to solve problems that are otherwise virtually intractable, such as modeling new molecules in pharmaceuticals.

Further off, they might also offer an answer when technology based on conventional silicon chips bumps up against the laws of physics and components cannot be made any smaller.

(Editing by David Holmes)

 http://news.yahoo.com/s/nm/20100602/sc_nm/us_toshiba_computing

New Research Reveals How DNA Could Power Computers

TechNewsDaily Staff, LiveScience.com Technewsdaily Staff

Engineers have long dreamed of using DNA as the backbone for the next generation of computer circuits. New research shows just how it might be done.

Instead of conventional circuits built of silicon that use electrical current, computer engineers could take advantage of the unique properties of DNA, the double-helix molecule that carries life's information.

"Conventional technology has reached its physical limits," said Chris Dwyer, assistant professor of electrical and computer engineering at Duke University's Pratt School of Engineering.

Dwyer recently demonstrated that by simply mixing customized snippets of DNA and other molecules, he could create billions of identical, tiny, waffle-looking structures.

These nanostructures can then be used as the building blocks for a variety of circuit-based applications, ranging from the biomedical to the computational.

Key to the promise of these DNA nanostructures is an ability to rapidly "switch" between zeros or ones - the basic on/off binary action that powers computation. Light can be used to stimulate similar binary responses from DNA-based switches, though at a much faster rate than in silicon.

"When light is shined on the chromophores" - parts of DNA responsible for its color - "they absorb it, exciting the electrons," Dwyer said. "The energy released passes to a different type of chromophore nearby that absorbs the energy and then emits light of a different wavelength. That difference means this output light can be easily differentiated from the input light, using a detector."

Dwyer added: "This is the first demonstration of such an active and rapid processing and sensing capacity at the molecular level."

Building computers with life's building blocks

With this bio-based system, Dwyer believes that logic circuits at the heart of computers can be produced inexpensively in almost limitless quantities. In a single day, the reasoning goes, a solitary grad student at a lab bench could produce more simple logic circuits than the world's entire output of silicon chips in a month.

DNA is a well-understood molecule made up of pairs of complimentary nucleotide bases that have an affinity for each other. Customized snippets of DNA can cheaply be synthesized by putting the pairs in any order.

In their experiments, the researchers exploited DNA's natural ability to latch onto corresponding and specific areas of other DNA snippets.

Dwyer used a jigsaw puzzle analogy to describe the process of what happens when all the waffle ingredients are mixed together in a container.

"It's like taking pieces of a puzzle, throwing them in a box and as you shake the box, the pieces gradually find their neighbors to form the puzzle," he said. "What we did was to take billions of these puzzle pieces, throwing them together, to form billions of copies of the same puzzle."

In the recent experiments, the waffle puzzle had 16 pieces, with the chromophores located atop the waffle's ridges. More complex circuits can be created by building structures composed of many of these small components, or by building larger waffles.

In addition to their use in computing, Dwyer said that since these nanostructures are basically sensors, many biomedical applications are possible. Tiny nanostructures could be built that could respond to different proteins that are markers for disease in a single drop of blood.

A study describing the results was published last month in the journal Small.

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http://news.yahoo.com/s/livescience/20100517/sc_livescience/newresearchrevealshowdnacouldpowercomputers

Molecular Computer Mimics Human Brain

Charles Q. Choi, TechNewsDaily Contributor

A superthin computer just two molecules thick can solve complex problems and, somewhat like the human brain, can evolve to improve and perform many operations simultaneously.

This molecular processor can also heal itself if there is a defect, researchers added.

Modern computers operate at staggering speeds, capable of carrying out more than 10 trillion instructions per second. However, they generally perform operations in sequence, one thing at a time.

Brain cells or neurons, fire "only" 1,000 times per second or so, but the fact that millions of them simultaneously work in parallel means they can complete tasks more efficiently than even the fastest supercomputer.

The connections between neurons also evolve over time, growing stronger or weaker as the brain works out the best way to solve problems. In this way, such networks can learn over time.

A molecular computer

Now an international research team from Japan and the United States has created a computer just two molecules thick that can replicate these traits of the human brain to a certain extent.

The building block of this computer is an organic compound known as 2,3-dichloro-5,6-dicyano-p-benzoquinone, or DDQ for short. This molecule can basically switch between four different electrically conductive states - think of a ring with four spokes.

The scientists deposited molecules of DDQ onto a surface of gold, which then spontaneously assembled into two layers, each a hexagonal grid of molecules.

The researchers next used the electrically charged tip of a scanning tunneling microscope to individually set molecules in the top layer to a desired state, essentially writing data into the system. (A scanning tunneling microscope operates somewhat like a blind person's fingers do with Braille writing - moving over a surface to detect microscopic bumps and valleys.)

Each molecule could wirelessly interact with its neighbors via their electric fields. These molecules continuously exchanged information in the form of electrons among themselves, at times causing molecules around them to change states. This is similar to how electricity flowing down wires makes transistors in microchips switch back and forth to encode data as ones or zeroes.

The results were patterns such as lines, triangles, hexagons and rhombuses, where each molecule within is set to a certain state.

Massively parallel 

Altogether, at least 300 molecules in the system interact together like a massively parallel computer, each changing states when data is written into the system. The patterns or "cellular automata" that result among the molecules function much like circuits on chips to direct the flow of electricity. The difference is that in this system, the patterns can evolve over time as new data is entered.

Also, like the brain but unlike other existing manmade computers, this new system can heal itself because the molecules that make up the computer can automatically reorganize themselves.

"This is brain-like computing," said researcher Ranjit Pati, a physicist at Michigan Technological University.

To probe the molecular computer's power, the researchers used it to successfully simulate two natural phenomena: the way heat diffuses through a material, and the way cancers grow in the body.

In principle, this new computer could also serve as a means to solve problems that conventional computers find too hard to tackle, "intractable problems that are considered impossible to finish within a finite time," explained lead researcher Anirban Bandyopadhyay, a physicist at the Japanese National Institute for Materials Science in Tsukuba.

These might include predicting the behavior of systems with many interacting bodies - anything from disease outbreaks to the evolution of galaxies, Michigan's Pati said.

One important weakness of the system is how it depends on scanning tunneling microscopy, which is a slow process. In the future, it may be possible to use multiple tips to simultaneously scan many molecules at one time, Pati suggested.

Since these molecules assemble themselves into grids, scaling them up to a larger system will not be a problem. The team's next target is a computer employing 1,000 molecular switches.

"The work is underway," Bandyopadhyay said.

Future research could also employ molecules that can get set to more than four states, for even more complex systems, Pati added.

The scientists detailed their findings online April 25 in the journal Nature Physics.

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http://news.yahoo.com/s/livescience/20100426/sc_livescience/molecularcomputermimicshumanbrain