New Hybrid Technology Could Bring 'Quantum Information Systems'

Science Daily — The merging of two technologies under development -- plasmonics and nanophotonics -- is promising the emergence of new "quantum information systems" far more powerful than today's computers.

The technology hinges on using single photons -- the tiny particles that make up light -- for switching and routing in future computers that might harness the exotic principles of quantum mechanics.

The quantum information processing technology would use structures called "metamaterials," artificial nanostructured media with exotic properties.

The metamaterials, when combined with tiny "optical emitters," could make possible a new hybrid technology that uses "quantum light" in future computers, said Vladimir Shalaev, scientific director of nanophotonics at Purdue University's Birck Nanotechnology Center and a distinguished professor of electrical and computer engineering.

The concept is described in an article published on October 28 in the journal Science. The article appeared in the magazine's Perspectives section and was written by Shalaev and Zubin Jacob, an assistant professor of electrical and computer engineering at the University of Alberta, Canada.

"A seamless interface between plasmonics and nanophotonics could guarantee the use of light to overcome limitations in the operational speed of conventional integrated circuits," Shalaev said.

Researchers are proposing the use of "plasmon-mediated interactions," or devices that manipulate individual photons and quasiparticles called plasmons that combine electrons and photons.

One of the approaches, pioneered at Harvard University, is a tiny nanowire that couples individual photons and plasmons. Another approach is to use hyperbolic metamaterials, suggested by Jacob; Igor Smolyaninov, a visiting research scientist at the University of Maryland; and Evgenii Narimanov, an associate professor of electrical and computer engineering at Purdue. Quantum-device applications using building blocks for such hyperbolic metamaterials have been demonstrated in Shalaev's group.

"We would like to record and read information with single photons, but we need a very efficient source of single photons," Shalaev said. "The challenge here is to increase the efficiency of generation of single photons in a broad spectrum, and that is where plasmonics and metamaterials come in."

Today's computers work by representing information as a series of ones and zeros, or binary digits called "bits."

Computers based on quantum physics would have quantum bits, or "qubits," that exist in both the on and off states simultaneously, dramatically increasing the computer's power and memory. Quantum computers would take advantage of a strange phenomenon described by quantum theory called "entanglement." Instead of only the states of one and zero, there are many possible "entangled quantum states" in between one and zero.

An obstacle in developing quantum information systems is finding a way to preserve the quantum information long enough to read and record it. One possible solution might be to use diamond with "nitrogen vacancies," defects that often occur naturally in the crystal lattice of diamonds but can also be produced by exposure to high-energy particles and heat.

"The nitrogen vacancy in diamond operates in a very broad spectral range and at room temperature, which is very important," Shalaev said.

The work is part of a new research field, called diamond photonics. Hyperbolic metamaterials integrated with nitrogen vacancies in diamond are expected to work as efficient "guns" of single photons generated in a broad spectral range, which could bring quantum information systems, he said.

Law of nature refuted

SWINBURNE UNIVERSITY OF TECHNOLOGY

The so-called fine-structure constant, denoted by the symbol ‘alpha' - seems to vary across the Universe. Image: catscandotcom/iStockphoto One of the laws of nature may vary across the Universe, according to a study published today in the journal Physical Review Letters. One of the most cherished principles in science - the constancy of physics - may not be true, according to research carried out at the University of New South Wales (UNSW), Swinburne University of Technology and the University of Cambridge. The study found that one of the four known fundamental forces, electromagnetism - measured by the so-called fine-structure constant and denoted by the symbol ‘alpha' - seems to vary across the Universe. The first hints that alpha might not be constant came a decade ago when Professor John Webb, Professor Victor Flambaum, and other colleagues at UNSW and elsewhere, analysed observations from the Keck Observatory, in Hawaii. Those observations were restricted to one broad area in the sky. However, now Webb and colleagues (PhD graduate Dr Julian King, PhD student Matthew Bainbridge and Professor Victor Flambaum at UNSW; Dr Michael Murphy at Swinburne University of Technology, and Professor Bob Carswell from Cambridge University) have doubled the number of observations and measured the value of alpha in about 300 distant galaxies, all at huge distances from Earth, and over a much wider area of the sky. The new observations were obtained using the European Southern Observatory's ‘Very Large Telescope' in Chile. "The results astonished us," said Professor Webb. "In one direction - from our location in the Universe - alpha gets gradually weaker, yet in the opposite direction it gets gradually stronger." "The discovery, if confirmed, has profound implications for our understanding of space and time and violates one of the fundamental principles underlying Einstein's General Relativity theory," Dr King added. "Such violations are actually expected in some more modern ‘Theories of Everything' that try to unify all the known fundamental forces," said Professor Flambaum. "The smooth continuous change in alpha may also imply the Universe is much larger than our observable part of it, possibly infinite." "Another currently popular idea is that many universes exist, each having its own set of physical laws," Dr Murphy said. "Even a slight change in the laws of Nature means they weren't ‘set in stone' when our Universe was born. The laws of Nature you see may depend on your ‘space-time address' - when and where you happen to live in the Universe." Professor Webb said these new findings also offer a very natural explanation for a question that puzzled scientists for decades: why do the laws of physics seem to be so finely-tuned for the existence of life? "The answer may be that other regions of the Universe are not quite so favourable for life as we know it, and that the laws of physics we measure in our part of the Universe are merely ‘local by-laws', in which case it is no particular surprise to find life here," he said. Editor's Note: Original news release can be found here.

Safer way to rid toxic waste

QUEENSLAND UNIVERSITY OF TECHNOLOGY

The new technology can remove radioactive material from contaminated water and aid clean-up efforts following nuclear disasters. Image: moorsky/iStockphoto Queensland University of Technology (QUT) researchers have developed new technology capable of removing radioactive material from contaminated water and aiding clean-up efforts following nuclear disasters. The innovation could also solve the problem of how to clean up millions of tonnes of water contaminated by dangerous radioactive material and safely store the concentrated waste. Professor Huai-Yong Zhu from QUT Chemistry said the world-first intelligent absorbent, which uses titanate nanofibre and nanotube technology, differed from current clean-up methods, such as layered clays and zeolites, because it could efficiently lock in deadly radioactive material from contaminated water. The used absorbents can then be safely disposed without the risk of leakage, even if the material became wet. "One gram of the nanofibres can effectively purify at least one tonne of polluted water," Professor Zhu said. "This saves large amounts of dangerous water needing to be stored somewhere and also prevents the risk of contaminated products leaking into the soil." The technology, which was developed in collaboration with the Australian Nuclear Science and Technology Organisation (ANSTO) and Pennsylvania State University in America, works by running the contaminated water through the fine nanotubes and fibres, which trap the radioactive Cesium (Cs+) ions through a structural change. "Every year we hear of at least one nuclear accident. Not only is there a risk of contamination where human error is concerned, but there is also a risk from natural disasters such as what we saw in Japan this year," he said. Professor Zhu and his research team believed the technology would also benefit industries as diverse as mining and medicine. By adding silver oxide nanocrystals to the outer surface, the nanostructures are able to capture and immobilise radioactive iodine (I-) ions used in treatments for thyroid cancer, in probes and markers for medical diagnosis, as well as found in leaks of nuclear accidents. "It is our view that just taking the radioactive material in the adsorbents isn't good enough. We should make it safe before disposing it," he said. "The same goes for Australian sites where we mine nuclear products. We need a solution before we have a problem, rather than looking for fixes when it could be too late." With a growing need to find alternatives to meet global energy needs, Professor Zhu said now was the time to put safeguards in place. "In France, 75 per cent of electricity is produced by nuclear power and in Belgium, which has a population of 10 million people there are six nuclear power stations," he said. "Even if we decide that nuclear energy is not the way we want to go, we will still need to clean-up what's been produced so far and store it safely," he said. "Australia is one of the largest producers of titania that are the raw materials used for fabricating the absorbents of titanate nanofibres and nanotubes. Now with the knowledge to produce the adsorbents, we have the technology to do the cleaning up for the world." Editor's Note: Original news release can be found here.