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Researchers bolster development of programmable quantum computers

University of Chicago researchers and their colleagues at University College London have performed a proof-of-concept experiment that will aid the future development of programmable quantum computers.

Many complex problems are difficult and slow to solve using conventional computers, and over the last several years, research has grown steadily toward developing quantum computation. In particular, optimization problems such as the "traveling salesman" problem, which calculates the shortest possible route needed to visit a set of towns, become intractable as the number of towns grows.

A quantum computer would exploit effects on the atomic and molecular scales to solve such problems dramatically faster than conventional computers. Recently a first generation of specialized computers has become available -- with a new architecture that exploits quantum mechanics to help solve problems akin to the traveling salesman problem, with up to a few hundred towns.

In a study published in the Proceedings of the National Academy of Sciences, a team from the James Franck Institute at UChicago and the London Centre for Nanotechnology at University College London describes an experiment that was performed on a crystal containing trillions, rather than hundreds, of quantum mechanical spins, which replicates some of the features of the current generation of much smaller, specialized computers.

The lead author is Michael Schmidt, PhD'12, now a research scientist with Intel in Portland. His co-authors are Daniel Silevitch, research scientist in the James Franck Institute; Thomas Rosenbaum, the John T. Wilson Distinguished Service Professor in Physics; and Prof. Gabriel Aeppli of University College London.

The crystalline quantum magnet used to perform this experiment contains atoms whose spins (magnetic orientation) oscillate. Thermal annealing and quantum annealing are the processes by which the researchers manipulated the magnetic spins in this experimental magnetic crystal. Many types of magnetic materials can orient spins in any direction, but this special crystal limits the orientation to either up or down.

Quantum annealing relates to quantum tunneling, a phenomenon that allows particles to pass through barriers via interactions that Newtonian physics cannot predict. "If you run the system in a regime where quantum tunneling is completely turned off, then you end up with one solution to your problem, and a different solution when quantum tunneling is turned on," Silevitch said.

In this magnetic crystal at temperatures near absolute zero (minus 459.67 degrees Fahrenheit), the speed and strength of thermal annealing can be controlled by rods of sapphire attached to a refrigerator via more or less contact with the crystal. At the same time, the rate of quantum annealing can be controlled by means of a magnetic field, which sets the rate of quantum tunneling in the magnetic sample.

Thermal annealing can only be turned down by cooling the system, but it cannot be turned off. But if the system runs in a mode where thermal annealing is turned down and quantum annealing is turned up, the result is a different state of magnetic spins, which represents a different solution to the computational problem.

The special purpose computer solves problems such as the traveling salesman problem in a semi-abstract landscape where the heights and depths of features represent the total distance traveled. The best solution corresponds to the deepest valley.

Finding the deepest valley can be visualized as a pool of water moving between valleys, either via a wave splashing over the intermediate saddle points and then descending, or via quantum tunneling between valleys.

The first approach represents thermal annealing, which is comparable to conventional computing methods. The second corresponds to quantum annealing, a characteristic of potentially more capable quantum computing.

Thermal annealing reaches a final state, or problem solution, by hopping over the energy barriers, then gradually restricting the size of the barrier that it can overcome via lowering the temperature. Quantum annealing, by contrast, reaches the final state via quantum tunneling through the barriers, then gradually clamping down (and ultimately turning off) the tunneling rate.

In thermal annealing, the "waves" slosh back and forth, and if they reach a sufficient height, they will splash over the hill and then drain into an adjacent valley.

High-temperature thermal annealing corresponds to violently sloshing water, which means that it can surmount high barriers. As the researchers slowly drop the strength of the waves, the water can only top middle-sized hills. With further cooling of the system, the waves can only wash over molehills.

A problem arises, however, for thermal annealing when a bowl-like valley sits next to a deeper, narrower well. In this situation, most of the sloshing water will end up at the bottom of the valley. Water naturally seeks its lowest level, but as the temperature drops and the wave heights become reduced, the entrance of the well becomes inaccessible.

Quantum annealing allows the water to pass through the hill via the quantum tunneling process.

"If you have this bowl, and then right next to it there's this really deep well, the odds of getting out of the bowl into the well through thermal annealing is very, very low," Silevitch explained. "You have to wait for a randomly big wave to come sloshing over. But with quantum annealing, you can go right through the hill and you can find that deep well, which is where you prefer to be."

The experiments found that when the system reached its final valley via thermal annealing alone, it was dramatically different from the state reached when the thermal annealing was weakened and quantum annealing was turned on.

After the application of quantum annealing, certain regions of the crystal were in "quantum superposition states," which can simultaneously exist in two different states according to the counter-intuitive rules of quantum physics. Other regions have the characteristics typical of the physics that predominates at macroscopic scales. Thermal annealing in these experiments leaves behind regions exclusively of the latter variety.

Applied to practical and programmable quantum optimization computers, the results imply that quantum optimizers could obtain different solutions to problems such as the traveling salesman problem, when compared with conventional techniques. The research team concluded that these findings would affect both the design and use of quantum optimization systems.

 

Futuristic robots allow doctors to examine patients from anywhere

Doctors at Rady Children's today introduced new telemedicine robots that put advanced video teleconferencing technology on wheels, allowing physicians to evaluate patients quickly and from anywhere.

Using a laptop, tablet or smartphone, doctors are now able to interact and perform their jobs in ways not previously possible. They can see, hear, be heard and move around in any remote facility, including being able to visually examine patients without being physically present.

"We've found the majority of patients treated with telemedicine technology have a favorable response," said Dr. Anthony Magit, director of Rady Children's telemedicine program. "Patients realize they are seeing specialists who might not be accessible to them in their own location, so they feel they are getting cutting edge, high-technology care from top experts."

With satellite locations ranging from 20 minutes to more than an hour away, the telemedicine robots allow Rady Children's experts to consult on cases in a more timely and efficient manner. Rady Children's currently has funding to purchase 16 of these advanced robots. Some of the robots are already in use at Rady Children's neonatal intensive care unit (NICU) satellite locations.

"In the past when I would get an urgent call about a patient while I was away from the NICU, I would either have to wait until I got to the hospital or I would be on the phone trying to understand what was happening," said Dr. Gail Knight, Clinical Chief of the Division of Neonatology. "Now I can pull off the road and simply call up the robot on my cell phone to see what is going on. It only takes 30 seconds."

Story Source:

The above story is based on materials provided by Rady Children's Hospital-San Diego. Note: Materials may be edited for content and length.

 

Future computers that are normally off

If a research team in Japan gets its wish, "normally off" computers may one day soon be replacing present computers in a move that would both eliminate volatile memory, which requires power to maintain stored data, and reduce the gigantic energy losses associated with it.

Most parts of present computers are made with volatile devices such as transistors and dynamic random access memory (DRAM), which loses information when powered off. So computers are designed on the premise that power is "normally on."

Back in 2000, the concept of "instant on" computers based on magnetoresistive random access memory (MRAM) emerged as a way to reduce that irritatingly long hang time associated with powering up -- but it comes with a big tradeoff because it requires using volatile devices that continue to devour energy after the initial power up.

By 2001, researchers in Japan figured out a way to eliminate this pointless energy loss by using a nonvolatile function of advanced spin-transfer torque magnetoresistive random access memory (STT-MRAM) technology to create a new type of computer: a "normally off" one.

Now, Koji Ando and his colleagues at the Japanese National Projects have broadly envisioned the future of STT-MRAM, and in the Journal of Applied Physics, which is produced by AIP Publishing, they describe how it will radically alter computer architectures and consumer electronics.

"Spintronics couples magnetism with electronics at the quantum mechanical level," explained Ando. "Indeed, STT-MRAM no longer requires an electromagnetic coil for both writing and reading information. We're excited by this paradigm shift and are working on developing a variety of technologies for next-generation electronics devices."

The potential for redesigning present-day technologies so that computer power consumption is zero during any short intervals when users are absent is that may lead to extremely energy-efficient personal devices powered by a hand-crank or embedded solar panel. Such devices would find use in a wide swath of applications ranging from mobile computing to wearable or embedded electronics, and they would be of particular interest to the healthcare, safety and educational industries.

Some hurdles remain, Ando said. "We need high-performance nonvolatile devices that don't require a power supply to retain information to create 'normally off' computers while simultaneously guaranteeing sufficiently high-speed operation to manipulate information," Ando said. "The main memory, for example, requires performance as fast as 10 to 30 nanoseconds, and a density as high as 1 Gigabit per chip."

If STT-MRAM is to play a key role for "normally off" computers, it will first require the integration of a variety of technologies, he added. "We're currently collaborating with researchers in several fields -- from materials science, device technology, circuit technology, memory and computer architectures, operating systems," Ando said.

Story Source:

The above story is based on materials provided by American Institute of Physics (AIP). Note: Materials may be edited for content and length.

   

Method offers potential for understanding anti-bacterial resistance

Biologists could gain a deeper understanding about how species have evolved -- and even find ways to address antibiotic resistance -- using tools that were developed recently at Stockholm's KTH Royal Institute of Technology.

A better method for identifying how genes evolve has been developed by an international team that includes Jens Lagergren, a professor in computer science and computational biology at KTH.

The new model and method offers a way to understand a gene's history, Lagergren says. But in the long term the research could potentially lead to better understanding of how species evolve and provide a basis for dealing with antibiotic resistance.

The evolution of a species can in many cases be depicted with a tree. The same can be said for describing the evolution of gene families, that is, closely-related genes that have similar functions with regard to the species they are found in.

Information carried by genes in one gene family can be altered by mutations of individual DNA positions, as well as through major events such as losses or duplications of entire genes.

The latter give rise to entirely new genes in a gene family. In bacteria, genes often are transferred between individuals within the same species. They also jump from one species to another, which is how antibiotic resistance spreads between different bacterial strains.

"Exploring how different gene families have emerged during evolution is important for understanding how different genes are related to one another," Lagergren says.

"Where there's a branch on gene tree, the gene has a new function," he says.

Lagregren worked with colleagues from KTH and Science for Life Laboratory (SciLifeLab) to develop probability models that provide a more detailed picture of how the gene tree has grown through evolution, and when genes eventually jumped from one species to another in the species tree.

By basing their methods on mathematical models and Bayesian analysis, the researchers succeeded in producing tools for biologists who are interested in jumping genes and the traits they carry with them.

"Bayesian analysis allows one to start from an observation that has been made in reality and see which model is most probable given this observation," Lagregren says. "This is too time-consuming to do by hand, but it is possible with the help of computers."

He applied the model to two sets of bacterial species, and found that the new method works much better than traditional, non-statistical methods.

"Right now it's pure, basic research to understand the genes' history," he says. "In the long run, however, the models can be used to provide a deeper understanding of how different species have evolved and are related to each other, not only through direct inheritance but also by gene transfer."

The method and model could be used in order to see the kinship between species more clearly than before.

And, Lagregren adds, the method could one day provide a basis for dealing with antibiotic resistance.

"The method describes an algorithm and associated software, which will be an important tool for researchers working with bacteria and the genes they transmit laterally, such as for antibiotic resistance," he says.

Story Source:

The above story is based on materials provided by KTH The Royal Institute of Technology. Note: Materials may be edited for content and length.

 

New Fusion Technology Increases Prostate Cancer Detection Accuracy to 97 Percent

Urologists at Rush University Medical Center are the first in Chicago to offer a powerful new tool for visualizing and monitoring the prostate in men who have high prostate-specific antigen (PSA) levels and in detecting prostate cancer more accurately.

The new technology combines or "fuses" magnetic resonance (MR) and ultrasound images uses electromagnetic tracking/guidance, similar to your car's GPS system. A tiny tracking sensor is attached to an ultrasound probe and generates a small, localized electromagnetic field that helps determine the location and orientation of the biopsy device. A sophisticated computer program maintains the fusion of MR and ultrasound images, even when a patient moves.

If necessary, physicians can make a precisely targeted biopsy or direct sampling of tissue in areas within the prostate that seem suspicious. Currently prostate biopsies are "blind," meaning physicians must randomly sample the prostate, an approach that has been in use since the 1980s.

"By fusing these MRI images with real-time ultrasound, prostate biopsy can now be targeted directly toward specific areas of interest in the prostate," said Dr. Ajay Nehra, chairman of urology at Rush University Medical Center.

The process involves a 20-minute procedure done in the clinic under local anesthesia, compared with less accurate and older method of prostate biopsy. Many men require multiple biopsies in order to make sure that all potentially cancerous areas are identified. This technology eliminates the need for multiple biopsies, at times up to 21.

"This is a new way of identifying and specifically targeting suspicious prostate lesions. We believe it may have the potential to be a new standard in prostate care," said Nehra.

"The use of fusion technology increases the accuracy of prostate biopsy to 97 percent," said Dr. Charles McKiel, Jr., professor of urology at Rush University Medical Center. "This technology allows us to see tumors that may be missed by conventional prostate biopsy."

Based on this diagnostic technology, doctors at Rush will soon begin a new clinical research trial called "focal therapy" for men with prostate cancer confined to one small area. Focal therapy treats only the area that is cancerous rather than the entire prostate gland, according to McKiel.

Other than skin cancer, prostate cancer has become the most common form of cancer in American men and the second-leading cause of cancer death in this population. According to the American Cancer Society, 1 of 6 men will be diagnosed with prostate cancer during his lifetime. It is the second leading cause of cancer death in men behind lung cancer.

Story Source:

The above story is based on materials provided by Rush University Medical Center. Note: Materials may be edited for content and length.

   

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