Thursday, May 5, 2011

Quantum simulation with light: Frustrations between photon pairs

Researchers from the Vienna Center for Quantum Science and Technology at the University of Vienna and the Institute of Quantum Optics and Quantum Information (IQOQI) at the Austrian Academy of Sciences used a quantum mechanical system in the laboratory to simulate complex many-body systems. This experiment, which is published in Nature Physics, promises future quantum simulators enormous potential insights into unknown quantum phenomena.

Already the behavior of relatively small quantum systems cannot be calculated because quantum states contain much more information than their classical counter-parts. However, if another quantum system is used to simulate the quantum system of interest, then answers about the properties of the complex quantum system can be obtained.

When is a quantum system frustrated?

Currently, many international groups are focusing their research on frustrated quantum systems, which have been conjectured to explain high-temperature superconductivity. A quantum system is frustrated if competing requirements cannot be satisfied simultaneously. The Viennese research group realized for the first time an experimental quantum simulation, where the frustration regarding the "pairing" of correlations was closely investigated.

Using two pairs of entangled photons, a frustrated quantum system could be simulated that consists of four particles. "Just the recent development of our quantum technology allows us to not only rebuild other quantum systems, but also to simulate its dynamics" says Philip Walther (University of Vienna). "Now we can prepare quantum states of individual photons to gain insights into other quantum systems," explains Xiao-song Ma (Austrian Academy of Sciences).Therefore, two in polarization entangled photons exhibit in many ways the same quantum physical properties as for example electrons in matter.

Conflict over partnerships

The research team of international scientists from China, Serbia, New Zeeland and Austria prepared single photons that were facing the conflict over partnerships between each other. Each photon can establish a single bond to only one partner exclusively, but wants to get correlated with several partners -- obviously this leads to frustration. As a result, the quantum system uses "tricks" that allow quantum fluctuations that different pairings can coexist as superposition.

The work of the Viennese group underlines that quantum simulations are a very good tool for calculating quantum states of matter and are thus opening the path for the investigation of more complex systems.

Story Source:

The above story is reprinted (with editorial adaptations) from materials provided by University of Vienna.

Journal Reference:

Xiao-song Ma, Borivoje Dakic, William Naylor, Anton Zeilinger, Philip Walther. Quantum simulation of the wavefunction to probe frustrated Heisenberg spin systems. Nature Physics, 2011; 7 (5): 399 DOI: 10.1038/nphys1919

Synthetic hydrogels improve testing of active substances in 3-D cell culture



The life science company Cellendes in Germany has developed synthetic hydrogels that make it possible to culture cells in three-dimensional environments. Their invention has fundamental advantages over other hydrogels for three-dimensional cultivation, also on the market.

Many researchers culture cells in flat dishes, two-dimensional culture systems. A disadvantage is that the cells behave differently than they would in a . To offer an environment that resembles the living organism better, Dr. Birgitte Angres and Dr. Helmut Wurst have developed synthetic transparent hydrogels for three-dimensional applications within their life science company Cellendes (Cell-Environment-Design).

“Compared to other hydrogels on the market ours can be much easier modified with bioactive factors such as peptides right at the bench. So customers can choose which peptides they want to include in their culture. They can either purchase them from us or have their own being synthesized. Secondly, the concentration of bioactive factors, such as peptides, in our gels can be much higher than in the competitors’ gels,” Dr. Helmut Wurst said.

The hydrogels are made in a few minutes by combining two solutions in the form of an activated polymer and a cross-linking agent. Through a chemical reaction the polymers use the agent to link themselves together and a three-dimensional network, where the average pore is about eight nanometers wide, forms. Before the linking occurs it is possible to bind biofactors to the polymer and mix in cells.

The biggest challenge, from a technical point of view, during the development of the hydrogels has been to make these components reproducible. “You can do it once and then the next time maybe a little bit different, but you want to make a reproducible quality of your different components and I think that is the biggest problem,” Wurst said.

At the moment Wurst and his colleagues are trying to make it possible to store and ship the gels at room temperature and not in refrigerated conditions, to save costs in shipping. They also want to make the gels form a little bit slower. “The gels form so fast that it is sometimes difficult to mix the two different solutions completely,” Wurst said.

Almost all of Cellendes’ customers are doing basic research within the field of the life sciences. However, their hydrogels could also be useful in the chemical industry and within drug and cosmetic development. “Efforts are made to reduce the number of experimental animal testings. In our system the cells are cultured in a more natural environment and could replace certain animal models,” Wurst said.

Within the European Commission-funded project ProNano - Promoting Technology Transfer of Nanosciences, Nanotechnologies, Materials and new Production Technologies, Cellendes researchers have been selected to receive coaching to make their results in nanotechnologies reach the market.

Source: (news : web)

Market lighting affects nutrients

Many people reach toward the back of the fresh-produce shelf to find the freshest salad greens with the latest expiration dates. But a study led by U.S. Department of Agriculture (USDA) scientists may prompt consumers to instead look for packages that receive the greatest exposure to light--usually those found closest to the front.

The study was led by postharvest plant physiologist Gene Lester while at the Agricultural Research Service (ARS) and Fruit Insects Research Unit in Weslaco, Texas. ARS is USDA's chief intramural scientific research agency.

Lester and colleagues Donald Makus and Mark Hodges found that spinach leaves exposed to continuous light during storage were, overall, more nutritionally dense than leaves exposed to continuous dark. Lester now works at the ARS Food Quality Laboratory in Beltsville, Md.

For the study, the researchers exposed spinach leaves to light similar to the 24-hour artificial fluorescent light received by spinach in packages located at the front of the display case. A second group was enclosed in two-layer-thick, brown-grocery-bag paper to represent the "dark treatment."

Both experimental groups were housed in market-type, light-transmissible polymer tubs with snap-tight lids and were kept in walk-in storage chambers at 4 degrees Celsius, the same temperature at which markets currently display packaged spinach. The light reaction of photosynthesis is not temperature-dependent and can occur at 4 degrees C in the right type of light.

The researchers found that the continuous light affected the leaves' photosynthetic system-resulting in a significant increase in levels of carotenoids and vitamins C, E, K, and B9, or folate.

While the simulated retail light conditions actually helped the stored leaves gain in content of several human-healthy vitamins, some wilting occurred after three days of storage in flat-leaf , but not crinkled-leaf types.

Results from this work were published in the Journal of Agricultural and Food Chemistry.

Provided by United States Department of Agriculture

Webcam technology used to measure medications' effects on the heart

A common component in webcams may help drug makers and prescribers address a common side-effect of drugs called cardiotoxicity, an unhealthy change in the way the heart beats. Researchers at Brigham and Women's Hospital (BWH) have used the basic webcam technology to create a tool to look at the effects of medications in real time on heart cells, called cardiomyocytes. These findings were published in the journal, Lab on a Chip on April 11, 2011.

Researchers developed a cost-effective, portable cell-based biosensor for real time cardiotoxicity detection using an image sensor from a webcam. They took cardiomyocytes, derived from mouse stem cells, and introduced the cells to different drugs. Using the biosensor, the researchers were able to monitor the beating rate of the cardiomyocytes in real time and detect any drug-induced changes in the beating rates.

The technology provides a simple approach to perform evaluative studies of different drugs effects on . Cardiotoxicity is a significant problem in drug development, with more than 30 percent of drugs withdrawn from the market between 1996 to 2006 related to cardiac dysfunction. "Assessing the toxic effects of new drugs during the early phases of drug development can accelerate the process, resulting in significant cost and time savings, and leading to faster treatment discovery," said Ali Khademhosseini, PhD, of the Center for Biomedical Engineering at the Department of Medicine at BWH.

"This technology could also play a role in personalized medicine," said Sang Bok Kim, PhD, a Research Fellow in the Renal Division at BWH. "By first extracting somatic cells from patients which can be reprogrammed to called induced pluripotent stem (iPS) cells. Then these iPS cells can be differentiated into cardiac cells to be studied, the biosensor can monitor the cardiac cells as they're introduced to a medication, providing a glimpse at how the drugs may affect the individual's heart, and thus shaping the treatment plan for that person."

Monitoring cardiac cells in the past required using expensive equipment that had a limited measurement area. This low cost (less than $10) is compatible with conventional equipment but will enable reliable, yet faster and more cost-effective studies.

"Our next goal is to combine our detection sensor with our microwell arrays and perform screening studies of thousands of drugs to cardiac cells simultaneously in a fast and reliable manner," said Dr. Khademhosseini.

Provided by Brigham and Women's Hospital