Quantum computer emulated by a classical system.

Drs. Granville Ott (left) and Brian La Cour (center) with student Michael Starkey (right) beside their prototype quantum emulation device. Credit Applied Research Laboratories, The University of Texas at Austin

Source: Phys.org

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Quantum computers are inherently different from their classical counterparts because they involve quantum phenomena, such as superposition and entanglement, which do not exist in classical digital computers. But in a new paper, physicists have shown that a classical analog computer can be used to emulate a quantum computer, along with quantum superposition and entanglement, with the result that the fully classical system behaves like a true quantum computer.
Physicist Brian La Cour and electrical engineer Granville Ott at Applied Research Laboratories, The University of Texas at Austin (ARL:UT), have published a paper on the classical emulation of a quantum computer in a recent issue of The New Journal of Physics. Besides having fundamental interest, using classical systems to emulate quantum computers could have practical advantages, since such quantum emulation devices would be easier to build and more robust to decoherence compared with true quantum computers.
"We hope that this work removes some of the mystery and 'weirdness' associated with quantum computing by providing a concrete, classical analog," La Cour told Phys.org. "The insights gained should help develop exciting new technology in both classical analog computing and true quantum computing."
As La Cour and Ott explain, quantum computers have been simulated in the past using software on a classical computer, but these simulations are merely numerical representations of the quantum computer's operations. In contrast, emulating a quantum computer involves physically representing the qubit structure and displaying actual quantum behavior. One key quantum behavior that can be emulated, but not simulated, is parallelism. Parallelism allows for multiple operations on the data to be performed simultaneously—a trait that arises from quantum superposition and entanglement, and enables quantum computers to operate at very fast speeds.
To emulate a quantum computer, the physicists' approach uses electronic signals to represent qubits, in which a qubit's state is encoded in the amplitudes and frequencies of the signals in a complex mathematical way. Although the scientists use electronic signals, they explain that any kind of signal, such as acoustic and electromagnetic waves, would also work.
Even though this classical system emulates quantum phenomena and behaves like a quantum computer, the scientists emphasize that it is still considered to be classical and not quantum. "This is an important point," La Cour explained. "Superposition is a property of waves adding coherently, a phenomenon that is exhibited by many classical systems, including ours.
"Entanglement is a more subtle issue," he continued, describing entanglement as a "purely mathematical property of waves."
"Since our classical signals are described by the same mathematics as a true quantum system, they can exhibit these same properties."
He added that this kind of entanglement does not violate Bell's inequality, which is a widely used way to test for entanglement.
"Entanglement as a statistical phenomenon, as exhibited by such things as violations of Bell's inequality, is rather a different beast," La Cour explained. "We believe that, by adding an emulation of quantum noise to the signal, our device would be capable of exhibiting this type of entanglement as well, as described in another recent publication."
In the current paper, La Cour and Ott describe how their system can be constructed using basic analog electronic components, and that the biggest challenge is to fit a large number of these components on a single integrated circuit in order to represent as many qubits as possible. Considering that today's best semiconductor technology can fit more than a billion transistors on an integrated circuit, the scientists estimate that this transistor density corresponds to about 30 qubits. An increase in transistor density of a factor of 1000, which according to Moore's law may be achieved in the next 20 to 30 years, would correspond to 40 qubits.
This 40-qubit limit is also enforced by a second, more fundamental restriction, which arises from the bandwidth of the signal. The scientists estimate that a signal duration of a reasonable 10 seconds can accommodate 40 qubits; increasing the duration to 10 hours would only increase this to 50 qubits, and a one-year duration would only accommodate 60 qubits. Due to this scaling behavior, the physicists even calculated that a signal duration of the approximate age of the universe (13.77 billion years) could accommodate about 95 qubits, while that of the Planck time scale (10^-43 seconds) would correspond to 176 qubits.
Considering that thousands of qubits are needed for some complex quantum computing tasks, such as certain encryption techniques, this scheme clearly faces some insurmountable limits. Nevertheless, the scientists note that 40 qubits is still sufficient for some low-qubit applications, such as quantum simulations. Because the quantum emulation device offers practical advantages over quantum computers and performance advantages over most classical computers, it could one day prove very useful. For now, the next step will be building the device.
"Efforts are currently underway to build a two-qubit prototype device capable of demonstrating entanglement," La Cour said. "The enclosed photo [see above] shows the current quantum emulation device as a lovely assortment of breadboarded electronics put together by one of my students, Mr. Michael Starkey. We are hoping to get future funding to support the development of an actual chip. Leveraging quantum parallelism, we believe that a coprocessor with as few as 10 qubits could rival the performance of a modern Intel Core at certain computational tasks. Fault tolerance is another important issue that we studying. Due to the similarities in mathematical structure, we believe the same quantum error correction algorithms used to make quantum computers fault tolerant could be used for our quantum emulation device as well."

The Internet of Things: Toolbox to Help Objects Communicating Via the Net.

Source: ScienceDaily

ScienceDaily (June 17, 2011) — Increasingly, the things people use on a daily basis can be connected to the Internet. An alarm clock not only rings, but can also switch on the coffee machine while turning on the light. But what is needed to ensure that the Internet of Things operates as efficiently as possible? Thus far, the Internet has been an arena reserved for people. But now more and more physical objects are being connected to the Internet: we read emails on our mobile telephones, we have electricity meters that report readings automatically, and pulse monitors and running shoes that publish information about our daily jog directly on Facebook.
Tools for collaboration The Internet of Things will introduce new smart objects to our homes. One challenge is to find effective solutions to enable different products to work together. Currently no standardised tools or distribution platforms exist in this area.
A group of Norwegian researchers have been addressing this issue. In the research project Infrastructure for Integrated Services (ISIS) they have created a platform for developing and distributing applications for the Internet of Things. The platform encompasses a programming tool for developers, called Arctis and the website ISIS Store for downloading applications. The project has received funding from the Research Council of Norway's Large-scale Programme VERDIKT.
Simple programming
Arctis was developed by researchers at the Norwegian University of Science and Technology (NTNU). One of them is postdoctoral researcher Frank Alexander Kraemer.
"In a 'smart' everyday life objects and applications often need to be connected to several different communication services, sensors and other components. At the same time they need to respond quickly to changes and the actions of users. This requires very good control over concurrence in the system, which can be difficult to achieve with normal programming," he explains.
Dr Kraemer believes that the tool will make it easier to create new applications, adapt them to existing applications and update software as necessary.
"Developing a simple application with Arctis can be as easy as fitting together two building blocks, but more advanced applications can also be created, depending on what you are looking for," Dr Kraemer continues.
Talking to each other
"It is the collaborative system ICE Composition Engine (ICE) that will govern the whole thing and allow the objects to talk to each other," explains Reidar Martin Svendsen, project manager at the Norwegian telecommunications company the Telenor Group.
ICE can both manage the communication between objects in your home and keep track of any updates. The system is installed on a modem, a decoder or an adapter in the home and provides the user with a local gateway which ensures that the Internet of Things will continue to work even when the user is offline.
Key developers
Telenor is seeking to become an operator for the Internet of Things by acting as a link between developers and end-users. But if the company is to succeed, a sufficient number of developers will need to choose to use its tools.
"We have established our own App Store where talented developers can publish the new applications they create and end-users can buy and download the applications they need. Basically, you can choose software according to your own needs and preferences," says Mr Svendsen.
The downloaded applications can be combined as needed using a software programme called Puzzle. The Puzzle programme is a user interface to the ICE system.
Safe connections
For the project to flourish, people have to be willing to pay for the applications. There are already many similar applications available online free-of-charge through the data infrastructure platform Pachube, for example. Why are users going to pay for something they can download legally and at no cost?
"It is better if a well-known operator is responsible for critical systems such as house alarms. For these types of systems you should go via the App Store to a supplier you trust. You don't know anything about the intentions of those who put out programmes free-of-charge on the Internet. But if your system needs updating or you require a service, it is an advantage to be using a reputable, recognised operator," explains Mr Svendsen.
"On the whole it will be up to the developers to decide what to charge for. At the ISIS Store there are currently a number of applications available that can be downloaded free-of-charge," he continues.

Story Source:
The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by The Research Council of Norway. The original article was written by Geir Aas/Else Lie; translation by Anna Godson/Carol B. Eckmann.

Faster and More Efficient Software for the US Air Force.

Source: ScienceDaily

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ScienceDaily (Jan. 12, 2010) — Researchers at the University of Nebraska in Lincoln have addressed the issue of faulty software by developing an algorithm and open source tool that is 300 times faster at generating tests and also reduces current software testing time.

The new algorithm has potential to increase the efficiency of the software testing process across systems.
The project, funded in part by an Air Force Office of Scientific Research (AFOSR) Young Investigator Award and through a National Science Foundation Early CAREER Award, is of particular interest to the military because of the potential to reduce errors in theater. This technology will also be helpful to the private sector where some agencies are reporting financial losses of up to 50 billion dollars per year because of poor software.
"Software failures have the potential to cause financial, environmental or bodily harm," said lead researcher, Dr. Myra Cohen. "Our techniques will help to improve the quality of software in the military to help ensure that those systems behave properly in the field."
"The ultimate goal of research like this is not just to reduce software testing costs, but to do so while maintaining or even increasing confidence in the tests themselves," said AFOSR Program Manager, Dr. David Luginbuhl who is overseeing Cohen's work.
"Although algorithms exist that can produce samples for testing, few can handle dependencies between features well. Either they run slowly or they select very large test schedules, which means that testing takes too long," said Cohen.
Her project, called "Just Enough Testing" aims to re-use test results across different systems that share similar sets of features so the time to test a single system is reduced.
Large and complex families of software systems are common, and within them, groups of interacting features may cause faults to occur. The scientists have examined ways to ensure that faults are found earlier and more often in these types of systems.
"In the long term, we expect that as software product lines are used to produce large numbers of systems, and as they mature over time, we will be able to deploy new systems faster and with less likelihood of failure," she said.

Story Source:
Adapted from materials provided by Air Force Office of Scientific Research.

'Wet' Computing Systems to Boost Processing Power.

Source: ScienceDaily

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ScienceDaily (Jan. 12, 2010) — A new kind of information processing technology inspired by chemical processes in living systems is being developed by researchers at the University of Southampton.

Dr Maurits de Planque and Dr Klaus-Peter Zauner at the University's School of Electronics and Computer Science (ECS) are working on a project which has just received €1.8 from the European Union's Future and Emerging Technologies (FET) Proactive Initiatives, which recognises ground-breaking work which has already demonstrated important potential.
The researchers, Dr de Planque, a biochemist, and Dr Zauner, a computer scientist, will adapt brain processes to a 'wet' information processing scenario by setting up chemicals in a tube which behave like the transistors in a computer chip
"What we are developing here is a very crude, minimal liquid brain and the final computer will be 'wet' just like our brain," said Dr Zauner. "People realise now that the best information processes we have are in our heads and as we are increasingly finding that silicon has its limitations in terms of information processing, we need to explore other approaches, which is exactly what we are doing here."
The project, entitled Artificial Wet Neuronal Networks from Compartmentalised Excitable Chemical Material, which is being co-ordinated by Friedrich Schiller University Jena with other project partners, the University of the West of England, Bristol and the Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw, will run for three years and involves three complementary objectives.
The first is to engineer lipid-coated water droplets, inspired by biological cells, containing an excitable chemical medium and then to connect the droplets into networks in which they can communicate through chemical signals. The second objective is to design information-processing architectures based on the droplets and to demonstrate purposeful information processing in droplet architectures. The third objective is to establish and explore the potential and limitations of droplet architectures.
"Our system will copy some key features of neuronal pathways in the brain and will be capable of excitation, self-repair and self-assembly," said Dr de Planque.

Story Source:
Adapted from materials provided by University of Southampton, via AlphaGalileo.

New multi-touch screen technology developed (with Video)

Source: Physorg.com

Scientists from New York University have formed a company to bring flexible multi-touch screens using a new technology to a range of devices, from e-readers to musical instruments. The new touch screens respond to all kinds of objects, as well as fingers and hands.

The team, led by Ken Perlin and Ilya Rosenberg from the Media Research Laboratory, formed their company Touchco to develop IFSR (interpolating force-sensitive resistance) technology, which uses resistors sensitive to the force or pressure applied to touch points. This, along with scanning technology and positional interpolation, allows for (theoretically) unlimited simultaneous touch inputs (in contrast to other touch technologies such as the capacitive touch screen used by iPhone, which can track limited touch points). It has low power requirements and is inexpensive, since Touchco expects to sell the screen material at $10 per square foot. The technology is easily scalable for use in small or large devices.

Perlin said that the IFSR technology is likely to appear in a new range of e-readers later this year, and will also be used in laptops or notebooks, and new types of musical instruments. In computer applications the touch pads allow the user to control the cursor with a light touch, but to select and manipulate objects when more pressure is applied.
The company has also been collaborating with Disney to develop a digital sketchbook that will use sensitive pressure sensors capable of differentiating between the touch of a hand, a pencil, brush or eraser. Drawing pictures is just one of many possible applications of the technology.

The touch pads consist of layers of FSR ink sandwiched between opaque or transparent sheets of plastic onto which conductive wires are printed. The total thickness is only 0.25 mm. When pressure is applied to an FSR sensor a current flows from the wires in one layer to the wires in the other layer, and the pressure applied is determined by the amount of electric current flowing from layer to layer. Arranging sensors in a grid would have been expensive and impractical, so Touchco developed scanners to measure the touches and determine their positions. Resolution is 254 µm (100 dpi), but this can be increased by decreasing the wire spacing.
Touchco has already begun selling developer kits to device manufacturers and expects to see IFSR technology finding many applications during 2010.

More information: Touchco: http://touchco.com/

Stanford Univesity: We're emulating the brain ...in silicon!

Source: Stanford University/Bioengineering Department

Welcome to Brains in Silicon. Learn about the lab, get to know the brains that work here, and find out about new projects that you could join. We have crafted two complementary objectives: To use existing knowledge of brain function in designing an affordable supercomputer—one that can itself serve as a tool to investigate brain function—feeding back and contributing to a fundamental, biological understanding of how the brain works.We model brains using an approach far more efficient than software simulation: We emulate the flow of ions directly with the flow of electrons—don't worry, on the outside it looks just like software.Welcome and enjoy your time here!

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First Intelligent Financial Search Engine Developed.

SOURCE

ScienceDaily (Sep. 30, 2009) — Researchers from the Carlos III University of Madrid (UCM3) have completed the development of the first search engine designed to search for information from the financial and stock market sector based on semantic technology, which enables one to make more accurate thematic searches adapted to the needs of each user.

Unlike conventional search engines, SONAR -so named by its creators- enables the user to perform structured searches which are not based solely on concordance with a series of key words. This corporate financial search engine based on semantic technology, as described on the project website (http://www.proyecto-sonar.org), was developed by researchers from the UC3M in partnership with the University of Murcia, el Instituto de Empresa (the Business Institute) and the company Indra.
According to its creators, it has two main advantages. First, its effectiveness in a concrete domain- that of finance- which is closely defined and has very precise vocabulary. According to Juan Miguel Gómez Berbís, from the Computer Department of the UC3M “This verticality distinguishes SONAR from other more generic search engines, such as Google or Bing” Second, its capacity to establish relations between news, share valuations and prices via logical reasoning.
The first prototype works by making use of semantic web elements. Basically, the system collects data from both public information sources (Internet) and private, corporate ones (Intranet), adds them to a repository of semantically recorded data (labelled and structured) and allows intelligent access to this data. To achieve this, the platform incorporates an inference engine, a mechanism capable of performing reasoning tasks on the recorded information, as well as a natural language processor, which helps the user to perform the search in the simplest way possible. In this way the results obtained are matched to requests, eliminating ambiguities in polysemic terms, for example in searches carried out by users on stored data. “SONAR enables us to establish relations between different sources of information and discover and expand our knowledge, while at the same time it allows us to classify them so that users can get much more benefit from the experience”
Potential users
This search tool is designed for both private investors and large financial concerns. Its creators anticipate that it will be a very useful tool for analysts and stockbrokers. “It will be especially useful to the finance departments of banks and saving banks or to add to an existing search engine added value over its competitors” Gómez Berbís points out. And the search for accurate, reliable, relevant information in this business area has become a key factor in a domain where speed and quality of data are critical factors with an exceptional impact on business processes.
According to the researchers, this project aims to respond to a need from the financial sector, that is, the analysis of a large volume of information in order to take decisions. In this way, the execution of this project will allow the financial community to have access to a set of intelligent systems for the aggregated search of information in the financial domain and enable them to improve procedures for integrating company information and processes.
Researchers are currently incorporating new functions into the search tool and also receiving requests to adapt it to other domains, such as transport and biotechnology. In any case, the project is constantly evolving in order to enhance accuracy and reliability. “In SONAR2 we are working on two Intelligent Decision Support Systems for Financial Investments, one based on Fundamental Analysis and the other on Technical Chartist Analysis, which assists the work of the trader and average investor”, reveals professor Gómez Berbis.
Adapted from materials provided by Universidad Carlos III de Madrid.

Ants Vs. Worms: New Computer Security Mimics Nature.

SOURCE

ScienceDaily (Sep. 28, 2009) — In the never-ending battle to protect computer networks from intruders, security experts are deploying a new defense modeled after one of nature’s hardiest creatures — the ant.

Unlike traditional security devices, which are static, these “digital ants” wander through computer networks looking for threats, such as “computer worms” — self-replicating programs designed to steal information or facilitate unauthorized use of machines. When a digital ant detects a threat, it doesn’t take long for an army of ants to converge at that location, drawing the attention of human operators who step in to investigate.
The concept, called “swarm intelligence,” promises to transform cyber security because it adapts readily to changing threats.
“In nature, we know that ants defend against threats very successfully,” explains Professor of Computer Science Errin Fulp, an expert in security and computer networks. “They can ramp up their defense rapidly, and then resume routine behavior quickly after an intruder has been stopped. We were trying to achieve that same framework in a computer system.”
Current security devices are designed to defend against all known threats at all times, but the bad guys who write malware — software created for malicious purposes — keep introducing slight variations to evade computer defenses.
As new variations are discovered and updates issued, security programs gobble more resources, antivirus scans take longer and machines run slower — a familiar problem for most computer users.
Glenn Fink, a research scientist at Pacific Northwest National Laboratory (PNNL) in Richland, Wash., came up with the idea of copying ant behavior. PNNL, one of 10 Department of Energy laboratories, conducts cutting-edge research in cyber security.
Fink was familiar with Fulp’s expertise developing faster scans using parallel processing — dividing computer data into batches like lines of shoppers going through grocery store checkouts, where each lane is focused on certain threats. He invited Fulp and Wake Forest graduate students Wes Featherstun and Brian Williams to join a project there this summer that tested digital ants on a network of 64 computers.
Swarm intelligence, the approach developed by PNNL and Wake Forest, divides up the process of searching for specific threats.
“Our idea is to deploy 3,000 different types of digital ants, each looking for evidence of a threat,” Fulp says. “As they move about the network, they leave digital trails modeled after the scent trails ants in nature use to guide other ants. Each time a digital ant identifies some evidence, it is programmed to leave behind a stronger scent. Stronger scent trails attract more ants, producing the swarm that marks a potential computer infection.”
In the study this summer, Fulp introduced a worm into the network, and the digital ants successfully found it. PNNL has extended the project this semester, and Featherstun and Williams plan to incorporate the research into their master’s theses.
Fulp says the new security approach is best suited for large networks that share many identical machines, such as those found in governments, large corporations and universities.
Computer users need not worry that a swarm of digital ants will decide to take up residence in their machine by mistake. Digital ants cannot survive without software “sentinels” located at each machine, which in turn report to network “sergeants” monitored by humans, who supervise the colony and maintain ultimate control.
Adapted from materials provided by Wake Forest University. Original article written by Eric Frazier, Office of Communications and External Relations.

Reconstruct Mars Automatically In Minutes.

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ScienceDaily (Sep. 18, 2009) — A computer system is under development that can automatically combine images of the Martian surface, captured by landers or rovers, in order to reproduce a three dimensional view of the red planet. The resulting model can be viewed from any angle, giving astronomers a realistic and immersive impression of the landscape.

The new development has been presented at the European Planetary Science Congress in Potsdam by Dr Michal Havlena.
“The feeling of ‘being right there’ will give scientists a much better understanding of the images. The only input we need are the captured raw images and the internal camera calibration. After minutes of computation on a standard PC, a three dimensional model of the captured scene is obtained,” said Dr Havlena.
The growing amount of available imagery from Mars is nearly impossible to handle for the manual image processing techniques used to date. The new automated method, which allows fast high quality image processing, was developed at the Center for Machine Perception of the Technical University of Prague, under the supervision of Tomas Pajdla, as a part of the EU FP7 Project PRoVisG.
From the technical point of view, the image processing consists of three stages: the first step is determining the image order. If the input images are unordered, i.e. they do not form a sequence but still are somehow connected, a state-of-the-art image indexing technique is able to find images of cameras observing the same part of the scene. To start with, up to a thousand features on each image are detected and “translated” into visual words, according to a visual vocabulary trained on images from Mars. Then, starting from an arbitrary image, the following image is selected if it shares the highest number of visual words with the previous image.
The second step of the pipeline, the so-called ‘structure-from-motion computation’, helps scientists determine the accurate camera positions and rotations in three dimensional space. Just five corresponding features are enough to obtain a relative camera pose between the two images that have been selected as sequential.
The last and most important step is the so-called ‘dense 3D model generation’ of the captured scene, which essentially creates and fuses the Martian surface depth maps. To do this, the model uses the disparities (parallaxes) present in images taken at two distinct camera positions, which were identified in the second step.
“The pipeline has already been used successfully to reconstruct a three dimensional model from nine images captured by the Phoenix Mars Lander, which were obtained just after performing some digging operation on the Mars surface,” said Dr Havlena.
“The challenge is now to reconstruct larger parts of the surface of the red planet, captured by the Mars Exploration Rovers Spirit and Opportunity,” concluded Dr Havlena.
Adapted from materials provided by Europlanet Media Centre, via AlphaGalileo.

Quantum Computing: From qubits to qudits, with five energy levels

Source: ScienceDaily

ScienceDaily (Aug. 13, 2009) — Scientists at UC Santa Barbara have devised a new type of superconducting circuit that behaves quantum mechanically – but has up to five levels of energy instead of the usual two. The findings are published in the August 7 issue of Science.

These circuits act like artificial atoms in that they can only gain or lose energy in packets, or quanta, by jumping between discrete energy levels. "In our previous work, we focused on systems with just two energy levels, 'qubits,' because they are the quantum analog of 'bits,' which have two states, on and off," said Matthew Neeley, first author and a graduate student at UCSB.
He explained that in this work they operated a quantum circuit as a more complicated artificial atom with up to five energy levels. The generic term for such a system is "qudit," where 'd' refers to the number of energy levels –– in this case, 'd' equals five.
"This is the quantum analog of a switch that has several allowed positions, rather than just two," said Neeley. "Because it has more energy levels, the physics of a qudit is richer than for just a single qubit. This allows us to explore certain aspects of quantum mechanics that go beyond what can be observed with a qubit."
Just as bits are used as the fundamental building blocks of computers, qubits could one day be used as building blocks of a quantum computer, a device that exploits the laws of quantum mechanics to perform certain computations faster than can be done with classical bits alone. "Qudits can be used in quantum computers as well, and there are even cases where qudits could be used to speed up certain operations with a quantum computer," said Neeley. "Most research to date has focused on qubit systems, but we hope our experimental demonstration will motivate more effort on qudits, as an addition to the quantum information processing toolbox."
The senior co-author of the paper is John M. Martinis, professor of physics at UCSB. Other co-authors from UCSB are: Markus Ansmann, Radoslaw C. Bialczak, Max Hofheinz, Erik Lucero, Aaron D. O'Connell, Daniel Sank, Haohua Wang, James Wenner, and Andrew N. Cleland. Another co-author, Michael R. Geller, is from the University of Georgia.
Adapted from materials provided by University of California - Santa Barbara.

This Article Will Self-destruct: Tool To Make Online Personal Data Vanish

SOURCE

ScienceDaily (July 22, 2009) — Computers have made it virtually impossible to leave the past behind. College Facebook posts or pictures can resurface during a job interview. A lost cell phone can expose personal photos or text messages. A legal investigation can subpoena the entire contents of a home or work computer, uncovering incriminating, inconvenient or just embarrassing details from the past.

The University of Washington has developed a way to make such information expire. After a set time period, electronic communications such as e-mail, Facebook posts and chat messages would automatically self-destruct, becoming irretrievable from all Web sites, inboxes, outboxes, backup sites and home computers. Not even the sender could retrieve them.
"If you care about privacy, the Internet today is a very scary place," said UW computer scientist Tadayoshi Kohno. "If people understood the implications of where and how their e-mail is stored, they might be more careful or not use it as often."
The team of UW computer scientists developed a prototype system called Vanish that can place a time limit on text uploaded to any Web service through a Web browser. After a set time text written using Vanish will, in essence, self-destruct. A paper about the project went public today and will be presented at the Usenix Security Symposium Aug. 10-14 in Montreal.
Co-authors on the paper are doctoral student Roxana Geambasu, assistant professor Tadayoshi Kohno, professor Hank Levy and undergraduate student Amit Levy, all with the UW's department of computer science and engineering. The research was funded by the National Science Foundation, the Alfred P. Sloan Foundation and Intel Corp.
"When you send out a sensitive e-mail to a few friends you have no idea where that e-mail is going to end up," Geambasu said. "For instance, your friend could lose her laptop or cell phone, her data could be exposed by malware or a hacker, or a subpoena could require your e-mail service to reveal your messages. If you want to ensure that your message never gets out, how do you do that?"
Many people believe that pressing the "delete" button will make their data go away.
"The reality is that many Web services archive data indefinitely, well after you've pressed delete," Geambasu said.
Simply encrypting the data can be risky in the long term, the researchers say. The data can be exposed years later, for example, by legal actions that force an individual or company to reveal the encryption key. Current trends in the computing and legal landscapes are making the problem more widespread.
"In today's world, private information is scattered all over the Internet, and we can't control the lifetime of that data," said Hank Levy. "And as we transition to a future based on cloud computing, where enormous, anonymous datacenters run the vast majority of our applications and store nearly all of our data, we will lose even more control."
The Vanish prototype washes away data using the natural turnover, called "churn," on large file-sharing systems known as peer-to-peer networks. For each message that it sends, Vanish creates a secret key, which it never reveals to the user, and then encrypts the message with that key. It then divides the key into dozens of pieces and sprinkles those pieces on random computers that belong to worldwide file-sharing networks, the same ones often used to share music or movie files. The file-sharing system constantly changes as computers join or leave the network, meaning that over time parts of the key become permanently inaccessible. Once enough key parts are lost, the original message can no longer be deciphered.
In the current Vanish prototype, the network's computers purge their memories every eight hours. (An option on Vanish lets users keep their data for any multiple of eight hours.)
Unlike existing commercial encryption services, a message sent using Vanish is kept private by an inherent property of the decentralized file-sharing networks it uses.
"A major advantage of Vanish is that users don't need to trust us, or any service that we provide, to protect or delete the data," Geambasu says.
Researchers liken using Vanish to writing a message in the sand at low tide, where it can be read for only a few hours before the tide comes in and permanently washes it away. Erasing the data doesn't require any special action by the sender, the recipient or any third party service.
"Our goal was really to come up with a system where, through a property of nature, the message, or the data, disappears," Levy says.
Vanish was released today as a free, open-source tool that works with the Firefox browser. To work, both the sender and the recipient must have installed the tool. The sender then highlights any sensitive text entered into the browser and presses the "Vanish" button. The tool encrypts the information with a key unknown even to the sender.
That text can be read, for a limited time only, when the recipient highlights the text and presses the "Vanish" button to unscramble it. After eight hours the message will be impossible to unscramble and will remain gibberish forever.
Vanish works with any text entered into a Web browser: Web-based e-mail such as Hotmail, Yahoo and Gmail, Web chat, or the social networking sites MySpace and Facebook. The Vanish prototype now works only for text, but researchers said the same technique could work for any type of data, such as digital photos.
It is technically possible to save information sent with Vanish. A recipient could print e-mail and save it, or cut and paste unencrypted text into a word-processing document, or photograph an unscrambled message. Vanish is meant to protect communication between two trusted parties, researchers say.
"Today many people pick up the phone when they want to talk with a lawyer or have a private conversation," Kohno said. "But more and more communication is happening online. Vanish is designed to give people the same privacy for e-mail and the Web that they expect for a phone conversation."
The paper and research prototype are at http://vanish.cs.washington.edu.
Adapted from materials provided by University of Washington.

Program For Cyber Security 'Neighborhood Watch' Developed

SOURCE

ScienceDaily (July 16, 2009) — U.S. Department of Energy laboratories fight off millions of cyber attacks every year, but a near real-time dialog between these labs about this hostile activity has never existed – until now.

Scientists at DOE's Argonne National Laboratory have devised a program that allows for Cyber Security defense systems to communicate when attacked and transmit that information to cyber systems at other institutions in the hopes of strengthening the overall cyber security posture of the complex.
"The Federated Model for Cyber Security acts as a virtual neighborhood watch program. If one institution is attacked; secure and timely communication to others in the Federation will aide in protecting them from that same attack through active response," cyber security officer Michael Skwarek said.
Prior to the development of the Federated Model for Cyber Security, the exchange of hostile activity was solely on the shoulders of the human element. In cyber attacks, every second counts and the quicker that such information can be securely shared, will assist in strengthening others against similar attacks. With millions of cyber security probes a day, the human element will not be successful alone.
"This program addresses the need for the exchange of hostile activity information, with the goal of reducing the time to react across the complex. History has shown, hostile activity is often targeted at more than one location, and having our defenses ready and armed will assist greatly." Skwarek said.
Currently, the program is capable of transmitting information regarding hostile IP addresses and domain names, and will soon be able to share hostile email address and web URLs to others in the Federation.
The development of this program led to Skwarek along with Argonne's cyber security team members Matt Kwiatkowski, Tami Martin, Scott Pinkerton, Chris Poetzel, Gene Rackow and Conrad Zadlo winning the DOE's 2009 Cyber Security Innovation and Technology Achievement Award.
The Federated Model for Cyber Security has proved to be an important cyber security and communication tool. Use in the private sector, as well as in institutions with heavy collaborative efforts, can realize an operational gain by leveraging the power of sharing and learning from others on what they see and defend against on a daily basis.
Adapted from materials provided by DOE/Argonne National Laboratory.

Tracking The Life And Death Of News

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ScienceDaily (July 14, 2009) — As more and more news appears on the Internet as well as in print, it becomes possible to map the global flow of news by observing it online. Using this strategy, Cornell computer scientists have managed to track and analyze the "news cycle" -- the way stories rise and fall in popularity.

Jon Kleinberg, the Tisch University Professor of Computer Science at Cornell, postdoctoral researcher Jure Leskovec and graduate student Lars Backstrom tracked 1.6 million online news sites, including 20,000 mainstream media sites and a vast array of blogs, over the three-month period leading up to the 2008 presidential election -- a total of 90 million articles, one of the largest analyses anywhere of online news. They found a consistent rhythm as stories rose into prominence and then fell off over just a few days, with a "heartbeat" pattern of handoffs between blogs and mainstream media. In mainstream media, they found, a story rises to prominence slowly then dies quickly; in the blogosphere, stories rise in popularity very quickly but then stay around longer, as discussion goes back and forth. Eventually though, almost every story is pushed aside by something newer.
"The movement of news to the Internet makes it possible to quantify something that was otherwise very hard to measure -- the temporal dynamics of the news," said Kleinberg. "We want to understand the full news ecosystem, and online news is now an accurate enough reflection of the full ecosystem to make this possible. This is one [very early] step toward creating tools that would help people understand the news, where it's coming from and how it's arising from the confluence of many sources."
The researchers also say their work suggests an answer to a longstanding question: Is the "news cycle" just a way to describe our perception of what's going on in the media, or is it a real phenomenon that can be measured? They opt for the latter, and offer a mathematical explanation of how it works.
The research was presented at the Association for Computing Machinery Special Interest Group on Conference on Knowledge Discovery and Data Mining Conference June 28-July 1 in Paris.
The ideal, Kleinberg said, would be to track "memes," or ideas, through cyberspace, but deciding what an article is about is still a major challenge for computing. The researchers sidestepped that obstacle by tracking quotations that appear in news stories, since quotes remain fairly consistent even though the overall story may be presented in very different ways by different writers.
Even quotes may change slightly or "mutate" as they pass from one article to another, so the researchers developed an algorithm that could identify and group similar but slightly different phrases. In simple terms, the computer identified short phrases that were part of longer phrases, using those connections to create "phrase clusters." Then they tracked the volume of posts in each phrase cluster over time. In the August and September data they found threads rising and falling on a more or less weekly basis, with major peaks corresponding to the Democratic and Republican conventions, the "lipstick on a pig" discussion, rising concern over the financial crisis and discussions of a bailout plan.
The slow rise of a new story in the mainstream, the researchers suggest, results from imitation -- as more sites carried a story, other sites were more likely to pick it up. But the life of a story is limited, as new stories quickly push out the old. A mathematical model based on the interaction of imitation and recency predicted the pattern fairly well, the researchers said, while predictions based on either imitation or recency alone couldn't come close.
Watching how stories moved between mainstream media and blogs revealed a sharp dip and rise the researchers described as a "heartbeat." When a story first appears, there is a small rise in activity in both spheres; as mainstream activity increases, the proportion blogs contribute becomes small; but soon the blog activity shoots up, peaking an average of 2.5 hours after the mainstream peak. Almost all stories started in the mainstream. Only 3.5 percent of the stories tracked appeared first dominantly in the blogosphere and then moved to the mainstream.
The mathematical model needs to be refined, the researchers said, and they suggested further study of how stories move between sites with opposing political orientation. "It will be useful to further understand the roles different participants play in the process," the researchers concluded, "as their collective behavior leads directly to the ways in which all of us experience news and its consequences."
Adapted from materials provided by Cornell University.

Quantum Computers And Tossing A Coin In The Microcosm

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ScienceDaily (July 9, 2009) — When you toss a coin, you either get heads or tails. By contrast, things are not so definite at the microcosmic level. An atomic 'coin' can display a superposition of heads and tails when it has been thrown. However, this only happens if you do not look at the coin. If you do, it decides in favour of one of the two states. If you leave the decision where a quantum particle should go to a coin like this, you get unusual effects. For the first time, physicists at the University of Bonn have demonstrated these effects in an experiment with caesium.

Let's assume we carried out the following experiment: we put a coin in the hand of a test person. We'll simply call this person Hans. Hans's task is now to toss the coin several times. Whenever the coin turns up 'heads', his task is to take a step to the right. By contrast, if it turns up 'tails', he takes a step to the left. After 10 throws we look where Hans is standing. Probably he won't have moved too far from his initial position, as 'heads' and 'tails' turn up more or less equally often. In order to walk 10 paces to the right, Hans would have to get 10 'heads' successively. And that tends not happen that often.
Now, we assume that Hans is a very patient person. He is so patient that he does this experiment 1000 times successively. After each go, we record his position. When at the end we display this result as a graph, we get a typical bell curve. Hans very often ends up somewhere close to his starting positions after 10 throws. By contrast, we seldom find him far to the left or right.
The experiment is called a 'random walk'. The phenomenon can be found in many areas of modern science, e.g. as Brownian motion. In the world of quantum physics, there is an analogy with intriguing new properties, the 'quantum walk'. Up to now, this was a more or less a theoretical construct, but physicists at the University of Bonn have now actually carried out this kind of 'quantum walk'.
A single caesium atom held in a kind of tweezers composed of laser beams served as a random walker and coin at the same time. Atoms can adopt different quantum mechanical states, similar to head and tails of a coin facing upwards. Yet at the microcosmic level everything is a little more complicated. This is because quantum particles can exist in a superposition of different states. Basically, in that case 'a bit of heads' and 'a bit of tails' are facing upwards. Physicists also call this superposition.
Using two conveyor belts made of laser beams, the Bonn physicists pulled their caesium atom in two opposite directions, the 'heads' part to the right, the 'tails' part to the left. 'This way we were able to move both states apart by fractions of a thousandth of a millimetre,' Dr. Artur Widera from the Bonn Institute of Applied Physics explains. After that, the scientists 'threw the dice once more' and put each of both components into a superposition of heads and tails again.
After several steps of this 'quantum walk' a caesium atom like this that has been stretched apart is basically everywhere. Only when you measure its position does it 'decide' at which position of the 'catwalk' it wants to turn up. The probability of its position is predominantly determined by a second effect of quantum mechanics. This is due to two parts of the atom being able to reinforce themselves or annihilate themselves. As in the case of light physicists call this interference.
As in the example of Hans the coin thrower, you can now carry out this 'quantum walk' many times. You then also get a curve which reflects the atom's probability of presence. And that is precisely what the physicists from Bonn measured. 'Our curve is clearly different from the results obtained in classical random walks. It does not have its maximum at the centre, but at the edges,' Artur Widera's colleague Michal Karski points out. 'This is exactly what we expect from theoretical considerations and what makes the quantum walk so attractive for applications.' For comparison the scientists destroyed the quantum mechanical superposition after every single 'throw of the coin'. Then the 'quantum walk' becomes a 'random walk', and the caesium atom behaves like Hans. 'And that is exactly the effect we see,' Michal Karski says.
Professor Dieter Meschede's group has been working on the development of so-called quantum computers now for many years. With the 'quantum walk' the team has now achieved a further seminal step on this path. 'With the effect we have demonstrated, entirely new algorithms can be implemented,' Artur Widera explains. Search processes are one example. Today, if you want to trace a single one in a row of zeros, you have to check all the digits individually. The time taken therefore increases linearly with the number of digits. By contrast, using the 'quantum walk' algorithm the random walker can search in many different places simultaneously. The search for the proverbial needle in a haystack would thus be greatly speeded up.
Their research will be published in the July 10 issue of the scientific journal Science.
Adapted from materials provided by University of Bonn.

DIY Production In 'Second Life' Factory

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ScienceDaily (July 7, 2009) — Anyone who wants to can now produce their own vehicle in a factory on the “Second Life” Internet platform. They can program the industrial robots, and transport and assemble the individual parts themselves. Learning platforms provide relevant background information.

In the “transparent factory”, car enthusiasts can watch vehicles being assembled part by part, and a new system set up by researchers of the Fraunhofer Institute for Manufacturing Engineering and Automation IPA even enables users to try their own hand at producing a quad bike, a four-wheeled motorbike. They can switch on conveyor belts, program industrial robots, and paint the frame themselves. At the end, they can zoom out of the factory hall with their finished product without paying a single cent. How is this possible? Because the factory does not exist in the real world but on the Internet platform of “Second Life”, a virtual world through which users can move in the form of a virtual figure known as an “avatar”.
“With the ‘factory of eMotions’, we want to familiarize people with a modern, technically advanced factory. We also want to demonstrate how the latest media can set things in motion,” says IPA scientist
Stefan Seitz. “Second Life has grown steadily: While in 2007, between 20,000 and 40,000 people were simultaneously online at any given time, this number has now risen to between 50,000 and 80,000.” In the factory, users first of all indicate which quad model they would like to produce. Powerful or fuel-saving? Black, silver or red? What type of wheel rims? They can choose from a variety of models as they please. Once their avatar has made a choice, production can begin. The parts list is sent out, and all components are manufactured, assembled and subjected to a quality inspection. The avatar can watch the production process and interact at certain stages. Learning platforms located at various points in the factory hall provide users with relevant background information. How is the production process controlled? How does a press work?
“The main challenge lay in reproducing the control logic for production – in other words, teaching the system how to produce a part on Machine A, transport it to Machine B and mount it there. Until now, the ‘Second Life’ platform has offered no support for this,” says Seitz. The researchers have developed a modular system which also enables any other product to be made. Industrial companies and private users can use the building blocks to set up their own virtual factories. The scientists have even integrated a speech recognition system, so the machines and robots can also be controlled by telephone. The factory will be revealed to the public in early July on the occasion of the IPA’s 50th anniversary.
Adapted from materials provided by Fraunhofer-Gesellschaft.

Physicists Find Way To Control Individual Bits In Quantum Computers.

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ScienceDaily (July 7, 2009) — Physicists at the National Institute of Standards and Technology (NIST) have overcome a hurdle in quantum computer development, having devised a viable way to manipulate a single "bit" in a quantum processor without disturbing the information stored in its neighbors. The approach, which makes novel use of polarized light to create "effective" magnetic fields, could bring the long-sought computers a step closer to reality.

A great challenge in creating a working quantum computer is maintaining control over the carriers of information, the "switches" in a quantum processor while isolating them from the environment. These quantum bits, or "qubits," have the uncanny ability to exist in both "on" and "off" positions simultaneously, giving quantum computers the power to solve problems conventional computers find intractable – such as breaking complex cryptographic codes.
One approach to quantum computer development aims to use a single isolated rubidium atom as a qubit. Each such rubidium atom can take on any of eight different energy states, so the design goal is to choose two of these energy states to represent the on and off positions. Ideally, these two states should be completely insensitive to stray magnetic fields that can destroy the qubit's ability to be simultaneously on and off, ruining calculations. However, choosing such "field-insensitive" states also makes the qubits less sensitive to those magnetic fields used intentionally to select and manipulate them. "It's a bit of a catch-22," says NIST's Nathan Lundblad. "The more sensitive to individual control you make the qubits, the more difficult it becomes to make them work properly."
To solve the problem of using magnetic fields to control the individual atoms while keeping stray fields at bay, the NIST team used two pairs of energy states within the same atom. Each pair is best suited to a different task: One pair is used as a "memory" qubit for storing information, while the second "working" pair comprises a qubit to be used for computation. While each pair of states is field- insensitive, transitions between the memory and working states are sensitive, and amenable to field control. When a memory qubit needs to perform a computation, a magnetic field can make it change hats. And it can do this without disturbing nearby memory qubits.
The NIST team demonstrated this approach in an array of atoms grouped into pairs, using the technique to address one member of each pair individually. Grouping the atoms into pairs, Lundblad says, allows the team to simplify the problem from selecting one qubit out of many to selecting one out of two – which, as they show in their paper, can be done by creating an effective magnetic field, not with electric current as is ordinarily done, but with a beam of polarized light.
The polarized-light technique, which the NIST team developed, can be extended to select specific qubits out of a large group, making it useful for addressing individual qubits in a quantum processor without affecting those nearby. "If a working quantum computer is ever to be built," Lundblad says, "these problems need to be addressed, and we think we've made a good case for how to do it." But, he adds, the long-term challenge to quantum computing remains: integrating all of the required ingredients into a single apparatus with many qubits.
Journal reference:
N. Lundblad, J.M. Obrecht, I.B. Spielman, and J.V. Porto. Field-sensitive addressing and control of field-insensitive neutral-atom qubits. Nature Physics, July 5, 2009
Adapted from materials provided by National Institute of Standards and Technology (NIST).

Computer Scientists Develop Model For Studying Arrangements Of Tissue Networks By Cell Division

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ScienceDaily (July 3, 2009) — Computer scientists at Harvard have developed a framework for studying the arrangement of tissue networks created by cell division across a diverse set of organisms, including fruit flies, tadpoles, and plants.

The finding, published in the June 2009 issue of PLoS Computational Biology, could lead to insights about how multicellular systems achieve (or fail to achieve) robustness from the seemingly random behavior of groups of cells and provide a roadmap for researchers seeking to artificially emulate complex biological behavior.
"We developed a model that allows us to study the topologies of tissues, or how cells connect to each other, and understand how that connectivity network is created through generations of cell division," says senior author Radhika Nagpal, Assistant Professor of Computer Science at the Harvard School of Engineering and Applied Sciences (SEAS) and a core faculty member of the Wyss Institute for Biologically Inspired Engineering. "Given a cell division strategy, even if cells divide at random, very predictable 'signature' features emerge at the tissue level."
Using their computational model, Nagpal and her collaborators demonstrated that the regularity of the tissue, such as the percentage of hexagons and the overall cell shape distribution, can act as an indicator for inferring properties about the cell division mechanism itself. In the epithelial tissues of growing organisms, from fruit flies to humans, the ability to cope with often unpredictable variations (referred to as robustness) is critical for normal development. Rapid growth, entailing large amounts of cell division, must be balanced with the proper regulation of overall tissue and organ architecture.
"Even with modern imaging methods, we can rarely directly 'ask' the cell how it decided upon which way to divide. The computational tool allows us to generate and eliminate hypotheses about cell division. Looking at the final assembled tissue gives us a clue about what assembly process was used," explains Nagpal.
The model also sheds light on a prior discovery made by the team: that many proliferating epithelia, from plants to frogs, show a nearly identical cell shape distribution. While the reasons are not clear, the authors suggest that the high regularity observed in nature requires a strong correlation between how neighboring cells divide. While plants and fruit flies, for example, seem to have conserved cell shape distributions, the two organisms have, based on the computational and experimental evidence, evolved distinct ways of achieving such a pattern.
"Ultimately, the work offers a beautiful example of the way biological development can take advantage of very local and often random processes to create large-scale robust systems. Cells react to local context but still create organisms with incredible global predictability," says Nagpal.
In the future, the team plans to use their approach to detect and study various mutations that adversely affect cell division process in epithelial tissues. Epithelial tissues are common throughout animals and form important structures in humans from skin to the inner lining of organs. Deviations from normal division can result in abnormal growth during early development and to the formation of cancers in adults.
"One day we may even be able to use our model to help researchers understand other kinds of natural cellular networks, from tissues to geological crack formations, and, by taking inspiration from biology, design more robust computer networks," adds Nagpal.
Nagpal's collaborators included Ankit B. Patel and William T. Gibson, both at Harvard, and Dr. Matthew C. Gibson at Stower's Institute.
Adapted from materials provided by Harvard University, via EurekAlert!, a service of AAAS.

Optical Computer Closer: Optical Transistor Made From Single Molecule

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ScienceDaily (July 2, 2009) — ETH Zurich researchers have successfully created an optical transistor from a single molecule. This has brought them one step closer to an optical computer.

Internet connections and computers need to be ever faster and more powerful nowadays. However, conventional central processing units (CPUs) limit the performance of computers, for example because they produce an enormous amount of heat. The millions of transistors that switch and amplify the electronic signals in the CPUs are responsible for this. One square centimeter of CPU can emit up to 125 watts of heat, which is more than ten times as much as a square centimeter of an electric hotplate.
Photons instead of electrons
This is why scientists have been trying for some time to find ways to produce integrated circuits that operate on the basis of photons instead of electrons. The reason is that photons do not only generate much less heat than electrons, but they also enable considerably higher data transfer rates.
Although a large part of telecommunications engineering nowadays is based on optical signal transmission, the necessary encoding of the information is generated using electronically controlled switches. A compact optical transistor is still a long way off. Vahid Sandoghdar, Professor at the Laboratory of Physical Chemistry of ETH Zurich, explains that, “Comparing the current state of this technology with that of electronics, we are somewhat closer to the vacuum tube amplifiers that were around in the fifties than we are to today’s integrated circuits.”
However, his research group has now achieved a decisive breakthrough by successfully creating an optical transistor with a single molecule. For this, they have made use of the fact that a molecule’s energy is quantized: when laser light strikes a molecule that is in its ground state, the light is absorbed. As a result, the laser beam is quenched. Conversely, it is possible to release the absorbed energy again in a targeted way with a second light beam. This occurs because the beam changes the molecule’s quantum state, with the result that the light beam is amplified. This so-called stimulated emission, which Albert Einstein described over 90 years ago, also forms the basis for the principle of the laser.
Focusing on a nano scale
Jaesuk Hwang, first author of the study and a scientific member of Sandoghdar’s nano-optics group, explains that, “Amplification in a conventional laser is achieved by an enormous number of molecules.” By focusing a laser beam on only a single tiny molecule, the ETH Zurich scientists have now been able to generate stimulated emission using just one molecule. They were helped in this by the fact that, at low temperatures, molecules seem to increase their apparent surface area for interaction with light . The researchers therefore needed to cool the molecule down to minus 272 degrees Celsius (minus 457.6 degrees Fahrenheit), i.e. one degree above absolute zero. In this case, the enlarged surface area corresponded approximately to the diameter of the focused laser beam.
Switching light with light
By using one laser beam to prepare the quantum state of a single molecule in a controlled fashion, scientists could significantly attenuate or amplify a second laser beam. This mode of operation is identical to that of a conventional transistor, in which electrical potential can be used to modulate a second signal.
Thus component parts such as the new single molecule transistor may also pave the way for a quantum computer. Sandoghdar says, “Many more years of research will still be needed before photons replace electrons in transistors. In the meantime, scientists will learn to manipulate and control quantum systems in a targeted way, moving them closer to the dream of a quantum computer.”
Journal reference:
J. Hwang, M. Pototschnig, R. Lettow, G. Zumofen, A. Renn, S. Götzinger, V. Sandoghda. A single-molecule opzical transistor. Nature, 460, 76-80 DOI: 10.1038/nature08134
Adapted from materials provided by ETH Zurich.

Quantum Communications One Step Closer: Novel Ion Trap For Sensing Force And Light Developed

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ScienceDaily (July 1, 2009) — Miniature devices for trapping ions (electrically charged atoms) are common components in atomic clocks and quantum computing research. Now, a novel ion trap geometry demonstrated at the National Institute of Standards and Technology (NIST) could usher in a new generation of applications because the device holds promise as a stylus for sensing very small forces or as an interface for efficient transfer of individual light particles for quantum communications.

The "stylus trap," built by physicists from NIST and Germany's University of Erlangen-Nuremberg, is described in Nature Physics. It uses fairly standard techniques to cool ions with laser light and trap them with electromagnetic fields. But whereas in conventional ion traps, the ions are surrounded by the trapping electrodes, in the stylus trap a single ion is captured above the tip of a set of steel electrodes, forming a point-like probe. The open trap geometry allows unprecedented access to the trapped ion, and the electrodes can be maneuvered close to surfaces. The researchers theoretically modeled and then built several different versions of the trap and characterized them using single magnesium ions.
The new trap, if used to measure forces with the ion as a stylus probe tip, is about one million times more sensitive than an atomic force microscope using a cantilever as a sensor because the ion is lighter in mass and reacts more strongly to small forces. In addition, ions offer combined sensitivity to both electric and magnetic fields or other force fields, producing a more versatile sensor than, for example, neutral atoms or quantum dots. By either scanning the ion trap near a surface or moving a sample near the trap, a user could map out the near-surface electric and magnetic fields. The ion is extremely sensitive to electric fields oscillating at between approximately 100 kilohertz and 10 megahertz.
The new trap also might be placed in the focus of a parabolic (cone-shaped) mirror so that light beams could be focused directly on the ion. Under the right conditions, single photons, particles of light, could be transferred between an optical fiber and the single ion with close to 95 percent efficiency. Efficient atom-fiber interfaces are crucial in long-distance quantum key cryptography (QKD), the best method known for protecting the privacy of a communications channel. In quantum computing research, fluorescent light emitted by ions could be collected with similar efficiency as a read-out signal. The new trap also could be used to compare heating rates of different electrode surfaces, a rapid approach to investigating a long-standing problem in the design of ion-trap quantum computers.
Research on the stylus trap was supported by the Intelligence Advanced Research Projects Activity.
Journal reference:
R. Maiwald, D. Leibfried, J. Britton, J.C. Bergquist, G. Leuchs, and D.J. Wineland. Stylus ion trap for enhanced access and sensing. Nature Physics, Online June 28
Adapted from materials provided by National Institute of Standards and Technology.