Dennis Kochmann Wins International Solid Mechanics Award

Caltech assistant professor of aerospace Dennis Kochmann received the 2012 IUTAM Bureau Prize in solid mechanics from the International Union of Theoretical and Applied Mechanics (IUTAM). Kochmann accepted the award at the organization's quadrennial congress in Beijing on August 24.

IUTAM Bureau Prizes are awarded once every four years to three individuals under 35 years of age. Kochmann won the prize for his paper and presentation in solid mechanics. IUTAM also awarded France's Mickaël Bosco for his lecture on fluid mechanics, and the organization's poster presentation prize went to Huachuan Wang of the United States.

"This prize is a great honor for me because it is awarded by the international solid mechanics community," says Kochmann. "It shows that the research we do in my still very young research group here at Caltech is well received."

Kochmann's presentation, "Making positive use of instability—ultra-high stiffness and damping composites and structures due to constrained instabilities," highlighted recent results of his research, describing how engineers can make positive use of mechanical instabilities.

"While engineering design commonly aims to prevent instabilities of any kind, leading to failure or collapse," Kochmann says, "controlled and careful use of mechanical instabilities can result in new material and structural systems that possess superior properties such as very high stiffness and damping."

More information on the activities of Kochmann's research group at Caltech can be found at

Brian Bell
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Weighing Molecules One at a Time

Caltech-led physicists create first-ever mechanical device that measures the mass of a single molecule

PASADENA, Calif.—A team led by scientists at the California Institute of Technology (Caltech) has made the first-ever mechanical device that can measure the mass of individual molecules one at a time.

This new technology, the researchers say, will eventually help doctors diagnose diseases, enable biologists to study viruses and probe the molecular machinery of cells, and even allow scientists to better measure nanoparticles and air pollution.

The team includes researchers from the Kavli Nanoscience Institute at Caltech and Commissariat à l'Energie Atomique et aux Energies Alternatives, Laboratoire d'électronique des technologies de l'information (CEA-LETI) in Grenoble, France. A description of this technology, which includes nanodevices prototyped in CEA-LETI's facilities, appears in the online version of the journal Nature Nanotechnology on August 26.

The device—which is only a couple millionths of a meter in size—consists of a tiny, vibrating bridge-like structure. When a particle or molecule lands on the bridge, its mass changes the oscillating frequency in a way that reveals how much the particle weighs.

"As each particle comes in, we can measure its mass," says Michael Roukes, the Robert M. Abbey Professor of Physics, Applied Physics, and Bioengineering at Caltech. "Nobody's ever done this before."

The new instrument is based on a technique Roukes and his colleagues developed over the last 12 years. In work published in 2009, they showed that a bridge-like device—called a nanoelectromechanical system (NEMS) resonator—could indeed measure the masses of individual particles, which were sprayed onto the apparatus. The difficulty, however, was that the measured shifts in frequencies depended not only on the particle's actual mass, but also on where the particle landed. Without knowing the particle's landing site, the researchers had to analyze measurements of about 500 identical particles in order to pinpoint its mass.

But with the new and improved technique, the scientists need only one particle to make a measurement. "The critical advance that we've made in this current work is that it now allows us to weigh molecules—one by one—as they come in," Roukes says.

To do so, the researchers analyzed how a particle shifts the bridge's vibrating frequency. All oscillatory motion is composed of so-called vibrational modes. If the bridge just shook in the first mode, it would sway side to side, with the center of the structure moving the most. The second vibrational mode is at a higher frequency, in which half of the bridge moves sideways in one direction as the other half goes in the opposite direction, forming an oscillating S-shaped wave that spans the length of the bridge. There is a third mode, a fourth mode, and so on. Whenever the bridge oscillates, its motion can be described as a mixture of these vibrational modes.

The team found that by looking at how the first two modes change frequencies when a particle lands, they could determine the particle's mass and position, explains Mehmet Selim Hanay, a postdoctoral researcher in Roukes's lab and first author of the paper. "With each measurement we can determine the mass of the particle, which wasn't possible in mechanical structures before."

Traditionally, molecules are weighed using a method called mass spectroscopy, in which tens of millions of molecules are ionized—so that they attain an electrical charge—and then interact with an electromagnetic field. By analyzing this interaction, scientists can deduce the mass of the molecules.

The problem with this method is that it does not work well for more massive particles—like proteins or viruses—which have a harder time gaining an electrical charge. As a result, their interactions with electromagnetic fields are too weak for the instrument to make sufficiently accurate measurements.

The new device, on the other hand, does work well for large particles. In fact, the researchers say, it can be integrated with existing commercial instruments to expand their capabilities, allowing them to measure a wider range of masses.

The researchers demonstrated how their new tool works by weighing a molecule called immunoglobulin M (IgM), an antibody produced by immune cells in the blood. By weighing each molecule—which can take on different structures with different masses in the body—the researchers were able to count and identify the various types of IgM. Not only was this the first time a biological molecule was weighed using a nanomechanical device, but the demonstration also served as a direct step toward biomedical applications. Future instruments could be used to monitor a patient's immune system or even diagnose immunological diseases. For example, a certain ratio of IgM molecules is a signature of a type of cancer called Waldenström macroglobulinemia. 

In the more distant future, the new instrument could give biologists a view into the molecular machinery of a cell. Proteins drive nearly all of a cell's functions, and their specific tasks depend on what sort of molecular structures attach to them—thereby adding more heft to the protein—during a process called posttranslational modification. By weighing each protein in a cell at various times, biologists would now be able to get a detailed snapshot of what each protein is doing at that particular moment in time.

Another advantage of the new device is that it is made using standard, semiconductor fabrication techniques, making it easy to mass-produce. That's crucial, since instruments that are efficient enough for doctors or biologists to use will need arrays of hundreds to tens of thousands of these bridges working in parallel. "With the incorporation of the devices that are made by techniques for large-scale integration, we're well on our way to creating such instruments," Roukes says. This new technology, the researchers say, will enable the development of a new generation of mass-spectrometry instruments.

"This result demonstrates how the Alliance for Nanosystems VLSI, initiated in 2006, creates a favorable environment to carry out innovative experiments with state-of-the-art, mass-produced devices," says Laurent Malier, the director of CEA-LETI. The Alliance for Nanosystems VLSI is the name of the partnership between Caltech's Kavli Nanoscience Institute and CEA-LETI. "These devices," he says,"will enable commercial applications, thanks to cost advantage and process repeatability."

In addition to Roukes and Hanay, the other researchers on the Nature Nanotechnology paper, "Single-protein nanomechanical mass spectrometry in real time," are Caltech graduate students Scott Kelber and Caryn Bullard; former Caltech research physicist Akshay Naik (now at the Centre for Nano Science and Engineering in India); Caltech research engineer Derrick Chi; and Sébastien Hentz, Eric Colinet, and Laurent Duraffourg of CEA-LETI's Micro and Nanotechnologies innovation campus (MINATEC). Support for this work was provided by the Kavli Nanoscience Institute at Caltech, the National Institutes of Health, the National Science Foundation, the Fondation pour la Recherche et l'Enseignement Superieur from the Institut Merieux, the Partnership University Fund of the French Embassy to the U.S.A., an NIH Director's Pioneer Award, the Agence Nationale pour la Recherche through the Carnot funding scheme, a Chaire d'Excellence from Fondation Nanosciences, and European Union CEA Eurotalent Fellowships.  

Marcus Woo
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It's Always Sunny in Caltech Lab

Researchers reproduce plasma loops to help understand solar physics

PASADENA, Calif.—In orbit around Earth is a wide range of satellites that we rely on for everything from television and radio feeds to GPS navigation. Although these spacecraft soar high above storms on Earth, they are still vulnerable to weather—only it's weather from the sun. Large solar flares—or plasma that erupts from the sun's surface—can cause widespread damage, both in space and on Earth, which is why researchers at the California Institute of Technology (Caltech) are working to learn more about the possible precursors to solar flares called plasma loops. Now, they have recreated these loops in the lab.

"We're studying how these solar loops work, which contributes to the knowledge of space weather," says Paul Bellan, professor of applied physics at Caltech, who compares the research to studying hurricanes. For example, you can't predict a hurricane unless you know more about the events that precede it, like high-pressure and low-pressure fronts. The same is true for solar flares. "It takes some time for the plasma to get to Earth from the sun, so it's possible that with more research, we could have up to a two-day warning period for massive solar flares."

The laboratory plasma loop studies were conducted by graduate student Eve Stenson together with Bellan and are reported in the August 13 issue of the journal Physical Review Letters.

They found that two magnetic forces control the behavior of arching loops of plasma, which is hot, ionized gas. "One force expands the arch radius and so lengthens the loop while the other continuously injects plasma from both ends into the loop," Bellan explains. "This latter force injects just the right amount of plasma to keep the density in the loop constant as it lengthens." 

The duo says that in simpler terms, this process is like squeezing toothpaste into a tube from both ends, except that the toothpaste has little magnets in it, so there are magnetic forces acting internally. Stenson and Bellan studied plasma loops that they generated with a pulse-powered, magnetized plasma gun. Inside a vacuum chamber, electromagnets create an arched magnetic field. Then, hydrogen and nitrogen gas is released at the two footpoints of the arch. Finally, a high-voltage electrical current is applied at the footpoints to ionize the gas and turn it into plasma, which travels at a minimum speed of about six miles per second.

"All three steps—the magnetic field, and the gas, and the high voltage—happen in just a flash of light inside the chamber," says Stenson. "We use high-speed cameras with optical filters to capture the behavior of the plasmas."

By color-coding the inflowing plasma, the optical filters vividly demonstrated the flow from the two ends of the loop. According to Bellan, no one has ever used this technique before. On camera, red plasma flows into the loop from one footpoint while blue plasma simultaneously flows into the loop from the other end.

"For each experiment, you'll only see the light from the hydrogen side or the nitrogen side in the images," explains Stenson. "But these experiments are very reproducible, so we can put separate images on top of each other to see both plasmas in one picture."

Next, Bellan's lab will test how two loops interact with each other. "We want to see if they can merge and form one big loop," says Bellan. "Some people believe that this is how larger plasma loops on the sun are formed."

Funding for the research outlined in the Physical Review Letters paper, "Magnetically Driven Flows in Arched Plasma Structures," came from the National Science Foundation, the U.S. Department of Energy, and the Air Force Office of Scientific Research. 

Katie Neith
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Caltech Professor Barry Simon Wins Henri Poincare Prize

Barry Simon, IBM Professor of Mathematics and Theoretical Physics at Caltech, is a 2012 recipient of the Henri Poincaré Prize, awarded by the International Association of Mathematical Physics and funded by the Daniel Iagolnitzer Foundation.

Originating in 1997, the prize is awarded every three years in recognition of outstanding contributions in mathematical physics and accomplishments leading to novel developments in the field.

According to his citation, Simon was recognized for "his impact on many areas of mathematical physics including, in particular, the spectral theory of Schroedinger operators, for his mentoring of generations of young scientists, and for his lucid and inspirational books.
The prize was awarded on August 6 at the International Congress of Mathematical Physics in Allborg, Denmark. Other 2012 Henri Poincaré Prize winners are Nalini Anantharaman of Université de Paris-Sud; Freeman Dyson of the Institute of Advanced Study, Princeton University; and Sylvia Serfaty, Université Pierre et Marie Curie, Paris, and the Courant Institute, New York University.
Brian Bell
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Caltech Physicist Wins $3 Million Fundamental Physics Prize

New award is largest academic prize in the world

PASADENA, Calif.—Alexei Kitaev, professor of theoretical physics, computer science, and mathematics at the California Institute of Technology (Caltech), has been named an inaugural winner of the Fundamental Physics Prize—a $3 million award that represents the largest academic prize given to an individual in the history of science.

The prize, funded by Yuri Milner, a Russian entrepreneur and venture capitalist, was given with "the aim of providing the recipients with more freedom and opportunity to pursue even greater future accomplishments," according to the Fundamental Physics Prize Foundation website. In addition to Kitaev, eight other physicists received the award, for a grand total of $27 million in prize money. The individual awards are more than twice what Nobel laureates receive, and that amount—about $1.2 million—is often split among a few winners.

"It was a great surprise and honor to learn that I was a recipient of the prize along with some very famous and renowned physicists," says Kitaev. "At first, I was confused because I didn't think that the money could be just for me—I assumed such a big prize would be shared among all the recipients. I feel very happy and extremely lucky."

Kitaev, a member of the new Institute for Quantum Information and Matter (IQIM) at Caltech, is known for developing algorithms and theories to enable quantum computing, which has the potential to perform in seconds certain tasks that would take an ordinary computer thousands of years to complete. The award citation recognized his "theoretical idea of implementing robust quantum memories and fault-tolerant quantum computation using topological quantum phases with anyons and unpaired Majorana modes."

"I'm delighted that Alexei is getting the recognition he so richly deserves for making the fundamental and profound contributions to one of the most exciting areas of fundamental physics," says Tom Soifer, professor of physics and chair of the Division of Physics, Mathematics and Astronomy at Caltech. "His work is blazing the path toward what we hope will be the next major technical revolution in computing, the realization of quantum computers."

With a joint appointment at Caltech in the Division of Physics, Mathematics and Astronomy and the Division of Engineering and Applied Science, Kitaev explores the mysterious behavior of quantum systems and their implications for developing practical applications, such as quantum computers.

"Every physicist is excited to get new opportunities to test theories, and quantum computing would eliminate a lot of stumbling blocks that we face in making connections between theory and experiments," says Kitaev, who was named a MacArthur Fellow in 2008. He is unsure how he will use the prize money. Beyond his family needs and personal spending, he would like to help support educational efforts.

Kitaev received an MS from the Moscow Institute of Physics and Technology in 1986 and his PhD from Russia's Landau Institute for Theoretical Physics in 1989, where he continued to work until 1998. He was a researcher at Microsoft Research from 1999 until 2001 and spent a year at Microsoft Station Q in 2005–2006. He first came to Caltech as a visiting associate and lecturer in 1998, and he was named professor of theoretical physics and computer science in 2002.

Milner chose the inaugural recipients of the prize, but these recipients will work together to choose next year's winner, or winners. The recipients are also invited to give annual public lectures as part of an effort to raise the profile of fundamental physics and communicate advances to a wider audience.

The other winners are Nima Arkani-Hamed, Juan Maldacena, Nathan Seiberg, and Edward Witten from the Institute for Advanced Study at Princeton University; Alan Guth from MIT; Maxim Kontsevich from the Institute of Advanced Scientific Studies in France; Andrei Linde from Stanford; and Ashoke Sen from the Harish-Chandra Research Institute in India.

Caltech's IQIM is a Physics Frontier Center supported by the National Science Foundation and the Gordon and Betty Moore Foundation.

Katie Neith
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Physicist Wins $3 Million Physics Prize
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White House Honors Caltech and JPL Scientists and Engineers

White House Honors Caltech and JPL Scientists and Engineers with the Presidential Early Career Award

PASADENA, Calif.—Chiara Daraio, professor of aeronautics and applied physics, and Christopher Hirata, professor of astrophysics, both at the California Institute of Technology (Caltech), and Ian Clark of NASA's Jet Propulsion Laboratory (JPL)—which is managed by Caltech—are winners of the Presidential Early Career Award for Scientists and Engineers. This is the highest award given by the United States government to science and engineering professionals in the early stages of their independent research careers.

Daraio was recognized by the Department of Defense for her "pioneering contributions to nonlinear mechanical phenomena in acoustic crystals, granular material, and multifunctional nanostructures, and for mentoring women and providing research opportunities for high school and undergraduate students."

Daraio arrived at Caltech in 2006. She leads a research group that focuses on the design, realization, and testing of materials with novel mechanical properties. Materials developed by Daraio's research group can be used in impact-mitigation systems, in protecting mechanical systems from undesired vibrations, and in new biomedical devices for imaging and diagnostics.

"I am very excited about this award. I wanted to be an inventor and engineer early on. I came to the U.S. as a graduate student and am grateful that here I could pursue my dreams," says Daraio. "Caltech has provided me with an excellent environment to realize my ideas, working with the world's best students, postdocs, and colleagues on the faculty."

"The entire Caltech community is proud to see Professor Daraio recognized with this presidential honor, not only for her pioneering research accomplishments, but also for her commitment to students and diversity," says Ares J. Rosakis, chair of Caltech's Division of Engineering and Applied Science, Theodore von Kármán Professor of Aeronautics, and professor of mechanical engineering. "Even though she is near the beginning of her career she already embodies the key attributes of the Division of Engineering and Applied Science at Caltech."

Daraio added, "This has been a very special year for me: I had a baby just two months ago, and a few weeks earlier became a U.S. citizen. The Presidential Early Career Award is the icing on the cake."

Daraio was born in Italy and received a degree in mechanical engineering from the Marche Polytechnic University in Ancona. She received both an MS and PhD in materials science and engineering from the University of California, San Diego.

Hirata was recognized by the Department of Energy for "innovative work reducing astrophysical uncertainties that limit the extraction of fundamental physics parameters from cosmological observations, for studies of the sensitivity of structure formation to the relative velocity between dark matter and baryons in the early universe, and for service on NASA/DOE Joint Dark Energy Mission working groups."

Hirata received his BS from Caltech in 2001, a time in which significant discoveries were being made in cosmology and high-energy physics. These discoveries guided him toward further studies into topics such as what happened in the first fraction of a second in the life of the universe, how galaxies are formed, and the fundamental nature and geometry of the universe. He earned his PhD at Princeton University and returned to Caltech as a faculty member in 2007.

"In the past decade, cosmology has been revolutionized by ever-improving observational capabilities. My colleagues and I have been developing the theoretical tools that enable us to connect the direct observables—the cosmic microwave background and the distribution of galaxies—to the underlying physical processes that occurred during the first fraction of a second after the big bang," says Hirata.

"I'm extremely pleased to see the national recognition of Chris Hirata's promise and achievement," says B. Thomas Soifer, chair of Caltech's Division of Physics, Mathematics and Astronomy, director of the Spitzer Science Center, and professor of physics. "His work is vital to our understanding of the formation and evolution of structures, such as galaxies, in the universe, and the award recognizes his leadership in this area."

"When I received word about winning this award, I was in the middle of debugging software code, so the work continues," Hirata says. "But it's nice to take a step back and see how far we have come. "

Clark was recognized by NASA for "exceptional leadership and achievement in the pursuit of advanced entry, descent and landing technologies and techniques for space-exploration missions."

"It's certainly quite an honor," says Clark. "However, there are remarkable achievements every day here at JPL/Caltech that are equally deserving of recognition. I wish we could honor the JPL and NASA teams for the amazing work on the Mars Science Laboratory as we prepare for it to land on Mars." 

"Discoveries in science and technology not only strengthen our economy, they inspire us as a people." President Obama said. "The impressive accomplishments of today's awardees so early in their careers promise even greater advances in the years ahead. "

The Presidential Early Career Award for Scientists and Engineers was established by President Clinton in 1996 and is coordinated by the President's Office of Science and Technology Policy. Awardees are selected for their pursuit of innovative research at the frontiers of science and technology, and their commitment to community service as demonstrated through scientific leadership, public education, or community outreach. Fourteen Caltech professors and researchers have won the award since its inception.

Caltech is recognized for its highly select student body of approximately 1,000 undergraduates and 1,300 graduate students, and for its outstanding faculty. Since 1923, Caltech faculty and alumni have garnered 32 Nobel Prizes and seven Crafoord Prizes. In addition to its prestigious on-campus research programs, Caltech operates the Jet Propulsion Laboratory (JPL); the W. M. Keck Observatory on Mauna Kea, in Hawaii; the Palomar Observatory; and the Laser Interferometer Gravitational-Wave Observatory (LIGO). Caltech is a private university in Pasadena, California. For more information, visit

Brian Bell
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Caltech Physicists are Awarded New Funding from the Simons Foundation

For nearly 20 years, the Simons Foundation has worked to advance mathematics and the physical sciences through grants and educational programs. Now the organization is taking its support of research one step further by naming 21 scientists as the first-ever Simons Investigators. Caltech physicists Chris Hirata and Hirosi Ooguri are among this inaugural group of recipients, each of whom are eligible to receive more than $1.3 million over the next ten years to fund innovative research.

According to the foundation, the goal of the new program is "to provide a stable base of support for outstanding scientists in their most productive years, enabling them to undertake long-term study of fundamental questions." Nine theoretical physicists, seven mathematicians, and five computer scientists were appointed as Simons Investigators. Each recipient will be granted funds to be applied to their individual research, their department, and their institution for an initial period of five years, beginning in August. The foundation anticipates renewing the grants for an additional five years in 2017.

Hirosi Ooguri, the Fred Kavli Professor of Theoretical Physics and Mathematics at Caltech and deputy chair of the Division of Physics, Mathematics and Astronomy, was recognized in his award citation as a "mathematical physicist and string theorist of exceptional creativity and breadth." He was chosen as an investigator for his "innovations in the use of topological string theory to compute Feynman diagrams in superstring models," as well as for his cutting-edge work on the relationship of supersymmetric gauge theories to string theory and to gravity.

"Theoretical physicists are like travelers without maps—to bring back wonderful things from far places, we need to take a long view and take risks," says Ooguri, who has been at Caltech since 2000. "The stable and unrestricted support from the Simons Investigator program will enable us to make such long journeys. I am excited about the opportunity and will try my best to live up to the expectation."

Chris Hirata, professor of astrophysics, was cited as "an outstanding young cosmologist and astrophysicist whose research ranges from purely theoretical investigations to original data analysis." He will receive funding for his work with experimental and observational groups on systematizing the extraction of cosmological data from the cross correlation of different extragalactic surveys—work that "is having an important impact on precision cosmology," according to the foundation.

"We are very proud that the Simons Foundation has recognized two of our outstanding faculty in theoretical physics through these awards," says Thomas Soifer, professor of physics, and chair of the Division of Physics, Mathematics and Astronomy at Caltech. "The Simons Foundation is visionary in recognizing the importance of significant, stable funding for these brilliant researchers, which will give them the resources so that they are limited in what they achieve only by their own imaginations."

The Simons Foundation is a private foundation based in New York City and was founded by mathematician James Simons and his wife, Marilyn. The organization also promotes research in the life sciences and launched the Simons Foundation Autism Research Initiative (SFARI), a program designed to improve the diagnosis and treatment of autism spectrum disorders. SFARI is a funding source for a number of research projects at Caltech.

Katie Neith
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A New Kind of Amplifier

Caltech researchers develop instrument for exploring the cosmos and the quantum world

PASADENA, Calif.—Researchers at the California Institute of Technology (Caltech) and NASA's Jet Propulsion Laboratory (JPL) have developed a new type of amplifier for boosting electrical signals. The device can be used for everything from studying stars, galaxies, and black holes to exploring the quantum world and developing quantum computers.

"This amplifier will redefine what it is possible to measure," says Jonas Zmuidzinas, Caltech's Merle Kingsley Professor of Physics, the chief technologist at JPL, and a member of the research team.

An amplifier is a device that increases the strength of a weak signal. "Amplifiers play a basic role in a wide range of scientific measurements and in electronics in general," says Peter Day, a visiting associate in physics at Caltech and a principal scientist at JPL. "For many tasks, current amplifiers are good enough. But for the most demanding applications, the shortcomings of the available technologies limit us." 

Conventional transistor amplifiers—like the ones that power your car speakers—work for a large span of frequencies. They can also boost signals ranging from the faint to the strong, and this so-called dynamic range enables your speakers to play both the quiet and loud parts of a song. But when an extremely sensitive amplifier is needed—for example, to boost the faint, high-frequency radio waves from distant galaxies—transistor amplifiers tend to introduce too much noise, resulting in a signal that is more powerful but less clear.

One type of highly sensitive amplifier is a parametric amplifier, which boosts a weak input signal by using a strong signal called the pump signal. As both signals travel through the instrument, the pump signal injects energy into the weak signal, therefore amplifying it.

About 50 years ago, Amnon Yariv, Caltech's Martin and Eileen Summerfield Professor of Applied Physics and Electrical Engineering, showed that this type of amplifier produces as little noise as possible: the only noise it must produce is the unavoidable noise caused by the jiggling of atoms and waves according to the laws of quantum mechanics. The problem with many parametric amplifiers and sensitive devices like it, however, is that they can only amplify a narrow frequency range and often have a poor dynamic range.

But the Caltech and JPL researchers say their new amplifier, which is a type of parametric amplifier, combines only the best features of other amplifiers. It operates over a frequency range more than ten times wider than other comparably sensitive amplifiers, can amplify strong signals without distortion, and introduces nearly the lowest amount of unavoidable noise. In principle, the researchers say, design improvements should be able to reduce that noise to the absolute minimum. Versions of the amplifier can be designed to work at frequencies ranging from a few gigahertz to a terahertz (1,000 GHz). For comparison, a gigahertz is about 10 times greater than commercial FM radio signals in the U.S., which range from about 88 to 108 megahertz (1 GHz is 1,000 MHz).

"Our new amplifier has it all," Zmuidzinas says. "You get to have your cake and eat it too."

The team recently described the new instrument in the journal Nature Physics.

One of the key features of the new parametric amplifier is that it incorporates superconductors—materials that allow an electric current to flow with zero resistance when lowered to certain temperatures. For their amplifier, the researchers are using titanium nitride (TiN) and niobium titanium nitride (NbTiN), which have just the right properties to allow the pump signal to amplify the weak signal.

Although the amplifier has a host of potential applications, the reason the researchers built the device was to help them study the universe. The team built the instrument to boost microwave signals, but the new design can be used to build amplifiers that help astronomers observe in a wide range of wavelengths, from radio waves to X rays.

For instance, the team says, the instrument can directly amplify radio signals from faint sources like distant galaxies, black holes, or other exotic cosmic objects. Boosting signals in millimeter to submillimeter wavelengths (between radio and infrared) will allow astronomers to study the cosmic microwave background—the afterglow of the big bang—and to peer behind the dusty clouds of galaxies to study the births of stars, or probe primeval galaxies. The team has already begun working to produce such devices for Caltech's Owens Valley Radio Observatory (OVRO) near Bishop, California, about 250 miles north of Los Angeles. 

These amplifiers, Zmuidzinas says, could be incorporated into telescope arrays like the Combined Array for Research in Millimeter-wave Astronomy at OVRO, of which Caltech is a consortium member, and the Atacama Large Millimeter/submillimeter Array in Chile.

Instead of directly amplifying an astronomical signal, the instrument can be used to boost the electronic signal from a light detector in an optical, ultraviolet, or even X-ray telescope, making it easier for astronomers to tease out faint objects.

Because the instrument is so sensitive and introduces minimal noise, it can also be used to explore the quantum world. For example, Keith Schwab, a professor of applied physics at Caltech, is planning to use the amplifier to measure the behavior of tiny mechanical devices that operate at the boundary between classical physics and the strange world of quantum mechanics. The amplifier could also be used in the development quantum computers—which are still beyond our technological reach but should be able to solve some of science's hardest problems much more quickly than any regular computer.

"It's hard to predict what all of the applications are going to end up being, but a nearly perfect amplifier is a pretty handy thing to have in your bag of tricks," Zmuidzinas says. And by creating their new device, the researchers have shown that it is indeed possible to build an essentially perfect amplifier. "Our instrument still has a few rough edges that need polishing before we would call it perfect, but we think our results so far show that we can get there."

The title of the Nature Physics paper is "A wideband, low-noise superconducting amplifier with high dynamic range." In addition to Zmuidzinas and Day, the other authors of the paper are Byeong Ho Eom, an associate research engineer at Caltech, and Henry LeDuc, a senior research scientist at JPL. This research was supported by NASA, the Keck Institute for Space Studies, and the JPL Research and Technology Development program.

Marcus Woo
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Peering Into the Heart of a Supernova

Caltech simulation points out how to detect a rapidly spinning stellar core

PASADENA, Calif.—Each century, about two massive stars in our own galaxy explode, producing magnificent supernovae. These stellar explosions send fundamental, uncharged particles called neutrinos streaming our way and generate ripples called gravitational waves in the fabric of space-time. Scientists are waiting for the neutrinos and gravitational waves from about 1,000 supernovae that have already exploded at distant locations in the Milky Way to reach us. Here on Earth, large, sensitive neutrino and gravitational-wave detectors have the ability to detect these respective signals, which will provide information about what happens in the core of collapsing massive stars just before they explode.

If we are to understand that data, however, scientists will need to know in advance how to interpret the information the detectors collect. To that end, researchers at the California Institute of Technology (Caltech) have found via computer simulation what they believe will be an unmistakable signature of a feature of such an event: if the interior of the dying star is spinning rapidly just before it explodes, the emitted neutrino and gravitational-wave signals will oscillate together at the same frequency.

"We saw this correlation in the results from our simulations and were completely surprised," says Christian Ott, an assistant professor of theoretical astrophysics at Caltech and the lead author on a paper describing the correlation, which appears in the current issue of the journal Physical Review D. "In the gravitational-wave signal alone, you get this oscillation even at slow rotation. But if the star is very rapidly spinning, you see the oscillation in the neutrinos and in the gravitational waves, which very clearly proves that the star was spinning quickly—that's your smoking-gun evidence."

Scientists do not yet know all the details that lead a massive star—one that is at least 10 times as massive as the Sun—to become a supernova. What they do know (which was first hypothesized by Caltech astronomer Fritz Zwicky and his colleague Walter Baade in 1934) is that when such a star runs out of fuel, it can no longer support itself against gravity's pull, and the star begins to collapse in upon itself, forming what is called a proto-neutron star. They also now know that another force, called the strong nuclear force, takes over and leads to the formation of a shock wave that begins to tear the stellar core apart. But this shock wave is not energetic enough to completely explode the star; it stalls part way through its destructive work.

There needs to be some mechanism—what scientists refer to as the "supernova mechanism"—that completes the explosion. But what could revive the shock? Current theory suggests several possibilities. Neutrinos could do the trick if they were absorbed just below the shock, re-energizing it. The proto-neutron star could also rotate rapidly enough, like a dynamo, to produce a magnetic field that could force the star's material into an energetic outflow, called a jet, through its poles, thereby reviving the shock and leading to explosion. It could also be a combination of these or other effects. The new correlation Ott's team has identified provides a way of determining whether the core's spin rate played a role in creating any detected supernova.

It would be difficult to glean such information from observations using a telescope, for example, because those provide only information from the surface of the star, not its interior. Neutrinos and gravitational waves, on the other hand, are emitted from inside the stellar core and barely interact with other particles as they zip through space at the speed of light. That means they carry unaltered information about the core with them. 

The ability neutrinos have to pass through matter, interacting only ever so weakly, also makes them notoriously difficult to detect. Nonetheless, neutrinos have been detected: twenty neutrinos from Supernova 1987a in the Large Magellanic Cloud were detected in February 1987. If a supernova went off in the Milky Way, it is estimated that current neutrino detectors would be able to pick up about 10,000 neutrinos. In addition, scientists and engineers now have detectors—such as the Laser Interferometer Gravitational-Wave Observatory, or LIGO, a collaborative project supported by the National Science Foundation and managed by Caltech and MIT—in place to detect and measure gravitational waves for the first time.

Ott's team happened across the correlation between the neutrino signal and the gravitational-wave signal when looking at data from a recent simulation. Previous simulations focusing on the gravitational-wave signal had not included the effect of neutrinos after the formation of a proto-neutron star. This time around, they wanted to look into that effect. 

"To our big surprise, it wasn't that the gravitational-wave signal changed significantly," Ott says. "The big new discovery was that the neutrino signal has these oscillations that are correlated with the gravitational-wave signal." The correlation was seen when the proto-neutron star reached high rotational velocities—spinning about 400 times per second.

Future simulation studies will look in a more fine-grained way at the range of rotation rates over which the correlated oscillations between the neutrino signal and the gravitational-wave signal occur. Hannah Klion, a Caltech undergraduate student who recently completed her freshman year, will conduct that research this summer as a Summer Undergraduate Research Fellowship (SURF) student in Ott's group. When the next nearby supernova occurs, the results could help scientists elucidate what happens in the moments right before a collapsed stellar core explodes.

In addition to Ott, other Caltech authors on the paper, "Correlated Gravitational Wave and Neutrino Signals from General-Relativistic Rapidly Rotating Iron Core Collapse," are Ernazar Abdikamalov, Evan O'Connor, Christian Reisswig, Roland Haas, and Peter Kalmus. Steve Drasco of the California Polytechnic State University in San Luis Obispo, Adam Burrows of Princeton University, and Erik Schnetter of the Perimeter Institute for Theoretical Physics in Ontario, Canada, are also coauthors. Ott is an Alfred P. Sloan Research Fellow.

Most of the computations were completed on the Zwicky Cluster in the Caltech Center for Advanced Computing Research. Ott built the cluster with a grant from the National Science Foundation. It is supported by the Sherman Fairchild Foundation.

Kimm Fesenmaier
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Physicists Discover a New Particle that May Be the Higgs Boson

International consortium of scientists includes a large Caltech contingent

PASADENA, Calif.—Physicists at the Large Hadron Collider (LHC) in Geneva, Switzerland, have discovered a new particle that may be the long-sought Higgs boson, the fundamental particle that is thought to endow elementary particles with mass. 

"This is a momentous time in the history of particle physics and in scientific exploration—the implications are profound," says Harvey Newman, professor of physics at the California Institute of Technology (Caltech). "This is experimental science at its best."

The international team of scientists and engineers—which includes a large contingent from Caltech, led by Newman and Maria Spiropulu, professor of physics—says it needs more data to determine for certain if the particle they've discovered is indeed the Higgs boson predicted by the Standard Model, the theory that describes how all particles interact. The results so far, however, show that it has many of the properties expected for such a particle. 

"One of the most exciting aspects of this observation is that the road remains open for a vast range of 'lookalike' alternatives, where any deviation from the Standard Model would point the way to the existence of other new particles or forces of nature," Newman says.

Regardless of the exact identity of the new particle, CERN's scientists say, the highly anticipated discovery heralds a new era in physics.

The physicists revealed their latest results at a seminar at the European Center for Nuclear Research (CERN) in Geneva, which was shared with the world with a live webcast and the EVO (Enabling Virtual Organizations) system developed at Caltech.

The discovery itself is based on the analysis of an unprecedented amount of data that was collected by the two main detectors at the LHC—the Compact Muon Solenoid (CMS) and A Toroidal LHC Apparatus (ATLAS). The data was collected with the LHC running at 7 teraelectron volts (TeV, a unit of energy) in 2011 and 8 TeV in 2012. The Caltech team is part of the CMS collaboration.

Using the CMS detector, the physicists identified signals that point to a new particle with a mass of 125 gigaelectron volts (GeV, a unit of mass; in comparison, the mass of a proton is about 1 GeV). The team running the ATLAS detector, which searches for the Higgs using a different method, reported similar results.

"This is an incredible, exciting moment," says Spiropulu. "Even these early results give us important hints as to how mass in the universe came to be. Together with hundreds of our colleagues Caltech scientists have worked for decades to reach this point: building multiple generations of experiments; designing and building detectors to precisely measure photons, electrons, and muons, which are keys to the discovery; and inventing worldwide systems that empower thousands of physicists throughout the world to collaborate day and night, share and analyze the data, and develop the new techniques leading to this great result."

To search for the Higgs, physicists have had to comb through the remains of trillions of particle collisions produced by the LHC, which accelerates protons around a ring almost five miles wide to nearly the speed of light. As the protons careen toward each other, a small fraction of them collide, creating other particles such as the Higgs. It is estimated that it takes one billion collisions to make just one Higgs boson.

The Higgs is fleeting, however, and quickly decays into lighter particles, which are the traces that allow the Higgs to be detected and analyzed. The Higgs is predicted to decay in several different ways, or channels, each resulting in different particles. CMS focuses mainly on the decay channels that result in two photons or two other particles called Z bosons. It was by measuring and analyzing these and other decay particles that the physicists were able to discover the potential Higgs.

When all the decays are taken into account in combination, the scientists announced, the data for a signal corresponding to a Standard Model Higgs boson have a statistical significance of five sigmas. This means the signal is highly unlikely to be the result of a statistical fluke caused by some rare, background fluctuation. Only when data are significant to five sigmas are physicists confident enough to declare a discovery.

Last December, evidence seen in the data from CMS generated plenty of excitement as a result of an excess of events—a slight surplus in particle collision events over what would have been expected if the Higgs does not exist—with a statistical significance of just three sigmas.

The Higgs boson is the last remaining fundamental particle predicted by the Standard Model yet to be detected, and hopes of detecting it was one of the chief reasons for building the LHC. The LHC accelerator, along with the CMS and ATLAS experiments, are arguably the largest and most complex scientific instruments ever built.

Despite its many successes, the Standard Model is incomplete—it does not incorporate gravity or dark matter, for example. One of the goals of physicists, then, is to develop more complete theories that better explain the composition of the universe and what happened during the first moments after the Big Bang. Discovering the Higgs boson—or a particle like it—is essential for developing these new theories.

The measurements of the new particle, the physicists say, are so far consistent—within statistical uncertainty—with the Higgs boson as predicted by the Standard Model. Still, they need more data to know for sure whether it is the predicted Higgs or something stranger, a Higgs lookalike—a prospect that many theorists have long been anticipating.  

By the end of 2012, the Caltech researchers say, the CMS collaboration expects to more than double its current total amount of data. With more data and analysis, the scientists might then be able to confirm whether the particle they announced is indeed the Higgs—and whether it is the Standard Model Higgs or a more exotic version.

Marcus Woo
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