Monday, April 1, 2013
Center for Student Services, 3rd Floor, Brennan Conference Room

Head TA Network Kick-off Meeting & Happy Hour

Francis Clauser

1913 – 2013

Francis H. Clauser (BS '34, MS '35, PhD '37), the Clark Blanchard Millikan Professor of Engineering, Emeritus, passed away on March 3, 2013, at age 99. Born in the decade following the Wright Brothers' first powered flight, he was a founder of modern aeronautics and helped usher in the Space Age.

Francis was the younger of identical twins born to Celeste and Claude Clauser in Kansas City, Missouri, on May 25, 1913. When Francis and his brother, Milton, were 17, their father died, leaving the boys to support their mother and younger sister, Betty. Fortunately, Celeste "was talented and resourceful," says Clauser's daughter, Caroline Ryan. "She made puppets with papier-mâché heads and elaborate costumes, and she and the boys supported the family by staging marionette shows to the accompaniment of a hand-cranked Victrola." The twins enrolled in Kansas City Junior College, but upon learning of Caltech's constellation of luminaries, they decided to apply as transfer students. When they were accepted, the entire family packed up and moved to Pasadena.

As Caltech undergrads, the twins joined a local magician's society, the Mystic Thirteen. Their act consisted of one brother doing a trick before disappearing behind a screen. The other brother would then emerge in a totally different outfit and perform another trick. They did this faster and faster until the costume changes got impossibly short, at which point the screen would "accidentally" fall to reveal one brother in bright red undershorts.

Upon earning bachelor's degrees in physics, the Clausers entered the aeronautics program run by Theodore von Kármán. Unable to tell the twins apart but well aware of their hijinks, von Kármán made it clear that he expected two separate and distinct dissertations, saying, "Each of you can do one, one of you can do both, or both of you can do both." Thus Milton and Francis produced an experiment-based thesis on "The Effect of Curvature on the Transition from Laminar to the Turbulent Boundary Layer," while Francis and Milton wrote a mathematical treatise on "New Methods of Solving the Equations for the Flow of a Compressible Fluid."

On July 30, 1937, a month after receiving their doctorates, Francis married Catharine McMillan, Caltech's humanities librarian and sister of future chemistry Nobel laureate Edwin McMillan (BS '28, MS '29), in a double ceremony with Milton and his bride, Virginia Randall.

The brothers joined the Douglas Aircraft Company in Santa Monica, where Francis soon became the director of aerodynamic design research. There he assembled a team that included several future Caltech faculty members and profoundly influenced aviation design by developing mathematical methods for shaping tails, wings, engine nacelles, and air scoops.  

When Germany fell to the Allies in 1945, Clauser "was temporarily inducted into the U.S. military as an instant full colonel" as part of Operation Paperclip, says his son, John Clauser. Such high ranks were routinely given to civilian experts sent into the war zone in order to expedite the American effort to collect as many of Germany's best scientists and as much of its key hardware as possible before the Russians did.

Soon after Clauser's return, Henry "Hap" Arnold, the commander of the Army Air Forces, commissioned Clauser's design team to study the feasibility of spaceflight. The 340-page "Preliminary Design of an Experimental World-Circling Spaceship," dated May 2, 1946, concluded that a rocket based on the German V-2 could put a 500-pound payload into orbit for at least 10 days and outlined the military, scientific, and telecommunications uses to which such a satellite might be put. Unfortunately the estimated cost—$150 million over five years—was deemed too high, and the US ceded first rights to the final frontier to Sputnik, launched by the USSR a decade later. The report also noted that "there is good reason to hope that future satellite vehicles will be built to carry human beings," recommending a winged, reusable spacecraft as the best way to return them safely to Earth. This report was the first to be produced by what Arnold dubbed the RAND (for Research and Development) Project; several of the people who wrote it went on to become founding members of the RAND Corporation when it was spun off from Douglas Aircraft in 1948.

Clauser, however, left the company in 1946 to found the aeronautics department at Johns Hopkins University. He chaired the department until 1960, recruiting leaders in the field from many countries to create a world-class research center. The department's facilities included three large wind tunnels, one of which was supersonic and "all of which Clauser personally designed," John says, "so that they exhibited very low residual turbulence in their test sections."

Turbulence and the so-called boundary layer, the thin layer of fluid immediately adjacent to a solid surface, had been particular interests of Clauser's since graduate school. In fact, his first assignment at Douglas had been to figure out why the DC-3, which had just debuted as a transcontinental passenger plane and would remain in military production through World War II, tended to roll onto its back upon stalling. An aerodynamic "stall" occurs when the tilt of a wing's leading edge—the so-called angle of attack—increases to the point where lift is no longer generated. Clauser realized that as one wing fell, the angle of attack at its tip would increase, making it stall more. To break this runaway feedback, he invented the now-standard "washout" wing twist, in which the wing tips are more or less horizontal and the angle of attack increases closer to the fuselage. Any stall thus begins near the fuselage, where the wing's lever action is minimal, while the ailerons out near the wing tips do not stall and the pilot remains in control of the aircraft.

Clauser wrote two seminal papers on the turbulent boundary layer in 1954 and 1956. As emeritus professor of aeronautics Donald Coles (MS '48, PhD '53) explains, "Normally, as you follow the boundary layer across the wing, the velocity profile will be controlled by the pressure variation. Clauser invented what he called 'equilibrium flows' in which he controlled the pressure gradient so that the velocity field didn't change as you went along the flow. The pressure was still rising, but he had a trick for adjusting the rate at which it rose, so that the velocity obeyed a 'similarity law.' It didn't matter where you measured the velocity profile, because it always followed the same curve. And anybody could duplicate his family of flows in their own wind tunnels just by properly shaping the channel."

This gradient generates the wing's lift and begins as a zone of low pressure near the wing's leading edge, extending outward and backward until ambient atmospheric pressure is restored. If not handled properly, it can force the airflow to leave the wing prematurely—as it did in the stall that had plagued the DC-3. The gradient's behavior depends on the interplay between the wing's shape and the boundary layer itself, which in turn is governed by a set of deceptively simple differential equations whose exact solutions often still tax modern supercomputers. Clauser's work was so important because in the days when designs were primarily worked out with slide rules and pad after pad of graph paper, the fewer variables one had to manipulate experimentally, the better.

"Clauser was one of the four founders of the science of boundary layers as it stands today," Coles says. "In a 10-year period, these people put together a consistent, coherent description that is still the place where you start teaching the subject."

Clauser was a member of the 1968 Task Force on Space, chaired by Nobel laureate Charles Townes (PhD '39). Clauser again championed the notion of a winged, reusable space vehicle. This time, the idea got traction and the Space Shuttle was born.

During the Hopkins years, Clauser acquired a reputation for educational innovation, establishing cross-disciplinary courses designed to illuminate basic principles that could later be applied to whatever field a student might choose. He was invited to the newly created University of California campus in Santa Cruz in 1965 to set up the engineering school, and he served variously as the academic vice chancellor, vice chancellor for science and engineering, and professor of applied science.

In 1969, Clauser returned to Caltech to chair the Division of Engineering and Applied Science. He stepped down in 1974 but remained the Clark Millikan Professor of Engineering until his retirement in 1980.

Clauser, having arrived at the dawn of the environmental movement, launched Caltech's interdisciplinary graduate program in environmental engineering science in 1971. The following year he established the Environmental Quality Laboratory, or EQL, as an "action-oriented unit," in his words, along the lines of JPL—"associated with Caltech, carrying on Caltech's high standards but not engaged in teaching." Organized in partnership with JPL, the RAND Corporation, and the Aerospace Corporation, the EQL studied the scientific, engineering, economic, and political aspects of issues such as pollution control, water and energy policy, and sewage disposal. 

The interdisciplinary applied physics option was initiated during Clauser's term as well, providing an academic home for the solid-state physicists and electronics engineers who were powering the computer revolution. Clauser also oversaw the construction of the Earle M. Jorgensen Laboratory of Information Science. This building housed not only computer scientists but the Campus Computing Center, which ran the mainframe computers that were becoming important research tools in many disciplines.

In 1973, Clauser established the Sherman Fairchild Distinguished Scholars Program, which he intended to be "as desirable and prestigious as a Guggenheim Fellowship" and which brought up to 30 eminent scientists per year to Caltech. The inaugural group included Apollo 17 astronaut Harrison Schmitt (BS '57), the only geologist to walk on the moon, and a then-obscure cosmologist named Stephen Hawking.

Upon his brother Milton's death in 1980, Clauser, his wife, and his sister-in-law established the annual Milton and Francis Clauser Doctoral Prize, awarded for the thesis judged to have the greatest potential for opening up entirely new lines of research.

A noted raconteur with a prodigious memory, Clauser was a regular at the legendary Round Table at the Caltech faculty club, the Athenaeum. Says Marshall Cohen, professor of astronomy, emeritus, "He was known as 'The Dean of the Round Table' for a couple of reasons: He was the oldest, and he would dominate the discussion. He'd say, 'Let's change the subject—I want to talk about the new style of sailboat.'" Politics, biblical archaeology, and ancient Egypt were other favorite topics, Cohen recalls. "He knew dates. And names. He knew dynasties. A decade ago I mentioned that I was interested in hieroglyphs. He said, 'I can recommend a book for you.' It turns out he and Catharine had taken a course in hieroglyphics back in the 1960s, and he still remembered the name of the textbook."

Clauser's favorite subject was travel. He and Catharine had driven through 117 countries and across every major desert on Earth—usually in a rented Volkswagen Beetle. One such trip went from Alaska to Tierra del Fuego, where he eased into the Straits of Magellan until the Bug's front bumper was submerged. Another trip followed the Silk Road through Central Asia.

The Clausers' most-storied trip took them from Tunis to Timbuktu. As recounted in Caltech's Engineering & Science magazine in 1972, the preferred method for crossing the Sahara was in Land Rovers traveling in pairs. The Clausers drove alone in a Renault R4, a vehicle light enough for them to push when it got stuck in the sand. Things went well for the first 1,600 miles or so, until the clutch gave out in central Niger. They hitched a ride to Tahoua, the nearest town, where, as Francis told E&S, they found "a 52nd-hand car dealer who let us have an ancient clutch for $24. Then we rented a set of tools for $10 from a German mechanic and went out and sat by the road for two hours before we caught a 70-mile ride back to our car." The next day, they dismantled the engine in front of an audience of Fulani herdsmen and Tuaregs on camels, only to discover that the new old clutch didn't fit. An examination of the old old clutch revealed that it had packed itself full of sand as they tobogganed through the dunes. They extracted the sand with a paring knife and a safety pin, and drove back to Tahoua, where they resold the new old clutch back to the 52nd-hand dealer for $20.

Catharine died in 1999, but Francis remained in the family home in La Cañada until he lost his right leg to the flesh-eating bacterium Clostridium septicum in 2008. He moved into Villa Gardens to recuperate—on the condition that he not miss lunch at the Round Table. A shuttle would drop him off daily, says Cohen, "but occasionally he'd drive himself home in his electric wheelchair by way of his dentist."

Clauser's publications included papers on nonlinear mechanics, guided missile technology, magnetohydrodynamics, and partial differential equations as well as a book, Plasma Dynamics, compiled in 1960 following a symposium he chaired on what was then a very young field. He was a Fellow of the American Institute of Aeronautics and Astronautics, the American Physical Society, and the American Association for the Advancement of Science. He was also a member of the National Academy of Engineering, the scientific research society Sigma Xi, the engineering honor society Tau Beta Pi, and Caltech's Gnome Club.  He was named a Distinguished Alumnus in 1966, one of the initial class of 23 to be so honored.

Clauser is survived by his sister, Betty Celeste Valois of Denver; his son, Wolf laureate in physics John Francis Clauser (BS '64) of Walnut Creek, California; and his daughter, Caroline Helen Ryan, of New York City. A memorial service will be held at 11:00 a.m. at the Caltech Athenaeum on May 25, the day that would have been his hundredth birthday.

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Douglas Smith
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Creating Indestructible Self-Healing Circuits

Caltech engineers build electronic chips that repair themselves

PASADENA, Calif.—Imagine that the chips in your smart phone or computer could repair and defend themselves on the fly, recovering in microseconds from problems ranging from less-than-ideal battery power to total transistor failure. It might sound like the stuff of science fiction, but a team of engineers at the California Institute of Technology (Caltech), for the first time ever, has developed just such self-healing integrated chips.

The team, made up of members of the High-Speed Integrated Circuits laboratory in Caltech's Division of Engineering and Applied Science, has demonstrated this self-healing capability in tiny power amplifiers. The amplifiers are so small, in fact, that 76 of the chips—including everything they need to self-heal—could fit on a single penny. In perhaps the most dramatic of their experiments, the team destroyed various parts of their chips by zapping them multiple times with a high-power laser, and then observed as the chips automatically developed a work-around in less than a second.

"It was incredible the first time the system kicked in and healed itself. It felt like we were witnessing the next step in the evolution of integrated circuits," says Ali Hajimiri, the Thomas G. Myers Professor of Electrical Engineering at Caltech. "We had literally just blasted half the amplifier and vaporized many of its components, such as transistors, and it was able to recover to nearly its ideal performance."

The team's results appear in the March issue of IEEE Transactions on Microwave Theory and Techniques.

Until now, even a single fault has often rendered an integrated-circuit chip completely useless. The Caltech engineers wanted to give integrated-circuit chips a healing ability akin to that of our own immune system—something capable of detecting and quickly responding to any number of possible assaults in order to keep the larger system working optimally. The power amplifier they devised employs a multitude of robust, on-chip sensors that monitor temperature, current, voltage, and power. The information from those sensors feeds into a custom-made application-specific integrated-circuit (ASIC) unit on the same chip, a central processor that acts as the "brain" of the system. The brain analyzes the amplifier's overall performance and determines if it needs to adjust any of the system's actuators—the changeable parts of the chip.

Interestingly, the chip's brain does not operate based on algorithms that know how to respond to every possible scenario. Instead, it draws conclusions based on the aggregate response of the sensors. "You tell the chip the results you want and let it figure out how to produce those results," says Steven Bowers, a graduate student in Hajimiri's lab and lead author of the new paper. "The challenge is that there are more than 100,000 transistors on each chip. We don't know all of the different things that might go wrong, and we don't need to. We have designed the system in a general enough way that it finds the optimum state for all of the actuators in any situation without external intervention."

Looking at 20 different chips, the team found that the amplifiers with the self-healing capability consumed about half as much power as those without, and their overall performance was much more predictable and reproducible. "We have shown that self-healing addresses four very different classes of problems," says Kaushik Dasgupta, another graduate student also working on the project. The classes of problems include static variation that is a product of variation across components; long-term aging problems that arise gradually as repeated use changes the internal properties of the system; and short-term variations that are induced by environmental conditions such as changes in load, temperature, and differences in the supply voltage; and, finally, accidental or deliberate catastrophic destruction of parts of the circuits.

The Caltech team chose to demonstrate this self-healing capability first in a power amplifier for millimeter-wave frequencies. Such high-frequency integrated chips are at the cutting edge of research and are useful for next-generation communications, imaging, sensing, and radar applications. By showing that the self-healing capability works well in such an advanced system, the researchers hope to show that the self-healing approach can be extended to virtually any other electronic system.

"Bringing this type of electronic immune system to integrated-circuit chips opens up a world of possibilities," says Hajimiri. "It is truly a shift in the way we view circuits and their ability to operate independently. They can now both diagnose and fix their own problems without any human intervention, moving one step closer to indestructible circuits."

Along with Hajimiri, Bowers, and Dasgupta, former Caltech postdoctoral scholar Kaushik Sengupta (PhD '12), who is now an assistant professor at Princeton University, is also a coauthor on the paper, "Integrated Self-Healing for mm-Wave Power Amplifiers." A preliminary report of this work won the best paper award at the 2012 IEEE Radio Frequency Integrated Circuits Symposium. The work was funded by the Defense Advanced Research Projects Agency and the Air Force Research Laboratory.

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Kimm Fesenmaier
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Under the Hood of the Earthquake Machine

Watson Lecture Preview

 

What makes an earthquake go off? Why are earthquakes so difficult to forecast? Professor of Mechanical Engineering and Geophysics Nadia Lapusta gives us a close-up look at the moving parts, as it were, at 8:00 p.m. on Wednesday, February 13, 2013, in Caltech's Beckman Auditorium. Admission is free.

 

Q: What do you do?

A: I study friction as it relates to earthquakes. At a depth of five miles, which is the average depth at which large earthquakes in Southern California occur, the compression on the two sides of the fault is roughly equivalent to a pressure of 1,500 atmospheres. So you can imagine that friction plays an important role. I make computational models that combine our theories about friction with laboratory studies of how materials behave. We try to reproduce what seismologists, geodesists, and geologists see actual earthquakes doing, in order to infer the physical laws that govern them.

Our planet's surface is made up of a bunch of plates that are always moving, and an earthquake happens when the locked boundaries of the plates rapidly catch up with the slow motion of the plates themselves. You get a sudden shearing—a sideways motion that generates the destructive waves that we perceive as shaking.

A number of factors affect this process. If you rub your palms together, you generate heat. An earthquake is a very intensive rubbing of palms, if you will, and so a lot of heat is produced—enough to weaken the rocks and perhaps even melt them.

However, there are pore fluids permeating the rocks—we often get our drinking water from underground aquifers, for example. As these fluids heat up, they expand, which modifies the shearing process. They produce expanding cushions of steam, essentially, which reduce the friction.

The waves generated by the shearing motion put an additional load on the fault ahead of the shear zone, so they actually affect how the shearing progresses. The shear tip sprouts at about three kilometers per second, or 6,700 miles per hour. So an earthquake is a highly dynamic, nonlinear system.

To make things even more interesting, a fault doesn't just sit still for hundreds of years, waiting for the next big earthquake. It's more like a living thing—there are slow slippages between earthquakes that constantly redistribute the forces in the system, and the exact point where an earthquake initiates depends a lot on these slow motions. So we simulate thousands of years of fault history that includes a few occasional, very fast events that last for a few seconds. These calculations are very time-consuming and memory-intense. The Geological and Planetary Sciences Division's supercomputer has several thousand processors, and we routinely use 200 to 400 of them, sometimes for weeks at a time. We would happily use the entire machine, but of course people would yell at us.

 

Q: How did you get into this line of work?

A: I've loved both mathematics and physics since I was a child. I was born in Ukraine, where my mom was a professor of applied mathematics and my dad was a civil engineer. They used to give me math and physics problems from a very early age. I did my undergraduate studies in applied mathematics in Kiev, and I was thinking of going into materials science. I came to the U.S. for graduate school, and my advisor at Harvard was working on materials failure and on earthquakes, which I found very interesting because it combined math and physics with a problem relevant to society.

My PhD was on frictional sliding and some initial models of earthquakes. Caltech is actually the perfect place to continue that, because it has world-class expertise in all relevant disciplines. I have wonderful colleagues, and the really fun part is working with them. I enjoy interacting with the experimentalists and talking to the people who make field observations or do radar measurements from satellites. They have different perspectives, different terminologies, and different views of the problem, so it's fun to try to explain to them what you mean, and to try to understand what they mean. And the most fun, of course, is when you come to an understanding that leads to new science in the end.

 

Q: Speaking of societal relevance, what does your work mean for us here in L.A.?

A: Large earthquakes, fortunately, are relatively rare, so we don't have detailed observations of very many of them. Our models, however, allow us to explore scenarios for potentially very damaging earthquakes that we haven't experienced. For example, faults have locked segments and creeping segments. The San Andreas fault has a creeping segment between Los Angeles and San Francisco, and the assumption has been that this segment will confine a large earthquake to either the southern or the northern part of the fault. Only one large urban area would be affected. However, our models show that a through-going rupture may be possible. If that happens, both Los Angeles and San Francisco are affected, and you have a much bigger problem on your hands.

 

Named for the late Caltech professor Earnest C. Watson, who founded the series in 1922, the Watson Lectures present Caltech and JPL researchers describing their work to the public. Many past Watson Lectures are available online at Caltech's iTunes U site.

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Douglas Smith
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Murray and Ortiz Elected to the National Academy of Engineering

Election brings Caltech faculty's membership in the academy to 35

PASADENA, Calif.—Richard M. Murray and Michael Ortiz of the California Institute of Technology (Caltech) have been elected to the National Academy of Engineering (NAE), an honor considered among the highest professional distinctions an engineer can receive. In total, the academy welcomed 69 new American members and 11 foreign associates this year.

"I am absolutely delighted that the Academy has elected Richard and Michael," says Ares Rosakis, the Theodore von Kármán Professor of Aeronautics, professor of mechanical engineering, and chair of the Division of Engineering and Applied Science at Caltech. "This is not only a recognition of their great contributions and unwavering commitment to engineering research and education, but also a confirmation of the great impact Caltech engineers and applied scientists are having on the field."

Richard Murray, the Thomas E. and Doris Everhart Professor of Control and Dynamical Systems and Bioengineering, was cited by the National Academy of Engineering for his "contributions in control theory and networked control systems with applications to aerospace engineering, robotics, and autonomy." His current work focuses on the application of feedback and control to networked systems, especially in the biological realm where he is interested in engineered biological circuits.

"It's a great honor to be elected as a member of the NAE," Murray says. "Caltech's strong support for junior faculty, our ability to recruit outstanding students and postdocs, and the highly collaborative nature of the academic environment have allowed my group to help identify important problem areas and make rapid progress in our research. I am particularly appreciative of all of the encouragement, mentoring, and support that I received as a junior faculty member from the Division of Engineering and Applied Science and my colleagues in mechanical engineering and control and dynamical systems."

Murray earned his BS in electrical engineering from Caltech in 1985, and his MS and PhD, both from the University of California, Berkeley in 1988 and 1990. He returned to his alma mater as an assistant professor of mechanical engineering in 1991 and was made an associate professor in 1997, a professor in 2000, the Everhart Professor of Control and Dynamical Systems in 2006, and the Everhart Professor of Control and Dynamical Systems and Bioengineering in 2009. He served as the chair of the Division of Engineering and Applied Science from 2000 until 2005 and as the director of Information Science and Technology from 2006 until 2009. Murray holds many distinctions. Among them, he is a fellow of the Institute for Electrical and Electronic Engineers, holds an honorary doctorate from Lund University, and won the 2006 Richard P. Feynman Prize for Excellence in Teaching.

Michael Ortiz, the Dotty and Dick Hayman Professor of Aeronautics and Mechanical Engineering, was cited for his "contributions to computational mechanics to advance the underpinnings of solid mechanics." He is currently the director of Caltech's Department of Energy/Predictive Science Academic Alliance Program's Center on High-Energy Density Dynamics of Materials. His research focuses on the multiscale modeling of materials in order to design and optimize novel materials.

"This is a wonderful and most pleasant surprise for me, especially given the support from colleagues and peers that it implies," Ortiz says of his election to the academy. "I regard this honor really as a recognition not only of the work done by myself, but also of the work of all my students and collaborators over the years. I am forever indebted to them."

Ortiz earned his BS in civil engineering from the Polytechnic University of Madrid, Spain, in 1977, and his MS and PhD in the same field from the University of California, Berkeley in 1978 and 1981. He served on the faculty at Brown University from 1984 until 1995, when he accepted a professorship at Caltech. Ortiz became the Dotty and Dick Hayman Professor of Aeronautics and Mechanical Engineering in 2004. He is a fellow of the American Academy of Arts and Sciences, the U.S. Association for Computational Mechanics and the International Association for Computational Mechanics, and has won many prizes, including the Humboldt Research Award for Senior U.S. Scientists and the Rodney Hill Prize in Solid Mechanics.

The election of Murray and Ortiz brings Caltech's total representation in the NAE to 35 faculty members and 11 trustees. The full class of new members brings the total NAE membership to 2,250 members and 211 foreign associates. 

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Kimm Fesenmaier
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Creating New Quantum Building Blocks

Caltech researcher says diamond defects could serve as nodes of a quantum network

PASADENA, Calif.—Scientists have long dreamed of creating a quantum computer—a device rooted in the bizarre phenomena that transpire at the level of the very small, where quantum mechanics rules the scene. It is believed that such new computers could process currently unsolvable problems in seconds.  

Researchers have tried using various quantum systems, such as atoms or ions, as the basic, transistor-like units in simple quantum computation devices. Now, laying the groundwork for an on-chip optical quantum network, a team of researchers, including Andrei Faraon from the California Institute of Technology (Caltech), has shown that defects in diamond can be used as quantum building blocks that interact with one another via photons, the basic units of light.

The device is simple enough—it involves a tiny ring resonator and a tunnel-like optical waveguide, which both funnel light. Both structures, each only a few hundred nanometers wide, are etched in a diamond membrane and positioned close together atop a glass substrate. Within the resonator lies a nitrogen-vacancy center (NV center)—a defect in the structure of diamond in which a nitrogen atom replaces a carbon atom, and in which a nearby spot usually reserved for another carbon atom is simply empty. Such NV centers are photoluminescent, meaning they absorb and emit photons.

"These NV centers are like the building blocks of the network, and we need to make them interact—like having an electrical current connecting one transistor to another," explains Faraon, lead author on a paper describing the work in the New Journal of Physics. "In this case, photons do that job."

In recent years, diamond has become a heavily researched material for use in quantum photonic devices in part because the diamond lattice is able to protect impurities from excessive interactions. The so-called quietness it affords enables impurities—such as NV centers—to store information unaltered for relatively long periods of time.  

To begin their experiment, the researchers first cool the device below 10 Kelvin (−441.67 degrees Fahrenheit) and then shine green laser light on the NV center, causing it to reach an excited state and then emit red light. As the red light circles within the resonator, it constructively interferes with itself, increasing its intensity. Slowly, the light then leaks into the nearby waveguide, which channels the photons out through gratings at either end, scattering the light out of the plane of the chip.

The emitted photons have the property of being correlated, or entangled, with the NV center from which they came. This mysterious quality of entanglement, which makes two quantum states inextricably linked in such a way that any information you learn about one provides information about the other, is a necessary ingredient for quantum computation. It enables a large amount of information to be stored and processed by fewer components that take up a small amount of space.

"Right now we only have one nitrogen-vacancy center that's emitting photons, but in the future we envision creating multiple NV centers that emit photons on the same chip," Faraon says. "By measuring these photons we could create entanglement among multiple NV centers on the chip."

And that's important because, in order to make a quantum computer, you would need millions—maybe billions—of these units. "As you can see, we're just working at making one or a few," Faraon says. "But there are other applications down the line that are easier to achieve." For example, a quantum network with a couple hundred units could simulate the behavior of a complex molecule—a task that conventional computers struggle with.

Going forward, Faraon plans to investigate whether other materials can behave similarly to diamond in an optical quantum network.

In addition to Faraon, the authors on the paper, "Quantum photonic devices in single-crystal diamond," are Charles Santori, Zhihong Huang, Kai-Mei Fu, Victor Acosta, David Fattal, and Raymond Beausoleil of Hewlett-Packard Laboratories, in Palo Alto, California. Fu is now an assistant professor at the University of Washington in Seattle, Washington. The work was supported by the Defense Advanced Research Projects Agency and The Regents of the University of California.  

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Jorgensen Laboratory Awarded LEED Platinum Certification

The recent renovations of the Jorgensen Laboratory included many upgrades that were designed to reflect Caltech's commitment to sustainability. Now the building has achieved LEED Platinum certification, the highest honor of the U.S. Green Building Council.

"Achieving Platinum certification on this building was particularly rewarding given the fact that the building will serve as a studio for sustainable energy research," says John Onderdonk, director of sustainability programs at Caltech.

LEED—Leadership in Energy and Environmental Design—is a voluntary program that provides verification of green building design through a survey of prerequisites and guideline credits. To obtain LEED certification, a building must earn a minimum of 40 points on a 110-point LEED rating system scale. Jorgensen received 87 points—80 is the minimum needed for Platinum certification—for its conservation features, which include a "green" roof, natural ventilation systems, use of on-campus solar photovoltaic power, and low-flow water fixtures, among other environmentally conscious details.

Jorgensen is one of 20 LEED Platinum-certified higher-education lab buildings in the country, and one of seven in the state. It is the second higher-education lab building in the state to receive LEED Platinum certification under the current rating system. Caltech's renovation of the Linde + Robinson Lab also received LEED Platinum status last year.

The Jorgensen Lab officially opened in October 2012 and houses scientists who are focused on clean-energy research

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Katie Neith
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Notes from the Back Row: "Engineering with Impact"

If you hit something hard enough, it will break, and the consequences can be catastrophic. A space rock roughly the size of Pasadena killed the dinosaurs when it hit the Earth at about 45,000 miles per hour, but even something as small as a bird hitting a turbine blade can bring down an airplane. The damage occurs in the blink of an eye as unimaginable pressures are fleetingly focused on the hapless chunk of rock or metal. The key to survival is to disperse those forces. But how? Caltech professor Ravi Ravichandran is trying to find out.

Guruswami "Ravi" Ravichandran is the John E. Goode, Jr., Professor of Aerospace and professor of mechanical engineering and the director of the Graduate Aerospace Laboratories at Caltech. His PhD thesis on the fracture dynamics of metals under extreme impacts, written at Brown University in 1986, remains one of the classic papers in the field.

At Caltech, Ravichandran studies impacts that pack a wallop of up to a million times the pressure of Earth's atmosphere. Such extreme pressures are actually quite mundane: a head-on collision at 65 miles per hour exerts a force of some 7,000 atmospheres during the millisecond that the vehicles' steel frames buckle. (By contrast, the pressure at the bottom of the Mariana Trench in the western Pacific, the deepest point in the world's oceans, is a mere 1,000 atmospheres.) In a typical experiment, a reconditioned naval gun from World War II shoots an aluminum projectile at a copper plate, compressing it by as much as 30 percent for a millionth of a second. Meanwhile, a laser "camera" records the ripples created by the projectile's kinetic energy as it turns into pressure waves within the copper plate.

The best way we know to dissipate these waves is to pass them through alternating layers of very stiff and very elastic materials. This is the principle behind body armor and bulletproof glass, as Ravichandran vividly demonstrated during his talk by showing a video clip produced by an armored-car company. In the clip, the company's CEO stood behind a bulletproof windshield while his assistant peppered it with three rounds from an AK-47. Spiderwebs of cracks formed in the inner layer of glass and license-plate-sized fragments of the outer layer were blasted free, but the layer of polymer sandwiched between the glass sheets stopped the slugs. If one layer of elastic is good, more layers should be even better. The logical extreme—an infinite number of layers—presents certain manufacturing challenges, so "we're extending this idea of layered media into particulate composites in order to make realistic engineering materials for shock-protection applications," Ravichandran says. Think high-tech sandbags, in other words.  

"Engineering with Impact" is available for download in HD from Caltech on iTunesU. (Episode 13)

Writer: 
Doug Smith
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TEDxCaltech: Advancing Humanoid Robots

This week we will be highlighting the student speakers who auditioned and were selected to give five-minute talks about their brain-related research at TEDxCaltech: The Brain, a special event that will take place on Friday, January 18, in Beckman Auditorium. 

In the spirit of ideas worth spreading, TED has created a program of local, self-organized events called TEDx. Speakers are asked to give the talk of their lives. Live video coverage of the TEDxCaltech experience will be available during the event at http://tedxcaltech.caltech.edu.

When Matanya Horowitz started his undergraduate work in 2006 at University of Colorado at Boulder, he knew that he wanted to work in robotics—mostly because he was disappointed that technology had not yet made good on his sci-fi–inspired dreams of humanoid robots.

"The best thing we had at the time was the Roomba, which is a great product, but compared to science fiction it seemed really diminutive," says Horowitz. He therefore decided to major in not just electrical engineering, but also economics, applied math, and computer science. "I thought that the answer to better robots would lie somewhere in the middle of these different subjects, and that maybe each one held a different key," he explains.

Now a doctoral student at Caltech—he earned his masters in the same four years as his multiple undergrad degrees—Horowitz is putting his range of academic experience to work in the labs of engineers Joel Burdick and John Doyle to help advance robotics and intelligent systems. As a member of the control and dynamical systems group, he is active in several Defense Advanced Research Projects Agency (DARPA) challenges that seek to develop better control mechanisms for robotic arms, as well as develop humanoid robots that can do human-like tasks in dangerous situations, such as disable bombs or enter nuclear power plants during an emergency. 

But beneficial advances in robotics also bring challenges. Inspired as a kid by the robot tales of Isaac Asimov, Horowitz has long been interested in how society might be affected by robots.

"As I began programming just on my own, I saw how easy it was to create something that at least seemed to act with intelligence," he says. "It was interesting to me that we were so close to humanoid robots and that doing these things was so easy. But we also have all these implications we need to think about."

Horowitz's TEDx talk will explore some of the challenges of building and controlling something that needs to interact in the physical world. He says he's thrilled to have the opportunity to speak at TEDx, not just for the chance to talk to a general audience about his work, but also to hopefully inspire others by his enthusiasm for the field.

"Recently, there has been such a monumental shift from what robots were capable of even just five years ago, and people should be really excited about this," says Horowitz. "We've been hearing about robots for 30, 40 years—they've always been 'right around the corner.' But now we can finally point to one and say, 'Here it is, literally coming around a corner.'"

 

 

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Katie Neith
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Friday, January 25, 2013
Annenberg 121

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