Professor Elected to Greek Academy

PASADENA, Calif.—Tom M. Apostol, professor of mathematics emeritus and the creator and project director of Project MATHEMATICS! at the California Institute of Technology, has been elected a corresponding member of the Academy of Athens.

Apostol, who is an American of Greek descent, is one of 355 members of the Academy, which was first established by Greek philosopher Plato and reconstituted by government decree in 1926. Only 40 chairs are occupied by foreign members.

The purpose of the academy is to cultivate and promote the sciences, letters and fine arts, and human knowledge. It does so by acting as a forum for lectures, issuing publications, setting up labs for academic research, supporting archaeological excavations, hosting competitions, and awarding medals and scholarships. The academy also submits expert opinions and decisions to the Greek government on matters that fall within its sphere of responsibility.

Apostol will be officially welcomed into the academy in Greece on May 8 and will give a lecture to the academy on "A Visual Approach to Calculus Problems in a Style Reminiscent of Archimedes."

Since joining the Caltech faculty in 1950, Apostol has earned an international reputation for his mathematical research and textbooks, some of which have been translated into Greek, Italian, Spanish, Portuguese, and Farsi. He spent four months in Greece as a visiting professor of mathematics at the University of Patras in 1978.

He is the producer of Project MATHEMATICS!, a series of videotapes and books for high school students. The tapes explore basic topics in mathematics in ways that cannot be done at the chalkboard or in a textbook. They use music, special effects and computer animation and are distributed on a nonprofit basis. The goal is to attract young people to mathematics and they have – more than 10 million students have seen the tapes, which have won many honors at film and video festivals. ### The Project MATHEMATICS! Web site is at CONTACT: Jill Perry, Media Relations Director (626) 395-3226,

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Caltech Receives Funding to Establish Network of Cosmic-Ray Detectors in High Schools

PASADENA, Calif.-Los Angeles-area high school students will team up with California Institute of Technology researchers to study ultrahigh-energy cosmic rays on their own campuses, thanks to a recent grant from the Weingart Foundation.

The Los Angeles--based foundation has donated $100,000 to Caltech to establish the California High School Cosmic-Ray Observatory (CHICOS) on four campuses in the Northridge area initially, expanding to 50 and possibly hundreds of sites eventually.

Of the four initial schools, three have a high number of students who are underrepresented in the sciences, which means the program may assist in increasing the number of future scientists in the United States. The schools are Sylmar, Van Nuys, and Harvard Westlake high schools and Sherman Oaks Continuing Education School.

The research will be coordinated by Professor Robert McKeown of the Kellogg Radiation Laboratory in the Division of Physics, Mathematics and Astronomy at Caltech. The program will also incorporate a high school teacher education component coordinated by Dr. Ryoichi Seki at California State University, Northridge. Teachers will develop curriculum materials to help their students participate in this research. Caltech will host a summer workshop where physics teachers and students can participate in the construction of new detector stations for deployment at additional sites.

"This grant will give many high school students a unique opportunity to participate in research science at the university level," said Caltech president David Baltimore. "It will serve as a model for future collaborations in other subjects between world-class research universities and high schools."

The project will involve the development and construction of detector hardware, associated electronics, and computer equipment to form a networked system among the high schools. A large array of this type will enable the study of ultrahigh-energy cosmic rays through the detection of "showers," several kilometers in radius, of secondary particles they create in the Earth's atmosphere. These are the highest-energy particles ever observed in nature and thus of great current interest in the astrophysics and particle-physics community. Thus, while establishing a state-of-the-art experimental facility, this project will provide an exceptional educational experience for local high school students. When a majority of the 50 sites are operating, it is expected that the project will yield significant scientific results that will be reported in the scientific literature.


CONTACT: Jill Perry Caltech Media Relations (626) 395-3226


Caltech Receives $10 Million Grant fromSherman Fairchild Foundation

PASADENA, Calif.— The California Institute of Technology has received a $10 million grant from the Sherman Fairchild Foundation to establish an endowment for the existing Sherman Fairchild Postdoctoral Scholars Program in theoretical physics, theoretical astrophysics, and mathematics.

This endowment provides the best young scholars in these areas with three- to six-year postdoctoral appointments, along with infrastructure support. The goal of the endowment is to furnish postdoctoral scholars with a supportive, unencumbered research environment and allow for collaboration with an international network of premier scientists.

The endowment will facilitate advanced research in areas such as particle, nuclear, and string theory; theoretical astrophysics and relativity; condensed-matter physics; atomic physics and quantum computation; and mathematical physics.

The Sherman Fairchild Foundation has been a significant benefactor to Caltech for many years, establishing the Distinguished Scholars Program and providing seed funding for the Center for Computational Research in Biology, and for the Sherman Fairchild Library of Engineering and Applied Science.

According to Caltech president David Baltimore, "Caltech is fortunate to have a long relationship with the Sherman Fairchild Foundation through which many of our most outstanding scientists have benefited. The foundation's exceptional commitment and foresight have ensured that our postdoctoral scholars have sufficient resources available to them so that they can achieve their maximum potential."

The Sherman Fairchild Foundation was incorporated in 1955 by Sherman M. Fairchild, inventor of the Fairchild aerial camera, chairman of Fairchild Camera Instrument Co. and of Fairchild Hiller Corp., owner of Fairchild Recording Equipment Co., and a director of IBM.

Contact: Deborah Williams-Hedges (626) 395-3227

Visit the Caltech Media Relations Web site at:



Caltech Faculty Member Receives Packard Fellowship

Pasadena—Rahul Pandharipande, associate professor of mathematics at the California Institute of Technology, has been awarded a $625,000 Packard Fellowship for his work in advanced mathematics and the study of the geometry of algebraic curves.

Every year the foundation selects 24 Fellows to receive these awards, which are distributed over five years.

The fellowship program was established in 1988 by the David and Lucile Packard Foundation to improve scientific research by "encouraging exceptional scientists and engineers to remain within academia to conduct basic research and to teach the next generation of science leaders."

Pandharipande's primary work is in the area of algebraic geometry. This important area has been central to advanced mathematical study over the last century, with essential links to both number theory and differential geometry.

In the past decade, the study of algebraic geometry has been revolutionized by the introduction of techniques used in the study of topological gravity: matrix models, integrable systems, and Gromov-Witten theory. Also, mathematical developments inspired by string theory have been rapid. Using newly discovered ideas, Pandharipande and collaborators have solved long-standing mathematical problems related to his area of research. His input has aided developments in theoretical physics; has helped solve geometric problems connected with string theory; and will help shed light on a number of issues in algebraic geometry.

Pandharipande joined the Caltech mathematics staff in 1998. Prior to that, he was an assistant professor at the University of Chicago, which included a one-year leave at Institut Mittag-Leffler in Sweden as a postdoctoral fellow. A recipient of numerous honors, Pandharipande received the A. P. Sloan Foundation Research Fellowship in 1999; a National Science Foundation (NSF) Postdoctoral Fellowship in 1995; and an NSF Graduate Fellowship in 1991.

Pandharipande earned his AB from Princeton in mathematics in 1990 and his PhD from Harvard in mathematics in 1994.

Born in India, Pandharipande grew up in Urbana-Champaign, Illinois, where both of his parents are professors at the University of Illinois.

Contact: Deborah Williams-Hedges (626) 395-3227

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NSF funds new Institute for Quantum Information at Caltech

The National Science Foundation has awarded a five-year, $5 million grant to the California Institute of Technology to create an institute devoted to quantum information science—a new field that could ultimately lead to devices such as quantum computers.

The announcement was part of a $90 million information technology research initiative the NSF announced today in Washington. The awards are aimed at seeding fundamental research in innovative applications of information technology.

Caltech's new Institute for Quantum Information will draw on several fields, including quantum physics, theoretical computer science, mathematics, and control and dynamical systems engineering, says founding director John Preskill, a professor of theoretical physics at Caltech.

"The goal of the institute will be to understand ways in which the principles of quantum physics can be exploited to enhance the performance of tasks involving the transmission, processing, and acquisition of information," says Preskill, who has worked on quantum computation algorithms for the last five years.

"The most potentially exciting aspect of the field is the promise of a quantum computer," he says. "If you could process quantum states instead of classical information, there are problems you could solve that could never be solved with classical technology."

Quantum computers would be more efficient than conventional computers because they would greatly reduce the number of steps the computer would have to jump through to solve many problems. For example, the encryption used to protect credit cards relies on the fact that it would take huge amounts of time for a conventional computer to break down a large number into its factors (the numbers one multiplies together that will equal this number).

It now takes the best computers several months to find the factors of a 130-digit number, and it would take 10 billion years to factor a 400-digit number—nearly the entire age of the universe. But a quantum computer with the same clock speed could factor the 400-digit number in about a minute, according to the figures Preskill has worked out.

At the same time, quantum information would provide a new means to thoroughly protect information from any intruder, Preskill says.

"By using quantum information, it's possible to make unbreakable codes, and this security is founded on fundamental physical laws," he says.

Also, the work of the new institute will advance research in the further miniaturization of classical electronic components. Quantum effects are becoming increasingly important for microelectronics as devices continue to shrink toward atomic dimensions.

In addition to Preskill, the Institute for Quantum Information will be led by two co-principal investigators who, in consultation with other Caltech researchers, will guide and supervise scientific activities. The initial co-principal investigators will be Jeff Kimble, an experimental physicist who has done groundbreaking work in the transmission of quantum information, and John Doyle, a professor of electrical engineering who is interested in control issues of quantum systems.

Other investigators at the institute will include Michelle Effros, Hideo Mabuchi, Michael Roukes, Axel Scherer, and Leonard Schulman, all Caltech faculty members. The institute will develop a substantial visitors' program and will aim at hiring postdoctoral researchers and graduate students who wish to enter the field of quantum information systems.

Contact: Robert Tindol (626) 395-3631


Two Caltech faculty named MacArthur Fellows

PASADENA—The California Institute of Technology has two new faculty geniuses, and each has been awarded $500,000 from the John D. and Catherine T. MacArthur Foundation to prove it.

Erik Winfree, an assistant professor of computer science and computation and neural systems, and Hideo Mabuchi, an assistant professor of physics, both received word last week that they are among the 25 new MacArthur Fellows in the program often referred to as the "Genius Grants." The awards are presented each year to individuals chosen for their exceptional creativity, accomplishments, and potential—no strings attached.

Mabuchi, a specialist in quantum optics, says he was surprised by the phone call and is not yet sure exactly what he'll do with the money.

"I may try to incorporate creativity into the type of science education we normally do at Caltech," he said. "Physics usually builds technical skills, so I would like to see if something could be done to encourage creative skills."

Mabuchi's research primarily explores the details of how microscopic quantum systems interact with macroscopic measurement and control devices used in the lab. This is an important avenue of work for future electronic devices, because as those devices become increasingly smaller, designers will find it more necessary to take quantum effects into consideration.

"Microelectronic devices are coming down to the size where you have to understand the physics very carefully," he said.

Winfree said he felt a "sense of freedom" when he received word of the award. Winfree's research emphasis is the emerging field of biomolecular computing, and he has been especially interested in DNA computing.

"I might, if I am lucky, be able to augment our understanding and imagination of computation in the molecular world," he said of his goals as a scientist. "The understanding of algorithms will serve as a key to understanding the behavior of complex systems such as the biological cell. The question is how to make this transfer of concepts concrete and useful.

"Thus, if my brief moment in the limelight is good for anything, I would like to champion—as others have before me—the notion that computer science is not just about computers. It is the study of processes that generate organization, wherever you find them: algorithms are a fundamental part of nature."

Winfree and Mabuchi, along with the other 23 winners this year, were nominated by an anonymous panel and then selected by a 13-member committee, also serving anonymously. The Fellows are required neither to submit specific projects to the foundation, nor to report on how the money is used.

An important underpinning of the program is the foundation's confidence that the Fellows are best able to decide how to use the money in furthering their work.





Physicists observe the quantum of heat flow

Physicists at the California Institute of Technology have announced the first observation of the quantum of thermal conductance. This discovery reveals a fundamental limit to the heat that can be conducted by objects of atomic dimensions.

The findings, reported in the April 27 issue of the journal Nature, could have profound implications for the future design of microscopic electronic devices and for the transmission of information, according to the research team leader, Caltech physics professor Michael Roukes.

The quantum of thermal conductance is best understood by beginning with a simple explanation of heat flow. In the everyday world, the amount of heat carried by an object can vary in a smooth and continuous way. Heat actually flows by means of collective, wavelike vibrations of the atoms that make up a solid material. Usually immense numbers of such waves, each inducing a unique type of synchronous motion of the atoms, act simultaneously to carry heat along a material.

Physicists know that waves sometimes act like particles and vice versa, so they've given these vibrations the particle-like name phonon (reminiscent of "electron" but named after the Greek root phon for sound.) For heat flow in the macroworld, since each phonon is just one among a sea of many others, an individual phonon's contribution alters the total only imperceptibly.

But in the nanoworld, this "phonon sea" is actually rather finite, quantum effects rule, and the heat conduction can become radically different. When an object becomes extremely small, only a limited number of phonons remain active and play a significant role in heat flow within it. In fact, in small devices at temperatures close to absolute zero, most types of motion become almost completely "frozen out," and heat must then be carried by only the several remaining types of wavelike motions that persist.

It has recently become apparent that, in this regime, a strict limit exists to the amount of heat that can be conducted in a small structure or device. Although never before observed, this maximum value is actually a fundamental law of nature, independent of composition or material. It stipulates that the only way thermal conductance can be increased in a very small device is simply to make the conductor larger.

The Nature paper reports that this fundamental limiting value, called the quantum of thermal conductance, can be observed by using tiny devices with specially patterned features only 100 billionths of a meter across (about 300 atoms wide). To carry out this work, Keith Schwab, a postdoctoral fellow in Roukes's group, developed special devices from silicon nitride with assistance from research staff member Erik Henriksen. The work was carried out in the group's nanofabrication and ultralow-temperature laboratories in Pasadena, in collaboration with University of Utah research professor, John Worlock, a visiting associate at Caltech.

The Roukes team has demonstrated that the maximum possible value of energy transported per wavelike motion (phonon mode) is a number composed of only fundamental physical constants and absolute temperature itself. (The relation is given by the product of pi squared, Boltzmann's constant squared, and absolute temperature, over three times Planck's constant.)

Numerically, at an ambient temperature of one kelvin, this quantized conductance roughly translates into a temperature rise of one kelvin upon the application of only a thousandth of a billionth of a watt of power (its precise value is 9.4 x 10^-13 W/K).]

Their new result has important implications for nanotechnology as well as for the transmission of information. Moore's Law, a popularized rule-of-thumb, can be used to loosely describe the continuous decrease in size of the individual building blocks (the transistors) that populate, now in the tens of millions, the integrated circuits forming today's powerful computer chips.

In the unrelenting technological drive toward increased function and decreased size, these individual transistor components have been scaled downward in size to a realm where the underlying physics of their operation can change. In the most extreme cases at the smallest scales, conventional operation may completely break down.

One example is the so-called "power dissipation problem" stemming from the fact that when each individual transistor on a microchip is turned on, each gives off a little heat. This accumulates to become a very significant problem when millions of such transistors, each in effect a microscopic heat generator, are placed in close proximity.

"This will become especially serious for future molecular-scale devices," says Roukes. "No matter how small it is, you always have to put a finite amount of power into a device to turn it on. In this quantum regime, when only a limited number of modes are capable of transferring heat, it will be crucial to take this fundamental limitation into account."

Separate theoretical studies carried out elsewhere indicate that this quantum of thermal conductance is universal, and independent of whether the heat is carried by electrons, phonons, or any other mechanism. "It would seem there is no way of escaping this fundamental law of nature," says Roukes.

These other studies indicate that the maximum thermal conductance, observed in this work, is linked to the maximum rate that information can flow into a device having a single quantum "channel." This surprising connection between information theory and thermodynamics is a manifestation of a deep connection between information and entropy.

"As we engineer smaller and higher speed computational elements, we will also encounter this fundamental quantum limitation in the rate of information flow," Schwab says.

The group's three-year effort followed upon work of Thomas Tighe, a previous postdoctoral fellow in the group, and culminated in new techniques for creating the miniature devices studied. At the heart of each device is an isolated heat reservoir, which the researchers term a "phonon cavity." It resembles a miniature plate freely suspended by four narrow beams. Each beam acts as a quasi one-dimensional "phonon waveguide" for heat flow, and it is precisely this reduced-dimensional flow that is the focus of the researchers' measurements.

On top of the cavity, Schwab and Henriksen patterned two small, separate patches of thin-film gold, described by Roukes as "puddles of electrons." In the course of a measurement, one of these is heated by passing a very small electrical current through it. Electrical connections allowing this current to flow were made using superconducting leads (patterned on top of the phonon waveguides).

This insures that heat is deposited only within the resistive gold film and, therefore, transferred only to the phonon cavity. To escape from the suspended device, the heat must eventually flow through the phonon waveguides. Since the waveguides' thermal conductance is weak, the phonon cavity temperature ultimately rises to a new, and hotter, steady-state level that directly reflects the thermal conductance of the phonon waveguides.

Measurement of the current-induced temperature rise within the small devices is a significant challenge in its own right, and required both ingenuity and the investment of a significant portion of the researchers' efforts. Most available thermometry techniques applicable at the nanoscale are electrical, and thus involve power levels that greatly exceed that used by the researchers in their measurements.

"The power level we used to carry out these experiments, about a femtowatt, is equivalent to the power your eye would receive from a 100-watt light bulb at a distance of about 60 miles," says Schwab. Instead of the standard electrical methods, the researchers coupled the second "electron puddle" to extremely sensitive dc SQUID (superconducting quantum interference device) circuitry.

This allowed them to observe the feeble current fluctuations that have a magnitude directly proportional to the absolute temperature of the nanoscale device. This so-called Johnson/Nyquist noise, which is also the origin of the electrical noise causing background hiss in audio systems, here plays a pivotal role by allowing the local temperature of the phonon cavity to be measured without perturbing the ultraminiature device.

In the end, because the researchers know the precise amount of heat deposited, and can directly measure the absolute temperature reached by the phonon cavity in response to it, they can directly measure the thermal conductance of the narrow beams acting as phonon waveguides. Simply stated, the ratio of the heat flowing through the waveguides to the rise in cavity temperature is the phonon thermal conductance of the quasi one-dimensional waveguides.

This work was carried out over the past three years within the research laboratories of Caltech Professor of Physics, Michael Roukes. Schwab, formerly a Sherman Fairchild Distinguished Postdoctoral Scholar within Roukes' group, is the principal author of the paper.

Schwab's life as a young postdoctoral scientist, and his role in the efforts to observe the quantum of thermal conductance, are the subjects of an upcoming documentary film by independent filmmaker Toni Sherwood. The title of the film is The Uncertainty Principle: Making of an American Scientist.

Coauthors of the paper are John Worlock, visiting associate at Caltech and research professor of physics at the University of Utah, a long time collaborator with Professor Roukes; and former research staff member Erik Henriksen.


Cosmologists reveal first detailed images of early universe

PASADENA—Caltech cosmologists and other scientists involved in an international collaboration have released the first detailed images of the universe in its infancy. The images reveal the structure that existed in the universe when it was 50,000 times younger and 1,000 times smaller and hotter than it is today.

Detailed analysis of the images is already shedding light on some of cosmology's outstanding mysteries, including the nature of the dark matter and energy that dominate intergalactic space, and whether space is "curved" or "flat." The team's results are being published in the April 27 issue of the scientific journal Nature.

Cosmologists believe that the universe was created approximately 12–15 billion years ago in an enormous explosion called the Big Bang. The intense heat that filled the embryonic universe is still detectable today as a faint glow of microwave radiation that is visible in all directions. This radiation is known as the cosmic microwave background (CMB).

Since the CMB was first discovered by a ground-based radio telescope in 1965, scientists have eagerly sought to obtain high-resolution images of this radiation. NASA's COBE (Cosmic Background Explorer) satellite discovered the first evidence for structures, or spatial variations, in the CMB in 1991.

The new experiment, dubbed BOOMERANG (Balloon Observations of Millimetric Extragalactic Radiation and Geophysics), obtained the images using a telescope suspended from a balloon that circumnavigated the Antarctic in late 1998.

The balloon carried the telescope at an altitude of almost 37 kilometers (120,000 feet) for 10 1/2 days. As it flew, an extremely sensitive detector system developed at Caltech recorded the faint signals from the early universe.

The BOOMERANG images are the first to bring the CMB into sharp focus. The images reveal hundreds of complex regions that are visible as tiny variations—typically only one ten-thousandth of a degree (0.0001 C)— in the temperature of the CMB. The complex patterns visible in the images confirm predictions of the patterns that would result from sound waves racing through the early universe, creating the structures that by now have evolved into giant clusters and super-clusters of galaxies.

"These images represent the ultimate limit of our vision," said U.S. team leader Andrew Lange, physics professor at Caltech.

"The enormous structures that they reveal predate the first star or galaxy in the universe."

Lange and Italian team leader Paolo deBernardis of the University of Rome, La Sapienza, together led the international team that developed the sophisticated experiment. The entire payload was integrated at Caltech for months of extensive testing before it was taken to Antarctica.

Already, analysis of the size of the structures has produced the most precise measurements to date of the geometry of space-time, which strongly indicate that the geometry of the universe is flat, not curved.

"It is really exciting to obtain such strong evidence for a flat universe. This result is in agreement with a fundamental prediction of the 'inflationary' theory of the universe," said Caltech Postdoctoral Scholar Eric Hivon.

The theory hypothesizes that the entire universe grew from a tiny sub-atomic region during a period of violent expansion that occurred a split second after the Big Bang. The enormous expansion stretched the geometry of space till it was precisely flat.

"These measurements represent a watershed event in cosmology" commented Mark Kamionkowski, professor of theoretical astrophysics at Caltech. "The results suggest that we are on the right track with inflation—a hitherto speculative theory for the origin of the universe—and thus open up a path toward scientifically addressing what happened in the very first micro-micro-second after the Big Bang."

"The key to BOOMERANG's ability to obtain these powerful new images," explained Lange, "is the marriage of a powerful new detector technology developed at Caltech and the Jet Propulsion Lab with the superb microwave telescope and cryogenic systems developed in Italy."

The telescope optics focus the radiation from the early universe onto button-size "bolometric" detectors cooled to a fraction of a degree above absolute zero. Extremely sensitive thermometers embedded in each detector record tiny changes in temperature as the telescope scans across the sky.

"These detectors can 'see' tiny differences in the temperature of the early universe in much the same way as the back of your hand responds to the heat from the sun," explained Caltech graduate student Brendan Crill.

"What really sets this detector system apart," continued Viktor Hristov, a senior electronics engineer at Caltech, "is the stability of the detectors and the electronics used to record the faint signals."

Caltech and JPL are responsible for fabricating a similar detector system for the Planck Surveyor, a satellite that will someday image the CMB over the entire sky from a vantage point 1 million miles from Earth.

In a complementary effort, another Caltech team led by Professor Anthony Readhead is now obtaining images of the CMB at even sharper resolution, using a specially built radio telescope, the Cosmic Background Imager (CBI), from a remote site in the Chilean Andes. BOOMERANG and CBI herald a new era of precision cosmological measurement that promises to provide new insights into fundamental physics.

The 36 BOOMERANG team members come from 16 universities and organizations in Canada, Italy, the United Kingdom, and the United States. Primary support for the BOOMERANG project comes from the Italian Space Agency, Italian Antarctic Research Programme; and the University of Rome, La Sapienza; from the Particle Physics and Astronomy Research Council in the United Kingdom; and from the National Science Foundation and NASA in the United States.

Robert Tindol

Caltech grad student's team first to detect radio emission from a brown dwarf

A graduate student in astronomy from the California Institute of Technology recently led a team of researchers in finding the first radio emission ever detected from a brown dwarf, an enigmatic object that is neither star nor planet, but something in between.

The discovery, reported in the March 15 issue of the journal Nature by lead author Edo Berger and his colleagues, demonstrates that brown dwarfs can flare 10,000 times more intensely than theory predicted. The results will likely force experts to rethink their theories about magnetism in brown dwarfs and gas giants, says Berger's supervisor, Shri Kulkarni, who is John E. and Catherine T. MacArthur Professor of Astronomy and Planetary Science at Caltech.

Berger was leader of a student team that made the discovery during a special National Science Foundation student summer program at the NSF's Very Large Array (VLA) near Socorro, New Mexico. The brown dwarf they observed is named LP944-20.

Berger and his colleagues decided to make a long-shot gamble in attempting to observe a brown dwarf from which X-ray flares had been recently discovered with NASA's Chandra X-ray satellite.

"We did some background reading and realized that, based on predictions, the brown dwarf would be undetectable with the VLA," said Berger. "But we decided to try it anyway."

After consulting with Dale Frail, an astronomer at the National Radio Astronomy Observatory (NRAO), Berger and his colleagues decided to utilize a block of observing time traditionally dedicated to the summer students.

The day after they collected their data, the students gathered at the NRAO array operations center in Socorro to process the data and make the images. Berger, who had prior experience processing VLA data, worked alone in the same room as the other students, who were working together on another computer. Berger finished first and was shocked at his image.

I saw a bright object at the exact position of the brown dwarf, and was pretty sure I had made a mistake," Berger said.

He waited for the others, who were working under the guidance of another NRAO astronomer. Ten minutes later, the others also produced an image on the screen in which the same bright object showed up at the brown dwarf's location.

Berger then began breaking up the approximately 90 minutes' worth of data into smaller segments. His results showed that the brown dwarf's radio emission had risen to a strong peak, then weakened. This demonstrated that the brown dwarf had flared.

"Then we got real excited," Berger said, adding that the students immediately sought and received additional observing time. Soon they had captured two more flares.

"The radio emission these students discovered coming from this brown dwarf is 10,000 times stronger than anyone expected," Frail said. "This is going to open up a whole new area of research for the VLA."

The existence of brown dwarfs—objects with masses intermediate between stars and planets—had long been suspected but never confirmed until 1995, when Kulkarni made the first observation at Caltech's Palomar Observatory. Since then, a large number of brown dwarfs have been identified in systematic surveys of the sky. Astronomers now believe that there are as many brown dwarfs as stars in our galaxy.

Flaring and quiescent radio emissions have been seen previously from stars and from the giant planets of our solar system, but never before from a brown dwarf. Moreover, the strength of the magnetic field near the brown dwarf—as inferred from the radio observations—is well below that of Jupiter and orders of magnitude below that of low-mass stars, said Kulkarni.

Conventional wisdom would require large magnetic fields to accelerate the energetic particles responsible for the radio emissions. The same conventional wisdom says that brown dwarfs are expected to generate only short-lived magnetic fields.

However, the persistence of the radio emission of LP944-20 shows that the picture is not complete, Kulkarni said.

"I am very pleased that a first-year Caltech graduate student was able to spearhead such an undertaking, which led to this big discovery," said Kulkarni. "This discovery will spur theorists into obtaining a better understanding of magnetism in stars and planets."

In addition to Berger and Frail, the other authors of the paper are Steven Ball of New Mexico Institute of Mining and Technology, Kate Becker of Oberlin University, Melanie Clark of Carleton College, Therese Fukuda of the University of Denver, Ian Hoffman of the University of New Mexico, Richard Mellon of Penn State, Emmanuel Momjian of the University of Kentucky, Michael Murphy of Amherst College, Stacy Teng of the University of Maryland, Timothy Woodruff of Southwestern University, Ashley Zauderer of Agnes Scott College, and Bob Zavala of New Mexico State University.

[Editors: Additional information on this discovery is available at the NRAO Web site at]


Physicists create atom-cavity microscope, track single atoms bound in orbit with single photons

PASADENA—In a promising development with applications to science at the single-atom level, physicists have constructed an "atom-cavity microscope" that tracks the motion of individual atoms.

California Institute of Technology physics professor H. Jeff Kimble, his Caltech colleagues, and collaborators from New Zealand report in the February 25 issue of Science that they have succeeded in monitoring the motion of individual cesium atoms bound in orbit by single photons inside a high-quality optical resonator. The atom is trapped in orbit by a weak light field, and the same light field can be used to observe the atom's motion within the cavity.

This advance is an important development toward the eventual realization of quantum technologies, which would enable quantum computation and communication.

The stage for this microscopic dance is the optical cavity, a pair of highly reflective mirrors that face each other only 10 microns (0.0004 inches) apart. The mirrors are so reflective that a photon, the fundamental quantum of light, enters the cavity and bounces back and forth between the mirrors hundreds of thousands of times before it escapes again through one of the mirrors.

In this way a single photon confined in the cavity builds up an electric field strong enough to influence the motion of an atom and even to bind the atom in orbit within the cavity.

Collaborating theorists A. Scott Parkins and Andrew Doherty in New Zealand first recognized the potential of this trapping technique, in which the atom and the cavity share a quantum of excitation.

"I like to think of it as an atom-cavity molecule," says Christina Hood, a Caltech graduate student and primary author of the paper. "In a molecule, two atoms give up their own electron orbits, their separate identities, to share electrons and form something qualitatively different. In the same sense, in our experiment the atom and the cavity field are bound together strongly by sharing a series of single photons."

How do the scientists actually "see" what is going on inside the tiny optical system? The Caltech group and others had already used similar cavities to sense single atoms whizzing through the cavity. To do this, they illuminate one mirror of the cavity and measure the light escaping from the opposite mirror. "The cavity is a resonator for light, like a half-filled soda bottle is for sound," says Theresa Lynn, a Caltech graduate student and coauthor of the paper. "What we do is similar to holding a tuning fork up to the bottle and listening to hear it resonate. You'll only hear a ring if the right amount of water is in the bottle."

In this case, amazingly, it's a single atom that plays the role of the water in the bottle, dramatically altering the resonance properties of the cavity by its presence or absence. By measuring the amount of light emerging from the cavity, the researchers can tell whether an atom is in the cavity or not.

The major step of the current work is that now they can determine precisely where the atom is located within the light field, creating "movies" of atomic motion in the space between the cavity mirrors. Examples of these movies can be viewed at the group's web site:

The movies show atoms trapped in the cavity as they orbit in a plane parallel to the cavity mirrors. The atoms have orbital periods of about 150 microseconds and are typically confined to within about 20 microns of the cavity's center axis.

The Kimble team was able to measure the atomic position to within about 2 microns in measurement times of about 10 microseconds. Continuous position measurements at this level of accuracy and speed allowed them to capture the orbital motions of the atoms.

"The interaction of the atom with the cavity field gives us advantages in two distinct ways," says Kimble. "On the one hand, it provides forces sufficient to trap the atom within the cavity at the level of single photons. On the other hand and more importantly, the strong interaction enables us to sense atomic motion in a fashion that has not been possible before," he says.

Both aspects are important to physicists who probe the limits of our ability to observe and to control the microscopic world, in which the rules and regulations are set by quantum mechanics. According to one basic rule of quantum mechanics, the Heisenberg uncertainty principle, any measurement performed on a system inherently disturbs the future evolution of that system. The principle presents a challenge to physicists who strive to control or "servo" individual quantum systems for use in quantum computation and other quantum technologies.

In collaboration with Caltech assistant professor Hideo Mabuchi, the Caltech team is pursuing extensions of the current research to implement real-time quantum feedback to control atomic motion within the cavity. The operating principles for such "quantum servos" are a topic of contemporary theoretical investigation at Caltech being pursued by Mabuchi, Doherty, and their colleagues.

The cavity as a powerful sensing tool by itself also presents possibilities outside the quantum realm. The same techniques that produce movies of orbiting atoms could be adapted to more general settings, such as to "watch" the dynamics of molecules engaged in chemical and biochemical reactions. Mabuchi is pursuing an independent effort along these lines to monitor single molecules engaged in important biological processes such as conformationally gated electron transfer.

Robert Tindol


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