Physics at the Large Hadron Collider

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Professor of Physics Harvey Newman has been searching for signs of dark matter, extra dimensions, and the elusive Higgs particle at the Large Hadron Collider in Geneva, Switzerland. He'll be reporting from the high-energy frontier of particle physics at 8:00 p.m. on Wednesday, January 9, 2013, in Caltech's Beckman Auditorium. Admission is free.

 

Q: What do you do?

A: I'm a high-energy physicist. Together with my colleague, Professor of Physics Maria Spiropulu, we explore the forces and matter that make up our universe, using the highest energies one can achieve at particle accelerators. These energies are now found in Switzerland, where CERN, the European Organization for Nuclear Research, sends protons traveling at 99.999997 percent of the speed of light crashing head-on into one another inside the Large Hadron Collider, better known as the LHC.

The LHC has two general-purpose detectors: our experiment, the Compact Muon Solenoid, or CMS, and ATLAS. "Compact" means "dense," not "small," and our experiment is relatively compact—it's only as tall as a four-story building, as opposed to ATLAS, which is like a six-story building.

Our lab had a primary role in designing the CMS's electromagnetic calorimeter, which detects high-energy photons and electrons using 76,000 crystals of lead tungstate. These crystals, which Caltech helped develop, together weigh 90 tons, and if they weren't so dense we would need even more of them in order to collect all those particles. And we need to see every particle, as we are looking for pairs of photons—a key signature of the Higgs particle that we've been focusing on for decades. We had first hints by the end of 2011, and by July 2012, CMS and ATLAS had accumulated sufficient evidence to announce the discovery of a Higgs-like particle.

 

Q: What is the Higgs, and why are you looking for it?

A: In 1964, Peter Higgs and others proposed the existence of a field that permeates all of space and would allow the generation of particle masses. The photon, which carries the electromagnetic force, has no mass, but the W and Z particles, which carry the weak force, do. But if you take the unified theory of the electromagnetic and weak interactions and try to put in a mass term for the W and one for the Z, the mathematics don't work. When you rewrite the theory to include the Higgs field, the Z and the W now have mass, the photon stays massless, and you get this other thing called the Higgs particle.

It is really quite amazing that relatively simple mathematical expressions describe how nature works. There's no reason for it, necessarily, but it is a characteristic of the world we live in. Fundamental expressions like F = ma [force equals mass times acceleration] have great predictive power in their own domains, and when you go outside those domains you have to look for something even more fundamental.

So it is for the so-called Standard Model of particle physics. It has been very successful until now, and yet we know that something lies beyond it. It does not have a candidate particle for dark matter, for example. It only describes normal matter, which is just 4 percent of the matter in the universe. And then there's dark energy, which we're not even sure has a "particles and fields" description. That's a frontier where we don't even know yet how to write things down. The Standard Model also does not work in the early universe. If you calculate the mass of the Higgs particle, the calculation blows up when we get to an energy scale that lies between where the universe is today and the moment of the Big Bang.

Caltech has a central role in the search for dark matter and whatever else lies beyond the Standard Model. It's a never-ending journey, and one that has inspired students at Caltech for decades.

 

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

A: I was in the fourth grade in PS 225 in Brooklyn, and one day Mrs. DeSimone put out a cart of books that went way beyond what was in our class. I read them all from end to end, and then I started to read everything in sight. I found Eric Rogers' Physics for the Inquiring Mind, which was a really odd book because there were all these hand drawings. It's clear that he was trying very hard to describe physics to the general public. It was also the biggest book in the library. So I carried it around, and I got fascinated by physics and astronomy, but my undergraduate advisor at MIT was in high-energy physics. I got to do experimental physics at age 17. As a grad student, I took the subway to Harvard to use the Cambridge electron accelerator, where my PhD work showed evidence of what turned out to be the so-called "charmed" quark, which was discovered the following year. That set the course of my career.

 

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From Theory to Reality: An Interview with Jason Alicea

Quantum computers—computers that harness the bizarre laws of quantum mechanics to become vastly more powerful than conventional computers—have been touted as the next leap in technology. Although useful quantum-computing technology is probably years—and possibly decades—away, physicists like Jason Alicea, who joined Caltech's faculty this fall as an associate professor of theoretical physics, are working hard to make it a reality. Alicea's research involves translating purely theoretical ideas into real-life experiments and applications. He recently answered a few questions about himself and his research.

What have you been working on lately in the field of quantum computing?

One thing that my colleagues [who include Caltech's Gil Refael and UC Santa Barbara's Matthew Fisher, both part of the Institute for Quantum Information and Matter at Caltech] and I did recently was to try to understand how to combine very simple components like semiconducting wires, ordinary superconductors, and magnetic fields to build a device that is capable of performing some rudimentary quantum-information processing without the infamous problem of decoherence—in which outside noise spoils the device's quantum properties and ruins any sort of computation it might be doing.

The physics we describe leads to blueprints for devices that may actually appear in a quantum computer down the road, although we're very far from that point.

The basic idea centers around exotic objects known as Majorana fermions that allow one to store and manipulate quantum information in a way that's protected against decoherence. The particular techniques that we originally envisioned turn out to have somewhat limited applications in quantum-information processing. But our ultimate dream would be to still use similar ideas—combining traditional conventional materials that are already available on people's shelves—to design a device that's capable of performing bona fide universal quantum computation without decoherence. We don't know how to do that, but we've made some small steps in that direction fairly recently. That's what I'm most excited about right now.

Were you always interested in science and physics when you were growing up?

Not really. I think this sets me apart from a lot of my colleagues. Often I ask people—like my fellow professors—when they became interested in physics and when they knew they wanted to be physicists. The answer I often get is that it was when they were four or five years old. I had the opposite experience. I didn't really know much about physics until I was fairly far along in college. I entered college as an engineering major with no intention of doing physics. When I was a sophomore and had to take some courses for my engineering curriculum, physics started to draw me in. I had a sort of midcollege crisis trying to decide what I was going to do. It was not an easy switch, but I decided that physics was a better course for me to follow.

Was there something particular about physics that you enjoyed?

Physics was actually extremely difficult for me. In the first physics class I took, I remember doing very poorly in the beginning and I had to work exceptionally hard, doing lots of extra problems that weren't assigned because I just wasn't used to thinking the way one has to in order to do physics. Overcoming that challenge was pretty enjoyable. I also think that I'm naturally more inclined toward fundamental questions of science as opposed to engineering. That wasn't something that was clear to me until I actually had some solid experience in physics.

What do you do when you're not doing physics?

I've been playing piano and keyboard since I was in high school, and when I was in college I played in a band. Recently, I've started to learn the guitar, writing some songs with a friend of mine. We aren't quite aiming to form a bona fide band, but we're looking to go to some open-mike nights. He's a great bass player and I'm the singer slash guitar player, but I'm good at neither. But that doesn't stop me from enjoying myself.

Alicea grew up in Brooklyn before moving to Florida in middle school. After receiving his BS in 2001 from the University of Florida, he came west to California, where he earned a PhD in physics from UC Santa Barbara in 2007. After a stint as a postdoc at Caltech, he spent time as an assistant professor of physics at UC Irvine before returning to Caltech.

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A Close Encounter of the First Kind

Mariner 2 visits Venus in the first successful interplanetary flyby

Fifty years ago today, on December 14, 1962, Mariner 2 became the world's first successful interplanetary mission when it swept some 21,000 miles above Venus's impenetrable veil of clouds. The flyby shattered any remaining illusions that Venus, Earth's near-twin in size and orbit, might be in any way habitable. It was known that Venus's atmosphere was incredibly dense and mostly carbon dioxide. Mariner discovered that it was at least 20 times more dense than Earth's (the latest estimate is 92 times as dense) and confirmed that this thick, insulating blanket trapped the sun's heat, making Venus's surface hot enough to melt lead—even on the night side.

Spaceflight is a high-risk business even today, but back then it was so dicey that JPL built everything in pairs. The Mariners' design was based on JPL's Ranger series of moon probes and used many of the same parts. Four Rangers had been launched by then, none of which had successfully completed their missions. And the moon is right next door, in planetary terms—a mere 239,000 miles, give or take, and a couple of days' journey. Mariner 2's flight path to Venus was a gently curving trajectory 182,000,000 miles long, and it would take 109 days to get there. Attempting a Venus shot was gutsy indeed.

The first Mariner didn't go well. It was blown up by Cape Canaveral's range safety officer within five minutes of launch on July 22, 1962. A succession of errors in the guidance system, including a typo in a critical line of computer code, was sending it plunging toward a watery doom—or worse, toward the Florida coast. Mariner 2 was dispatched to Canaveral post haste, and on August 27, a little more than a month later, it managed to make it into space successfully.

The spacecraft carried six instruments, four of which were designed to study deep space throughout the entire trip. A micrometeorite counter tallied hits from cosmic dust particles, which proved to be far less abundant out in the void than they were near Earth. The plasma detector, designed to study the portion of the sun's outermost atmosphere called the corona, revealed the existence of the solar wind—a continuous stream of plasma "blowing off the boiling surface of the sun into interplanetary space," as Caltech's Engineering & Science magazine reported in October 1962, when Mariner was still millions of miles from Venus. The wind "at times reaches hurricane force with outbursts, such as solar flares, on the sun. Even though this gas is exceedingly tenuous under any terrestrial scale, it is definitely dense enough, and is moving fast enough, to be able to push the interplanetary magnetic field around as it sees fit."

Mariner's magnetometer offered another surprise: Venus, unlike Earth, had no detectable magnetic field. This hinted that Venus probably rotated too slowly to generate one; Mariner's charged-particle detector corroborated this by showing that Venus has no radiation belts equivalent to Earth's Van Allen belts, either.

As Mariner approached Venus, the other two instruments were turned on: a microwave radiometer to measure surface temperatures, and an infrared radiometer to do the same for the atmosphere. Mariner carried no cameras; since Venus was a featureless ball of clouds, there didn't seem to be any point in dragging the extra weight along.

Meanwhile, down on the ground, Caltech postdocs Bruce Murray and Robert Wildey (BS '57, MS '58, PhD '62) and staff scientist Jim Westphal were scanning the face of Venus through the 200-inch Hale Telescope at Palomar Observatory, using a recently declassified infrared detector that had been developed for the heat-seeking Sidewinder missile. The system worked in the 10-micron band—wavelengths about 20 times longer than visible light—and performed up to 50 times better than civilian technology. The detector, a germanium crystal doped with mercury atoms, owed its extreme sensitivity to being cooled to –423° F in a bath of liquid hydrogen. (And yes, the Sidewinders carried a small supply of liquid hydrogen, which would boil off during flight—the thing was designed to blow up anyway.) "It was a mess," Murray, now a professor of planetary science and geology, emeritus, recalled in his Caltech oral history. "It leaked a lot."

Caltech physics professor Gerry Neugebauer (PhD '60) was on Mariner's infrared radiometer team, and about two weeks before the Venus encounter somebody realized that it might be a good idea to try to get some confirmatory data from the ground in case the spacecraft saw something big. The planetary scientists were granted a block of "twilight time" when the sky was too bright for deep-space observations, and in the hours before sunrise on the nights of December 13 through 16, the mighty 200-inch telescope was turned toward Venus. At that focal length, a patch of clouds just a few hundred miles in diameter filled the field of view, but this extreme close-up wasn't recorded as a picture. Instead, a pen line on a paper strip chart wobbled up and down with the intensity of the light received. The telescope methodically worked along horizontal tracks from top to bottom, taking as many as 30 passes to cover the disk.

"On the first night, which was the 13th, we got just these few scans, because we hadn't the slightest idea what we were doing," recalled Westphal (who also became a Caltech professor of planetary science) in an oral history for the Smithsonian Air and Space Museum. Even so, "higher up, the thing was obviously brighter on one side than it was on the other. [On] the other side of the planet, the inverse was true." Wildey wasn't on the mountain that first night, says Westphal, so "Bruce and I . . . stood there and we looked at the damn strip chart [in] the morning twilight; and we said, what do you suppose that is?" They drew a circle representing Venus and laid the strips of paper with the scans on top of it, "and since both of us had a background in geology, we kind of contoured it. . . . Cold at the top, cold at the bottom, and hot at the middle. We both stood there, and we grinned, and we said, we know which way the pole of Venus is!" The tilt of a planet's axis and the rate at which it spins are usually measured by tracking the progress of some landmark across the face of the disk, an impossible feat given Venus's cloud cover. But the atmosphere on a rotating planet will always have a band of warm air running along the equator and cold regions at the poles. "We knew something very fundamental about Venus that nobody [else] knew," Westphal continued.

Not even the Mariner team knew—the spacecraft's radiometers were programmed to scan across the planet's limb, or edge, looking sideways thorough the atmosphere in order to find out how the temperature varied with depth. These scans proved that Venus's stultifying heat was, in fact, radiating from its surface; the atmosphere's upper reaches turned out to be ice-cold.

JPL lost contact with Mariner 2 on January 2, 1963. The spacecraft is still in orbit around the sun, but a replica built at JPL from spare parts is on display in the Smithsonian's Air and Space Museum.

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Caltech-Led Astronomers Discover Galaxies Near Cosmic Dawn

Researchers conduct first census of the most primitive and distant galaxies seen

PASADENA, Calif.—A team of astronomers led by the California Institute of Technology (Caltech) has used NASA's Hubble Space Telescope to discover seven of the most primitive and distant galaxies ever seen.

One of the galaxies, the astronomers say, might be the all-time record holder—the galaxy as observed existed when the universe was merely 380 million years old. All of the newly discovered galaxies formed more than 13 billion years ago, when the universe was just about 4 percent of its present age, a period astronomers call the "cosmic dawn," when the first galaxies were born. The universe is now 13.7 billion years old.

The new observations span a period between 350 million and 600 million years after the Big Bang and represent the first reliable census of galaxies at such an early time in cosmic history, the team says. The astronomers found that the number of galaxies steadily increased as time went on, supporting the idea that the first galaxies didn't form in a sudden burst but gradually assembled their stars.

Because it takes light billions of years to travel such vast distances, astronomical images show how the universe looked during the period, billions of years ago, when that light first embarked on its journey. The farther away astronomers peer into space, the further back in time they are looking.

In the new study, which was recently accepted for publication in the Astrophysical Journal Letters, the team has explored the deepest reaches of the cosmos—and therefore the most distant past—that has ever been studied with Hubble.

"We've made the longest exposure that Hubble has ever taken, capturing some of the faintest and most distant galaxies," says Richard Ellis, the Steele Family Professor of Astronomy at Caltech and the first author of the paper. "The added depth and our carefully designed observing strategy have been the key features of our campaign to reliably probe this early period of cosmic history."

The results are the first from a new Hubble survey that focused on a small patch of sky known as the Hubble Ultra Deep Field (HUDF), which was first studied nine years ago. The astronomers used Hubble's Wide Field Camera 3 (WFC3) to observe the HUDF in near-infrared light over a period of six weeks during August and September 2012.

To determine the distances to these galaxies, the team measured their colors using four filters that allow Hubble to capture near-infrared light at specific wavelengths. "We employed a filter that has not been used in deep imaging before, and undertook much deeper exposures in some filters than in earlier work, in order to convincingly reject the possibility that some of our galaxies might be foreground objects," says team member James Dunlop of the Institute for Astronomy at the University of Edinburgh.

The carefully chosen filters allowed the astronomers to measure the light that was absorbed by neutral hydrogen, which filled the universe beginning about 400,000 years after the Big Bang. Stars and galaxies started to form roughly 200 million years after the Big Bang. As they did, they bathed the cosmos with ultraviolet light, which ionized the neutral hydrogen by stripping an electron from each hydrogen atom. This so-called "epoch of reionization" lasted until the universe was about a billion years old.

If everything in the universe were stationary, astronomers would see that only a specific wavelength of light was absorbed by neutral hydrogen. But the universe is expanding, and this stretches the wavelengths of light coming from galaxies. The amount that the light is stretched—called the redshift—depends on distance: the farther away a galaxy is, the greater the redshift.

As a result of this cosmic expansion, astronomers observe that the absorption of light by neutral hydrogen occurs at longer wavelengths for more distant galaxies. The filters enabled the researchers to determine at which wavelength the light was absorbed; this revealed the distance to the galaxy—and therefore the period in cosmic history when it is being formed. Using this technique to penetrate further and further back in time, the team found a steadily decreasing number of galaxies.

"Our data confirms that reionization is a drawn-out process occurring over several hundred million years with galaxies slowly building up their stars and chemical elements," says coauthor Brant Robertson of the University of Arizona in Tucson. "There wasn't a single dramatic moment when galaxies formed; it's a gradual process."

The new observations—which pushed Hubble to its technical limits—hint at what is to come with next-generation infrared space telescopes, the researchers say. To probe even further back in time to see ever more primitive galaxies, astronomers will need to observe in wavelengths longer than those that can be detected by Hubble. That's because cosmic expansion has stretched the light from the most distant galaxies so much that they glow predominantly in the infrared. The upcoming James Webb Space Telescope, slated for launch in a few years, will target those galaxies.

"Although we may have reached back as far as Hubble will see, Hubble has, in a sense, set the stage for Webb," says team member Anton Koekemoer of the Space Telescope Science Institute in Baltimore. "Our work indicates there is a rich field of even earlier galaxies that Webb will be able to study."

The title of the Astrophysical Journal Letters paper is, "The Abundance of Star-Forming Galaxies in the Redshift Range 8.5 to 12: New Results from the 2012 Hubble Ultra Deep Field Campaign." In addition to Ellis, Dunlop, Robertson, and Koekemoer, the other authors on the Astrophysical Journal Letters paper are Matthew Schenker of Caltech; Ross McLure, Rebecca Bowler, Alexander Rogers, Emma Curtis-Lake, and Michele Cirasuolo of the Institute for Astronomy at the University of Edinburgh; Yoshiaki Ono and Masami Ouchi of the University of Tokyo; Evan Schneider of the University of Arizona; Daniel Stark of the University of Cambridge; Stéphane Charlot of the Institut d'Astrophysique de Paris; and Steven Furlanetto of UCLA. The research was supported by the Space Telescope Science Institute, the European Research Council, the Royal Society, and the Leverhulme Trust.

Science Contacts:

Richard Ellis, Steele Professor of Astronomy
rse@astro.caltech.edu
(626) 676-5530

Matt Schenker, graduate student
schenker@astro.caltech.edu
(516) 428-0587

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Top 12 in 2012

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Credit: Benjamin Deverman/Caltech

Gene therapy for boosting nerve-cell repair

Caltech scientists have developed a gene therapy that helps the brain replace its nerve-cell-protecting myelin sheaths—and the cells that produce those sheaths—when they are destroyed by diseases like multiple sclerosis and by spinal-cord injuries. Myelin ensures that nerve cells can send signals quickly and efficiently.

Credit: L. Moser and P. M. Bellan, Caltech

Understanding solar flares

By studying jets of plasma in the lab, Caltech researchers discovered a surprising phenomenon that may be important for understanding how solar flares occur and for developing nuclear fusion as an energy source. Solar flares are bursts of energy from the sun that launch chunks of plasma that can damage orbiting satellites and cause the northern and southern lights on Earth.

Coincidence—or physics?

Caltech planetary scientists provided a new explanation for why the "man in the moon" faces Earth. Their research indicates that the "man"—an illusion caused by dark-colored volcanic plains—faces us because of the rate at which the moon's spin rate slowed before becoming locked in its current orientation, even though the odds favored the moon's other, more mountainous side.

Choking when the stakes are high

In studying brain activity and behavior, Caltech biologists and social scientists learned that the more someone is afraid of loss, the worse they will perform on a given task—and that, the more loss-averse they are, the more likely it is that their performance will peak at a level far below their actual capacity.

Credit: NASA/JPL-Caltech

Eyeing the X-ray universe

NASA's NuSTAR telescope, a Caltech-led and -designed mission to explore the high-energy X-ray universe and to uncover the secrets of black holes, of remnants of dead stars, of energetic cosmic explosions, and even of the sun, was launched on June 13. The instrument is the most powerful high-energy X-ray telescope ever developed and will produce images that are 10 times sharper than any that have been taken before at these energies.

Credit: CERN

Uncovering the Higgs Boson

This summer's likely discovery of the long-sought and highly elusive Higgs boson, the fundamental particle that is thought to endow elementary particles with mass, was made possible in part by contributions from a large contingent of Caltech researchers. They have worked on this problem with colleagues around the globe for decades, building experiments, designing detectors to measure particles ever more precisely, and inventing communication systems and data storage and transfer networks to share information among thousands of physicists worldwide.

Credit: Peter Day

Amplifying research

Researchers at Caltech and NASA's Jet Propulsion Laboratory developed a new kind of amplifier that can be used for everything from exploring the cosmos to examining the quantum world. This new device operates at a frequency range more than 10 times wider than that of other similar kinds of devices, can amplify strong signals without distortion, and introduces the lowest amount of unavoidable noise.

Swims like a jellyfish

Caltech bioengineers partnered with researchers at Harvard University to build a freely moving artificial jellyfish from scratch. The researchers fashioned the jellyfish from silicon and muscle cells into what they've dubbed Medusoid; in the lab, the scientists were able to replicate some of the jellyfish's key mechanical functions, such as swimming and creating feeding currents. The work will help improve researchers' understanding of tissues and how they work, and may inform future efforts in tissue engineering and the design of pumps for the human heart.

Credit: NASA/JPL-Caltech

Touchdown confirmed

After more than eight years of planning, about 354 million miles of space travel, and seven minutes of terror, NASA's Mars Science Laboratory successfully landed on the Red Planet on August 5. The roving analytical laboratory, named Curiosity, is now using its 10 scientific instruments and 17 cameras to search Mars for environments that either were once—or are now—habitable.

Credit: Caltech/Michael Hoffmann

Powering toilets for the developing world

Caltech engineers built a solar-powered toilet that can safely dispose of human waste for just five cents per use per day. The toilet design, which won the Bill and Melinda Gates Foundation's Reinventing the Toilet Challenge, uses the sun to power a reactor that breaks down water and human waste into fertilizer and hydrogen. The hydrogen can be stored as energy in hydrogen fuel cells.

Credit: Caltech / Scott Kelberg and Michael Roukes

Weighing molecules

A Caltech-led team of physicists created the first-ever mechanical device that can measure the mass of an individual molecule. The tool could eventually help doctors to diagnose diseases, and will enable scientists to study viruses, examine the molecular machinery of cells, and better measure nanoparticles and air pollution.

Splitting water

This year, two separate Caltech research groups made key advances in the quest to extract hydrogen from water for energy use. In June, a team of chemical engineers devised a nontoxic, noncorrosive way to split water molecules at relatively low temperatures; this method may prove useful in the application of waste heat to hydrogen production. Then, in September, a group of Caltech chemists identified the mechanism by which some water-splitting catalysts work; their findings should light the way toward the development of cheaper and better catalysts.

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In 2012, Caltech faculty and students pursued research into just about every aspect of our world and beyond—from understanding human behavior, to exploring other planets, to developing sustainable waste solutions for the developing world.

In other words, 2012 was another year of discovery at Caltech. Here are a dozen research stories, which were among the most widely read and shared articles from Caltech.edu.

Did we skip your favorite? Connect with Caltech on Facebook to share your pick.

H. Jeff Kimble to Receive Quantum Physics Award

The German Physical Society (Deutsche Physikalische Gesellschaft, or DPG) and the Optical Society of America (OSA) have selected Caltech physics professor H. Jeff Kimble to receive the Herbert Walther Award for his "pioneering experimental contributions to quantum optics, cavity quantum electrodynamics, and quantum information science."

"It is a special honor for me to receive this award since I have the greatest respect for Professor Walther, beginning when we first met when I was a graduate student and continuing over almost 30 years as scientific colleagues and competitors," says Kimble, William L. Valentine Professor and professor of physics at Caltech. "Walther made historic contributions to physics that have shaped the future that we now all enjoy."

The Herbert Walther Award highlights scientific contributions in quantum optics and atomic physics and recognizes individuals for their efforts to promote excellence in the international scientific community. Kimble will accept the award at the Laser World of Photonics Conference in Munich, Germany, in May 2013.

Kimble became a professor of physics at Caltech in 1989. He was named Valentine Professor in 1997 and director of the Institute for Quantum Information and Matter at Caltech in 2011. He has cemented his reputation in quantum optics through discoveries relating to quantum measurement and quantum information science.

Kimble's research has led to greater understanding of novel quantum states of the electromagnetic field, such as "squeezed" and "antibunched" light. His demonstration in 1995 of a quantum phase gate that operated at the single photon level and was suitable for the implementation of rudimentary quantum logic has been considered seminal in establishing the experimental foundations of quantum information science. Kimble and his colleagues have also made important contributions to theoretical physics, including a new paradigm for the realization of distributed quantum networks.

The Herbert Walther Award was first given by the DPG and OSA in 2007. The namesake of the award, Herbert Walther, was a well-known scientist and educator from the Max Planck Institute for Quantum Optics (of which he was founding director) and Ludwig Maximilians University, Munich, who made significant contributions to the field of laser physics and optics; he passed away in 2006. Past recipients of the award include Alain Aspect, Marlan O. Scully, Serge Haroche, and David J. Wineland.

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The Miracle and Beauty of Physics: An Interview with Cliff Cheung

When you lift a paper clip off a table with a small magnet, you're accomplishing a remarkable feat: the tiny magnet is overcoming the gravitational pull from the entire Earth. Why does gravity seem so weak compared to electromagnetism and the other fundamental forces of nature? This vast discrepancy in scale—how a small magnet can beat out a whole planet—is related to what physicists call the hierarchy problem.

Cliff Cheung—who joined Caltech this fall as an assistant professor of theoretical physics—is fascinated by this "very deep puzzle" (which may be solved through supersymmetry, a class of theories in which every fundamental particle has a partner particle, as well as by dark matter, the mysterious stuff that accounts for nearly a quarter of the universe). Recently, Cheung—who also plays guitar and piano, sings, and writes music—answered a few questions about coming to Caltech and his passion for physics.

What are you looking forward to about Caltech?

The environment here is fantastic. Caltech puts a lot of firepower behind a very small number of people. It's like having an academic steamroller on your side, so to speak. In my case, Caltech has been incredibly generous and supportive in all respects so far.

I'm super excited to be joining the theory group in particular, which is a powerhouse in a range of topics, including particle physics, cosmology, and string theory. Personally, it's surreal and humbling to be here given Caltech's legendary physics legacy.

Why do you think physics is exciting?

It works. When I was a student seeing the Standard Model [the theory of how all fundamental particles behave and interact] for the first time, I remembering thinking, this theory is very strange and very alien. But then you actually start calculating and you see what it predicts—and it works! There's a certain miracle in being able to write down something on a piece of paper which explains almost every experiment on record. That miracle is what excites a lot of us.

When someone writes down a formula or a theory, any physicist worth his salt can judge: is this beautiful or is this ugly? Equations that describe the universe can have a certain kind of elegance or they may not. In this sense, the ideas that we discuss have an intrinsic beauty.

That sense of beauty seems to emphasize the point that science, and physics in particular, is a very human endeavor.

That's right. It's much less cold than you think. This isn't meant to detract from what we do, but there is a certain subjectivity that I think is a very good thing. The fact that there are experiments to keep us honest is essential—at least for a particle physicist like myself. But at the same time we can enjoy the beauty of the models we write down

How did you become interested in physics?

I've had a couple of formative experiences. When I was in high school there was this wonderful program at Columbia University where you took a test and if you passed they let you take a class on the weekends. It's what nerds do. Anyway, I remember taking this class on special relativity, which to a high-school student is eye opening, but not so foreign as to be disconcerting. Special relativity is really just mechanics, but with a twist. Seeing these ideas for the first time made me think, I want to do this

This experience connected with me because I felt like I could really see the history as I learned the physics. I imagined Einstein in a room, writing down the equations for his gedanken [thought] experiments and I realized that just by thinking, it was possible to determine tangible and deep facts about the world around us. That's a pretty powerful thing. Learning that this was possible—that you could come up with the rules without actually playing the game—was absolutely amazing to me. You just had to use your brain. 

Born in Cleveland, Cheung grew up in the suburbs of New York City. He went on to Yale, where he received his BS in 2004. He finished his PhD from Harvard in 2009, before spending the past few years at UC Berkeley and Lawrence Berkeley National Laboratory as a postdoc.

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A Sky Full of Planets

Think back to the last time you saw the Milky Way—that faint stripe of stars that thickens and brightens as you get farther from city lights. At least 200 billion stars fill the Milky Way, our galaxy. How many planets might orbit those stars? What would those worlds be like? Twenty years ago, it was anybody's guess.  

In the 1990s, astronomers began to discover planets around other stars—so-called exoplanets. Since then, the confirmed count of exoplanets has skyrocketed to more than 850, with thousands of candidates awaiting follow-up. Astronomers now estimate that the stars in our Milky Way have an average of at least one planet each. (The next time you look up into the night sky, think about that.)

The sudden prospect of characterizing so many solar systems in our own galaxy has brought together two once-isolated camps: planetary scientists, who generally focus on the inside of our solar system, and astronomers, who mostly look beyond it. Planetary scientists see an opportunity to learn about our solar system and its origins by putting it into the context of a huge ensemble of other solar systems, and astronomers have a keen interest in what planetary scientists might help them discover about planet formation on a galactic or even larger scale.

To those ends, nine Caltech astronomers and planetary scientists are forming a Center for Planetary Astronomy. Joining together in a single research center will help them maintain fruitful collaborations, collectively attract research funding and fellowships for young scholars, and recruit top students and postdoctoral scholars.

The nascent center's members bring complementary perspectives to the characterization of our newly discovered neighbors. Planetary science professor Geoff Blake, astronomy professor Lynn Hillenbrand, and senior research associate John Carpenter study planet-forming disks of gas and dust around young stars. Mike Brown, the Richard and Barbara Rosenberg Professor and professor of planetary astronomy, and Caltech's infamous Pluto-killer, studies fossil rubble from just such a disk—a fantastic array of thousands of planetesimals and chunks of rock and ice on the fringes of our solar system, known as the Kuiper belt, that yields clues to the primordial solar system. The remaining scientists are focused more on the planets themselves. John Johnson, an assistant professor of planetary astronomy, focuses on the detection and characterization of exoplanets, searches for worlds like Earth, and investigates how stars' masses affect planet formation by studying the relationships between exoplanets and the very different types of stars that they orbit. Heather Knutson, an assistant professor of planetary science, characterizes exoplanets' compositions, temperatures, atmospheres, and even their weather. Yuk Yung, the Smits Family Professor of Planetary Science, studies the atmospheres of planets, and Dave Stevenson, the Marvin L. Goldberger Professor of Planetary Science, studies planetary interiors and how they evolve. Gregg Hallinan, an assistant professor of astronomy, is trying to detect radio signals from exoplanets, which would indicate the presence of magnetic fields that could be a signature of habitability.

The center's members are excited about its potential contribution to the major discoveries that are sure to come in this field. "The unique combination of Caltech's top-ranked astronomical facilities, astronomy program, and planetary science program will allow us to access the deep and broad knowledge about planets and planetary systems that only comes from such a joint endeavor," says Brown.

Says Knutson, "I was trained as an astronomer, but what I do is planetary science. Caltech is one of the few places where we have great conversations between the two groups. And Caltech's resources, in terms of telescopes, give us the opportunity to move quickly and think big." 

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High-Energy Physicists Smash Records for Network Data Transfer

New methods for efficient use of long-range networks will support cutting-edge science

PASADENA, Calif.—Physicists led by the California Institute of Technology (Caltech) have smashed yet another series of records for data-transfer speed. The international team of high-energy physicists, computer scientists, and network engineers reached a transfer rate of 339 gigabits per second (Gbps)—equivalent to moving four million gigabytes (or one million full length movies) per day, nearly doubling last year's record. The team also reached a new record for a two-way transfer on a single link by sending data at 187 Gbps between Victoria, Canada, and Salt Lake City.

The achievements, the researchers say, pave the way for the next level of data-intensive science—in fields such as high-energy physics, astrophysics, genomics, meteorology, and global climate tracking. For example, last summer's discovery at the Large Hadron Collider (LHC) in Geneva of a new particle that may be the long-sought Higgs boson was made possible by a global network of computational and data-storage facilities that transferred more than 100 petabytes (100 million gigabytes) of data in the past year alone. As the LHC continues to slam protons together at higher rates and with more energy, the experiments will produce an even larger flood of data—reaching the exabyte range (a billion gigabytes).

The researchers, led by Caltech, the University of Victoria, and the University of Michigan, together with Brookhaven National Lab, Vanderbilt University, and other partners, demonstrated their achievement at the SuperComputing 2012 (SC12) conference, November 12–16 in Salt Lake City. They used wide-area network circuits connecting Caltech, the University of Victoria Computing Center in British Columbia, the University of Michigan, and the Salt Palace Convention Center in Utah. While setting the records, they also demonstrated other state-of-the-art methods such as software-defined intercontinental networks and direct interconnections between computer memories over the network between Pasadena and Salt Lake City.

"By sharing our methods and tools with scientists in many fields, we aim to further enable the next round of scientific discoveries, taking full advantage of 100-Gbps networks now, and higher-speed networks in the near future," says Harvey Newman, professor of physics at Caltech and the leader of the team. "In particular, we hope that these developments will afford physicists and students throughout the world the opportunity to participate directly in the LHC's next round of discoveries as they emerge."

As the demand for "Big Data" continues to grow exponentially—both in major science projects and in the world at large—the team says they look forward to next year's round of tests using network and data-storage technologies that are just beginning to emerge. Armed with these new technologies and methods, the Caltech team estimates that they may reach 1 terabit-per-second (a thousand gbps) data transfers over long-range networks by next fall. 

More information about the demonstration can be found at http://supercomputing.caltech.edu/.
 

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Tuesday, April 9, 2013
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