PHYSICS DEPARTMENT

Nationwide, the percentage of students majoring in Physics is about 0.3%. At Williams, the physics majors comprise 3-4% of the class, i.e. about 10 times the national average. The average number of majors per class at Ph.D. granting institutions is 11, while at Williams, we graduated 20 physics & astrophysics major this June. Though these numbers may not seem large in absolute terms (there is still plenty of opportunity for student/faculty interaction in and out of the classroom!), it does mean that Williams is a nationally significant producer of future scientists. About half of our majors choose to go on to graduate programs in physics, biophysics, astrophysics, engineering, computer science, mathematics or other scientific fields–along with the odd composer or economist thrown in for good measure. In the fall of 2005, our graduates will begin Ph.D. programs at Berkeley, Princeton, Caltech, and Michigan, among others.

Eric Daub ’04, Prof. Daniel Aalberts and 2004 Leroy Apker Award winner Nathan Hodas ’04.

We are very proud to report that Nathan Hodas ’04 was selected as the recipient of the 2004 Leroy Apker Award. This national award is given by the major professional organization of physicists, the American Physical Society “to recognize outstanding achievements in physics by undergraduate students and thereby provide encouragement to young physicists who have demonstrated great potential for future scientific accomplishment”. Two Apker awards are given annually, and the competition is intense. Nathan was honored for his diverse research accomplishments, principally, for projects under the guidance of Prof. Daniel Aalberts. Nathan’s thesis: “The Stacked or Freely Jointed Chain Model: Single-Strand Stacking in Nucleic Acids” describes a new polymer physics model in which the backbone features sharp kinks rather than gentle bending. Nathan also co-authored two papers, which have been, published in the journal Nucleic Acids Research. One was an algorithm to calculate optimal binding free energies of small RNA fragments onto larger RNA. The other was a study of the pseudoknot RNA folds, which are important structures in viruses and catalytic RNAs. Nathan received his prize and delivered an invited talk at the 2005 APS March meeting in Los Angeles, which his advisor Daniel Aalberts also attended. In addition to an honorarium for Nathan, the department will receive a $5000 award to further support undergraduate research. Nathan has completed one year in the physics Ph.D. program at Caltech, and plans to pursue his interest in biophysics.

Remarkably, Nathan is the third Williams student to win this national award in the past six years. Both S. Charles Doret ‘02 and Brian Gerke ’99 were Apker winners. Charlie worked with Prof. Majumder in the area of high-precision atomic spectroscopy while at Williams and is presently pursuing a Ph.D. in experimental atomic physics at Harvard University. Brian, who also worked with Prof. Daniel Aalberts in the area of computational biological physics, is presently in the Ph.D. program at U.C. Berkeley. This unparalleled success in producing award-winning graduates is a testament to the excellent physics students whom we are privileged to teach here, and to the effectiveness of our overall research program and our research-training enterprise.

The college has identified a number of curricular areas where it wants to expand offerings. Of particular interest to the Physics department are interdisciplinary courses and tutorials. These are both areas where the department has already made a major investment of faculty time and effort and we are hopeful that the college will be able to provide the resources to support these efforts in the long run.

In the area of interdisciplinary courses, we are currently offering a 300 level course on Protecting Information: Applications of Abstract Algebra and Quantum Physics (PHYS 316) with the Math Department. This course enrolled a remarkable 45 students this spring. We also teach Materials Science: The Chemistry and Physics of Materials (PHYS 332) with the Chemistry Department and Computational Biology (PHYS 315) taught by Prof. Daniel Aalberts and cross-listed with the Computer Science Department.

The Physics Department has been an early and enthusiastic supporter of tutorials. We have evolved a variation on the canonical tutorial format that works well for physics. The weekly cycle starts Thursday evening when students read a chapter in the text (sometimes along with an article from the literature). Friday there is a one-hour lecture/discussion session for the whole class. Students then spend a few days working on problem sets. Tuesday or Wednesday, each pair of students meets with the professor for an hour presenting their solutions thus far and discussing any questions that have arisen. Thursday, students turn in written solutions and the whole cycle begins again. While this is a demanding schedule for students (and faculty!), we find that the extra effort is well rewarded by the improvement in student’s problem solving skills. We have converted our standard upper level courses on Electromagnetic Theory (PHYS 405T), Classical Mechanics (PHYS 411T) and Applications of Quantum Mechanics (PHYS 402T) into tutorials. Most of our graduate school bound students take at least two such tutorials. When we interview our graduating seniors, they report that physics tutorials they have taken were among the most challenging and also the most rewarding of their educational experiences at Williams.

Several years ago, the College received an extraordinarily generous bequest for the support of teaching and research in the Physics Department. Mrs. Frances McElfresh Perry has left the college some 12 million dollars in honor of her father, Prof. William Edward McElfresh, who taught at Williams 1902-1936. Prof. McElfresh was chair of the Physics Department from 1905 until his retirement. In part due to the generosity of this gift, the department has also secured substantial funds from the college to undertake a comprehensive teaching laboratory revitalization plan. New labs are being developed, and additional equipment purchases for laboratories throughout our curriculum. As always, our focus is on the pedagogical impact of the equipment as we strive to expose our students to exciting state-of-the-art experiments and techniques. The College also has committed to providing us with a set of ‘McElfresh’ summer research fellowships for summer student support that can sustain a large and vital summer research program in the physics department for the long-term. In the summer of 2005, 20 Williams students will be working with faculty members in the physics department on a wide variety of experimental and theoretical research projects.

Associate Professor Daniel Aalberts spent his sabbatical researching RNA pseudoknot folds, developing models of pre-mRNA splicing, and producing an algorithm to calculate optical RNA binding. His work is supported by an NIH grant. His thesis student, Nathan Hodas ’04, won the American Physical Society’s Apker Award for outstanding undergraduate research.

2004-2005 was a year with many administrative responsibilities for Associate Professor Sarah Bolton, who chaired the Faculty Steering Committee and worked extensively on the college’s diversity initiatives. During the fall term, she worked with Professor Stuart Crampton to teach Classical Mechanics (PHYS 411T), a tutorial, to a record 27 juniors and seniors. In the spring, she taught Electromagnetism and the Physics of Matter (PHYS 132) to 70 students, almost all of whom used the course to prepare for medical school. Bolton spent the summer of 2004 in the lab studying fast processes in nanometer scale semiconductors with research students Jennifer Simmons ’05 and Dan Weintraub ’05. This work was continued by Jenni in her senior thesis, and now forms the basis for Creston Herold ’06 and Sam Clapp ’06, who will pick up the experiments this summer. In addition to her on-campus responsibilities, Bolton continued to serve as a reviewer for the National Science Foundation, Research Corporation, Physical Review, and Optics Communications. In May, Bolton attended the International Quantum Electronics Conference in Baltimore, MD, for which she is a member of the program committee. Bolton’s research is supported by a continuing grant from the National Science Foundation.

Professor Stuart Crampton has founded the North Berkshire Center for Religion and Science (NBCRS) with Williams College Chaplain Rick Spalding. Its purpose is to promote constructive discussions of the relationship of science and religion within the college and out in the local community. NBCRS will sponsor faculty seminars, community seminars involving local clergy paired with scientists from their congregations, and other discussion groups at the college and in the community. NBCRS will also promote and disseminate discussion materials through a special shelf in Schow Library and a web site. NBCRS is supported by a three-year grant from the Metanexus Institute, matched by the college. Crampton served last summer and fall as a consultant to the Murdock Trust, a foundation supporting science in the five northwest states. Crampton also continues as a consultant for the Sherman Fairchild Scientific Equipment program and as a member of the Board of Directors of Research Corporation, America’s oldest science-related foundation.

Professor Kevin Jones spent the year on sabbatical at the National Institute of Standards and Technology in Gaithersburg, MD where he has been a frequent visitor in the group headed by Nobel Laureate William Phillips. He is involved with two experiments at NIST. One starts by using laser cooling techniques to produce samples of atoms at 1/1000 degree or less above absolute zero. When these atoms are exposed to properly tuned laser light they can be “photoassociated” to produce diatomic molecules. Spectra produced by this photoassociation technique have proven to carry a great deal of information about both the molecules and the collision properties of the ultracold atoms. It is even possible to use the photoassociation process to modify the collision properties of the atoms. Jones has participated in many of the developments in this field. The other experimental direction Jones has been pursuing at NIST is a relatively new effort aimed toward the production of correlated pairs of photons. By crossing two strong laser beams in a cell containing Rubidium vapor it is possible to produce new beams of light moving in different directions from the original ones. It is thought that the non-linear optical process that produces these new beams produces photons in pairs. If various technical problems can be overcome, this system is potentially of interest as a source of photon pairs each with a narrowly defined frequency bandwidth. Such a source might be useful for quantum computation and quantum cryptography schemes.

A major portion of Jones’ sabbatical was directed at writing, with NIST colleagues, a review paper on the field of photoassociation spectroscopy. This review is destined for publication in Reviews of Modern Physics. The theme he chose to emphasize was how this technique has permitted the study of “physicists molecules,” i.e. those where the molecular properties can be related, with high precision, to the properties of the two constituent atoms. This review was prepared at the invitation of the journal’s editors who seek out noted researchers to write articles, which summarize recent progress in various fields of physics.

In addition, Jones has been very busy writing several other research papers. With colleagues at NIST he wrote a paper for the Physical Review that showed in detail how far one could go in measuring and modeling subtle features of the molecules observed by photoassociation spectroscopy. A question from a colleague at MIT led to a collaboration on a paper which is about to be submitted to the Physical Review. He is also putting the finishing touches on another paper with NIST colleagues, one that brings together ideas from the non-linear optics experiment with those from the photoassociation work. In particular, they show that it is possible to observe in photoassociation spectra an effect that is very similar to the widely studied non-linear optics phenomena of electromagnetically induced transparency.

Jones reports that a particularly pleasant feature of his sabbatical has been the chance to work with Colin McCormick ’95. After Williams, Colin was a Herchel Smith Fellow at Cambridge University in England. He then went to Berkeley for his PhD, spent a year in Washington, DC as a congressional fellow and in the fall came to NIST as a postdoctoral researcher. Colin has made great progress in pushing forward the non-linear optics experiment. In June 2005, he reported on the latest results at the 17^th International Conference on Laser Spectroscopy held in Cairngorms National Park, Scotland. Colin compared notes with the prominent French physicist Prof. Alain Aspect of the Institut d’Optique.

During 2004-2005, Prof. Tiku Majumder continued his duties as Physics Department chair. In addition to this responsibility, he chaired a College-wide ad hoc committee which completed a thorough revision of the current student course evaluation system at Williams. In the fall, he taught Introductory Quantum Mechanics (PHYS 301) (including the associated advanced lab component) to a class of 22 majors. This spring he taught Waves and Optics (PHYS 202) to an enthusiastic group of incoming physics majors.

During the summer of 2004, Prof. Majumder supervised three students in the summer research program. Mark Burkhardt ’04, having just graduated in June 2004, spent his second summer in the lab prior to beginning the Physics Ph.D. program at Stanford University in fall 2004. Mark worked with two rising seniors, Joe Kerckhoff ’05 and Colin Bruzewicz ’05 (both veterans of the Majumder lab) as these students began their thesis research. Postdoctoral associate, Dr. Ralph Uhl, continues to be an invaluable member to the group, helping to supervise the students, pushing projects forward in the lab, and even offering able and welcome assistance in the teaching laboratories this year.

The Majumder group continues to pursue high-precision diode laser spectroscopy of thallium in their atomic physics lab. This year, both seniors developed new systems for studying a very weak transition in thallium, which necessitated new spectroscopic methods. Colin worked on an optical system consisting of a high-finesse Fabry-Perot cavity to be inserted into our atomic beam apparatus with the goal of measuring small atom-induced phase shifts. Joe pushed forward on several fronts (both experimental and calculational) toward a new atomic-physics-based test of time reversal symmetry. This requires the use of an optical ring cavity interaction region, new signal-processing electronics, and a frequency-stabilized laser. The details of our new scheme to lock our diode laser to this forbidden atomic transition were written up and submitted to the journal, Review of Scientific Instruments in June 2005.

Dr. Uhl attended the annual Division of Atomic, Molecular, and Optical Physics meeting of the American Physical Society (Lincoln, NE, May 2005) and presented a poster on recent work in the group. Majumder was elected to become vice-chair (and then chair) of the Gordon Conference, and will be responsible for organizing the scientific program of this important meeting when it is next held in 2007 and again in 2009. The summer of 2005 promises to be a very active one in the Majumder lab. Joe Kerckhoff ’05 is staying around the lab prior to starting in the Physics Ph.D. program at Caltech next fall, while incoming thesis student Dave Butts ’06, and rising juniors Margaret Pigman ’06 and Dan Sussman ’06 are already busy carrying forward the projects begun by Joe and Colin this year.

Professor Jefferson Strait and his students have built and are studying an optical fiber laser that produces pulses of light about one picosecond long. Unlike most lasers, which use mirrors to confine light to the laser cavity, an optical fiber laser uses a loop of fiber as its cavity. A section of fiber doped with erbium serves as the gain medium. It lases at 1.55 µm, conveniently the same wavelength at which optical fiber is most transparent and therefore most suitable for telecommunications.

During the summer of 2004, Aubryn Murray ’05 and Joe Shoer ’06 worked with Strait studying how polarization influences the operation of the fiber laser. Aubryn wrote a mathematical model for the polarization of the light inside the fiber. During the school year, she went on to write her senior honors thesis showing how the model agrees closely with the observed operation of the laser. Now that she has graduated, Aubryn is headed off to England to study engineering on a Herchel Smith Fellowship at Cambridge University.

Joe Shoer ’06 is continuing to work with Strait and Toby Schneider ’07 has joined the group during the summer of 2005. Now that they understand the role of polarization in the fiber laser, Strait and his students are using the laser as a test bed for studying how short pulses of light propagate in fiber. They hope to demonstrate that the fiber laser tends to produce soliton pulses, a pulse shape that should propagate for long distances without degradation.

Strait served as pre-engineering advisor during the fall term and continues to serve as department webmaster.

In the fall term, Assistant Professor David Tucker-Smith taught Particles and Waves–Enriched (PHYS 141) for the second year. In the spring, he taught a tutorial, Applications of Quantum Mechanics (PHYS 402T) for the first time.

During the summer of 2004, Tucker-Smith studied particle physics models of leptogenesis with John BackusMayes ’05 and Sean O’Brien ’05. These models aim to explain the origin of the matter-antimatter asymmetry present in the universe today. Both John and Sean continued their work during the academic year in their senior theses. They derived new constraints on the parameter space of a particular model, called Dirac leptogenesis, by requiring consistency with the known baryon-to-photon ratio and with neutrino oscillation data. These constraints allowed them to determine conditions in which the problems associated with gravitino overproduction in conventional supersymmetric theories of leptogenesis are resolved. In the summer of 2005, Tucker-Smith will work with Ersen Bilgin ’06, Utsav KC ’06, and Owen Simpson ’07 on new projects in particle theory.

In other research activity, Tucker-Smith collaborated with Prof. Yasunori Nomura and Brock Tweedie of U.C. Berkeley to develop a novel framework for supersymmetry breaking. The hope is that this model will reduce the fine-tuning of parameters needed for supersymmetric theories to be consistent with current experimental data, an issue that Tucker-Smith has been exploring further with Nomura and Prof. Z. Chacko, of the University of Arizona. Tucker-Smith will present this research in July at the HEP 2005 conference in Lisbon.

During the summer of 2004, Professor Dwight Whitaker began his sabbatical year continuing his research on producing a Bose-Einstein condensate (BEC) in his lab at Williams. With the assistance of summer student Utsav KC ’06 and thesis student Justin Brown ’05 his lab has now successfully transferred atoms from a magneto-optical trap into a dipole trap produced from a high powered CO₂ laser beam. Currently they are able to transfer over a million atoms into a laser trap at a temperature of 50 micoKelvin. This represents a favorable starting point to evaporatively cool the atoms to the BEC transition temperature. This summer Brian Munroe ’07, Arjun Sharma ’07, Paul Lindemann ’06, and former thesis student Justin Brown join Professor Whitaker in his lab where they are using evaporative cooling techniques to cool trapped clouds to near quantum degeneracy.

In addition to his work studying cold atoms, Professor Whitaker has also taken on a new collaboration with Joan Edwards in Biology and Marta Laskowski at Oberlin College to study the rapid motion of plants. Last summer this group used a high-speed video system capable of recording images at 10,000 frames per second to record the explosive opening of bunchberry flowers. It was observed that these flowers can bloom in under 0.5 ms, which is the fastest plant movement ever recorded and about twenty times faster than the opening of a Venus Flytrap. Preliminary results of this research were published in the journal Nature and went on to receive a great deal of media attention including the Science Times section of The New York Times. This summer the group will continue this research with new plant samples.

A major research project for Professor William Wootters over the past few years has been to develop and explore an alternative representation of quantum mechanics, applicable to discrete systems such as the spin of a single electron or a quantum computer comprising “many” electrons’ spins. The new representation uses generalizations of position and momentum that follow the arithmetic rules of a “finite field”. Last summer Prof. Wootters and two former students, Kate Gibbons ’03 and Matt Hoffman ’04 finished revising their paper on this subject for Physical Review A. Prof. Wootters has continued to pursue this line of research and has presented the results at conferences and in seminars. Last summer he also worked on two completely different research projects with Ersen Bilgin ’06 and Josh Cooperman ’05. Ersen constructed simple but elegant hidden-variable models of quantum systems involving negative probabilities. Josh became interested in what is called the “timeless” formulation of quantum mechanics in which the concept of time is treated as secondary and derived rather than as primary. In particular, Josh asked how one could understand the law of increasing entropy within this formulation, a law that seems to depend crucially on the existence of time. Josh’s summer work led to a senior honors thesis on this subject.

During the Winter Study period, Prof. Wootters supervised Brian Simanek ’07 in an independent study of cryptography, and collaborated with Rob Terchunian ’06 in a research project following up on the work of Gibbons and Hoffman.

In the fall semester, Prof. Wootters taught Seminar in Modern Physics (PHYS 151), a course designed for advance-placed first-year students. In the spring, he taught Mathematical Methods for Scientists (PHYS/MATH 210) and, with mathematics Professor Susan Loepp, Protecting Information: Applications of Abstract Algebra and Quantum Physics (PHYS/MATH 316).

Bryce Babcock, Staff Physicist and Coordinator of Science Facilities, continued his collaborations with Professor Jay Pasachoff and Dr. Steven Souza. Their efforts focused on developing new CCD systems for their planetary occultation work with James Elliot’s group at MIT. In July, Babcock and student Joseph Gangestad ’06 traveled to Cerro Armazones Observatory near Antofagasta, Chile to observe an occultation of a star by Charon, Pluto’s moon. Further details regarding this effort may be found in the Astronomy Department section.

A welcome event this winter was the National Instruments announcement that it was finally providing drivers for the Mac OS X operating system. As a result, Babcock worked with Instructional Technology this spring to replace the aging data acquisition cards in use in introductory instructional labs in Physics, Neuroscience and Biology. This involved designing a new printed circuit interface and rewriting software programs used in these labs. In addition to his efforts developing research and instructional apparatus for the sciences, Babcock serves on the Animal Care, Safety, WilliamsScene and Science Executive Committees. He edits the Report of Science at Williams, the annual review of science activities at Williams, which is published in both print and web accessible versions (see <www.williams.edu/go/sciencecenter/center/>.)

[Colloquia are held jointly with Astronomy. See Astronomy section for additional listings.]

Class of 1960’s Scholar Program Colloquia:
Dr.. Jonathan Friedman, Amherst College

“Single-Molecule Nanomagnets: Tunneling, Interference and Quantum Computing”
Dr. Gordon Jones ’89, Hamilton College

“3He-based Neutron Polarizers
Dr. Matthew DeCamp ’96, MIT – Cambridge, MA

“Time Resolved X-ray Diffraction”
Dr. Jason Zimba ’91, Bennington College

“Go Pistons!”
Jinhua Wang, Cold Spring Harbor Lab

“Computational Analysis on Pre-mRNA Alternative Splicing”
Brian Wecht ’97, MIT – Cambridge, MA

“Exact Results from Supersymmetric Field Theories”
Dr. David Park, Williams College, Einstein Centennial

“Photons and the Birth of Quantum Theory”
“Are Atoms Real? A Serious Answer to a Serious Question”
“The Invention of Relativity Theory”
Brian Cathcart, Author of “The Fly in the Cathedral”

“Gentlemen at Work: How the Atom was Split”?
Dr. Elena Caceres, Brown University

“String Theory and Quantum Chromodynamics”
“Strings, Branes and QCD”
Dr. L. Mahadevan, Harvard University, Division of Engineering and Applied Sciences

“Water Movements in Soft Materials: from Passive Gels to Active Plants”
Dr. William Loinaz, Amherst College

“Peering Beyond the Standard Model”
Other Colloquia:
Dr. Kristopher R. Tapp, Williams College Mathematics Dept.

“Yang-Mills Connections”

Sarah Bolton

“Nonlinear Dynamics in Ultrafast Lasers”
Physics Department summer lecture series, July 2004
Protik (Tiku) Majumder

“Searching for New Physics in Thallium”
Physics Department summer seminar series, July 2004
David Tucker-Smith

“Gauge Theories and Geometry”
Mathematics Faculty Seminar

Daniel Aalberts

“Quantifying Optimal Accuracy of Local Primary Sequence Bioinformatics Methods”
American Physical Society March meeting, Los Angeles, CA

“Statistical Mechanical Modeling of mRNA Splice Site Identification”
University of Illinois at Chicago, Chicago, IL

“Single-Strand Stacking Free Energy from Beacon Kinetics”
University of Pennsylvania, Philadelphia, PA
Kevin Jones

with Colin McCormick and Paul Lett (presented by McCormick)
“EIT Enhancement of Two-beam Excited Conical Emission in Hot Rubidium Vapor”
International Conference on Laser Spectroscopy, Cairngorms, Scotland, June 19-24, 2005

with M. Johanning, R. Dumke, J. D. Weinstein, and P.D. Lett (presented by Johanning)
“Dark Superposition States Between Ultra-cold Atoms and Molecules Generated by Photoassociation”
European Quantum Electronics Conference Munich, Germany, June 12-17, 2005
Protik (Tiku) Majumder

Poster session at the biennial Atomic Physics Gordon Conference, June 2005
David Tucker-Smith

“Fine-Tuning in Warped Supersymmetric Models”
Massachusetts Institute of Technology, Cambridge, MA
Dwight Whitaker

“Spin Waves in an Ultra-cold Atomic Vapor”
Rensselaer Polytechnic Institute, Troy, New York
University of Connecticut, Storrs, CT
William Wootters

“Picturing Qubits in Phase Space”
Quantum Information Theory: Present Status and Future Directions
Isaac Newton Institute, Cambridge, UK, August 2004

“Quantum Measurements and Finite Geometry”
Isaac Newton Institute, Cambridge, UK, August 2004

“Quantum Entanglement as a Resource for Communication”
University of New Hampshire, October 2004

“Quantum Entanglement”
Adelphi University, December 2004

“The Fisher Metric and the Structure of Quantum Mechanics”
New Directions in the Foundations of Physics, College Park, MD, April 2005