Spring

confirmed for Feb. 15: Prof. Ken Segall (Colgate)
confirmed for Feb. 22: Prof. Bob Romer (Amherst College)
confirmed for Mar. 1: Prof. Jack Harris (Yale)
confirmed for Mar. 8: Prof. Lorenzo Sorbo (UMass Amherst)
confirmed for Mar. 12: Prof. Alan Guth (MIT) (Five Colleges talk)
confirmed for Mar. 15: Dr. Wei Chen (Stony Brook)
confirmed for Mar. 29: Prof. Michael Golay (MIT)
confirmed for Apr. 5: Prof. Kathy Aidala (Mt. Holyoke)
confirmed for Apr. 12: Prof. Jefferson W. Tester (MIT)
confirmed for Apr. 19: Prof. Ward Lopes (Mt. Holyoke)
confirmed for Apr. 26: Prof. Brian Anderson (Arizona)
confirmed for May 3: honors thesis talks (Amherst College)

Pending

invited but not confirmed: Prof. Tatsu Takeuchi (Virginia Tech)

Title: Solids behaving like molecules: the curious properties of some lanthanum ruthenates

Title: Title: Everything You Ever Wanted to Know about Graduate School, and the Universe, in Less That One Hour

Abstract:

The discovery of perturbations in the Cosmic Microwave Background(CMB) ushered in a new era of experimental cosmology. One of the most exciting new signatures in the CMB is that of polarization, which is already informing the time scales of reionization, and could possibly help probe inflationary time scales in the universe, beginning about 10-43 seconds after the big bang. The Q/U Imaging Experiement (QUIET) will probe this signature with unprecedented accuracy and help inform next-generation experiments. In addition to discussing QUIET, I will talk about the process of applying, choosing, and going to graduate school, with the hope of clarifying the procedure.

Title: Resources in Understanding Electromagnetism: Building a Conceptual Bridgefor Physics Learners and Teachers

Abstract:

Since the early 1980s, research in the field of Physics Education has enhanced the physics educators toolbox. We have a host of innovative tools which can promote interactive engagement in the classroom, however many students still struggle with fundamental concepts in electromagnetism. WPI and MIT are developing a set of educational materials to be used in conjunction with a suite of electromagnetism visualizations created by researchers and computer developers at MIT*. We will provide a set of problems which feature integrated visualizations in the context of electromagnetism, and we will discuss preliminary findings from a recent pilot study.

Title: Quantum Coherence in Superconducting Devices

Abstract:

Superconducting devices are ideal systems for exploring quantum coherence at the scale of circuits on a chip. Such investigations could advance fundamental understanding of quantum mechanics at large scales and help develop the building blocks, or qubits, for implementing a quantum computer. One such circuit, the flux qubit, is composed of a superconducting loop and Josephson junctions. I will present measurements performed at the University of California, Berkeley of quantum coherence in these devices, as well as experiments on coupled flux qubits. In addition, I will discuss the prospects for using nanofabricated superconducting structures to probe the quantum coherent properties of vortices, which are quantized bundles of magnetic flux threading a superconductor.

Title: Magnetic Quantum Tunneling: Insights from Molecules and Magnetic Resonance

Abstract:

The miniaturization of magnetic devices to molecular dimensions is critical to advances in magnetic information processing. However, quantum mechanics begins to play a significant role at these dimensions, leading to novel phenomena which are incredibly sensitive to the detailed atomic scale structure of the device. Consequently, conventional top-down approaches to producing nanoscale magnetic particles have serious limitations. For this reason, there is a growing interest in chemical syntheses that provide a bottom-up or molecule-based approach, with atomic scale control of magnetic structure. I will begin this talk with an overview of the fascinating quantum effects that have been discovered from studies of so-called single-molecule magnets (SMMs), including: quantum tunneling of the magnetic moment from 'up' to 'down' through a magnetic anisotropy barrier; and quantum interference between different tunneling trajectories of the magnetization vector (spin) as it rotates from 'up' to 'down' over the Bloch sphere. I will then go on to describe the unique insights that can be obtained concerning these quantum phenomena using novel high-frequency and high-magnetic-field electron paramagnetic resonance techniques.

Title: The Oklo Natural Nuclear Reactor and the Time Stability of the Fundamental Constants of Nature

Abstract:

Two billion years ago, a uranium deposit in Oklo, Gabon,Africa achieved criticality and a nuclear chain reaction was sustained in the deposit for about 100,000 years. Such a reactor was possible because the relative isotopic abundance of U-235 was much greater in the past. By analyzing the isotopic abundances of stable fission products in the deposit, it is possible to determine whether low energy neutron absorption resonance energies were different in the past, and thereby determine whether the fundamental constants of physics have changed. A precise recent analysis of isotopic abundances implied that the fine structure constant has fractionally changed by as much as 45 parts per billion,with six sigma confidence. However, additional modeling of the reactor indicates that this should interpreted as an upper limit on a possible change, and at present is the most restrictive limit.

Title: Quantum Christmas Lights: Fluorescence Intermittency from Single Quantum Rods

Abstract:

How do single quantum objects, such as molecules and semiconductor nanoparticles, emit light? One intriguing feature of the fluorescence observed from a wide variety of single fluorophores is intermittency, colloquially called blinking. Under steady excitation, single fluorophores do not emit light steadily, but turn on and off, remaining on or off for milliseconds to minutes at a time. Intermittency is fairly well understood in many molecular systems, but it is still poorly understood in semiconductor nanocrystals, tiny crystalline particles of a semiconductor such as cadmium selenide that are only a few nanometers across. Such nanocrystals are the subject of extensive study, both for the prospect of optoelectronic applications and for the fundamental physics of light emission from quantum particles. This talk will introduce the general field of single-nanocrystal fluorescence and present our results on fluorescence intermittency in single rod-shaped nanocrystals.

Title: How Big is the "Natural" g-factor? New Answers to an Old Question

Abstract:

The gyromagnetic ratio or "g-factor" measures the size of a particle's magnetic dipole moment scaled by the Bohr magneton and the spin. Every student of quantum mechanics learns that the "natural" value for this quantity in the case of a spin 1/2---Dirac---particle is g=2 and this value is spectacularly confirmed in experiments involving the electron and muon. The question then arises as to what the "natural" value is for a particle having arbitrary spin. This query was answered in 1953 by Belinfante who proposed that for a particle of spin S---gs=1/S. The so-called "Belinfante conjecture" was then "proved" by various authors over the intervening years. However, recently the question has been reexamined and it has been proposed that the "natural" value should be gs=2, independent of spin. The previous arguments for both viewpoints will be reviewed and a new argument will be presented, which strongly favors gs=2.

Title: Implementing Quantum Computing

Abstract:

A "standard model" for the physical implementation of a quantum computer was laid out some years ago. It indicated a set of capabilities that had to be achieved to make quantum processing possible: 1) systems with well-characterized qubits must be constructed. 2) These qubits should be initializable to the "0" state. 3) It must be possible to control the one- and two-qubit Hamiltonian of the system, so that unitary quantum logic gates are enacted. 4) Decoherence and imprecision of gate operations must be kept very low. 5) Reliable measurements of the quantum state of individual qubits must be possible. In this talk I will indicate progress towards these goals, after first reviewing why we want to do quantum computation.

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Title: Transitioning to a Sustainable Energy Future

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Faced with the issue of providing clean, secure and sustainable energy that is essential to maintaining our social and economic well being, many argue that the U.S. and other developed countries should be pursuing options more aggressively. There are a number of environmental, social, and economic reasons why a transition from our current hydrocarbon-based energy supply system is needed for the long term. While renewable energy from solar, wind, biomass, geothermal, and hydro sources offers the potential for achieving a more sustainable system, the transition to a renewable energy future has been painfully slow. This seminar will examine both the context and options for accelerating such a change. Two specific examples will be explored in detail: 1. geothermal energy for electricity and heat and 2. biomass for transportation fuels.

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