October 6, 2009
Kiko Galvez, Colgate University
Quantum Interference of Light: From Fundamentals to Qubits
Recent technological advances have allowed numerous fundamental tests
of quantum mechanics via violations of Bell's inequalities of various
forms and situations. The use of quantal systems to encode and manipulate
information in a non-classical way has led to the rise of a new
interdisciplinary field of quantum information. At the heart of both is
quantum interference. This rise to prominence has also led us to
reconsider how we introduce quantum mechanics in instruction, moving away
from "shut up and calculate" to measuring violations of Bell's
inequalities as an undergraduate lab. At the colloquium I will present
several experiments on quantum interference of light with the thread of
reinventing how to introduce quantum mechanics even to first year
students, but also understanding the more sophisticated role that photons
play in discovering new ways in which quantum mechanics can be implemented
for quantum information.
September 22, 2009
Steve
Smith, Stony Brook University
The Photophysics of Vision
Rhodopsin is a highly specialized G protein-coupled receptor (GPCR)
that is activated by the rapid photochemical isomerization of its
covalently bound 11-cis retinal chromophore, aka vitamin A. Absorption of
light results in the cis-to-trans conversion of the retinal along a
torsional coordinate in the electronic excited state of molecule in less
than ~200 femtoseconds. The rapid structural change in the retinal leads
to steric strain in the receptor, which is released on the timescale of
milliseconds and causes a conformational change in the receptor. I will
describe structural studies using Nuclear Magnetic Resonance (NMR)
spectroscopy to describe how this visual receptor transduces light into a
chemical and biological signal.
March 10, 2009
Miles Padgett,
University of Glasgow
Light's Twist
It is 15 years since Les Allen et al. recognised that light beams could
be made in the laboratory which carried an Orbital Angular Momentum. Since
that time much of my own group's work has been the exploration of this
phenomenon, ranging from optical spanners and rotational frequency shifts
to an angular form of Heisenberg's uncertainty principle. This lecture
will, however, concentrate upon two of our current interests namely the
role that angular momentum plays in the 3D structure of random speckle and
most recently the quantum entanglement of spatial modes in parametric
down-conversion.
February 3, 2009
John
Marburger, Stony Brook
The Curious History of Heisenberg's Uncertainty Relation
In his famous 1927 paper Heisenberg derived the product of
uncertainties
in position and momentum for a Gaussian wave packet, and gave physical
arguments for more general situations. Only later, in lectures at Chicago
University, did Heisenberg derive the rigorous inequality we associate
today with uncertainty relations. He cited a work by E.H. Kennard in
connection with his derivation, and historians credit Kennard with the
first proof. In 2007 I compared Heisenberg's Chicago proof with Kennard's
and found they are completely different and that Kennard's version is
fatally flawed. Probably the familiar proof based on Schwarz's inequality
is due to Pauli. Heisenberg's intention for the uncertainty relations is
obsolete, but they and their subsequent refinements are relevant to
non-classical 'squeezed' states of light which are shifted ground states
of the general linear quantum system.
February 10, 2009
Jim Simons, Renaissance Technologies Corporation
Mathematics, Common Sense, and Good Luck
November 25, 2008
David
DeMille, Yale
University
Diatomic Molecules as Quantum Tools
Our group has undertaken a program to apply the techniques of modern
atomic physics--cooling, trapping, and ultra-precise control and
measurement--to the more complex system of diatomic molecules. The
vibrational and rotational degree of freedom in molecules makes these
systems qualitatively different than atoms. Control over these properties
is enabling new and powerful ways to attack a broad range of problems,
ranging all the way from particle physics and cosmology to quantum
information processing and quantum chemistry. This talk will give an
overview of the field, along with some specific examples of our recent
work.
September 23, 2008
Anand Sivaramakrishnan, American Museum of
Natural History
Planet-hunting with adaptive optics and interferometry
Extending particular frontiers of instrumentation can result in major
advances in astronomical understanding. The study of planet and star
formation is in the midst of such an expansion now. Bright speckles around
a stellar image swamp any faint planetary companion's signal. This speckle
noise results from tiny residual errors in the almost perfect optics of
today's telescopes. Instruments dedicated to direct detection and
characterization of extrasolar planets must combat this speckle noise to
deliver science.
I will explain the imaging problem, show how adaptive
optics coronagraphy reduces speckle noise, and present some of our
ground-breaking coronagraphic results. We recently captured the first
image of a solar-system scale planet-forming disk around a young star,
opening up search spaces inaccessible to even the Hubble Space Telescope.
I will also describe a new approach, the non-redundant masking of a
telescope aperture, which eliminates speckle noise. With such aperture
masking we can peer closer to a star than has hitherto been possible. We
hope to implement this technique on NASA's flagship mission, the 6.5-m IR
James Webb Space Telescope, scheduled for launch in 2013.
March 11, 2008
Joe
Eberly, University of Rochester
Mysteries of Quantum Entanglement
The invention of the two-photon Clauser interferometer signalled a
completely new domain of spectroscopy. It allowed direct experimental
demonstration for the first time of non-local, non-realist phenomena in
physics. I will describe an idealized version of this interferometer and
various phenomena at the interface between classical and quantum physics
that are related to it (e.g. Schroedinger's Cat). An indirect consequence
is that decay to steady state is not always what we were taught. Recent
experiments on photons and atoms demonstrate the difference between local
decay and non-local decay of entangled quantum systems. Even when decay
of a system is locally smoothly asymptotic, non-local entanglement may be
non-smooth and disappear discontinuously. This "sudden death" constitutes
a strongly counterintuitive trait of entanglement,
confirming earlier predictions, but not yet really explained.
Februrary 19, 2008
Hal
Metcalf, Stony Brook
Entropy Exchange in Laser Cooling
Laser cooling is usually viewed as compression in velocity space by a
velocity-dependent force but such forces do not conserve energy. A proper
description must include the light field that absorbs the energy from
spontaneous emission, so the light field must be part of the system. It is
usually presumed that spontaneous emission is necessary to remove the
entropy lost by the atoms, and a closer look suggests that this happens by
redistributing the light among the empty states of the radiation field.
But the laser beams themselves have sufficient entropy capacity so that
stimulated emission can do precisely the same thing. Thus the system
doesn’t undergo a loss of entropy but merely its redistribution among its
parts of the system. The entropy in the light field is not dissipated
until the outgoing beams hit the walls in a non-conservative, irreversible
process.
November 13, 2007
Pierre Meystre, Optical Sciences Center,
University of Arizona
Cooling of nanoscale mirrors
The observation of quantum dynamics in truly macroscopic objects
appears increasingly feasible as a result of recent experimental advances
thatinclude novel cooling techniques and progress in nanofabrication. This
is an exciting prospect, as it would enable us to explore the
quantum-classical boundary as well as to test quantum mechanics in an
entirely new regime. The implementation of characteristically quantum
mechanical phenomena at a macroscopic scale also promises technological
benefits for areas from quantum measurement to the interferometric
detection of gravitational waves and to atomic force microscopy.
A promising route to these objectives is through the use of
optomechanical systems, particularly optical cavities where the support of
one of the mirrors is a nanoscale cantilever. The talk will review recent
developments in the optical cooling of these moving mirrors and discuss
the prospects for reaching their quantum mechanical ground state of
vibration. Future directions, including the realization of ro-vibrational
quantum entanglement in these systems, will also be touched upon.
October 30, 2007
Paul Brumer,
University of Toronto
Quantum Interference in the Control of Molecular Processes
Coherent Control offers a powerful approach to the control of atomic
and molecular processes. By manipulating quantum interference effects,
primarily through laser excitation, control over multipath molecular
processes can be achieved. This lecture will provide an introductory
overview of coherent control, followed by a summary of new developments in
the control of both bound state and scattering processes.
October 23, 2007
Thomas Weinacht, Stony
Brook
Observing and Controlling Atomic and Molecular Dynamics
Ultrafast laser pulses can be used to initiate and capture atomic and
molecular motion in real time. Shaping these pulses allows us to control
the dynamics we observe. I will discuss some experiments that follow bond
breaking and formation driven by an ultrafast laser pulse. I will also
discuss an experiment where a shaped ultrafast laser pulse is used to
control lasing of an atomic ensemble. I will conclude with some future
prospects and goals.
February 27, 2007
Marusa Bradac, KIPAC Institute SLAC
Shedding Light on Dark Matter: Seeing the Invisible with Gravitational
Lensing
The cluster of galaxies 1E0657-56 has been the subject of intense
ongoing research in the last few years. This system is remarkably
well-suited to addressing outstanding issues in both cosmology and
fundamental physics. It is one of the hottest and most luminous X-ray
clusters known and is unique in being a major supersonic cluster merger
occurring nearly in the plane of the sky, earning it the nickname "the
Bullet Cluster". In this talk I will present our measurements of the
composition of this system, show the evidence for existence of dark
matter, and describe limits that can be placed on the intrinsic properties
of dark matter particles. In addition, I will explain how this cluster
offers a serious challenge to MOdified Newtonian Dynamics (MOND) theories.
October 24, 2006
Bill Phillips, University of Maryland
A Bose Condensate in an Optical Lattice: cold atoms meet solid state
An atomic-gas Bose-Einstein Condensate, placed in the periodic
light-shift potential of an optical standing wave, exhibits many features
that are similar to the familiar problem of electrons moving in the
periodic potential of a solid-state crystal lattice. Among the differences
are that the BEC represents a wavefunction whose coherence extends over
the entire lattice, with what is essentially a single quasi momentum and
that the lattice potential can be turned on and off or accelerated through
space. Experiments that are not easily done with solids are often
straightforward with optical lattices, sometimes with surprising results.
February 7, 2006
Uwe Bergmann, Stanford Synchrotron Radiation
Laboratory
Archimedes Manuscript under X-ray Vision
Archimedes (287 - 212 BC) is considered one of the most brilliant
thinkers of all times. The 10th century parchment document known as the
Archimedes Palimpsest is the unique source for two of the Greek's
treatises - the Stomachion, and The Method of Mechanical Theorems. It is
also the only source for On Floating Bodies in Greek. The privately owned
palimpsest is the subject of an integrated campaign of conservation,
imaging, and scholarship being undertaken at the Walters Art Museum in
Baltimore. Much of the text has been imaged by various optical techniques,
but even today significant gaps remain in our knowledge of the text of
Archimedes, while texts by other authors - potentially of major
significance - remain yet unread.
A breakthrough in uncovering the remaining unread text has
recently been achieved. Using x-ray fluorescence imaging at the iron
K-edge, it was possible to uncover text from faint traces of the partly
erased iron gall ink. The x-ray image revealed Archimedes text hidden
underneath 20th century gold forgeries and covered by 12th century
biblical writings. Some of this text has not been read since more than a
millennium. Please join me in a fascinating journey of a 1000 year old
parchment from its origin in the Mediterranean city of Constantinople to
an x-ray beamline at the Stanford Synchrotron Radiation Laboratory.
February 8, 2005
Michael Berry, Bristol
The hierarchy of
optical singularities: a long and unfinished symphony