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Seminars
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Seminars
will be held held
at room S-141 in the Physics and
Astronomy Department building on
Mondays at 4:00 PM, unless noted
otherwise.
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Fall 2018
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October 1, 2018
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Prof.
Joseph
H.
Eberly
University
of Rochester
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Can
there be a
Role for
Entanglement
in Entirely
Classical
Physics?
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(Host:
Hal Metcalf)
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The
impression
obtained from
most
textbooks, and
from
discussions
with most
physicists, is
that the
presence of
entanglement
provides a
clear
indication of
a quantum
mechanical
state or
process. Schrödinger
is responsible
for importing
the word
entanglement
into physics.
This was
connected to
the state of
his famous
Cat, when he
responded to
the
Einstein-Podolsky-Rosen
analysis of
the joint
behavior of
remote quantum
parties [1].
The EPR paper
was Schrödinger's
first citation
and his second
citation was
to a
mathematical
result
containing the
essential
point of
entanglement.
It was first
reported by
Erhard Schmidt
in 1907, two
decades before
quantum
mechanics had
even been
invented. Now
relieved of
the need to
understand
quantum
mechanics, in
order to
employ
entanglement,
we have been
using
classical
optics to
exhibit
features
arising
specifically
from
entanglement
[2]. One
example will
be the
definition and
experimental
observation of
previously
unknown
optical
coherences
[3,4].
[1] E. Schrödinger,
Math. Proc.
Cambridge
Phil. Soc.,
v31, pp 555-
563 (1935).
[2] Xiao-Feng
Qian and J.H.
Eberly, Optics
Letters, v36,
4110 (2011).
[3] X.-F.
Qian, T.
Malhotra, A.
Nick
Vamivakas, and
Joseph H.
Eberly, Phys.
Rev. Letters
v117, 153901
(2016).
[4] J.H.
Eberly, X.-F.
Qian, and A.N.
Vamivakas,
Optica v4,
1113 (2017).
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October 25, 2018 (Thurs, 1pm)
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Dr.
Thomas Wolf
SLAC
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Investigating
ultrafast
processes in
photoexcited
molecules with
x-rays and
electrons
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(Host:
Tom Allison)
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Ultrafast
dynamics in
photoexcited
molecules are
based on the
interplay of
electronic and
nuclear
degrees of
freedom under
violation of
the
Born-Oppenheimer
approximation.
Comprehensive
understanding
of the
underlying
processes can
only be
achieved with
detailed
knowledge of
both
electronic and
nuclear
dynamics. I
want to show
at two
examples, what
we can learn
from
experimental
methods with
selective
sensitivity to
ultrafast
changes in
either the
electronic or
the nuclear
structure of
molecules. In
the first part
of the talk, I
will focus on
our
investigation
of the
ultrafast
photoprotection
mechanism in
the nucleobase
thymine with
time-resolved
near-edge soft
x-ray
absorption
spectroscopy
at LCLS. The
site
specificity of
soft x-ray
spectroscopy
can here be
transformed
into selective
sensitivity to
changes in the
electronic
structure of
thymine. The
experimental
data
unambiguously
show that the
molecule
undergoes
internal
conversion
through a
conical
intersection
between two
excited states
within 60 fs
after
photoexcitation.
In the second
part of my
talk, I want
to present
results from
an
investigation
of the
photoinduced
ring opening
of
1,3-cyclohexadiene
at SLAC's
ultrafast
electron
diffraction
(UED)
facility. The
large
accessible
momentum
transfer range
in the
diffraction
data permits
us to directly
and
selectively
follow
transient
changes of the
nuclear
structure in
time. In the
case of
cyclohexadiene,
we observe the
bond
dissociation
and ring
opening on the
level of
individual
atomic
distances. The
photochemical
reaction
product
1,3,5-hexatriene
exhibits
several
isomers with
low barriers.
We can follow
coherent
oscillations
of the
hexatriene
population
between
different
isomer minima
following the
ring-opening
on a
sub-picosecond
timescale. Our
experimental
results are in
good agreement
with ab initio
excited state
wavepacket
simulations.
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October 29, 2018
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Prof.
Swati
Singh
Williams
College
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Using
macroscopic
quantum
systems as
detectors
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(Host:
Hal Metcalf)
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When
properly
engineered,
simple quantum
systems such
as harmonic
oscillators or
spins can be
excellent
detectors of
feeble forces
and fields.
Following a
general
introduction
to this fast
growing area
of research I
will focus on
two simple and
experimentally
realizable
examples: a
nitrogen
vacancy (NV)
center in
diamond
interacting
with its
many-body
environment,
and
acoustic modes
of superfluid
helium
interacting
with
gravitational
waves.
In the first
case, I will
demonstrate
within a
semi-classical
description
that it is
possible to
understand
(and even
control) the
quantum
many-body
environment of
the of the NV
center,
thereby
enabling
several
magnetometry
applications.
In the second
example I will
show that for
reasonable
experimental
parameters, a
hybrid quantum
system
consisting of
superfluid
helium coupled
to
superconducting
cavity could
enable the
detection of
gravitational
waves from
nearby
pulsars.
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November 19, 2018
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Judith
Mizrachi
Stony
Brook University
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Super
Resolution
Oblique Light
Sheet
Microscopy
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(Host:
Hal Metcalf)
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The
ability to
examine the
brain at the
mesoscale
whole-brain
and nanometer
scale local
level is
instrumental
to
understanding
how brain
structure
gives rise to
sensory,
motor, and
cognitive
functions.
Visualization
of
nanometer-scale
structures,
such as
synapse
density and
distribution,
provides
deeper
understanding
of normal
brain function
and has the
potential to
reveal
structural
underpinnings
of
neuropsychiatric
disorders.
Large scale
and nanometer
scale
structures can
be studied
separately, be
we lack
methodologies
that could
provide whole
brain
volumetric
imaging,
neural
tracing, and
3D
super-resolution
imaging of a
mammalian
brain
simultaneously.
Our project
aims to
develop such a
method by
combining
oblique
lightsheet
tomography
(OLST), which
can image an
entire mouse
brain at
light-resolution
level, and 3D
superresolution
light sheet
microscopy for
the
examination of
synapses with
nanometer
scale
resolution in
selected brain
areas. The
method
comprises an
automated
combination of
light sheet
fluorescence
microscopy
(LSFM),
vibratome
sectioning,
pixel-wise 3D
deconvolution,
custom image
reconstruction
software,
super-resolution
optical
fluctuation
imaging (SOFI)
processing,
and axial
super-resolution
imaging with a
cylindrical
lens. The
proposed
device and
technique will
be the first
instrument
capable of
generating
volumetric
whole brain
images and 3D
super-resolution
images for the
same mouse
brain
simultaneously.
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December 10, 2018
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Dr.
Jeremy Reeves
Boston
University
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MEMS.
Nanomanufacturing,
and Tunable
Metamaterials
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(Host:
Dominik
Schnebke)
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I
present a set
of techniques
developed for
the nanoscale
patterning of
three-dimensional
elastic
mechanical
metamaterials.
Leveraging a
variety of
fabrication
technologies,
metallic
patterns are
fabricated on
3D-printed
polymer
scaffolds.
Generally,
high
resolution
metallic
patterning of
substrates
such as these
would be
impossible
using
conventional
photolithographic
techniques.
However, utilizing
microelectromechanical
systems (MEMS)
devices to
manipulate a
micro-scale
stencil,
precise
patterning of
traditionally
challenging
substrates can
be achieved.
Here, I
discuss a
metamaterial
with resonant
response in
the
mid-infrared
fabricated
using these
techniques.
Methods for
tuning the
frequency
response of
this
metamaterial
are presented
alongside
techniques to
create truly
3D structures
spanning many
length scales.
I will also
discuss
potential
applications
of the
fabricated
metamaterials.
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