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Seminars
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Seminars
will be held in room S-141 in the Physics and
Astronomy Department building on Mondays at 4:00 PM, unless noted
otherwise. When necessary, virtual seminar
Zoom login instructions will be sent out via
email.
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Fall
2024
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August
26, 2024
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Vaibhav
Singh
Matsika
Lab,
Department of
Chemistry,
Temple
University
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Accelerating
surface hopping
molecular dynamics by
interfacing Newton-X
with GPU-based
software TeraChem
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(Host:
Tom Weinacht)
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Photochemistry,
the study of light's
interaction with
molecules, has
deepened our
understanding of
phenomena such as
DNA damage from UV
radiation and
environmental issues
like ozone
depletion.
Computational
chemists use
electronic structure
theory and
semi-classical
methods, like
surface hopping
molecular dynamics
(SHMD), to simulate
the photochemistry
of molecules.
However, these
simulations can be
extremely
time-consuming,
especially for
molecules with
multi-reference
character and
chemistry occurring
on picosecond
timescales. To
address this
challenge, I present
the interface
between Newton-X and
TeraChem, which
leverages GPUs to
significantly
accelerate SHMD
simulations. This
interface was used
to benchmark the
molecule uracil,
showing that a
calculation that
would traditionally
take 111 days using
CASSCF(14,10)
through the Newton-X
and COLUMBUS
interface can now be
completed in just 4
days using the
FOMO-CASCI method
implemented in
TeraChem. This
advancement enables
scientists to study
photochemical
processes on longer
timescales, offering
new insights into
the effects of
photochemistry.
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September
16, 2024
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Prof.
Dr. Alejandro
Saenz
Department of
Physics,
Humboldt
University of
Berlin
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Impact
of Molecular Physics
on Our Current
Knowledge of the
Neutrino Mass
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(Host:
Jesús
Pérez Ríos)
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Although the
neutrino is the most
abundant known
massive particle in
the universe, many
of its most basic
properties are still
unknown. This
includes not only,
e. g., the question
whether neutrinos
are Dirac or
Majorana particles
(in the latter case
their own
anti-particles), but
even such a
seemingly simple
observable as its
rest mass. In fact,
while the neutrinos
were supposed to be
mass-less according
to the standard
model until the
1990s (and thus
according to most
text books at that
time), the
experimental
confirmation of
neutrino
oscillations has
proven that they
possess a non-zero
mass (and that mass
eigenstates are not
identical to the
flavor states). The
most accurate purely
kinematical
determination of an
upper limit on the
neutrino mass, more
accurately the mass
eigenstate
corresponding to an
electronic
antineutrino, stems
from tritium
neutrino-mass
experiments. In such
experiments, the
kinetic-energy
distribution of the
β electrons emitted
in the radioactive
decay of molecular
tritium is analyzed.
Very recently, the
Karlsruhe neutrino
experiment KATRIN
has provided the so
far lowest upper
bound to the
neutrino mass (mν
< 0.9 eV c–2
at 90% confidence
level), for the
first time breaking
the (“magic”) 1 eV c–2
threshold [1]. Since
the energy released
in the β decay is
not only shared by
the emitted (and
measured) electron
and the neutrino,
but also by the
remaining molecular
ion 3HeT+,
the analysis of an
experiment like
KATRIN requires the
very precise
knowledge with which
probability which
amount of energy is
left in this ion,
the so-called
molecular
final-state
distribution. So
far, this
information is only
available from
theoretical
calculations. After
a brief introduction
into the KATRIN
experiment, this
talk will discuss
the challenges in
precisely
calculating the
molecular
final-states
distribution and in
quantifying the
uncertainty of the
finally extracted
neutrino mass due to
limitations in the
calculation of this
distribution.
[1]
Direct
neutrino-mass
measurement with
sub-electronvolt
sensitivity, Aker
et al. (The KATRIN
collaboration), Nature
Physics 18
160 (2022)
[Editorial:
Newsworthy
neutrinos,
Nature Physics
18, 121
(2022)
News and Views:
Still too small to
be measured, Nature
Physics 18,
128 (2022)]
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September
23, 2024
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Prof.
Gyu-Boong Jo
Department of
Physics
Hong Kong
University of
Science and
Technology
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Dipolar
BKT
(Berezinskii-Kosterlitz-Thouless)
superfluid in two
dimensions
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(Host:
Dominik
Schneble)
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Quantum
Simulation is an
ambitious program
that aims to use a
synthetic quantum
system, like atoms
and light, to
simulate and explore
condensed matter,
high energy and
nuclear systems,
resolving long-term
issues and
uncovering new
phenomena. It is
also an important
component in the
development of
quantum technology.
Here, I present a
few examples that
showcase these
developments.
First, I will
highlight the rapid
progress in dipolar
atomic systems and
address an
outstanding open
question regarding
the impact of
anisotropic dipolar
interactions on
Berezinskii-Kosterlitz-Thouless
superfluidity in two
dimensions.The study
of this new phase of
dipolar matter is
now within our reach
and holds the
potential to reveal
complex order
quantitatively.
Towards the end of
the talk, I will
touch upon other
exotic non-Hermitian
regimes that can be
simulated with
neutral atoms in
open quantum systems
with spin-orbit
couplings.
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October
7, 2024
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Prof.
Niranjan
Shivaram,
Dept. of
Physics and
Astronomy,
Purdue
University
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Ultrafast
Electron Dynamics
Measured with
Ultrafast Field
Observables
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(Host:
Tom
Weinacht)
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Electron
dynamics in matter
typically occur on
time scales ranging
from femtoseconds to
attoseconds. Such
ultrafast dynamics
can be 'strobed'
using femtosecond
and attosecond laser
pulses. The optical
technology to
generate and measure
attosecond pulses
received the Physics
Nobel Prize in 2023.
Numerous measurement
approaches have been
developed over the
past three decades
to track electron
dynamics using these
ultrashort pulses.
Nonlinear optical
wavemixing
spectroscopy such as
four-wave mixing
spectroscopy is a
powerful approach to
measure ultrafast
dynamics because it
could provide access
to detailed
information such as
transient electronic
symmetries in
molecules. In this
talk, I will
describe our recent
work where we
combined femtosecond
electric field
measurement with
four-wave mixing
spectroscopy to
demonstrate the
sensitivity of field
observables to
electronic
symmetries in
molecules. I will
then present
preliminary results
of transient
absorption
spectroscopy
experiments
involving
femtosecond
vacuum-ultraviolet
pulses and near
infrared pulses in
electronically
excited molecules.
Finally, I will
conclude by briefly
discussing a new
direction of
research in my group
to generate
entangled photons in
the
extreme-ultraviolet
regime as a novel
source for
attosecond
spectroscopy.
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October
21, 2024
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Jose
Godinez
USC
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TBD
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(Host:
Tom
Weinacht)
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October
28, 2024
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Prof.
Swati Singh
Depts. of ECE,
Physics, MSE
University of
Delaware
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Characterizing
the quantum properties
of ultralight dark
matter- an open
quantum systems
approach
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(Host:
Hal
Metcalf)
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Obtaining
insight into the
constituents of dark
matter and their
interactions with
normal, i.e.,
Standard Model (SM)
matter, has inspired
a wide range of
large and
small-scale
experimental efforts
that harness current
technology to look
for the feeble
interactions between
SM matter and dark
matter with
unprecedented
precision. This is
particularly
relevant for the
case of ultralight
bosonic dark matter
(UBDM), where dark
matter is assumed to
be a bosonic
field/particle
present in high
occupation numbers
around the earth.
After reviewing the
state of the field,
and the role of AMO
systems, in
particular for its
detection, I will
apply theoretical
quantum optics
techniques to
provide insight into
the nature of such
dark matter.
Specifically, we
apply the quantum
theory of optical
coherence to
characterize the
statistical
properties of the
UBDM field and an
open quantum system
approach to the
interaction between
the UBDM field and a
detector. I will
discuss how our
theoretical
treatment has
implications in
uncovering the
astrophysical
history of the UBDM
field, as well as
informing quantum
metrology-based
strategies for its
detection.
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November
18, 2024
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Prof.
Dylan Yost
Department of
Physics
Colorado State
University
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Precision
Hydrogen Spectroscopy
and Tests of Quantum
Electrodynamics at CSU
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(Host:
Tom
Allison)
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Quantum
electrodynamics
(QED) is the most
highly tested theory
in science, with
predictions made and
experimentally
confirmed at the
parts-per-trillion
level. Because
of this extremely
accurate theory,
testing QED
predictions with
increased precision
can provide more
accurate
determinations of
fundamental
constants or reveal
deviations that
indicate new
physics. In
this talk, I will
discuss our lab’s
efforts to test QED
predictions through
two avenues.
The first is our
ongoing effort in
precision hydrogen
spectroscopy where
we are currently
focused on measuring
relatively narrow
2S-nS two-photon
transitions. The
second is a new
experimental effort
where we will
attempt to detect
photon-photon
interaction using
femtosecond lasers
coupled to high
finesse optical
cavities.
Bio:
Dylan Yost received
his PhD on work with
vacuum-ultraviolet
frequency combs from
the University of
Colorado in
2011. In 2012,
he was a Humboldt
Fellow at the Max
Planck Institute for
Quantum Optics and
worked on precision
hydrogen
spectroscopy.
He is currently an
associate professor
at Colorado State
University. He
has received an NSF
CAREER award and the
NIST Precision
Measurement Grant
for his hydrogen
spectroscopy
experiments and was
recently named an
APS fellow.
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November
25, 2024
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TBD
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TBD
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(Host:
TBD)
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December
2, 2024
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TBD
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TBD
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(Host:
TBD)
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December
9, 2024
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TBD
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TBD
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(Host:
TBD)
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December
16, 2024
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TBD
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TBD
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(Host:
TBD)
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December
23, 2024
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TBD
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TBD
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(Host:
TBD)
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