Spring/Summer 2018

January 22, 2018

Prof.
Ting Yu
Stevens
Institute of
Technology

NonMarkovian
Dynamics of
Open Quantum
Systems:
Recent
Development

(Host:
Jin Wang)


In this talk I will
report our
recent work on
quantum
dynamics of
open systems
coupled to an
external
environment.
We will study
the crossover
property
between
nonMarkovian
and Markov
dynamics
induced by a
hierarchical
environment
consisting of
a
cavityreservoir
system. We
show how the
nonMarkovian
character of
the system of
interest is
influenced by
the coupling
strength
between the
qubit and
cavity and the
correlation
time of the
reservoir. In
particular, we
found a new
phenomenon
whereby the
qubit
Markovian and
nonMarkovian
transition
exhibits an
anomalous
pattern in a
parameter
space depicted
by the
coupling
strength and
the
correlation
time of the
reservoir. In
addition, I
will report
some recent
developments
of quantum
trajectory
methods for
cavity QED
systems.




January 25, 2018 (11am,
YITP)

Dr.
Stephen Libby
Lawrence
Livermore
Nat'l
Laboratory

Cold Atom Sensing,
Gravity,
Tomography,
and Gyroscopes

(Host:
George
Sterman, YITP)


The
ability to use
lasers to cool
atoms to
microkelvin
temperatures
and to
subsequently
control their
quantum
mechanical
behavior has
led to the
development of
exquisitely
precise
'quantum'
sensors.2
Applications
of these
sensors
include the
measurement of
local
gravitational
anomalies to
unprecedented
accuracy and
very accurate,
highly stable
gyroscopes.
Our LLNL 
AOSense, Inc.
collaboration
is pursuing
diverse
applications
of these
sensors that
directly
exploit their
extraordinary
scale factor
stability, low
noise and bias
drift
characteristics.
These
applications
include
shielded
threat
detection in
passing
vehicles,
emergency
response, and
treaty
verification,
all of which
require rapid,
passive
methods to
determine
hidden mass
configurations
precisely
and/or verify
the masses
present in
containers.
Such dense,
localized
objects can in
principle be
discovered and
accurately
measured by
their effect
on the local
gravitational
field.
Furthermore,
near field
measurements
of these
gravitational
perturbations
from multiple
vantage points
allow for a
kind of
gravitational
'tomography,'
leading to the
realtime
determination
of the hidden
mass
distribution.
Additionally,
we are
interested in
the potential
of atom
interferometer
Sagnac
gyroscopes to
do accurate
'dead
reckoning'
navigation
without the
aid of GPS.4
After
reviewing the
physics of
atom
interferometry
in atomic
fountainMachZehnder
and Sagnac
configurations,
I will
describe the
development of
a 'gravity
tomography'
signal
analysis
system for
vehicle
portals,
including the
optimal
synthesis of
the
gravitational
sensor signals
with
complementary
radiation
detection.




February 26, 2018

Prof.
Daniel Turner
NYU

Spectroscopic Observation
of Triplet
Separation as
a Driving
Force of
Singlet
Fission

(Host:
Tom Allison)


Singlet
fission, a
multistep
molecular
process in
which one
photon
generates two
triplet
excitons,
holds great
technological
promise. Here,
by applying a
combination of
transient
transmittance
and
twodimensional
electronic
spectroscopy
with 5 fs
laser pulses,
we resolve the
full set of
fission steps
before the
onset of spin
dephasing. In
addition to
its role as a
viable singlet
fission
material,
singlecrystalline
rubrene is
selected
because its
energetics and
transition
dipole
alignment
uniquely allow
for the
unambiguous
identification
of the various
fission steps
through their
contributions
to distinct
spectroscopic
features. The
measurements
reveal that
the
neighboring
correlated
triplet pair
achieves its
maximum
population
within 20 fs.
Subsequent
growth of the
triplet signal
on picosecond
time scales is
attributable
to spatial
separation of
the triplets,
proceeding
nonadiabatically
through weakly
coupled but
nearresonant
states. As
such, we
provide
evidence in
crystalline
rubrene for a
singlet
fission step
that, until
now, has not
been
convincingly
observed.




March 5, 2018

Prof.
Carlos
Trallero
University of
Connecticut

An attosecond
selfreferencing
interferometer
for phase
measurement
and control of
electronic
wavepackets

(Host:
Tom Weinacht)


We
use an
equivalent to
the Young
doubleslit
interferometer
for attosecond
pulses to
control and
directly
measure the
phase of
electrons in
the continuum.
We can perform
this with a
resolution of
12.5
attoseconds
(half the
atomic unit of
time) and with
subattosecond
precision.




April 23, 2018

Prof.
Mengkun Liu
Stony Brook
University

Recent Development in
Scatteringtype
Scanning
Nearfield
Optical
Microscope

(Host:
Tom Bergeman)


In
this talk, I
will go over
the basics of
optical
nearfield
techniques and
discuss how
they can be
used to probe
frequency and
momentum
dependent
dielectric
constants of
materials at
the nanometer
scale.
Specifically,
I will discuss
the details of
modeling
scatteringtype
scanning
nearfield
infrared
microscopy and
its
application in
understanding
the phase
change
materials and
twodimensional
materials over
a broad
spectral range
(33 cm1 to
2500 cm1). I
will also
discuss the
future
development of
nanooptics
probes
including the
cryogenic
capabilities
and its
coupling to
ultrafast
pumpprobe
spectroscopy
including both
the IR and THz
frequency
range. These
developments
set the stage
for future
spectroscopic
investigations
to access the
fundamental
properties of
complex
materials at
the nanoscale.
I will also
try my best to
spice it up
with some
quantum
analogy in it.




June 25, 2018

Stefan
Evans
University of
Arizona

On vacuum structure and
light
propagation

(Host:
Hal Matcakf)


Nonzero
divergences of
laser beam
fields suggest
nonzero
charges in a
vacuum void of
matter,
requiring
solutions to
the paraxial
wave equation
to be remedied
with
introduction
of a
longitudinal
polarization.
This motivated
a search for
nonlinear
vacuum
effects,
modifying
Maxwell's
equations such
that a freely
propagating
laser beam
induces charge
in the vacuum.
We investigate
behavior of
the
EulerHeisenberg
effective
potential,
first derived
in 1936. This
effective
potential
characterizing
the behavior
of virtual
electronpositron
pairs in the
vacuum is
still
progressing as
a theory
today, en
route to
describing
quantum vacuum
effects on
light
propagation.




June 27, 2018 (3:00PM)

Dr.
Hamed Merdji
LIDYL, CEA,
CNRS,
Universite
ParisSaclay,
France

Recent progresses in high
harmonic
generation in
2D and 3D
semiconductors

(Host:
Tom Allison)


Optoelectronic
is extending
to the highly
nonlinear
regime and
petahertz
frequencies. A
recent impact
of this
capability of
controlling
the response
of above band
gap electrons
under strong
fields is the
emergence of
high harmonic
generation
(HHG) in
crystal. An
increased
number of
studies on HHG
in crystals
has been
reported so
far in various
bulk
semiconductors
and very
recently in 2D
materials like
graphene
[16]. Here, I
will review
our
recent
progresses on
HHG in
semiconductors,
from basics to
applications
in petahertz
optoelectronic.
Using a 2µm
thulium
femtosecond
fibre laser we
have explored
various band
gap crystals.
As a first
illustration I
will present
results on
CaCO3 and GaN
crystal and
show a strong
laser
polarization
dependence
that can be
used to gate
isolated
attosecond
pulses. I will
then report on
very recent
insight into
the nonlinear
harmonic
response of
strongly
correlated
materials. The
harmonic
signal
exhibits
signatures of
the few
optical cycles
insulator to
metal phase
transition
[7]. As last
material of
interest, I
will present
results on HHG
in graphene.
We generated
up to the 9th
harmonic order
from trilayer
and monolayer
graphene on
quartz which
tend to be
more intense
than free
standing
graphene.
Ellipticity
measurements
show a
stronger
harmonic
signal for a
linearly
polarized beam
than a
circularly
polarized one.
I will explain
why this
results
deviates from
the work
reported by
Yoshikawa et
al.6 and how
polarization
spectroscopy
of the
harmonics
emission
allows
exploring
nonconical
section of the
graphene band
structure [8].
Finally,
inspired by
recent work
[9,10], I will
conclude by
drawing a
perspective
about how
these various
2D and 3D
crystals, with
unique
properties,
can be used to
control
electronic
currents at
petahertz
frequencies.
1. Ghimire, S.
et al.
Observation of
highorder
harmonic
generation in
a bulk
crystal. Nat.
Phys. 7,
138–141
(2011).
2. Luu, T. T.
et al. Extreme
ultraviolet
highharmonic
spectroscopy
of solids.
Nature 521,
498–502
(2015).
3.
Ndabashimiye,
G. et al.
Solidstate
harmonics
beyond the
atomic limit.
Nature 534,
520–523
(2016).
4. You, Y. S.,
et al.
Anisotropic
highharmonic
generation in
bulk crystals.
Nat. Phys. 13,
345–349
(2017).
5. Liu H. et
al.
Highharmonic
generation
from an
atomically
thin
semiconductor.
Nat. Phys. 13,
262–265
(2017).
6. Yoshikawa,
N., et al.
Highharmonic
generation in
graphene
enhanced by
elliptically
polarized
light
excitation.
Science, 356,
736738
(2017).
7. Kholdtsova
M. et al. in
preparation
8. Kaassamani
S. et al. in
preparation
9.
Hohenleuter,
M. et al.
Realtime
observation of
interfering
crystal
electrons in
HHG. Nature
523, 572575
(2015).
10. Langer, F.
et al.,
Lightwavedriven
quasiparticle
collisions on
a subcycle
timescale.
Nature 533,
225–229 (12
May 2016).




June 27, 2018 (3:30PM)

Dr.
Tais Gorkhover
SLAC

Xray Fourier holography
takes off

(Host:
Tom Allison)


The
advance of
Xray Free
Electron
Lasers (FELs)
with intense
and
femtosecondshort
opens the door
for
singleshot
studies of
noncrystalline
nanoparticles
with high
spatial and
temporal
resolutions.
The samples
are injected
into the FEL
focus and
elastically
scatter
photons from
the incoming
Xray
pulse.
The diffracted
photons form
an image
containing the
structural
information of
the intact
sample.
Coherent Xray
diffractive
imaging,
however,
suffers from
intrinsic loss
of phase.
Therefore
structure
recovery is
often
complicated
and not always
uniquelydefined.
Xray
holography can
help overcome
the phase
problem, but
is inherently
hard to
implement for
randomly
injected
samples. I
will introduce
inflight
holography,
which can be
used for
random
specimen and
reference
configurations.




June 29, 2018 (2:00PM)

Dr.
Simeon
Bogdanov
Purdue
University.

Quantum plasmonics with
color centers
in diamond

(Host:Hal
Metcalf)


Quantum
photonic
technologies
impose
stringent and
often
contradictory
requirements
on the design
of integrated
optical
components. In
particular,
high quality
factors
offered by
dielectric
nanostructures
impose a limit
on the
achievable
brightness of
singlephoton
sources.
Plasmonic
materials
promise to
confer novel
properties to
integrated
quantum
devices that
are not
achievable
with
dielectric
materials,
such as
ultrafast
operation,
nanoscale
footprint and
very strong
lightmatter
interaction.
We will review
our recent
experiments on
coupling color
centers in
diamond such
as
nitrogenvacancies
(NV) and
germaniumvacancies
(GeV) to
plasmonic
nanostructures.
We will
particularly
focus on the
realization of
an ultrafast
and
ultrabright
singlephoton
source and on
the study of
NV’s spin
readout in the
Purcell
regime. We
will discuss
potential
applications
of these
results for
quantum
photonics and
nanoscale
magnetometry.




July 13, 2018

Dr.
Leland
Aldridge
Yale
University.

On the Question of
Cooling
without
Spontaneous
Emission via
the
Bichromatic
Force

(Host:Hal
Metcalf)


The
bichromatic
force, a
stimulated
optical force,
has been
observed to
slow cool
atomic and
molecular
beams on which
it acts. The
exact
mechanism of
cooling and
the role that
spontaneous
emission plays
are still open
questions. I
present
semiclassical
simulations of
BCF in an
explicitly
decayfree
ensemble of
twolevel
systems. In
these
simulations,
increases in
positionmomentum
phase space
density were
observed to
occur
transiently.
This apparent
cooling is
consistent
with exchange
of entropy
between the
external and
internal
degrees of
freedom of the
system.




August 15, 2018 (4:00PM)

Prof.
JinTae Kim
Chosun
University,
South Korea

Progress on hyperfine
analysis of
deeply bound
electronic
states of the
85Rb133Cs
molecule
through
shortrange
photoassociation

(Host:Tom
Bergeman)


Various
hyperfine
structures of
deeply bound
rovibronic
levels of the
strongly
perturbed
electronic
states of
ultracold 85Rb
133Cs with
\Omega=1 through
a short range
photoassociation
have been
investigated.
These hyperfine
experimental
spectra match
well with
simulated
eigenvalues
considering the
magnetic
hyperfine terms
such as nuclear
spinelectron
orbital angular
momentum, Fermi
contact, and
dipolar electron
spinnuclear
spin
interactions.
Different
transition
amplitudes of
rotational
levels between
the electronic
states with
unresolved
hyperfine
structures and
atomic
scattering waves
make it possible
to identify
electronic
states
^3\Pi_{0^+} and
^3\Pi_{0^} with
different
symmetries. A
basis
transformation
between free
atomic
scattering
states and the
molecular
hyperfine states
of deeply bound
molecular
electronic
states
(\Omega=1) with
resolved
hyperfine
structures to
estimate
transition
amplitudes will
also be
presented. 


