Batsheva de Rothschild Seminar
&
ISF - Israel Science Foundation workshop on
Light-matter Interaction:
Focus on Novel Observable nonHermitian Phenomena
Kibbutz Ein-Gedi
April 21st-26th, 2013
Sponsors:
The Israel Academy of Sciences & Humanities - The Batsheva de Rothschild Fund
Israel Science Foundation
Technion institute of advanced studies in theoretical chemistry
Organizers:
Nimrod Moiseyev (Technion)
Moti Segev (Technion)
Yaron Silberberg (Weizmann)
Doron Cohen (Ben-Gurion)
Coordinators:
Gila Gutman- reservation, accommodation and transportation correspondence
Abstracts
Sunday
21/4/2103
16:15-18:30
Motivation for using non-Hermitian formalism
Michael Berry, H H Wills Physics Laboratory, University of Bristol, UK
NH: PT’s big brother
Hermitian (H) and PT symmetric hamiltonians are overlapping subsets of the class of all (mostly
nonhermitian - NH) operators governing physical evolution. Recent claims that PT is physically more
fundamental than H are critically examined. The interesting behaviour of nonhermitian PT symmetric
operators is associated with degeneracies, and is not characteristic of PT but rather is a property of the wider
class of all NH operators, understood in light and atom optics for many years.
Avraham Nitzan, Tel-Aviv University
Non-Hermitian quantum mechanics in molecular transport problems
Molecular transport problems, by definition, involve open quantum systems, where description by nonhermitian Hamiltonians evolve naturally from the need to describe such processes within a finite
computational framework. The derivation of the golden rule from steady state quantum mechanics provides
the simplest example. The use of absorbing boundary conditions in scattering computations is another
conceptually simple example that serves to illustrate the possibility to choose between phenomenological
absorbing boundary conditions and exact calculation of the system's self energy. More general situations that
lead to stochastic dynamics will be also discussed and the difference between population and phase relaxation
will be emphasized. Finally, modifications of the system Hamiltonian that reflect measurement processes will
be illustrated.
Lenz Cederbaum, Heidelberg University
ICD and Dynamic Interference in Free Electron Lasers by non-Hermitian Quantum Mechanics
Monday
22/4/2103
8:45-10:45
Non-Hermitian degeneracy (Exceptional points)
Raam Uzdin , The Hebrew University of Jerusalem
Time dependent non-unitary systems and non-Hermitian resources
After briefly exploring a few effects unique to non-Hermitian time-dependent Hamiltonians, we will show
that the energy difference of the instantaneous Hamiltonian does not completely capture the Hamiltonian
capability to change states. This is related to the fact that non-Hermitian degeneracies have another energy
scale which does not appear in the Hermitian case. We will present an alternative formalism and then quantify
the minimal resources needed for "magic" non unitary operations such as "faster than Hermitian" motion, and
perfect state discrimination of non-orthogonal states.
Eva-Maria Graefe, Imperial College
Signatures of three coalescing eigenfunctions
Parameter dependent non-Hermitian quantum systems typically not only possess eigenvalue degeneracies, but
also degeneracies of the corresponding eigenfunctions at exceptional points. Here we present a
characterisation of behaviours of symmetric Hamiltonians with three coalescing eigenfunctions, using
perturbation theory for non-Hermitian operators. Two main types of parameter perturbations need to be
distinguished, which lead to characteristic eigenvalue and eigenvector patterns under cyclic variation. A
physical system is introduced for which both behaviours might be experimentally accessible.
Uwe Guenther ,Helmholtz center Dresden
Nonlinear PT-symmetric plaquettes
Nonlinear coupled gain-loss oscillator oligomers (plaquettes) of 4-node and 5-node type in a 2D-plane are
studied. Their specific PT-symmetry properties are investigated, the occurrence of exceptional points (up to
third-order) as well as their various nonlinear dynamical regimes.
collaboration with: Kai Li, Panayotis Kevrekidis and Boris Malomed
paper: J Phys A 45 (2012) 444021
11:15-12:50
Realization of exceptional points
Achim Richter , Technische Universität Darmstadt, Germany
Exceptional Points in Microwave Billiards with and without Time Reversal Symmetry *
After a brief introduction into generic features of microwave resonators as quantum billiards and open
scattering systems it is discussed how eigenvalues, eigenfunctions and eigenvectors of a dissipative time
reversal invariant and non-invariant system, respectively, close to and at an exceptional point (EP) are
determined experimentally [1,2]. The full EP-Hamiltonian can be extracted from the measured scattering
matrix. While the EP is encircled the eigenvectors gather geometric phases and in addition amplitudes
different from unity. Finally, the presence of parity-time (PT) symmetry for the non-Hermitian two-state
Hamiltonian in the vicinity of the EP is shown.
* Work supported within the SFB634 by the Deutsche Forschungsgemeinschaft
[1] C. Dembowski, H.-D. Gräf, H.L. Harney, A. Heine, W.D. Heiss, H. Rehfeld, and A. Richter, Phys. Rev.
Lett. 86, 787 (2001)
[2] B. Dietz, H. L. Harney, O.N. Kirillov, M. Miski-Oglu, A. Richter, and Florian Schäfer,
Phys. Rev. Lett. 106, 150403 (2011)
[3] S. Bittner, B. Dietz, U. Günther, H.L. Harney, M. Miski-Oglu, A. Richter, and F. Schäfer,
Phys. Rev. Lett. 108, 024101 (2012)
Demetrios Christodoulidies ,University of Central Florida
Non-Hermitian and PT-symmetric Optical Systems
17:00-18:20
Realization of exceptional points
Holger Cartarius, Stuttgart University
Exceptional points and PT symmetry in Bose-Einstein condensates
Work done together with: D. Dast, R. Eichler, D. Haag, W. D. Heiss, M. Kreibich, J. Main, G. Wunner
In Bose-Einstein condensates exceptional points appear in various cases. They are, e.g. connected with
stability thresholds of the s-wave scattering length below which a collapse of the condensate sets in. Recently
it has been shown that exceptional points also appear for Bose-Einstein condensates in an external PTsymmetric potential. To study the effects of PT symmetry in Bose-Einstein condensates we follow a proposal
by Klaiman et al. of a Bose-Einstein condensate in a double-well setup. Particles removed from one well and
coherently injected into the other can be described by an imaginary gain-loss parameter rendering the external
potential complex PT symmetric. It has been shown that PT-symmetric wave functions exist and thus the PT
symmetry is not destroyed by the nonlinearity of the Gross-Pitaevskii equation. In agreement with their
counterparts in linear quantum mechanics they merge in a second-order exceptional point (EP2). A crucial
difference is the bifurcation of PT-broken states from one of the PT-symmetric eigenstates for gain-loss
parameters far below the EP2. The new bifurcation point turns out to be a third-order exceptional point (EP3).
We investigate the exceptional points appearing in Bose-Einstein condensates and describe their physical
consequences, i.e. PT symmetry breaking and an important influence on the dynamics of the condensate's
wave function. Suggestions for experimental realizations are presented.
Stefan Rotter ,Vienna University, Institute for Theoretical Physics
Pump-Controlled Exceptional Points and Random Laser Emission
I will show that the above-threshold behavior of a laser can be strongly affected by exceptional points which
are induced by pumping the laser non-uniformly [1]. In the vicinity of these points the laser may turn off even
when the overall pump power deposited in the system is increased. In extension of this work, we could
recently demonstrate that suitably optimized pump profiles allow us to control the angular emission pattern of
a random laser such as to achieve highly directional emission or any other desired pattern [2].
[1] Liertzer, Ge, Cerjan, Stone, Tureci, and Rotter, Phys. Rev. Lett. 108, 173901 (2012).
[2] Hisch, Liertzer, Pogany, Mintert, Rotter (to be submitted)
19:30-20:50
Dynamical control by external fields
Daniel Strasser ,The Hebrew University of Jerusalem
Multiple detachment of SF6- molecular ions by shaped intense laser pulses
Since the development of intense femtosecond laser technologies, significant effort was made towards
understanding of the basic interaction of such intense laser pulses with matter. In particular, the study of
multiple ionization of neutral atoms and high order harmonic generation led to the development of a
simplified semi-classical understanding of these highly non-perturbative mechanisms, commonly known as
the “three step model”. Furthermore, this basic understanding enabled the technological breakthroughs that
allow generating record breaking attosecond pulses, and to perform time resolved experiments on the
attoscond timescale. In my presentation I will discuss our recent experimental work, using fast beam
photofragment spectroscopy to explore the interaction of shaped intense laser pulses with the SF6- negatively
charged molecular ion.
Peter Schmelcher, Centre for Optical Quantum Technologies, Luruper Chaussee 149, 22761 Hamburg, and
Centre for Ultrafast Imaging, Luruper Chaussee 149, 22761 Hamburg, Germany
Ultralong-range molecules in external fields
We explore the possibility to shape and control the properties and behaviour of ultralong-range molecules
with external electric or electric and magnetic fields. The interaction of the neutral ground state atom with the
highly excited Rydberg electron is described via a Fermi-pseudopotential approximation, including s-wave
and p-wave contributions. Using a non-relativistic pseudopotential for the binding of the electron to the ionic
core, which properly describes the quantum defects of the scattering of the electron off the core, a basis is
obtained within which the combined molecular Rydberg-perturber Hamiltonian in the presence of the external
fields is diagonalized. As a result the adiabatic Born-Oppenheimer potential energy surfaces, which determine
the molecular configurations and dynamics, are obtained. Varying the electric field strength the oscillating
energy surfaces possessing many well-separated and pronounced local potential wells, can be shifted with
respect to each other. In particular, it is possible to avoid the intersection of p-wave dominated states with swave dominated ones, which is ubiquitous in the absence of fields, close to the equilibrium vibrational
ground states. This leads to an enhanced stability of the ultralong-range molecular states. The corresponding
vibrational dynamics is analyzed. Finally, we present a preparation scheme for high-l molecular electronic
states via a two photon excitation process.
In a second step, we show the existence of ultra-long-range giant dipole molecules in crossed electric and
magnetic fields formed by a neutral alkali ground state atom that is bound to the decentered electronic wave
function of a giant dipole atom. Giant dipole atoms in crossed fields are of peculiar shape: their highly excited
electronic wave function is due to the combined. action of electric and magnetic fields strongly decentered and
localized completely off the ionic core. The neutral ground state atom is bound to this isolated Rydberg cloud
and, opposite to the standard e.g. trilobite molecules, does not possess any radiative decay channel. The
resulting molecules are truly giant with internuclear distances up to several $\mu m$. We analyze the resulting
three-dimensional adiabatic potential energy surfaces depending on the degree of electronic excitation:
Disturbed torus-like multi-well structure are observed for excited states which can, due to avoided crossings,
show an increasing topological complexity. Binding energies and the vibrational motion in the energetically
lowest surfaces are analyzed by means of perturbation theory and exact diagonalization techniques.
Finally, we demonstrate the existence of intersection manifolds of excited electronic states that potentially
lead to an 'ultrafast' vibrational decay of the ground state atom dynamics.
Tuesday
23/4/2103
8:30-10:45
Non Hermitian optics
A. Douglas Stone , Dept. of Applied Physics – Yale University
For Light-Matter Interactions: Focus on Novel Observable Non-Hermitian Phenomena
Lasers and Anti-lasers: Non-Hermitian to the Max
Amplifiers and attenuators in optics are prototype non-hermitian systems described by non-energy conserving
electromagnetic wave equations. A laser at threshold is the extreme case where the amplification goes to
infinity, the system starts to self-oscillate, and the non-linearity of the gain medium is required to stabilize the
steady-state. Recently we have developed, and will review here, Steady-state Ab initio Laser Theory (SALT),
which calculates directly all of the lasing properties in the non-linear multimode steady-state, treating the nonhermiticity exactly, for complex laser cavities and pumping schemes. SALT emphasizes that a laser is a
certain kind of non-hermitian scattering system, and the laser threshold corresponds to a pole of the S-matrix
on the real axis. Applying time-reversal to the threshold laser equation maps it to an S-matrix with a zero on
the real axis, describing a coherent perfect absorber (CPA), a lossy cavity which perfectly absorbs the timereverse of the lasing mode in steady state. Finally, a cavity with parity-time symmetry, and sufficient
gain/loss, can function simultaneously as a CPA and laser, with a pole and zero coincident on the real axis.
More generally, cavities with non-uniform gain or loss are described by non-hermitian equations, which have
exceptional points that determine the motion of poles and zeros, and lead to novel, observable optical
phenomena involving lasing and perfect absorption.
Tsampikos Kottos, Wesleyan University
Taming wave propagation via Parity-Time symmetry
Using integrated photonics and electronics as a play-fields we show how one can construct new circuitry
designs that allow for asymmetric wave transport by making use of novel properties emerging from PTsymmetries.
Jan Wiersig , University of Magdeburg
Non-Hermitian phenomena in passive optical microcavities
Optical microcavities are inherently open systems due to leakage of light through the cavity’s boundary.
In the past such systems have been successfully described by non-Hermitian effective Hamiltonians .
In this talk, two interesting phenomena based on the non-Herminicity are discussed. The first one can be
observed when two microdisk cavities are coupled to form a photonic molecule. Experimental and numerical
data is presented which demonstrates that near an avoided resonance crossing the quality factor of one mode
can significantly increase above the non-resonant values of both modes.
The second phenomenon shows up in deformed or otherwise slightly perturbed microdisks which do not
possess any mirror symmetry. A theoretical analysis and numerical simulations show that the long-lived
modes in such cavities come in highly non-orthogonal pairs of modes. Within each pair a propagation
direction (clockwise or counterclockwise) dominates. The physical origin of this ‘chirality’ is asymmetric
backscattering of clockwise and counterclockwise propagating waves. This phenomenon is linked to the
presence of non-Hermitian degeneracies. Finally, such asymmetric cavities are coupled to form optical
waveguides with unusual dispersion properties.
11:15-12:35
Non Hermitian optics (cont.)
Hui Cao ,Yale University
Time-Reversed Lasing and Interferometric Control of Absorption
Optical absorption is usually considered deleterious, something to avoid if at all possible. We show that a
perfect absorption not only leads to complete coupling of light into plasmonic nanostructures, but also
produces subwavelength focusing by suppressing diffraction. Based on the time-reversed process of lasing
action, we propose and demonstrate an interferometric control of coherent light absorption.
Mikael Rechtsman,Technion
Photonic Topological Insulators
16:00-18:00
Non Hermitian optics (cont.)
Barbara Dietz ,TU Darmstadt
Bound States in Bent Waveguides: Analytical and Experimental Approach
Bound states in quantum wires or open electromagnetic waveguides with curves, bends or bulges have
received much interest since their existence is a purely wave-dynamical phenomenon which has no classical
analogue. We present microwave experiments with sharply bent waveguides may have arbitrarily many bound
states depending on the angle of the bend: new bound states emerge at certain critical angles. Several
waveguides with bending angles close to these critical ones were investigated. In particular, we studied the
features of the transition from bound to unbound states caused by the variation of the bending angle.
Furthermore, the effect of the finite length of the waveguide was investigated. With the help of an effective
potential approach we computed the bound states and the critical bending angles [1]. The analytical results
were confirmed by numerical calculations as well as experimental measurements of the spectra and electric
field intensity distributions of electromagnetic waveguides.
The work was supported by the DFG within SFB 634.
[1] S. Bittner, B. Dietz, M. Miski-Oglu, A. Richter, C. Ripp, E. Sadurní, and W. P. Schleich, Phys. Rev. E, in
press
Konstantinos G. Makris, Department of Electrical Engineering, Princeton University
Wave propagation in PT-symmetric optical potentials
The first experimental observation of parity-time (PT) symmetry breaking in any physical system was recently
demonstrated. In this context of PT-symmetric Optics, we examine the characteristics of multimode PTsymmetric potentials. The existence of many spatial supermodes leads to multiple spectral phase transitions,
and vortex optical currents in the transverse poynting vector. Resent results regarding diffraction dynamics
close to the exceptional points of PT lattices, negative refraction effects, as well as, scattering in PT optical
cavities will also be presented.
Li Ge, Princeton University
Antisymmetric PT-photonic structures with balanced positive and negative index materials
In this talk I will discuss a new class of synthetic optical materials in which the refractive index satisfies
n(-x)=-n*(x). We term such systems antisymmetric parity-time (APT) structures. Unlike PT- symmetric
systems which require balanced gain and loss, i.e. n(-x)=n*(x), APT systems consist of balanced positive and
negative index materials. Despite the seemingly PT-symmetric optical potential V(x)=n(x)^2\omega^2/c^2,
APT systems are not invariant under combined PT operations due to the discontinuity of the spatial derivative
of the wavefunction. We show that APT systems can display intriguing properties such as spontaneous phase
transition of the scattering matrix, bidirectional invisibility, and a continuous lasing spectrum.
Wednesday 24/4/2103
8:30-10:45
Strong Laser Physics
Nirit Dudovich , Weizmann Institute of Science
When does an electron exit a tunneling barrier?
Tunneling of a particle through a barrier is one of the most fundamental and ubiquitous quantum processes.
When induced by an intense laser field, electron tunneling from atoms and molecules initiates a broad range
of processes that evolve on the attosecond time-scale1,2. As the liberated electron is driven by the laser field, it
can return to the parent ion and recombine to the initial (ground) state, releasing its energy in an attosecond
burst of light. This process, known as High Harmonic Generation (HHG) provides an excellent spatiotemporal filter for the electron motion. The angstrom-scale spatial resolution is determined by the size of the
atomic ground state to which the electron must recombine. The attosecond temporal resolution arises from the
mapping between the photon energy (harmonic order) and the return time of the corresponding electron
trajectory.
In the talk I will describe how by adding a weak perturbation allows us to probe both the ionization times and
the recollision times in simple atomic systems3. Our results which deviate from the simple classical model are
in good agreement with the quantum path analysis. Next, I will describe how a similar approach enables us to
measure the instantaneous tunneling probability within the optical cycle. Finally, I will discuss the probing of
molecular systems where more than one ionization channel participates the process4,5. As an example I will
show how multiple channel ionization is probed in aligned CO2 molecules. I will describe how the high
sensitivity of the measurement allows us to probe subtle differences between two ionization channels 3. This
experiment provides an additional, important step towards the ability to resolve multielectron phenomena -- a
long term goal of attosecond studies.
1.
2.
3.
4.
Keldysh, L. V. Ionization in the field of a strong electromagnetic wave. Sov. Phys. JETP 20, 1307–1314 (1965)
P. B. Corkum and F. Krausz, Attosecond science, Nature Physics 3, 381 (2007).
D. Shafir et al., “Resolving the time when an electron exits a tunneling barrier, Nature 485, 343 (2012).
B. K. McFarland, J. P. Farrell, P. H. Bucksbaum and M. Gühr, High Harmonic Generation from Multiple Orbitals in
N2, Science 322, 1232-1235 (2008).
5. Olga Smirnova et al., High harmonic interferometry of multi-electron dynamics in molecules. Nature 460, 972-977
(2009).
Oren Cohen, Technion
Generation of high-order harmonics with controlled polarization: from linear through
elliptic to circular polarization
We demonstrate, theoretically and experimentally, that the polarization of high-order harmonics driven by
counter-rotating elliptically-polarized bichromatic pulse are fully controllable: from linear through elliptic to
circular polarization. We also observe new selection rules.
Barak Dayan , Weizmann Institute of Science
11:15-13:15
Strong Laser Physics (cont.)
Avner Fleischer , Technion
Where does a photo-electron appear in the continuum ?
In tunnel ionization of atoms by strong laser fields it is known that the electron appears in the continuum at
the outer turning point of the tunnel barrier. It is reasonable to assume that a reduction in the number of
photons which participate in the ionization will shift the appearance location of the ionized electron towards
the origin. Here we verify this assumption and suggest a measurement that could reveal where an electron
appears in the continuum. As a result of interferences between the electronic wavelets which are released into
the continuum, the photoionization rate of atoms is modified by the presence of a weak dc field in an
oscillatory manner. By measuring the phase of the oscillations, the average appearance position of the photoionized electron in the continuum can be retrieved
Vitali Averbukh, Imperial College
New ideas for attosecond time-resolved spectroscopies of electron hole dynamics
In this talk I will present two of our recent ideas for new attosecond time-resolved measurements of electron
hole dynamics:
* Single-photon laser enabled Auger spectroscopy
* High-harmonic generation spectroscopy of Auger-type transitions
Unlike attosecond streaking, the proposed spectroscopies do not rely on photo- or secondary electron emission
and are applicable to ultrafast electronic processes involving bound-bound transitions, such as electron
correlation-driven charge migration. We simulate the new attosecond spectroscopies using both model and
ab initio methods. Specific applications include hole migration in glycine, atomic Auger and Coster-Kronig
decays as well as quasi-exponential dynamics of molecular orbital breakdown in trans-butadiene.
Alexandra Landsman ,Princeton
16:00-18:00
Strong Laser Physics (cont.)
Zohar Amitay ,Technion
Coherence Generation and Control in the Free-to-Bound Binary Reaction of Hot Atom-Atom
Photoassociation
A long-standing yet unrealized dream since the early days of coherent control is coherent control of general
photo-induced bimolecular chemical reactions. Realizing this dream will create a new type of photochemistry
that coherently photo-induces new chemical reactions and selectively controls the yields and branching ratios
in existing and new photo-reactions.
As significant steps along this direction, we present here experimental and theoretical control results for the
free-to-bound binary reaction of multiphoton femtosecond photoassociation of thermally hot atoms (hot fsPA). In this process, a (shaped) femtosecond pulse induces a chemical bond formation between the colliding
hot atoms via a free-to-bound multiphoton transition, and generates a bound excited diatomic molecule.
Coherent control of hot fs-PA is, on one hand, an important model for femtosecond control of simple binary
photo-reactions and, on the other hand, an essential prerequisite for femtosecond control of more complicated
binary reactions using extended multi-pulse schemes that employ the fs-PA as a first step.
Our results are presented for fs-PA of hot magnesium atoms into bound magnesium dimer molecules, i.e.,
Mg+MgMg2*, with the thermal ensemble of Mg atoms held at a temperature of 1000 K. The process is
induced by intense (shaped) femtosecond pulses (70-fs transform-limited duration; 840-nm central
wavelength) in the strong-field regime.
The experimental results, accompanied by a comprehensive theoretical model and calculations, include the
first-time demonstration and observation of the following: (i) The formation of diatomic molecules with
vibrational and rotational coherence in the process of photoassociation. This corresponds to the generation of
the photo-associated molecules in a coherent superposition of rovibrational states. Generating vibrational
coherence is essential in order to utilize hot fs-PA as a basis for chemical reaction coherent control, since the
vibrational degrees of freedom determine the fate of bond making and breaking. (ii) Inducing the fs-PA
process via multiphoton excitations. This significantly extends the variety of molecular species and reactions
that are candidates for chemical reaction control. (iii) Femtosecond coherent control of the photoassociation
process. In the first part, the multiphoton photoassociation probability (yield) is coherently controlled by
linearly-chirped shaped pulses, and a very strong enhancement is achieved with a proper positive chirp. Then,
PA yield control that involves also intermediate field-free coherent rovibrational dynamics is demonstrated
using shaped pulses with triangular spectral phase patterns (in the shape of V or).
Pananghat Balanarayan, Technion
High-frequency strong laser physics and chemistry: Linear Stark effect for atoms and strong chemical
bond in rare-gas dimer
Current trends in laser technology have reached the regime of studying atoms stabilized against ionization,
going beyond the perturbation theory.
In this work, properties of a laser-dressed sulfur atom are examined in this stabilization regime. The electronic
structure of a sulfur atom changes dramatically as it interacts with strong high frequency laser fields.
Degenerate molecular-like states are obtained for the ground state triplet of the laser-dressed sulfur atom for
high-frequency and moderate intensity laser parameters. The degenerate ground state is obtained for a laser
intensity which is smaller by more than one order of magnitude than the intensity required for hydrogen
atoms due to many electron screening effects. An infinitesimally weak static field mixes these degenerate
states to give rise to asymmetric states with large permanent dipole moments.
Hence, a strong linear Stark effect rather than the usual quadratic one is obtained.
The van der Waals complex of the helium dimer has a very small binding energy and a bond distance of 52
Angstrom. The free field potential has been found to support a single vibrational bound state, that has been
detected in diffraction grating experiments. With a high intensity and high frequency laser, stable helium
dimer molecules with a binding energy of 12.5 eV, which are much stronger than conventional molecular
hydrogen bonds, are produced. The bond distance of the dimer produced by the strong laser field is equal to
2.01 Angstroms. All these effects are seen in the high frequency high intensity regime of the laser within the
zeroth order Kramer-Henneberger states of the laser dressed atoms and molecules.
Ido Gilary, Technion
Time asymmetric state exchange mechanism
19:30:21:20
Dynamical control in optical lattices
Immanuel Bloch ,Max Planck Institute for quantum optics
From Rydberg Crystals to Bound Magnons - Probing the Non-Equilibrium Dynamics of Ultracold
Atoms in Optical Lattices
Ultracold atoms in optical lattice form an ideal testbed to probe the non-equilibrium dynamics of quantum
many-body systems. In particular recent high-resolution imaging and control techniques allow to probe
dynamically evolving non-local correlations in an unprecedented way. As an example, I will focus in my talk
on the dynamical excitation of spatially ordered Rydberg structures that are formed through laser exctiation
from ground state Mott insulating atoms. In addition, I will show how single-spin and spin-pair impuritites
can be used to directly reveal polaron dynamics in a strongy interacting superfluid or the bound state of two
magnons in a quantum ferromagnet. New atom interferometric schemes to directly probe the Green's function
of a many-body system through the impurity dynamics will be discussed.
Hossein Sadeghpour, ITAMP, Harvard
Anomalous heating noise in ion traps: what is it and can it be mitigated?
Thursday
25/4/2103
8:30-10:30
Dynamical control by external fields (cont.)
Uri Peskin, Technion
Coherently controlled conductance in single molecule junctions
Molecular junctions, in which a single molecule is coupled to two macroscopic electrodes, provide a unique
scenario to study charge and energy transport through molecular systems in both equilibrium and nonequilibrium conditions. In the talk, we shall discuss new possibilities for utilizing the unique transport
properties of molecular junctions for electronic and energy-conversion devices. Having a molecule as the
‘bottle neck’, the characteristic length and time scales imply that coherent (phase conserving) transport
dominates the transport properties, and suggests that these systems can be coherently controlled. In particular
we shall focus on a molecular coherent ‘electron pump’ which converts radiation field into directed electronic
current. The principle of operation will be analyzed theoretically under conditions ranging from a sudden
pulse to cw excitation, and the principles of coherent control by the radiation field in the presence of decoherence by the leads will be outlined. Finally, we shall propose an experimental design for measuring field
induced dynamics in molecular junctions (with sub pico-second resolution) using steady state current
measurements
Johannes Feist , University Autónoma de Madrid, Spain
Condensation of ultralight particles: towards a quantum degenerate gas of plexcitons
Condensation of bosons, where a single quantum state is macroscopically populated, is a fascinating
phenomenon spanning diverse areas of physics. It lies at the heart of superfluidity and superconductivity, as
well as the Bose-Einstein condensation of ultracold dilute atoms, which was achieved close to twenty years
ago. An important goal is to find systems in which condensation takes place at higher temperatures, even at or
above room temperature. Bosonic quasi-particles in solids are excellent candidates due to their light effective
masses, and signatures of condensation have been observed for semiconductor excitons and exciton-polaritons
at temperatures of a few K, as well as for magnons and cavity photons at room temperature.
I will present and discuss experimental signatures of quantum condensation of plexcitons at room
temperature. Plexcitons are bosonic quasiparticles formed by strong coupling between organic molecule
excitons and surface plasmon polaritons (quasi-bound modes confined on a subwavelength scale at metaldielectric interfaces). Our system consists of a periodic array of metallic nanorods covered by a polymer layer
doped with an organic dye. By increasing the plexciton density through optical pumping, we observe
signatures of thermalization and condensation, such as the emergence of Bogoliubov-Goldstone modes,
despite the nonequilibrium character of this driven and dissipative system.
Ed Narevicius, Weizmann Institute of Science
Chemistry of the Quantum Kind
There has been a long-standing quest to observe chemical reactions at low temperatures where reaction rates
and pathways are governed by quantum mechanical effects. So far this field of Quantum Chemistry has been
dominated by theory. The difficulty has been to realize in the laboratory low enough collisional velocities
between neutral reactants, so that the quantum wave nature could be observed. We will discuss our merged
neutral supersonic beams method that enabled the observation of clear quantum effects in low temperature
reactions. We observed orbiting resonances in the Penning ionization reaction of argon and molecular
hydrogen with metastable helium leading to a sharp increase in the absolute reaction rate in the energy range
corresponding to a few degrees kelvin down to 10 mK. Our method is widely applicable to many canonical
chemical reactions, and will enable experimental studies of Quantum Chemistry.
11:00-13:15
Quantum chaos and complexity in decay, emission, and
relaxation processes
Patrick Sebbah ,Langevin Institute
Emission control of a random laser : Turning a random laser into a tunable singlemode laser by active
pump shaping
We present an innovative mirrorless optofluidic random laser where the optical cavity has been replaced by a
random scattering structure. We achieve emission control at any desired wavelength by iteratively shaping the
optical pump profile. This method is proposed to explore pump-induced exceptional points in lasers.
Ulrich Kuhl , Marburg University
Experimental realization of Resonant assisted tunneling in open systems
In quantum mechanical billards with a mixed phase space direct tunneling from regular islands to the chaotic
sea is well known [1],[2]. For quantum mechanical maps it was shown, that the tunneling rates are determined
by another effect the so-called resonance-assisted tunneling [3], which is an indirect process whire another
stable island. To verify this theory a Cosin-shaped microwave resonator with absorbers was designed, where
the absorbers are located in such a way that the chaotic sea is replaced by the continuum. The experimental
results are in good agreement with the theoretical predictions
Ofir Alon ,Haifa University
Many body decay by tunneling and wave chaos in BEC
17:00-18:20
Novel phenomena in control of light matter interactions
David Tannor, Weizmann Institute of Science
Phase Space Approach to Quantum Mechanical Calculations for Large Systems: Application to
Attosecond Electron Dynamics
We present a method for solving both the time-independent and time-dependent Schrödinger equations based
on the von Neumann (vN) lattice of phase space Gaussians. By incorporating periodic boundary conditions
into the vN lattice we solve a longstanding problem of convergence of the vN method. This opens the door to
tailoring quantum calculations to the underlying classical phase space structure while retaining the accuracy of
the Fourier grid basis. In the classical limit the method reaches the remarkable efficiency of 1 basis function
per 1 eigenstate. The method can be combined with a wavelet-like scaling of the basis functions, which is
particularly useful for Coulombic potentials. We illustrate the method by calculating the vibrational dynamics
of polyatomic systems as well as simulating attosecond electron dynamics in the presence of combined strong
XUV and NIR laser fields .
.1A. Shimshovitz and D. J. Tannor, Phase Space Approach to Solving the Time-independent Schrödinger
Equation, Phys. Rev. Lett. 109, 070402 (2012.)
.2N. Takemoto, A. Shimshovitz and D. J. Tannor, Phase Space Approach to Solving the Time-dependent
Schrödinger Equation: Application to the Simulation and Control of Attosecond Electron Dynamics in the
Presence of a Strong Laser Field, J. Chem. Phys. 137, 011102 (2012) (Communication.)
3. A. Shimshovitz and D. J. Tannor, Phase Space Wavelets for Solving Coulomb Problems, J. Chem. Phys.
137, 101103 (2012) (Communication).
Sandy Ruhman, The Hebrew University of Jerusalem
Time asymmetric dynamics in biological systems
Download

Cover page and abstracts of talks

get an essay or any other
homework writing help
for a fair price!
check it here!