26 research outputs found
Phase Space Tomography of Classical and Nonclassical Vibrational States of Atoms in an Optical Lattice
Atoms trapped in optical lattice have long been a system of interest in the
AMO community, and in recent years much study has been devoted to both short-
and long-range coherence in this system, as well as to its possible
applications to quantum information processing. Here we demonstrate for the
first time complete determination of the quantum phase space distributions for
an ensemble of atoms in such a lattice, including a negative Wigner
function for atoms in an inverted state.Comment: Submitted to Journal of Optics B: Quantum and Semiclassical Optics.
Special issue in connection with the 9th International Conference on Squeezed
States and Uncertainty Relations, to be held in Besancon, France, on 2-6 May
200
Coherent control of population transfer between vibrational states in an optical lattice via two-path quantum interference
We demonstrate coherent control of population transfer between vibrational
states in an optical lattice by using interference between a one-phonon
transition at and a two-phonon transition at . The
and transitions are driven by phase- and amplitude-modulation of the
lattice laser beams, respectively. By varying the relative phase between these
two pathways, we control the branching ratio of transitions to the first
excited state and to the higher states. Our best result shows an improvement of
the branching ratio by a factor of 3.50.7. Such quantum control techniques
may find broad application in suppressing leakage errors in a variety of
quantum information architectures.Comment: 5 pages, 4 figure
Observation of high-order quantum resonances in the kicked rotor
Quantum resonances in the kicked rotor are characterized by a dramatically
increased energy absorption rate, in stark contrast to the momentum
localization generally observed. These resonances occur when the scaled
Planck's constant hbar=(r/s)*4pi, for any integers r and s. However only the
hbar=r*2pi resonances are easily observable. We have observed high-order
quantum resonances (s>2) utilizing a sample of low temperature, non-condensed
atoms and a pulsed optical standing wave. Resonances are observed for
hbar=(r/16)*4pi r=2-6. Quantum numerical simulations suggest that our
observation of high-order resonances indicates a larger coherence length than
expected from an initially thermal atomic sample
Coherence freeze in an optical lattice investigated via pump-probe spectroscopy
Motivated by our observation of fast echo decay and a surprising coherence
freeze, we have developed a pump-probe spectroscopy technique for vibrational
states of ultracold Rb atoms in an optical lattice to gain information
about the memory dynamics of the system. We use pump-probe spectroscopy to
monitor the time-dependent changes of frequencies experienced by atoms and to
characterize the probability distribution of these frequency trajectories. We
show that the inferred distribution, unlike a naive microscopic model of the
lattice, correctly predicts the main features of the observed echo decay.Comment: 4 pages, 5 figure
Broadband electronic two-dimensional spectroscopy in the deep UV
We developed an all-reflective fully-noncollinear setup for two-dimensional electronic spectroscopy in the broadband UV (2DUV) with great phase stability (L/150) and applied it to the UV-chromophores dissolved in ethanol using 8-fs UV-pulses, generated in the 245-300 nm range. We are able to resolve 2D-spectra in the ~6000 cm-1 spectral window
Measurement and characterization of sub-5 fs broadband UV pulses in the 230-350 nm range
We report a new design of all-reflective 3rd-order frequency resolved optical gating setup (FROG) for measurement and characterization of ultrashort UV-pulses in the 230-350 nm range and tested it using 7.3 fs pulses generated in the 250-300 nm range. This setup allows also heterodyne detection which significantly increases its sensitivity
Semi-analytical Solution for Postbuckling Behavior of Highly Deformable Nanobeams
In this paper, exact analytical solutions are developed to
describe the size-dependent nonlinear bending behavior of
cantilever nano-beams subjected to an end force. Geometric
and equilibrium equations of the deformed element are used in
conjunction with a nonlocal differential constitutive relation to
obtain large deformation of the nano-beam. Here, the nanobeam is considered to be inextensible and the Euler-Bernoulli
hypotheses are adopted. Applicability and accuracy of the
present formulations are confirmed by comparing the
predicted results with those reported in the literature.
Furthermore, by using the exact solution presented in this
investigation, the deformed configurations of the nano-beams
are determined for different loading conditions. Our results
reveal that the nano-beam exhibits a softening behavior when
nonlocality is increasing
Investigating Quantum Electronic or Vibronic Coherences via Energy Migration Dynamics in Light-Harvesting Complex II
The possibility of quantum electronic coherence in photosynthetic complexes is a hotly-debated topic. Our two-dimensional spectroscopic results at physiologically-relevant temperatures attribute these commonly-seen oscillations to vibrational, instead of excitonic, origins. Expanding our laser excitation wavelength into the vibronic shoulder of the complex should provide the smoking gun for the vibrational nature of the oscillations
Dynamic Functional Connectivity in the Musical Brain
Musical training causes structural and functional changes in the brain due to its sensory-motor demands. This leads to differences in how musicians perceive and process music as compared to non-musicians, thereby providing insights into brain adaptations and plasticity. Correlational studies and network analysis investigations have indicated the presence of large-scale brain networks involved in the processing of music and have highlighted differences between musicians and non-musicians. However, studies on functional connectivity in the brain during music listening tasks have thus far focused solely on static network analysis. Dynamic Functional Connectivity (DFC) studies have lately been found useful in unearthing meaningful, time-varying functional connectivity information in both resting-state and task-based experimental settings. In this study, we examine DFC in the fMRI obtained from two groups of participants, 18 musicians and 18 non-musicians, while they listened to a musical stimulus in a naturalistic setting. We utilize spatial Group Independent Component Analysis (ICA), sliding time window correlations, and a deterministic agglomerative clustering of windowed correlation matrices to identify quasi-stable Functional Connectivity (FC) states in the two groups. To compute cluster centroids that represent FC states, we devise and present a method that primarily utilizes windowed correlation matrices occurring repeatedly over time and across participants, while excluding matrices corresponding to spontaneous fluctuations. Preliminary analysis indicate states with greater visuo-sensorimotor integration in musicians, larger presence of DMN states in non-musicians, and variability in states found in musicians due to differences in training and prior experiences.peerReviewe