430 research outputs found
Molecular Quantum Computing by an Optimal Control Algorithm for Unitary Transformations
Quantum computation is based on implementing selected unitary transformations
which represent algorithms. A generalized optimal control theory is used to
find the driving field that generates a prespecified unitary transformation.
The approach is illustrated in the implementation of one and two qubits gates
in model molecular systems.Comment: 10 pages, 2 figure
Foundations for Cooperating with Control Noise in the Manipulation of Quantum Dynamics
This paper develops the theoretical foundations for the ability of a control
field to cooperate with noise in the manipulation of quantum dynamics. The
noise enters as run-to-run variations in the control amplitudes, phases and
frequencies with the observation being an ensemble average over many runs as is
commonly done in the laboratory. Weak field perturbation theory is developed to
show that noise in the amplitude and frequency components of the control field
can enhance the process of population transfer in a multilevel ladder system.
The analytical results in this paper support the point that under suitable
conditions an optimal field can cooperate with noise to improve the control
outcome.Comment: submitted to Phys. Rev.
Analytical solution of the optimal laser control problem in two-level systems
The optimal control of two-level systems by time-dependent laser fields is
studied using a variational theory. We obtain, for the first time, general
analytical expressions for the optimal pulse shapes leading to global
maximization or minimization of different physical quantities. We present
solutions which reproduce and improve previous numerical results.Comment: 12 pages, 2 figure
Deterministic spatio-temporal control of nano-optical fields in optical antennas and nano transmission lines
We show that pulse shaping techniques can be applied to tailor the ultrafast
temporal response of the strongly confined and enhanced optical near fields in
the feed gap of resonant optical antennas (ROAs). Using finite-difference
time-domain (FDTD) simulations followed by Fourier transformation, we obtain
the impulse response of a nano structure in the frequency domain, which allows
obtaining its temporal response to any arbitrary pulse shape. We apply the
method to achieve deterministic optimal temporal field compression in ROAs with
reduced symmetry and in a two-wire transmission line connected to a symmetric
dipole antenna. The method described here will be of importance for experiments
involving coherent control of field propagation in nanophotonic structures and
of light-induced processes in nanometer scale volumes.Comment: 5 pages, 5 figure
Non-Destructive Identification of Cold and Extremely Localized Single Molecular Ions
A simple and non-destructive method for identification of a single molecular
ion sympathetically cooled by a single laser cooled atomic ion in a linear Paul
trap is demonstrated. The technique is based on a precise determination of the
molecular ion mass through a measurement of the eigenfrequency of a common
motional mode of the two ions. The demonstrated mass resolution is sufficiently
high that a particular molecular ion species can be distinguished from other
equally charged atomic or molecular ions having the same total number of
nucleons
Nine years of comparative effectiveness research education and training: initiative supported by the PhRMA Foundation
The term comparative effectiveness research (CER) took center stage with passage of the American Recovery and Reinvestment Act (2009). The companion US$1.1 billion in funding prompted the launch of initiatives to train the scientific workforce capable of conducting and using CER. Passage of the Patient Protection and Affordable Care Act (2010) focused these initiatives on patients, coining the term ‘patient-centered outcomes research’ (PCOR). Educational and training initiatives were soon launched. This report describes the initiative of the Pharmaceutical Research and Manufacturers Association of America (PhRMA) Foundation. Through provision of grant funding to six academic Centers of Excellence, to spearheading and sponsoring three national conferences, the PhRMA Foundation has made significant contributions to creation of the scientific workforce that conducts and uses CER/PCOR
Coherent control for the spherical symmetric box potential in short and intensive XUV laser fields
Coherent control calculations are presented for a spherically symmetric box
potential for non-resonant two photon transition probabilities. With the help
of a genetic algorithm (GA) the population of the excited states are maximized
and minimized. The external driving field is a superposition of three intensive
extreme ultraviolet (XUV) linearly polarized laser pulses with different
frequencies in the femtosecond duration range. We solved the quantum mechanical
problem within the dipole approximation. Our investigation clearly shows that
the dynamics of the electron current has a strong correlation with the
optimized and neutralizing pulse shape.Comment: 11 Pages 3 Figure
Electronic Coherence Dephasing in Excitonic Molecular Complexes: Role of Markov and Secular Approximations
We compare four different types of equations of motion for reduced density
matrix of a system of molecular excitons interacting with thermodynamic bath.
All four equations are of second order in the linear system-bath interaction
Hamiltonian, with different approximations applied in their derivation. In
particular we compare time-nonlocal equations obtained from so-called
Nakajima-Zwanzig identity and the time-local equations resulting from the
partial ordering prescription of the cummulant expansion. In each of these
equations we alternatively apply secular approximation to decouple population
and coherence dynamics from each other. We focus on the dynamics of intraband
electronic coherences of the excitonic system which can be traced by coherent
two-dimensional spectroscopy. We discuss the applicability of the four
relaxation theories to simulations of population and coherence dynamics, and
identify features of the two-dimensional coherent spectrum that allow us to
distinguish time-nonlocal effects.Comment: 14 pages, 8 figure
All-optical retrieval of the global phase for two-dimensional Fourier-transform spectroscopy
A combination of spatial interference patterns and spectral interferometry
are used to find the global phase for non-collinear two-dimensional
Fourier-transform (2DFT) spectra. Results are compared with those using the
spectrally resolved transient absorption (STRA) method to find the global phase
when excitation is with co-linear polarization. Additionally cross-linear
polarized 2DFT spectra are correctly phased using the all-optical technique,
where the SRTA is not applicable.Comment: 6 pages, 7 figures, journal publicatio
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