283 research outputs found
A Method of Developing Analytical Multipartite Delocalization Measures for Mixed W-like States
We present a method of developing analytical measures of -partite
delocalization in arbitrary -body W-like states, otherwise known as mixed
states in the single excitation subspace. These measures calculate the distance
of a state to its closest reference state with entanglement. We find that
the reference state is determined by the purity of the state undergoing
measurement. Measures with up to 6-body delocalization for a 6-body system are
derived in full, while an algorithm for general -partite measures is given.Comment: 8 pages, 3 figure
Quantum-coherence and correlations in π-conjugated molecules and multichromophoric systems
AbstractChemistry is intrinsically founded on quantum mechanical principles and examples of quantum-mechanical phenomena abound on a range of energy and length scales. In this article some examples of quantum-mechanical phenomena that can be probed by optical spectroscopy are discussed. Recent experimental studies of quantumcoherence in electronic energy transfer in π-conjugated polymers are reported as examples of weak correlations. The nature of the electron-hole binding energy for excitons in organic systems is investigated as a case of intermediate correlations. Possible experimental probes of strong correlations involved in chemical reactions are critically examined in the final section of the paper
Damping and higher multipole effects in the quantum electrodynamical model for electronic energy transfer in the condensed phase
Thermal light cannot be represented as a statistical mixture of single pulses
We ask whether or not thermal light can be represented as a mixture of single
broadband coherent pulses. We find that it cannot. Such a mixture is simply not
rich enough to mimic thermal light; indeed, it cannot even reproduce the
first-order correlation function. We show that it is possible to construct a
modified mixture of single coherent pulses that does yield the correct
first-order correlation function at equal space points. However, as we then
demonstrate, such a mixture cannot reproduce the second-order correlation
function.Comment: 5 pages, 2 figures. Published versio
Anisotropic conjugated polymer chain conformation tailors the energy migration in nanofibers
Conjugated polymers are complex multi-chromophore systems, with emission
properties strongly dependent on the electronic energy transfer through active
sub-units. Although the packing of the conjugated chains in the solid state is
known to be a key factor to tailor the electronic energy transfer and the
resulting optical properties, most of the current solution-based processing
methods do not allow for effectively controlling the molecular order, thus
making the full unveiling of energy transfer mechanisms very complex. Here we
report on conjugated polymer fibers with tailored internal molecular order,
leading to a significant enhancement of the emission quantum yield. Steady
state and femtosecond time-resolved polarized spectroscopies evidence that
excitation is directed toward those chromophores oriented along the fiber axis,
on a typical timescale of picoseconds. These aligned and more extended
chromophores, resulting from the high stretching rate and electric field
applied during the fiber spinning process, lead to improved emission
properties. Conjugated polymer fibers are relevant to develop optoelectronic
plastic devices with enhanced and anisotropic properties.Comment: 43 pages, 15 figures, 1 table in Journal of the American Chemical
Society, (2016
Symmetric Rotating Wave Approximation for the Generalized Single-Mode Spin-Boson System
The single-mode spin-boson model exhibits behavior not included in the
rotating wave approximation (RWA) in the ultra and deep-strong coupling
regimes, where counter-rotating contributions become important. We introduce a
symmetric rotating wave approximation that treats rotating and counter-rotating
terms equally, preserves the invariances of the Hamiltonian with respect to its
parameters, and reproduces several qualitative features of the spin-boson
spectrum not present in the original rotating wave approximation both
off-resonance and at deep strong coupling. The symmetric rotating wave
approximation allows for the treatment of certain ultra and deep-strong
coupling regimes with similar accuracy and mathematical simplicity as does the
RWA in the weak coupling regime. Additionally, we symmetrize the generalized
form of the rotating wave approximation to obtain the same qualitative
correspondence with the addition of improved quantitative agreement with the
exact numerical results. The method is readily extended to higher accuracy if
needed. Finally, we introduce the two-photon parity operator for the two-photon
Rabi Hamiltonian and obtain its generalized symmetric rotating wave
approximation. The existence of this operator reveals a parity symmetry similar
to that in the Rabi Hamiltonian as well as another symmetry that is unique to
the two-photon case, providing insight into the mathematical structure of the
two-photon spectrum, significantly simplifying the numerics, and revealing some
interesting dynamical properties.Comment: 11 pages, 5 figure
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