91 research outputs found
Decoherence and Spin Echo in Biological Systems
The spin echo approach is extended to include bio-complexes for which the
interaction with dynamical noise is strong. Significant restoration of the free
induction decay signal due to homogeneous (decoherence) and inhomogeneous
(dephasing) broadening is demonstrated analytically and numerically, for both
an individual dimer of interacting chlorophylls and for an ensemble of dimers.
This approach is based on an exact and closed system of ordinary differential
equations that can be easily solved for a wide range of parameters that are
relevant for bio-applications.Comment: 5 pages, 5 figure
Single-Spin Microscope with Sub-Nanoscale Resolution Based on Optically Detected Magnetic Resonance
We summarize our new scanning magnetic 3-D imaging system. This scanning
system uses optically detected magnetic resonance in a single nitrogen vacancy
center in a diamond nanocrystal. The theoretical analysis and the first
experimental demonstrations have proved that this method has single spin
sensitivity and a sub-nanoscale spatial resolution at room temperature.Comment: 4 pages, 2 figure
Stability of the Ground State of a Harmonic Oscillator in a Monochromatic Wave
Classical and quantum dynamics of a harmonic oscillator in a monochromatic
wave is studied in the exact resonance and near resonance cases. This model
describes, in particular, a dynamics of a cold ion trapped in a linear ion trap
and interacting with two lasers fields with close frequencies. Analytically and
numerically a stability of the ``classical ground state'' (CGS) -- the vicinity
of the point () -- is analyzed. In the quantum case, the method for
studying a stability of the quantum ground state (QGS) is suggested, based on
the quasienergy representation. The dynamics depends on four parameters: the
detuning from the resonance, , where and
are, respectively, the wave and the oscillator's frequencies; the
positive integer (resonance) number, ; the dimensionless Planck constant,
, and the dimensionless wave amplitude, . For , the CGS
and the QGS are unstable for resonance numbers . For small
, the QGS becomes more stable with increasing and decreasing
. When increases, the influence of chaos on the stability of the
QGS is analyzed for different parameters of the model, , and
.Comment: RevTeX, 38 pages, 24 figure
Non-Hermitian Adiabatic Quantum Optimization
We propose a novel non-Hermitian adiabatic quantum optimization algorithm.
One of the new ideas is to use a non-Hermitian auxiliary "initial'' Hamiltonian
that provides an effective level repulsion for the main Hamiltonian. This
effect enables us to develop an adiabatic theory which determines ground state
much more efficiently than Hermitian methods.Comment: Minor corrections, 1 figure, 9 page
Improving the sensitivity of FM spectroscopy using nano-mechanical cantilevers
It is suggested that nano-mechanical cantilevers can be employed as high-Q
filters to circumvent laser noise limitations on the sensitivity of frequency
modulation spectroscopy. In this approach a cantilever is actuated by the
radiation pressure of the amplitude modulated light that emerges from an
absorber. Numerical estimates indicate that laser intensity noise will not
prevent a cantilever from operating in the thermal noise limit, where the high
Q's of cantilevers are most advantageous.Comment: 5 pages, 1 figur
Quantum Dynamical Effects as a Singular Perturbation for Observables in Open Quasi-Classical Nonlinear Mesoscopic Systems
We review our results on a mathematical dynamical theory for observables for
open many-body quantum nonlinear bosonic systems for a very general class of
Hamiltonians. We show that non-quadratic (nonlinear) terms in a Hamiltonian
provide a singular "quantum" perturbation for observables in some "mesoscopic"
region of parameters. In particular, quantum effects result in secular terms in
the dynamical evolution, that grow in time. We argue that even for open quantum
nonlinear systems in the deep quasi-classical region, these quantum effects can
survive after decoherence and relaxation processes take place. We demonstrate
that these quantum effects in open quantum systems can be observed, for
example, in the frequency Fourier spectrum of the dynamical observables, or in
the corresponding spectral density of noise. Estimates are presented for
Bose-Einstein condensates, low temperature mechanical resonators, and nonlinear
optical systems prepared in large amplitude coherent states. In particular, we
show that for Bose-Einstein condensate systems the characteristic time of
deviation of quantum dynamics for observables from the corresponding classical
dynamics coincides with the characteristic time-scale of the well-known quantum
nonlinear effect of phase diffusion.Comment: changed content
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