160 research outputs found
Non-classical properties of quantum wave packets propagating in a Kerr-like medium
We investigate non-classical effects such as fractional revivals, squeezing
and higher-order squeezing of photon-added coherent states propagating through
a Kerr-like medium.The Wigner functions corresponding to these states at the
instants of fractional revivals are obtained, and the extent of
non-classicality quantified.Comment: 8 pages, 10 figure
Time dependent partial waves and vortex rings in the dynamics of wave packets
We have found a new class of time dependent partial waves which are solutions
of time dependent Schr\"odinger equation for three dimensional harmonic
oscillator. We also showed the decomposition of coherent states of harmonic
oscillator into these partial waves. This decomposition appears perticularly
convenient for a description of the dynamics of a wave packet representing a
particle with spin when the spin--orbit interaction is present in the
hamiltonian. An example of an evolution of a localized wave packet into a torus
and backwards, for a particular initial conditions is analysed in analytical
terms and shown with a computer graphics.Comment: 10 pages, LaTeX, 6 postscript figures, submitted to J. Phys. A: Math.
Ge
Surprises in the suddenly-expanded infinite well
I study the time-evolution of a particle prepared in the ground state of an
infinite well after the latter is suddenly expanded. It turns out that the
probability density shows up quite a surprising behaviour:
for definite times, {\it plateaux} appear for which is
constant on finite intervals for . Elements of theoretical explanation are
given by analyzing the singular component of the second derivative
. Analytical closed expressions are obtained for some
specific times, which easily allow to show that, at these times, the density
organizes itself into regular patterns provided the size of the box in large
enough; more, above some critical time-dependent size, the density patterns are
independent of the expansion parameter. It is seen how the density at these
times simply results from a construction game with definite rules acting on the
pieces of the initial density.Comment: 24 pages, 14 figure
Laser Induced Selective Alignment of Water Spin Isomers
We consider laser alignment of ortho and para spin isomers of water molecules
by using strong and short off-resonance laser pulses. A single pulse is found
to create a distinct transient alignment and antialignment of the isomeric
species. We suggest selective alignment of one isomeric species (leaving the
other species randomly aligned) by a pair of two laser pulses.Comment: 6 pages, 4 figures, 3 table
Geometric phase effects for wavepacket revivals
The study of wavepacket revivals is extended to the case of Hamiltonians
which are made time-dependent through the adiabatic cycling of some parameters.
It is shown that the quantal geometric phase (Berry's phase) causes the revived
packet to be displaced along the classical trajectory, by an amount equal to
the classical geometric phase (Hannay's angle), in one degree of freedom. A
physical example illustrating this effect in three degrees of freedom is
mentioned.Comment: Revtex, 11 pages, no figures
Superrevivals in the quantum dynamics of a particle confined in a finite square well potential
We examine the revival features in wave packet dynamics of a particle
confined in a finite square well potential. The possibility of tunneling
modifies the revival pattern as compared to an infinite square well potential.
We study the dependence of the revival times on the depth of the square well
and predict the existence of superrevivals. The nature of these superrevivals
is compared with similar features seen in the dynamics of wavepackets in an
anharmonic oscillator potential.Comment: 8 pages in Latex two-column format with 5 figures (eps). To appear in
Physical Review
Echo in Optical Lattices: Stimulated Revival of Breathing Oscillations
We analyze a stimulated revival (echo) effect for the breathing modes of the
atomic oscillations in optical lattices. The effect arises from the dephasing
due to the weak anharmonicity being partly reversed in time by means of
additional parametric excitation of the optical lattice. The shape of the echo
response is obtained by numerically simulating the equation of motion for the
atoms with subsequent averaging over the thermal initial conditions. A
qualitative analysis of the phenomenon shows that the suggested echo mechanism
combines the features of both spin and phonon echoes.Comment: 13 pages, 3 figure
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