32 research outputs found
Light trapping in high-density ultracold atomic gases for quantum memory applications
High-density and ultracold atomic gases have emerged as promising media for
storage of individual photons for quantum memory applications. In this paper we
provide an overview of our theoretical and experimental efforts in this
direction, with particular attention paid to manipulation of light storage (a)
through complex recurrent optical scattering processes in very high density
gases (b) by an external control field in a characteristic electromagnetically
induced transparency configuration.Comment: Submitted to Journal of Modern Optics, Special 2010 PQE Issu
AdS/CFT correspondence via R-current correlation functions revisited
Motivated by realizing open/closed string duality in the work by Gopakumar
[Phys. Rev. D70:025009,2004], we study two and three-point correlation
functions of R-current vector fields in N=4 super Yang-Mills theory. These
correlation functions in free field limit can be derived from the worldline
formalism and written as heat kernel integrals in the position space. We show
that reparametrizing these integrals converts them to the expected AdS
supergravity results which are known in terms of bulk to boundary propagator.
We expect that this reparametrization corresponds to transforming open string
moduli parameterization to the closed string ones.Comment: 23 pages, v2: calculations clarified, references added, v3: sections
re-arranged with more explanations, 4 figures and an appendix adde
Polarization of high-energy electrons traversing a laser beam
When polarized electrons traverse a region where the laser light is focused
their polarization varies even if their energy and direction of motion are not
changed. This effect is due to interference of the incoming electron wave and
an electron wave scattered at zero angle. Equations are obtained which
determine the variation of the electron density matrix, and their solutions are
given. The change in the electron polarization depends not only on the Compton
cross section but on the real part of the forward Compton amplitude as well. It
should be taken into account, for example, in simulations of the
conversion for future colliders.Comment: 11 pages, LaTeX , 2 postscript figures include
Gauge Dependence of Four-Fermion QED Green Function and a Breakdown of Gauge Invariance in Atom-Like Bound State Calculations
We derive a relation between four-fermion QED Green functions of different
covariant gauges which defines the gauge dependence completely. We use the
derived gauge dependence to check the gauge invariance of atom-like bound state
calculations. We find that the existing QED procedure does not provide gauge
invariant binding energies. A way to a corrected gauge invariant procedure is
pointed out.Comment: 11 pages, LaTex, no figures, to appear in Nucl. Phys.
Variation in polarization of high-energy -quanta traversing a bunch of polarized laser photons
The elastic light-light scattering below the threshold of the pair
production leads to a variation in polarization of hard -quanta
traversing without loss a region where the laser light is focused. Equations
are obtained which determine the variation of Stokes parameters of
-quanta in this case, and their solutions are given. It is pointed out
that this effect can be observed in the experiment E-144 at SLAC. It should be
taken into account (and, perhaps, it can be used) in experiments at future
colliders.Comment: 8 pages, LaTeX, 2 PS figure
Photon Splitting in a Very Strong Magnetic Field
Photon splitting in a very strong magnetic field is analyzed for energy
. The amplitude obtained on the base of operator-diagram technique
is used. It is shown that in a magnetic field much higher than critical one the
splitting amplitude is independent on the field. Our calculation is in a good
agreement with previous results of Adler and in a strong contradiction with
recent paper of Mentzel et al.Comment: 5 pages,Revtex , 4 figure
Hard Constituent Quarks and Electroweak Properties of Pseudoscalar Mesons
The high momentum components generated in the wave function of pseudoscalar
mes* by the one-gluon-exchange interaction are investigated within a
relativistic constituent quark model. Adopting the light-cone formalism, the
sensitivity of the weak decay constant and the charge form factor to hard
constituent quarks is illustrated.Comment: 11 pages and 5 figs. (to be requested), LaTeX, INFN-ISS 94/3. To
appear in Physics Lett.
Relativistic semiclassical approach in strong-field nonlinear photoionization
Nonlinear relativistic ionization phenomena induced by a strong laser
radiation with elliptically polarization are considered. The starting point is
the classical relativistic action for a free electron moving in the
electromagnetic field created by a strong laser beam. The application of the
relativistic action to the classical barrier-suppression ionization is briefly
discussed. Further the relativistic version of the Landau-Dykhne formula is
employed to consider the semiclassical sub-barrier ionization. Simple
analytical expressions have been found for: (i) the rates of the strong-field
nonlinear ionization including relativistic initial and final state effects;
(ii) the most probable value of the components of the photoelectron final state
momentum; (iii) the most probable direction of photoelectron emission and (iv)
the distribution of the photoelectron momentum near its maximum value.Comment: 13 pages, 3 figures, to be published in Phys. Rev.
Light scattering and localization in an ultracold and dense atomic system
The quantum optical response of high density ultracold atomic systems is
critical to a wide range of fundamentally and technically important physical
processes. These include quantum image storage, optically based quantum
repeaters and ultracold molecule formation. We present here a microscopic
analysis of the light scattering on such a system, and we compare it with a
corresponding description based on macroscopic Maxwell theory. Results are
discussed in the context of the spectral resonance structure, time-dependent
response, and the light localization problem
Quantum hologram of macroscopically entangled light via the mechanism of diffuse light storage
In the present paper we consider a quantum memory scheme for light diffusely
propagating through a spatially disordered atomic gas. The diffuse trapping of
the signal light pulse can be naturally integrated with the mechanism of
stimulated Raman conversion into a long-lived spin coherence. Then the quantum
state of the light can be mapped onto the disordered atomic spin subsystem and
can be stored in it for a relatively long time. The proposed memory scheme can
be applicable for storage of the macroscopic analog of the Bell
state and the prepared entangled atomic state performs its quantum hologram,
which suggests the possibility of further quantum information processing.Comment: Submitted to Journal of Physics B: Atomic, Molecular and Optical
Physics. Special Issue on Quantum Memorie