10 research outputs found
Image and Coherence Transfer in the Stimulated Down-conversion Process
The intensity transverse profile of the light produced in the process of
stimulated down-conversion is derived. A quantum-mechanical treatment is used.
We show that the angular spectrum of the pump laser can be transferred to the
stimulated down-converted beam, so that images can also be transferred from the
pump to the down-converted beam. We also show that the transfer can occur from
the stimulating beam to the down-converted one. Finally, we study the process
of diffraction through an arbitrarily shaped screen. For the special case of a
double-slit, the interference pattern is explicitly obtained. The visibility
for the spontaneous emitted light is in accordance with the van Cittert -
Zernike theorem for incoherent light, while the visibility for the stimulated
emitted light is unity. The overall visibility is in accordance with previous
experimental results
Quantum Erasure by Transverse Indistinguishability
We show that the first experiment with double-slits and twin photons detected
in coincidence can be understood as a quantum eraser. The ``which path''
information is erased by transverse indistinguishability obtained by means of
mode filtering in the twin conjugated beam. A delayed choice quantum eraser
based on the same scheme is proposed.Comment: Submitted for publication in Optics Communication
Quantum Distillation Of Position Entanglement With The Polarization Degrees Of Freedom
Sources of entangled photon pairs using two parametric down-converters are
capable of generating interchangeable entanglement in two different degrees of
freedom. The connection between these two degrees of freedom allows the control
of the entanglement properties of one, by acting on the other degree of
freedom. We demonstrate experimentally, the quantum distillation of the
position entanglement using polarization analyzers.Comment: Submitted for publication in Optics Communication
Image formation by manipulation of the entangled angular spectrum
We demonstrate theoretical and experimentally how it is possible to
manipulate an entangled angular spectrum of twin beams, in order to reconstruct
correlated images with coincidence detection. The entangled angular spectrum
comes from the pump and the image is obtained only if signal and idler are
properly treated.Comment: Submitted for publication in Optics Communication
Spatial antibunching of photons with parametric down-conversion
The theoretical framework behind a recent experiment by Nogueira et. al.
[Phys. Rev. Lett. 86}, 4009 (2001)] of spatial antibunching in a two-photon
state generated by collinear type II parametric down-conversion and a
birefringent double-slit is presented. The fourth-order quantum correlation
function is evaluated and shown to violate the classical Schwarz-type
inequality, ensuring that the field does not have a classical analog. We expect
these results to be useful in the rapidly growing fields of quantum imaging and
quantum information.Comment: 5 pages, 3 figures. Minor changes made, accepted for publication in
PR
Soliton back-action evading measurement using spectral filtering
We report on a back-action evading (BAE) measurement of the photon number of
fiber optical solitons operating in the quantum regime. We employ a novel
detection scheme based on spectral filtering of colliding optical solitons. The
measurements of the BAE criteria demonstrate significant quantum state
preparation and transfer of the input signal to the signal and probe outputs
exiting the apparatus, displaying the quantum-nondemolition (QND) behavior of
the experiment.Comment: 5 pages, 5 figure
Quantum walks: a comprehensive review
Quantum walks, the quantum mechanical counterpart of classical random walks,
is an advanced tool for building quantum algorithms that has been recently
shown to constitute a universal model of quantum computation. Quantum walks is
now a solid field of research of quantum computation full of exciting open
problems for physicists, computer scientists, mathematicians and engineers.
In this paper we review theoretical advances on the foundations of both
discrete- and continuous-time quantum walks, together with the role that
randomness plays in quantum walks, the connections between the mathematical
models of coined discrete quantum walks and continuous quantum walks, the
quantumness of quantum walks, a summary of papers published on discrete quantum
walks and entanglement as well as a succinct review of experimental proposals
and realizations of discrete-time quantum walks. Furthermore, we have reviewed
several algorithms based on both discrete- and continuous-time quantum walks as
well as a most important result: the computational universality of both
continuous- and discrete- time quantum walks.Comment: Paper accepted for publication in Quantum Information Processing
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