2,993 research outputs found
Atomic Focusing by Quantum Fields: Entanglement Properties
The coherent manipulation of the atomic matter waves is of great interest
both in science and technology. In order to study how an atom optic device
alters the coherence of an atomic beam, we consider the quantum lens proposed
by Averbukh et al [1] to show the discrete nature of the electromagnetic field.
We extend the analysis of this quantum lens to the study of another essentially
quantum property present in the focusing process, i.e., the atom-field
entanglement, and show how the initial atomic coherence and purity are affected
by the entanglement. The dynamics of this process is obtained in closed form.
We calculate the beam quality factor and the trace of the square of the reduced
density matrix as a function of the average photon number in order to analyze
the coherence and purity of the atomic beam during the focusing process.Comment: 10 pages, 4 figure
Exotic looped trajectories via quantum marking
We provide an analytical and theoretical study of exotic looped trajectories
(ELTs) in a double-slit interferometer with quantum marking. We use an excited
Rydberg-like atom and which-way detectors such as superconducting cavities,
just as in the Scully-Englert-Walther interferometer. We indicate appropriate
conditions on the atomic beam or superconducting cavities so that we determine
an interference pattern and fringe visibility exclusive from the ELTs. We
quantitatively describe our results for Rubidium atoms and propose this
framework as an alternative scheme to the double-slit experiment modified to
interfere only these exotic trajectories.Comment: 10 pages, 5 figure
Entanglement and scattering in quantum electrodynamics: S-matrix information from an entangled spectator particle
We consider a general quantum field relativistic scattering involving two
half spin fermions, and , which are initially entangled with another
fermion that does not participate in the scattering dynamics. We construct
general expressions for the reduced spin matrices for the out-state considering
a general tripartite spin-entangled state. In particular we study an inelastic
QED process at tree-level, namely and a half
spin fermion as an spectator particle which can be entangled to the
system in the following ways: W state, GHZ state, and , where are the Bell basis states and is a spin
superposition state of system . We calculate the von-Neumann entropy
variation before and after the scattering for the particle and show that
spin measurements in contain numerical information about the total cross
section of the process. We compare the initial states W and GHZ as well as
study the role played by the parameter in the evaluation of the
entropy variations and the cross section encoded in the spectator particle.Comment: 12 pages, 10 figure
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