8,966 research outputs found
New algorithms to obtain analytical solutions of Einstein's equations in isotropic coordinates
The main objective of this work, is to show two inequivalent methods to
obtain new spherical symmetric solutions of Einstein's Equations with
anisotropy in the pressures in isotropic coordinates. This was done inspired by
the MGD method, which is known to be valid for line elements in Schwarzschild
coordinates. As example, we obtained four analytical solutions using Gold III
as seed solution. Two solutions, out of four, (one for each algorithm), satisfy
the physical acceptability conditions.Comment: 14 pages, 24 figures, results were improve
Hamilton-Jacobi Theory in k-Symplectic Field Theories
In this paper we extend the geometric formalism of Hamilton-Jacobi theory for
Mechanics to the case of classical field theories in the k-symplectic
framework
Entanglement swapping between spacelike separated atoms
We show a mechanism that projects a pair of neutral two-level atoms from an
initially uncorrelated state to a maximally entangled state while they remain
spacelike separated. The atoms begin both excited in a common electromagnetic
vacuum, and the radiation is collected with a partial Bell-state analyzer. If
the interaction time is short enough and a certain two-photon Bell state is
detected after the interaction, a high degree of entanglement, even maximal,
can be generated while one atom is outside the light cone of the other, for
arbitrary large interatomic distances.Comment: v2: version accepted in Phys. Rev.
Detecting ground state qubit self-excitations in circuit QED: slow quantum anti-Zeno effect
In this work we study an ultrastrong coupled qubit-cavity system subjected to
slow repeated measurements. We demonstrate that even under a few imperfect
measurements it is possible to detect transitions of the qubit from its free
ground state to the excited state. The excitation probability grows
exponentially fast in analogy with the quantum anti-Zeno effect. The dynamics
and physics described in this paper is accessible to current superconducting
circuit technology.Comment: 6 pages, 6 figures. v2: extended published versio
Generation of atom-atom correlations inside and outside the mutual light cone
We analyze whether a pair of neutral two level atoms can become entangled in
a finite time while they remain causally disconnected. The interaction with the
e. m. field is treated perturbatively in the electric dipole approximation. We
start from an initial vacuum state and obtain the final atomic correlations for
the cases where n = 0, 1, or 2 photons are produced in a time t, and also when
the final field state is unknown. Our results show that correlations are
sizable inside and outside the mutual light cone for n= 1 and 2, and also that
quantum correlations become classical by tracing over the field state. For n =
0 we obtain entanglement generation by photon propagation between the atoms,
the correlations come from the indistinguishability of the source for n = 1,
and may give rise to entanglement swapping for n = 2.Comment: v2: Minor changes, references added. v3: full revision, appendix
added. v4: Minor changes. Accepted in Phys. Rev.
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