7,606 research outputs found
Nuclear response functions with finite range Gogny force: tensor terms and instabilities
A fully-antisymmetrized random phase approximation calculation employing the
continued fraction technique is performed to study nuclear matter response
functions with the finite range Gogny force. The most commonly used parameter
sets of this force, as well as some recent generalizations that include the
tensor terms are considered and the corresponding response functions are shown.
The calculations are performed at the first and second order in the continued
fraction expansion and the explicit expressions for the second order tensor
contributions are given. Comparison between first and second order continued
fraction expansion results are provided. The differences between the responses
obtained at the two orders turn to be more pronounced for the forces including
tensor terms than for the standard Gogny ones. In the vector channels the
responses calculated with Gogny forces including tensor terms are characterized
by a large heterogeneity, reflecting the different choices for the tensor part
of the interaction. For sake of comparison the response functions obtained
considering a G-matrix based nuclear interaction are also shown. As first
application of the present calculation, the possible existence of spurious
finite-size instabilities of the Gogny forces with or without tensor terms has
been investigated. The positive conclusion is that all the Gogny forces, but
the GT2 one, are free of spurious finite-size instabilities. In perspective,
the tool developed in the present paper can be inserted in the fitting
procedure to construct new Gogny-type forces
Multiparticle Quantum Superposition and Stimulated Entanglement by Parity Selective Amplification of Entangled States
A multiparticle quantum superposition state has been generated by a novel
phase-selective parametric amplifier of an entangled two-photon state. This
realization is expected to open a new field of investigations on the
persistence of the validity of the standard quantum theory for systems of
increasing complexity, in a quasi decoherence-free environment. Because of its
nonlocal structure the new system is expected to play a relevant role in the
modern endeavor on quantum information and in the basic physics of
entanglement.Comment: 13 pages and 3 figure
Continuous variable cloning via network of parametric gates
We propose an experimental scheme for the cloning machine of continuous
quantum variables through a network of parametric amplifiers working as
input-output four-port gates.Comment: 4 pages, 2 figures. To appear on Phys. Rev. Let
Generation of polarization entangled photon pairs by a single crystal interferometric source pumped by femtosecond laser pulses
Photon pairs, highly entangled in polarization have been generated under
femtosecond laser pulse excitation by a type I crystal source, operating in a
single arm interferometric scheme. The relevant effects of temporal walk-off
existing in these conditions between the ordinary and extraordinary photons
were experimentally investigated. By introducing a suitable temporal
compensation between the two orthogonal polarization components highly
entangled pulsed states were obtained
Realization of Universal Optimal Quantum Machines by Projective Operators and Stochastic Maps
Optimal quantum machines can be implemented by linear projective operations.
In the present work a general qubit symmetrization theory is presented by
investigating the close links to the qubit purification process and to the
programmable teleportation of any generic optimal anti-unitary map. In
addition, the contextual realization of the N ->M cloning map and of the
teleportation of the N->(M-N) universal NOT gate is analyzed by a novel and
very general angular momentum theory. An extended set of experimental
realizations by state symmetrization linear optical procedures is reported.
These include the 1->2 cloning process, the UNOT gate and the quantum
tomographic characterization of the optimal partial transpose map of
polarization encoded qubits.Comment: 11 pages, 7 figure
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