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vol. 125
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issue 2
638-641
EN
We construct a novel model for a single photon, bearing an internal dynamics. In our model, the photon, while travelling with a speed very close to c (the ultimate speed of light in empty space), is considered to oscillate, in its own frame, with its given frequency f. The envelope of the photon's instantaneous maximum amplitude, which we will call from here on straight "amplitude", is assumed to travel with exactly c, which makes that the center of the photon ought to travel with a speed little less than c. It is interesting to add that, in the present approach, the higher the frequency of the photon at hand, the narrower is its amplitude of oscillation. It is further assumed that the photon has a rest mass which we call "kernel", carrying the translational motion of it. This allows us to estimate the rest mass of the given photon, based on adopted initial conditions of the early universe, based on the recent Yarman and Kholmetskii model (resolving, amongst other things, the dark energy quest). One then comes out with the result that all observable photons (i.e. either high energy gamma rays or very low frequency radio waves), travel practically with the same speed, which is virtually c, the measured ultimate speed. A model regarding the internal dynamics in question is further offered.
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vol. 125
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issue 2
606-607
EN
Quantum Fisher information has recently been an essential tool for analyzing the phase sensitivity of the quantum states in various quantum tasks, requiring high precision, such as quantum clock synchronization, positioning and many applications which include quantum interferometers. Due to the interactions with the environment, all quantum systems are subject to various decoherence effects. Therefore the research on quantum Fisher information under decoherence has been recently attracting more attention. In this work, analyzing the quantum Fisher information, we study the phase sensitivity of bipartite quantum correlations, in particular four Bell pairs amplitude damping channels. For a specific Bell state we arrive at similar results of Greenberger-Horne-Zeilinger (GHZ) states (as expected). For the other three Bell states, we present our results which point the interesting behavior of quantum Fisher information with respect to the decoherence rate. We also find the regions where the quantum Fisher information exhibits discontinuities.
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Quantum Fisher Information of Bipartitions of W States

88%
EN
We study the quantum Fisher information (QFI) of W states and W-like states under decoherence. In particular, we find that on the contrary to amplitude damping and depolarizing decoherence, a W-like state of 3 qubits obtained by discarding 1 qubit of a genuine W state of 4 qubits is more robust than a genuine W state of 3 qubits under amplitude amplifying and phase damping decoherence.
EN
In order to create polarization based entanglement networks of W₄ state, we propose an optical setup, which uses only four horizontally polarized photons as resource which implies no entanglement requirement as a resource. This setup can generate target state deterministically, by operating several quantum optical gates, which can be realized with current photonics technology. The setup we propose is composed of one Not, two Hadamard, five Controlled Not (CNot) and one Toffoli gate.
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