N. Zagury
Federal University of Rio de Janeiro
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Publication
Featured researches published by N. Zagury.
Physical Review A | 2006
M. França Santos; Perola Milman; L. Davidovich; N. Zagury
We propose a method for directly probing the dynamics of disentanglement of an initial two-qubit entangled state under the action of a reservoir. We show that it is possible to detect disentanglement, for experimentally realizable examples of decaying systems, through the measurement of a single observable, which is invariant throughout the decay. The systems under consideration may lead to either finite-time or asymptotic disentanglement. A general prescription for measuring this observable, which yields an operational meaning to entanglement measures, is proposed, and exemplified for cavity quantum electrodynamics and trapped ions.
Physical Review Letters | 2006
R. Gúzman; J. C. Retamal; E. Solano; N. Zagury
We propose a method of generating unitarily single and two-mode field squeezing in an optical cavity with an atomic cloud. Through a suitable laser system, we are able to engineer a squeeze field operator decoupled from the atomic degrees of freedom, yielding a large squeeze parameter that is scaled up by the number of atoms, and realizing degenerate and nondegenerate parametric amplification. By means of the input-output theory we show that ideal squeezed states and perfect squeezing could be approached at the output. The scheme is robust to decoherence processes.
Physical Review Letters | 2012
B. M. Escher; L. Davidovich; N. Zagury; R. L. de Matos Filho
The minimum achievable statistical uncertainty in the estimation of physical parameters is determined by the quantum Fisher information. Its computation for noisy systems is still a challenging problem. Using a variational approach, we present an equation for obtaining the quantum Fisher information, which has an explicit dependence on the mathematical description of the noise. This method is applied to obtain a useful analytical bound to the quantum precision in the estimation of phase-shifts under phase diffusion, which shows that the estimation uncertainty cannot be smaller than a noise-dependent constant.
Physical Review Letters | 2001
E. Solano; R. L. de Matos Filho; N. Zagury
We propose a scalable procedure to generate superpositions of motional coherent states and also entangled vibronic states in N trapped ions. Beyond their fundamental importance, these states may be of interest for quantum information processing and may be used in experimental studies on decoherence.
European Physical Journal D | 2001
E. Solano; C. L. Cesar; R. L. de Matos Filho; N. Zagury
Abstract:We study a method for the implementation of a reliable teleportation protocol (theoretically, 100% of success) of internal states in trapped ions. The generation of the quantum channel (any of four Bell states) may be done respecting technical limitations on individual addressing and without claiming the Lamb-Dicke regime. An adequate Bell analyzer, that transforms unitarily the Bell basis into a completely disentangled one, is considered. Probable sources of error and fidelity estimations of the teleportation process are studied. Finally, we discuss experimental issues, proposing a scenario in which the present scheme could be implemented.
Physical Review A | 2007
S. P. Walborn; D. S. Ether; R. L. de Matos Filho; N. Zagury
We propose a quantum teleportation scheme for the angular spectrum of a single-photon field, which allows for the transmission of a large amount of information. Our proposal also provides a method to tune the frequencies of spatially entangled fields, which is useful for interactions with stationary qubits.
Physical Review A | 2000
E. Solano; P. Milman; R. L. de Matos Filho; N. Zagury
We present a selective vibronic interaction for manipulating motional states in two trapped ions, acting resonantly on a previously chosen vibronic subspace and dispersively on all others. This is done respecting technical limitations on ionic laser individual addressing. We discuss the generation of Fock states and entanglement in the ionic collective motional degrees of freedom, among other applications.
Physical Review A | 2015
G. Bié Alves; B. M. Escher; R. L. de Matos Filho; N. Zagury; L. Davidovich
The implementation of weak-value amplification requires the pre- and post-selection of states of a quantum system, followed by the observation of the response of the meter, which interacts weakly with the system. Data acquisition from the meter is conditioned to successful post-selection events. Here we derive an optimal post-selection procedure for estimating the coupling constant between system and meter, and show that it leads both to weak-value amplification and to the saturation of the quantum Fisher information, under conditions fulfilled by all previously reported experiments on the amplification of weak signals. For most of the pre-selected states, full information on the coupling constant can be extracted from the meter data set alone, while for a small fraction of the space of pre-selected states, it must be obtained from the post-selection statistics.
Journal of Optics B-quantum and Semiclassical Optics | 2002
E. Solano; R. L. de Matos; N. Zagury
We consider a resonant bichromatic excitation of N trapped ions that generates displacement and squeezing in their collective motion conditioned to their ionic internal state, producing eventually Schrodinger cat states and entangled squeezing. Furthermore, we study the case of tetrachromatic illumination for producing the so-called entangled coherent states in two motional normal modes.
Optics Communications | 2010
F. Lastra; G. Romero; C. E. López; N. Zagury; J. C. Retamal
We study the evolution of entangled coherent states of the two quantized electromagnetic fields under dissipation. Characteristic time scales for the decay of the negativity are found in the case of large values of the phase space distance among the states of each mode. We also study how the entanglement emerges among the reservoirs.