arXiv subjects

W. B. Cardoso

Publications and source records attributed to W. B. Cardoso.

30 records · Page 2Linked to original sources

arXiv2009

Lump-like Structures in Scalar-field Models

In this work we investigate the presence of lump-like solutions in models described by a single real scalar field. We take advantage of a procedure recently used to describe explicit analytical solutions and we study several distinct models, showing how the parameters can be used to control the specific features of the lump-like structures. The proposed models are of direct interest to the construction of q-balls, to induce tachyonic excitations and gravitating structures of nontopological profile on braneworld models with a single extra dimension, to map solitons in optical fibers, and to describe collective excitations in Bose-Einstein condensates.

hep-th↗

arXiv2009

Quantum teleportation in superconducting charge qubits

In this paper we propose a scheme to implement a quantum teleportation based on the current experimental design [Nature (London) 431, 162 (2004); ibid 445, 515 (2007)] in which superconducting charge qubits are capacitively coupled to a single high-Q superconducting coplanar resonator. As advantage of this architecture, it permits the use of multiqubit gates between non-nearest qubits and the realization of parallel gates. We consider the case of two qubits inside the resonator, where the teleportation is accomplished.

quant-ph↗

arXiv2009

Partial teleportation of entangled atomic states

In this paper we propose a scheme for partially teleporting entangled atomic states. Our scheme can be implemented using only four two-level atoms interacting either resonantly or off-resonantly with a single cavity-QED. The estimative of losses occurring during this partial teleportation process is accomplished through the phenomenological operator approach technique.

quant-ph↗

arXiv2009

Generation of four-qubit cluster of entangled coherent states in bimodal QED cavities

A recent work [1] proposed a type of cluster entangled coherent states and its generation. Here we present an alternative experimental arrangement for its generation in bimodal QED cavities. The scheme employs a single two-level atom that interacts dispersively with cavity modes initially prepared in coherent states. The fidelity and success probability of the state preparation are obtained considering the influence of atomic velocity spread and atomic efficiency detection.

quant-ph↗

arXiv2009

Solitons with Cubic and Quintic Nonlinearities Modulated in Space and Time

This work deals with soliton solutions of the nonlinear Schroedinger equation with cubic and quintic nonlinearities. We extend the procedure put forward in a recent Letter and we solve the equation in the presence of linear background, and cubic and quintic interactions which are modulated in space and time. As a result, we show how a simple parameter can be used to generate brightlike or darklike localized nonlinear waves which oscillate in several distinct ways, driven by the space and time dependence of the parameters that control the trapping potential, and the cubic and quintic nonlinearities.

quant-ph↗

arXiv2009

Bright and Dark Solitons in a Periodically Attractive and Expulsive Potential with Nonlinearities Modulated in Space and Time

This work deals with soliton solutions of the nonlinear Schroedinger equation with a diversity of nonlinearities. We solve the equation in a potential which oscillates in time between attractive and expulsive behavior, in the presence of nonlinearities which are modulated in space and time. Despite the presence of the periodically expulsive behavior of the potential, the results show that the nonlinear equation can support a diversity of localized excitations of the bright and dark type which are remarkably robust.

quant-ph↗

arXiv2008

Generation of arbitrary Fock states via resonant interactions in cavity QED

We propose a scheme to generate arbitrary Fock states |N> in a cavity QED using N resonant Rydberg atoms. The atom-field interaction times are controlled via Stark-shifts adjusted in a way that each atom transfers a photon to the cavity, turning atomic detections useless. Fluctuations affecting the control of the atom-field interactions are also considered.

quant-ph↗

arXiv2007

Accuracy of a teleported trapped field state inside a single bimodal cavity

We propose a simplified scheme to teleport a superposition of coherent states from one mode to another of the same bimodal lossy cavity. Based on current experimental capabilities, we present a calculation of the fidelity that can be achieved, demonstrating accurate teleportation if the mean photon number of each mode is at most 1.5. Our scheme applies as well for teleportation of coherent states from one mode of a cavity to another mode of a second cavity, both cavities embedded in a common reservoir.

quant-ph↗

arXiv2007

Truncated states obtained by iteration

Quantum states of the electromagnetic field are of considerable importance, finding potential application in various areas of physics, as diverse as solid state physics, quantum communication and cosmology. In this paper we introduce the concept of truncated states obtained via iterative processes (TSI) and study its statistical features, making an analogy with dynamical systems theory (DST). As a specific example, we have studied TSI for the doubling and the logistic functions, which are standard functions in studying chaos. TSI for both the doubling and logistic functions exhibit certain similar patterns when their statistical features are compared from the point of view of DST. A general method to engineer TSI in the running-wave domain is employed, which includes the errors due to the nonidealities of detectors and photocounts.

quant-ph↗

arXiv2006

Superposition of coherent states prepared in one mode of a dissipative bimodal cavity

We solve the problem of the temporal evolution of one of two-modes embedded in a same dissipative environment and investigate the role of the losses after the preparation of a coherent state in only one of the two modes. Based on current cavity QED technology, we present a calculation of the fidelity of a superposition of coherent states engineered in a bimodal high-Q cavity. Our calculation demonstrates that the engineered superposition retains coherence for large times when the mean photon number of the prepared mode is on the order of unity.

quant-ph↗

arXiv2006

Statistical properties of the truncated state with random coefficients

In this Letter we introduce the truncated state with random coefficients (TSRC). As the coefficients of the TSRC have in principle no algorithm to produce them, our question is concerned about to what type of properties will characterize the TSRC. A general method to engineer TSRC in the running-wave domain is employed, which includes the errors due to the nonidealities of detectors and photocounts.

quant-ph↗

arXiv2006

Teleportation of entangled states without Bell-state measurement

In a recent paper [Phys. Rev. A 70, 025803 (2004)] we presented a scheme to teleport an entanglement of zero- and one-photon states from a bimodal cavity to another one, with 100% success probability. Here, inspired on recent results in the literature, we have modified our previous proposal to teleport the same entangled state without using Bell-state measurements. For comparison, the time spent, the fidelity, and the success probability for this teleportation are considered.

quant-ph↗