F. L. Semiao

Cluster-type entangled coherent states

We present the cluster-type entangled coherent states (CTECS) and discuss their properties. A cavity QED generation scheme using suitable choices of atom-cavity interactions, obtained via detunings adjustments and the application of classical external fields, is also presented. After the realization of simple atomic measurements, CTECS representing nonlocal electromagnetic fields in separate cavities can be generated.

Entanglement between motional states of a single trapped ion and light

We propose a generation method of Bell-type states involving light and the vibrational motion of a single trapped ion. The trap itself is supposed to be placed inside a high-

Bipartite quantum channels using multipartite cluster-type entangled coherent states

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Coherent-state superpositions in cavity quantum electrodynamics with trapped ions

cavity sustaining a single mode, quantized electromagnetic field. Entangled light-motional states may be readily generated if a conditional measurement of the ions internal electronic state is made after an appropriate interaction time and a suitable preparation of the initial state. We show that all four Bell states may be generated using different motional sidebands (either blue or red), as well as adequate ionic relative phases.

Spontaneous emission and teleportation in cavity QED

We propose a particular encoding for bipartite entangled states derived from multipartite cluster-type entangled coherent states (CTECSs). We investigate the effects of amplitude damping on the entanglement content of this bipartite state, as well as its usefulness as a quantum channel for teleportation. We find interesting relationships among the amplitude of the coherent states constituting the CTECSs, the number of subsystems forming the logical qubits (redundancy), and the extent to which amplitude damping affects the entanglement of the channel. For instance, in the sense of sudden death of entanglement, given a fixed value of the initial coherent state amplitude, the entanglement life span is shortened if redundancy is increased.

A proposal of quantum logic gates using cold trapped ions in a cavity

We investigate how superpositions of motional coherent states naturally arise in the dynamics of a two-level trapped ion coupled to the quantized field inside a cavity. We extend our considerations, including a more realistic setup where the cavity is not ideal and photons may leak through its mirrors. We found that a detection of a photon outside the cavity would leave the ion in a pure state. The statistics of the ionic state still keeps some interference effects that might be observed in the weak-coupling regime.

Nonclassical effects in cold trapped ions inside a cavity

In this work, we consider atomic spontaneous emission in a system consisting of two identical two-level atoms interacting dispersively with the quantized electromagnetic field in a high-Q cavity. We investigate the destructive effect of the atomic decay on the generation of maximally entangled states, following the proposal by Zheng S B and Guo G C (2000 Phys. Rev. Lett. 85 2392). In particular, we analyse the fidelity of teleportation performed using such a noisy channel and calculate the maximum spontaneous decay rate we may have in order to realize teleportation.

Effective cross-Kerr nonlinearity and robust phase gates with trapped ions

We propose a scheme for implementation of logical gates in a trapped ion inside a high finesse cavity. The ion is interacting with a (classical) laser field as well as with the (quantized) cavity field. We demonstrate that simply by tuning the ionic internal levels with the frequencies of the fields, it is possible to construct a controlled-NOT gate in a three step procedure, having the ions internal levels as well as vibrational (motional) levels as qubits. The cavity field is used as an auxiliary qubit and basically remains in the vacuum state.

Unconditional Bell-type state generation for spatially separate trapped ions

We investigate the dynamics of a cold trapped ion coupled to the quantized field inside a high-finesse cavity, considering exact resonance between the ionic internal levels and the field (carrier transition). We derive an intensity-dependent Hamiltonian in which terms proportional to the square of the Lamb-Dicke parameter

Two-photon interaction between trapped ions and cavity fields

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