Narrow Results

The laser field interacting with single trapped ion in a carrier excitation frame in the presence of an external field is investigated. Detailed analytical expressions are given, taking into account carrier excitation configurations. We study the evolution of the population inversion, fidelity, ion-field entanglement, Fisher information and the geometric phase. The results indicate the influence of the external field on the information quantities to describe some physical phenomena. The relation between the population inversion, fidelity, von Neumann entropy, Fisher information, and geometric phase are explored during the time evolution.

We propose a scheme for implementing a single-ion Stochastic Quantum Processor using a single cold trapped ion. The processor implements an arbitrary rotation around the z axis of the Bloch sphere of a data qubit, given two program qubits, that is, the operation realized on the data is determined by using different program qubits and not by varying the gate itself. Unfortunately this cannot be done deterministically, and must be necessarily stochastic. In this proposal the operation is applied successfully with probability p = 3/4.

In this paper, the interaction between two trap ions with laser beam and electromagnetic field containing the Stark shift terms has been investigated. The analytical solution for the differential equations which describes the system Hamiltonian is obtained. The dynamical behavior for the entanglement, entropy squeezing and purity of system are discussed. Some important physical characteristics such as revivals and collapses for the occupation of the trapped ion, entanglement sudden death (birth) and single trapped ion entropy squeezing are discussed. In addition, the influence of Lamb–Dicke parameter and the initial states on the evolution of the entanglement, linear entropy are studied. Finally, some remarks about the obtained results are given briefly.

In this paper, a scheme is presented to implement the 1→2 universal quantum cloning machine (UQCM) with trapped ions. In this way, we also show that quantum information can be directly transferred from one ion to another. The distinct advantage of the scheme lies in the fact that it does not use the vibrational mode as the data bus. The vibrational mode is only virtually excited, which makes our scheme insensitive to heating, provided the system remains in the Lamb–Dicke regime.

We propose two schemes via adiabatic evolution of dark eigenstates in an ion trap system. One is an entanglement generation of multi-ion cluster states, the other is entanglement concentration via entanglement swapping. Our schemes are robust against moderate fluctuations of experimental parameters since we utilize the adiabatic passage in the main procedure. The current idea can be generalized to other systems.

In this paper, we propose a scheme to implement two-qubit Deutsch–Jozsa algorithm with trapped ions. The distinct advantage of the scheme lies in the fact that it does not use the vibrational mode as the data bus. The vibrational mode is only virtually excited, which makes our scheme insensitive to heating provided that the system remains in the Lamb–Dicke regime.

The time evolution of the atomic Wehrl entropy and long-lived entanglement generation using a single trapped ion interacting with a laser field are analyzed. Starting from the Heisenberg equation of motion, an exact solution of the system is obtained by indicating that there are some interesting features when a time-dependent modulating function is considered. We demonstrate that the long-living quantum entanglement can be obtained using the time-independent interaction when the field is initially in a pair cat states.

The status of Time in the Quantum Theory remains even today a largely open question. In particular, the existence of a Quantum Time Operator that would describe the distribution of decay times of an unstable quantum system (in analogy with the Position operator that is associated to the position distribution) remained a polemichal question during several decades. Recently, we conceived experimental proposals involving CP violating processes (of single mesons and entangled pairs of mesons) that can be considered as crucial experiments aimed at testing the existence of a Quantum Time Operator. In the present paper, we shall present a similar proposal that can be realized with a single trapped ion. These proposals aim at bringing fundamental problems related to the status of Time in the Quantum Theory to the realm of experimental physics.

We propose the use of atomic Wehrl entropy associated to the reduced atomic density operator as an entanglement indicator of bipartite systems. This is applied to a two-level system (one single harmonically trapped ion) by taking into account the linear center-of-mass-motional degree of freedom. Detailed analytical and explicit expressions are given, taking into account different configurations. The results show the important roles played by the laser phase and initial state setting in the evolution of the atomic Q-function, atomic Wehrl entropy and marginal atomic Q-function. Our procedure of using atomic Wehrl entropy may be applied to a system with Hilbert space of high dimension.

Death of entanglement between light and the vibrational motion of a single trapped ion in the dispersive regime with a reservoir is investigated. It is found that with phase-damped cavity, the purity of the light-motional states is lost forever, unlike the purity of the ion's internal states which have regular patterns and they do not decay. The asymptotic behavior of the states of the light, the ion-motional and the total system fall into a mixed state. The entanglement and purity have strong sensitivity to the phase damping and the ionic distribution angle. The entanglement sudden death has been treated as it arises from the effect of phase damping on mixed as well as pure states.

The entanglement in a system of a single two-level trapped ion and a single-mode quantized field in a coherent state inside a phase-damped cavity is investigated. Analytic results under certain parametric conditions are obtained, by means of which we analyze the influence of dissipation on the atomic Fisher information and its marginal distribution. An interesting relation between the temporal entanglement sudden birth, sudden death, atomic Fisher information and the dissipation effect is observed.