Quantum information transfer for qutrits

We propose a scheme for the transfer of quantum information among distant qutrits. We apply this scheme to the distribution of entanglement among distant nodes and to the generation of multipartite antisymmetric states. We also discuss applications to quantum secret sharing

Detuning effects in the one-photon mazer

The quantum theory of the mazer in the non-resonant case (a detuning between the cavity mode and the atomic transition frequencies is present) is written. The generalization from the resonant case is far from being direct. Interesting effects of the mazer physics are pointed out. In particular, it is shown that the cavity may slow down or speed up the atoms according to the sign of the detuning and that the induced emission process may be completely blocked by use of a positive detuning. It is also shown that the detuning adds a potential step effect not present at resonance and that the use of positive detunings defines a well-controlled cooling mechanism. In the special case of a mesa cavity mode function, generalized expressions for the reflection and transmission coefficients have been obtained. The general properties of the induced emission probability are finally discussed in the hot, intermediate and cold atom regimes. Comparison with the resonant case is given.Comment: 9 pages, 8 figure

Entangled coherent states under dissipation

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.Comment: 13 pages and 4 figures, published versio

Quantitative Treatment of Decoherence

We outline different approaches to define and quantify decoherence. We argue that a measure based on a properly defined norm of deviation of the density matrix is appropriate for quantifying decoherence in quantum registers. For a semiconductor double quantum dot qubit, evaluation of this measure is reviewed. For a general class of decoherence processes, including those occurring in semiconductor qubits, we argue that this measure is additive: It scales linearly with the number of qubits.Comment: Revised version, 26 pages, in LaTeX, 3 EPS figure

Qutrit quantum computer with trapped ions

The physical implementation of a qutrit quantum computer in the context of trapped ions was studied. A universal two-qutrit gate which corresponded to a controlled-NOT gate between qutrits was considered. It was found that using this gate and a general gate of an individual qutrit, any gate can be decomposed into a sequence of these gates

An algebraic approach to the Jaynes-Cummings model with dissipation

An alternative approach for the Jaynes-Cummings model with dissipation is presented. An analytic solution of the master equation is obtained in the strong field regime. The extension to other models is discussed

Macroscopic field superpositions from collective interactions

We study the generation of both coherent superpositions and mixtures of field states through the interaction of an initially coherent field state with a collection of two-level atoms. The proposed scheme to build up a given superposition is based on effective dispersive interactions which arise from both the large detuning limit and the strong-field limit. The coherent superposition is obtained by interacting with a classical field after the cluster leaves the cavity followed by a measurement of the atomic population