J. A. Roversi

Quantum state reconstruction in the presence of dissipation

Abstract We propose a realistic scheme to determine the quantum state of a single-mode cavity field even after it has started to decay due to the coupling with an environment. Although dissipation destroys quantum coherences, we show that at zero temperature enough information about the initial state remains, in an observable quantity, to allow the reconstruction of its Wigner function. 42.50.-p, 03.65.Bz, 42.50.Dv.

Long-time-scale revivals in ion traps

In this paper we investigate the interaction of a single ion in a trap with laser beams. Our approach, based on unitary transformating the Hamiltonian, allows its exact diagonalization without performing the Lamb-Dicke approximation. We obtain a transformed Jaynes-Cummings-type Hamiltonian, and we demonstrate the existence of super-revivals in that system.

Recovering coherence from decoherence: A method of quantum-state reconstruction

We present a feasible scheme for reconstructing the quantum state of a field prepared inside a lossy cavity. Quantum coherences are normally destroyed by dissipation, but we show that at zero temperature we are able to retrieve enough information about the initial state, making possible to recover its Wigner function as well as other quasiprobabilities. We provide a numerical simulation of a Schrodinger cat-state reconstruction.

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-

Quantum state transfer between atoms located in coupled optical cavities

Q

Quantum state engineering via unitary transformations

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.

Quantum superpositions of binomial states of light

We investigated the interaction between two coupled cavities, each one of them interacting with a two-level atom in its interior. We observed that if one of the atoms is in a superposition state and the other parts of the system are in their fundamental states, it is possible to transfer this state to the atom in the other cavity through the temporal evolution of the system. The time-evolution behaviour of the system during this transfer was studied and we observed its dependence with the frequency of the atom and the coupling constant between the atom and its respective cavity.

Unitary transformation approach for the trapped ion dynamics

We construct a Hamiltonian for the generation of arbitrary pure states of the quantized electromagnetic field. The proposition is based upon the fact that a unitary transformation for the generation of number states has already been found. The general unitary transformation here obtained would allow the use of nonlinear interactions for the production of pure states. We discuss the applicability of this method by giving examples of generation of simple superposition states. We also compare our Hamiltonian with the one resulting from the interaction of trapped ions with two laser fields.

Transfer of coherence from atoms to mixed field states in a two-photon lossless micromaser

We introduce new kinds of states of electromagnetic field, which are quantum superpositions of binomial states. They not only exhibit remarkable non-classical properties but can also interpolate between the Schrodinger cat type of states and the number states in a particularly interesting way. We basically discuss some of their main statistical properties, as well as schemes for their generation. We also employ quasiprobability distributions in phase space.

Cavity field reconstruction at finite temperature

We present a method of treating the problem of the interaction of a single trapped ion with laser beams based on successive applications of unitary transformations onto the Hamiltonian. This allows the diagonalization of the Hamiltonian, by means of recursive relations, without performing the Lamb-Dicke approximation.