S. Solimeno

Full characterization of Gaussian bipartite entangled states by a single homodyne detector

We present the full experimental reconstruction of Gaussian entangled states generated by a type-II optical parametric oscillator below threshold. Our scheme provides the entire covariance matrix using a single homodyne detector and allows for the complete characterization of bipartite Gaussian states, including the evaluation of purity, entanglement, and nonclassical photon correlations, without a priori assumptions on the state under investigation. Our results show that single homodyne schemes are convenient and robust setups for the full characterization of optical parametric oscillator signals and represent a tool for quantum technology based on continuous variable entanglement.

On the coherent states, displacement operators and quasidistributions associated with deformed quantum oscillators

The Wigner (W), Husimi-Kano (Q) and Glauber-Sudarshan (P) quasidistributions are generalized to f-deformed quasidistributions which extend the parametric family of s-ordered quasidistributions of Cahill and Glauber. The deformation procedure is obtained via a canonical nonisometric transform of the displacement operators which preserves the form of the standard creation-annihilation commutation relation, hence the Heisenberg-Weyl algebra, but changes the scalar product in the Hilbert space of the oscillator states. A whole class of new resolutions of the identity is introduced. The time evolution equation for the new generalized quasidistributions is derived.

Homodyne estimation of quantum state purity by exploiting the covariant uncertainty relation

We experimentally verify the uncertainty relations for the mixed states in tomographic representation by measuring the radiation field tomograms, i.e. homodyne distributions. Thermal states of a single-mode radiation field are discussed in detail as a paradigm of the mixed quantum state. On considering the connection between generalized uncertainty relations and optical tomograms, it is seen that the purity of the states can be retrieved by statistical analysis of the homodyne data. The purity parameter assumes a relevant role in quantum information where the effective fidelities of protocols depend critically on the purity of the information carrier states. In this context, the homodyne detector becomes an easy-to-handle purity-meter for the state on line with a running quantum information protocol.

Trapped ions in laser fields: a benchmark for deformed quantum oscillators

Some properties of the nonlinear coherent states (NCS), recognized by Vogel and de Matos Filho as dark states of a trapped ion, are extended to NCS on a circle, for which the Wigner functions are presented. These states are obtained by applying a suitable displacement operator

Characterization of bipartite states using a single homodyne detector

{D}_{h}(ensuremath{alpha})

Transmittivity measurements by means of squeezed vacuum light

to the vacuum state. The unity resolutions in terms of the projectors

Non-Gaussian states produced by close-to-threshold optical parametric oscillators: Role of classical and quantum fluctuations

|ensuremath{alpha},h〉〈ensuremath{alpha}{,h}^{ensuremath{-}1}|,|ensuremath{alpha}{,h}^{ensuremath{-}1}〉〈ensuremath{alpha},h|

Effective method to estimate multidimensional Gaussian states

are presented together with a measure allowing a resolution in terms of

Evolution of the N-ion Jaynes?Cummings model beyond the standard rotating wave approximation

|ensuremath{alpha},h〉〈ensuremath{alpha},h|.