Wednesday, March 25, 2009

Entanglement Test on a Microscopic-Macroscopic System
by F. De Martini, et. al.

A macrostate consisting of N~3.5×104 photons in a quantum superposition and entangled with a far apart single-photon state (microstate) is generated. Precisely, an entangled photon pair is created by a nonlinear optical process; then one photon of the pair is injected into an optical parametric amplifier operating for any input polarization state, i.e., into a phase-covariant cloning machine. Such transformation establishes a connection between the single photon and the multiparticle fields. We then demonstrate the nonseparability of the bipartite system by adopting a local filtering technique within a positive operator valued measurement.

**Groupmeeting by Amir Feizpour**

Wednesday, March 11, 2009

The Wigner Distribution Function and its Optical Production
by H.O. Bartelt, et. al.

An optical signal (image etc.) can be described by its complex amplitude u (x,y), or by its spatial frequency spectrum. Both descriptions are complete and also equivalent, because one can be derived from the other by a Fourier transformation. Neither the complex amplitude nor the spatial frequency spectrum is suitable for answering a question like "what is the spatial frequency in a certain part of the image?". Here the term "local spectrum" is adequate. A rigorous definition of the "local spectrum" can be based on the Wigner distribution function. We developed optical methods for producing this "local spectrum" and we applied these methods to the investigation of sound patterns.

**Groupmeeting by Asma Al-Qasimi**

Thursday, March 5, 2009

Unambiguous modification of non-orthogonal qubit states
by F.A. Torres-Ruiz et. al.

A probabilistic method for the unambiguous modification of non-orthogonal quantum states is proposed. This is based on conclusive modifications of the inner product between two pure quantum states in a discrimination-like process. We experimentally implemented this protocol by using two-photon polarization states generated in the process of spontaneous parametric down conversion. In the experiment, for codifying initial quantum states, we consider single photon states and heralded detection. As application, we show that when our protocol is applied to partially entangled states it allows a fine control of the amount of entanglement of the modified states.

**Groupmeeting by Fabian Torres-Ruiz**