Universal ultrabright source of entangled photon states: generation and tomographic analysis of Werner states and of Maximally Entangled Mixed States

摘要

A novel ultrabright parametric source of polarization entangled photon pairswith striking spatial characteristics is reported. The distribution of theoutput electromagnetic k-modes excited by Spontaneous Parametris DownConversion and coupled to the output detectors can be very broad. It couldcoincide with the full set of phase-matched excited modes, at least inprinciple. In this case a relevant conditional quasi-pure output state shouldbe realized. By these (approximate) states realized over a fullEntanglement-Ring output distribution, the non local properties of thegenerated entanglement has been tested by standard Bell measurements and byOu-Mandel interferometry. A novel ''mode-patchwork'' technique based on thequantum superposition principle is adopted to synthesize in a straightforwardand reliable way any kind of mixed-states, of large conceptual andtechnological interest in modern Quantum Information. Tunable Werner states andMaximally Entangled Mixed States (MEMS) have indeed been created by the newtechnique and investigated by quantum tomography. A thorough study of theentropic and nonlocal properties of these states has been undertakenexperimentally and theoretically, by a unifying variational approach.