Irrelevance of photon events distinguishability in a class of Bell experiments

We show that the possibility of distinguishing between single- and two-photon detection events, usually not met in the actual experiments, is not a necessary requirement for proof that the experiments of Alley and Shih [Phys. Rev. Lett. 61, 2921 (1988)] and Ou and Mandel [Phys. Rev. Lett. 61, 50 (1988)] are modulo a fair sampling assumption, valid tests of local realism. We also give the critical parameters for the experiments to be unconditional tests of local realism, and show that some other interesting phenomena (involving bosonic-type particle indistinguishability) can be observed during such tests

Interferometric Bell-state preparation using femtosecond-pulse-pumped Spontaneous Parametric Down-Conversion

We present theoretical and experimental study of preparing maximally entangled two-photon polarization states, or Bell states, using femtosecond pulse pumped spontaneous parametric down-conversion (SPDC). First, we show how the inherent distinguishability in femtosecond pulse pumped type-II SPDC can be removed by using an interferometric technique without spectral and amplitude post-selection. We then analyze the recently introduced Bell state preparation scheme using type-I SPDC. Theoretically, both methods offer the same results, however, type-I SPDC provides experimentally superior methods of preparing Bell states in femtosecond pulse pumped SPDC. Such a pulsed source of highly entangled photon pairs is useful in quantum communications, quantum cryptography, quantum teleportation, etc.Comment: 11 pages, two-column format, to appear in PR

Miocene foraminifera from the Finniss Clay and Cadell Marl, western Murray Basin: taxonomic and taphonomic contrasts and their environmental significance.

Sandwiched between Miocene limestones of the Mannum Formation and Morgan Limestone in the western Murray Basin, the Finniss Clay and Cadell Marl contain different foraminiferal faunas with varying taphonomic grades. At the Mannum Pumping Station section, the Finniss Clay fauna has a low diversity, frequent shallow-water forms, and a poor taphonomic grade. In what was the deeper part of the basin at Waikerie, a diverse fauna with well-preserved small species is recorded in sediments equivalent to the Finniss Clay. In contrast, the Cadell Marl from various localities comprises a well-preserved and diverse biofacies with both shallow and deeper water taxa. These contrasts suggest different depositional environments: shallower and warm during deposition of the Finniss Clay and nutrient-rich, dysaerobic and deeper water during deposition of the Cadell Marl. The shallowing event indicated by faunas from the Finniss Clay was due to falling sea level close to the early/middle Miocene boundary, whereas the Cadell fauna appears to reflect the global carbon buildup at the peak of the Monterey carbon excursion during the Miocene climatic optimum, about 16 million years ago. © 1999 Association of Australasian Palaeontologists.Li, Qianyu McGowran, Bria