Storage of light: A useful concept?

We show both analytically and numerically that photons from a probe pulse are not stored in several recent experiments. Rather, they are absorbed to produce a two-photon excitation. More importantly, when an identical coupling pulse is re-injected into the medium, we show that the regenerated optical field has a pulse width that is very different from the original probe field. It is therefore, not a faithful copy of the original probe pulse.Comment: 5 pages, 3 figures. Correct LaTEX listings of reference

One-step error correction for multipartite polarization entanglement

We present two economical one-step error-correction protocols for multipartite polarization-entangled systems in a Greenberger-Horne-Zeilinger state. One uses spatial entanglement to correct errors in the polarization entanglement of an N-photon system, resorting to linear optical elements. The other uses frequency entanglement to correct errors in the polarization entanglement of an N-photon system. The parties in quantum communication can obtain a maximally entangled state from each N-photon system transmitted with one step in these two protocols, and both of their success probabilities are 100%, in principle. That is, they both work in a deterministic way, and they do not largely consume the less-entangled photon systems, which is far different from conventional multipartite entanglement purification schemes. These features may make these two protocols more useful for practical applications in long-distance quantum communication.Comment: 8 pages, 2 figure

Yuan Real Exchange Rate Undervaluation, 1997-2006. How Much, How Often? Not Much, Not Often

Yuan real effective exchange rate misalignment is esitimated in a behavioral equilibrium exchange rate (BEER) model for the period 1997 to third quarter 2007. Using the Beveridge-Nelson decomposition a vector error correction model (VECM) of the exchange rate as a function of macroeconomic fundamentals, including government expenditures, economic openness, the balance of trade surplus, and net foreign assets, is estimated. We find that the Chinese Yuan has been fluctuating moderately around its long run equilibrium value with undervaluation up to 4% and overvaluation up to 6% at various points in time since 1997. This result is consistent with findings of many of the most recent studies employing alternative econometric methodologies to determine the equilibrium exchange rate. While the Yuan real effective exchange rate has deviated from equilibrium, and it is sticky, taking over five years to correct 50% of the short run misalignment, it does not appear to have been consistently undervalued as has been widely argued.http://deepblue.lib.umich.edu/bitstream/2027.42/64348/1/wp934.pd

Assessing the Effects of NAFTA ON Canada/US Agricultural Trade

While there seems to be an agreement that Canada-US Free Trade Agreement (CUSTA)/North American Free Trade Agreement (NAFTA) have benefited member countries, some analysts have argued that the agreements had little effect on the bilateral Canada/US agricultural trade as many other factors have contributed to the increased trade flows. Results from this study reveal that the aggregate bilateral agricultural trade flows have generally experienced a steady growth since the implementation of NAFTA with trade flows seemingly favoring Canada more than the US since 1992. At the industry level, the impacts of NAFTA on Canada/US agricultural trade were varied with the sub-sectors analyzed responding differently to the bilateral trade liberalization.CUSTA/NAFTA, agricultural trade, liberalization, integration, trade flows, International Relations/Trade,