Coupled Landau-Zener-Stuckelberg Quantum Dot Interferometers

We investigate the interplay between long-range and direct photon-assisted transport in a triple quantum dot chain where local ac voltages are applied to the outer dots. We propose the phase difference between the two ac voltages as an external parameter, which can be easily tuned to manipulate the current characteristics. For gate voltages in phase opposition we find quantum destructive interferences analogous to the interferences in closed-loop undriven triple dots. As the voltages oscillate in phase, interferences between multiple paths give rise to dark states. Those totally cancel the current, and could be experimentally resolved.Comment: 6 pages, 4 figure

Superexchange blockade in triple quantum dots

We propose the interaction of two electrons in a triple quantum dot as a minimal system to control long range superexchange transitions. These are probed by transport spectroscopy. Narrow resonances appear indicating the transfer of charge from one side of the sample to the other with the central one being occupied only virtually. We predict that two different intermediate states establish the two arms of a one dimensional interferometer. Configurations of destructive interference of the two superexchage trajectories totally block the current through the system. We emphasize the role of spin correlations giving rise to lifetime-enhanced resonances.Comment: 5 pages, 4 figures. Published versio

Reserves Over the Transitions to Floating and to Inflation Targeting: Lessons From the Developed World

This paper highlights the evolution of official international reserves in developed countries that transited towards Inflation Targeting (IT) and/or floating exchange rates. We find several results that are of interest to policymakers in emerging countries, such as Brazil, Chile and Mexico, which have revamped their monetary and exchange rate arrangements along those lines. First, the adoption of a floating exchange rate and an IT framework are associated with a persistent 10% to 20% reduction in real official reserves held at the Central Bank. Second, this reduction in official reserves corresponds mainly to a reallocation of international liquidity towards the private financial sector, that accommodates part of the effect on the level or composition of the net foreign asset position of the countries. Third, there is a clear change in the correlation between interest rate differentials and the dynamics of official reserves, strongly supporting the Mundell-Fleming result regarding the exogeneity of money supply under floating exchange rates. Fourth, the latter also shows that, once constraints on exchange rate volatility are removed, the stock of reserves can be determined independently by the Central Bank, according to cost-benefit analysis, without hindering the credibility of the combination of a floating regime and inflation targeting.