Does Exchange Rate Risk Matter for Welfare?

second order solution, exchange rates

Measurement-device-independent entanglement and randomness estimation in quantum networks

Detection of entanglement in quantum networks consisting of many parties is one of the important steps towards building quantum communication and computation networks. We consider a scenario where the measurement devices used for this certification are uncharacterised. In this case, it is well known that by using quantum states as inputs for the measurement devices it is possible to detect any entangled state (a situation known as measurement device-independent entanglement witnessing). Here we go beyond entanglement detection and provide methods to estimate the amount of entanglement in a quantum network. We also consider the task of randomness certification and show that randomness can be certified in a variety of cases, including single-partite experiments or setups using only separable states.Comment: 10 pages, 1 figure, close to published versio

All sets of incompatible measurements give an advantage in quantum state discrimination

Some quantum measurements can not be performed simultaneously, i.e. they are incompatible. Here we show that every set of incompatible measurements provides an advantage over compatible ones in a suitably chosen quantum state discrimination task. This is proven by showing that the Robustness of Incompatibility, a quantifier of how much noise a set of measurements tolerates before becoming compatible, has an operational interpretation as the advantage in an optimally chosen discrimination task. We also show that if we take a resource-theory perspective of measurement incompatibility, then the guessing probability in discrimination tasks of this type forms a complete set of monotones that completely characterize the partial order in the resource theory. Finally, we make use of previously known relations between measurement incompatibility and Einstein-Podolsky-Rosen steering to also relate the later with quantum state discrimination.Comment: 10 pages, no figure

All entangled states can demonstrate non-classical teleportation

Quantum teleportation, the process by which Alice can transfer an unknown quantum state to Bob by using pre-shared entanglement and classical communication, is one of the cornerstones of quantum information. The standard benchmark for certifying quantum teleportation consists in surpassing the maximum average fidelity between the teleported and the target states that can be achieved classically. According to this figure of merit, not all entangled states are useful for teleportation. Here we propose a new benchmark that uses the full information available in a teleportation experiment and prove that all entangled states can implement a quantum channel which can not be reproduced classically. We introduce the idea of non-classical teleportation witness to certify if a teleportation experiment is genuinely quantum and discuss how to quantify this phenomenon. Our work provides new techniques for studying teleportation that can be immediately applied to certify the quality of quantum technologies.Comment: v5: correction made (Tau_R is proportional to E_R in the case of a partial Bell state measurement). Main results untouche

Estimating entanglement in teleportation experiments

Quantum state teleportation is a protocol where a shared entangled state is used as a quantum channel to transmit quantum information between distinct locations. Here we consider the task of estimating entanglement in teleportation experiments. We show that the data accessible in a teleportation experiment allows to put a lower bound on some entanglement measures, such as entanglement negativity and robustness. Furthermore, we show cases in which the lower bounds are tight. The introduced lower bounds can also be interpreted as quantifiers of the nonclassicality of a teleportation experiment. Thus, our findings provide a quantitative relation between teleportation and entanglement.Comment: The title is changed and the manuscript is significantly restructured. Codes available at https://github.com/paulskrzypczyk/nonclassicalteleportation/blob/master/Quantifying%20teleportation.ipyn

Does Exchange Rate Risk Matter for Welfare?

Volatility in exchange rates is a prominent feature of open economies, a fact which has motivated elaborate attempts in many countries at exchange rate management. This paper analyzes quantitatively the welfare effects of exchange rate risk in a general two-country environment. It finds that the effects of uncertainty tend to be small for the types of simplified cases considered in past literature. But it identifies other cases, not considered previously, in which these effects can be significantly larger. These include habit persistence, where agents are more sensitive to risk, and also incomplete asset market structures which allow for asymmetries between countries. The latter case suggests that countries which are hosts to an international reserve currency, such as the U.S. or members of the euro zone, may accrue