Beating the PNS attack in practical quantum cryptography

In practical quantum key distribution, weak coherent state is often used and the channel transmittance can be very small therefore the protocol could be totally insecure under the photon-number-splitting attack. We propose an efficient method to verify the upper bound of the fraction of counts caused by multi-photon pluses transmitted from Alice to Bob, given whatever type of Eve's action. The protocol simply uses two coherent states for the signal pulses and vacuum for decoy pulse. Our verified upper bound is sufficiently tight for QKD with very lossy channel, in both asymptotic case and non-asymptotic case. The coherent states with mean photon number from 0.2 to 0.5 can be used in practical quantum cryptography. We show that so far our protocol is the $only$ decoy-state protocol that really works for currently existing set-ups.Comment: So far this is the unique decoy-state protocol which really works efficiently in practice. Prior art results are commented in both main context and the Appendi

Insecurity of position-based quantum cryptography protocols against entanglement attacks

Recently, position-based quantum cryptography has been claimed to be unconditionally secure. In contrary, here we show that the existing proposals for position-based quantum cryptography are, in fact, insecure if entanglement is shared among two adversaries. Specifically, we demonstrate how the adversaries can incorporate ideas of quantum teleportation and quantum secret sharing to compromise the security with certainty. The common flaw to all current protocols is that the Pauli operators always map a codeword to a codeword (up to an irrelevant overall phase). We propose a modified scheme lacking this property in which the same cheating strategy used to undermine the previous protocols can succeed with a rate at most 85%. We conjecture that the modified protocol is unconditionally secure and prove this to be true when the shared quantum resource between the adversaries is a two- or three- level system

Early childhood during Indonesia's wildfires: health outcomes and long-run schooling achievements

This paper empirically investigates the relationship between early childhood health conditions and subsequent educational achievements in a large sample of Indonesian children. I use a long-term panel data set and apply a maternal fixed effect plus an instrumental variables estimator in order to control for possible correlation between some of the components of the error term and the main independent variable, which is likely to cause a bias in the estimates. Differences in health status between siblings are identified by using exposure in early years of life to drought, wildfires, and associated smoke/haze, which seriously affected some parts of Indonesia in late 1997. The estimation results show that health capital (measured by height-for-age z-scores during childhood) significantly and positively affects the number of completed grades of schooling and the readiness to enter school. Nevertheless, I do not find significant evidence of an effect on cognitive test scores

Secure and efficient decoy-state quantum key distribution with inexact pulse intensities

We present a general theorem for the efficient verification of the lower bound of single-photon transmittance. We show how to do decoy-state quantum key distribution efficiently with large random errors in the intensity control. In our protocol, the linear terms of fluctuation disappear and only the quadratic terms take effect. We then show the unconditional security of decoy-state method with whatever error pattern in intensities of decoy pulses and signal pulses provided that the intensity of each decoy pulse is less than $\mu$ and the intensity of each signal pulse is larger than $\mu'$

Drivers of changes in child nutritional conditions: A panel data-based study on Indonesian households, 1997–2014

Using panel data from Indonesia, this paper analyzes short and long-term drivers of nutritional conditions among children aged 0–15 years. I estimate a Mundlak model in order to better account for the relatively larger “between” variation that is found in the data, and to control for endogeneity biases that may arise due to the correlation of unobserved heterogeneity and observed explanatory variables. As results suggest, children with older, more experienced mothers, and those breastfed, exhibit improved height outcomes, aligning with existing research on breastfeeding's positive health effects. While prior research emphasized the importance of maternal education, this study reveals that, once accounting for father's education, the long-term effect of the mother's education loses statistical significance. Finally, the findings of this study suggest that household wealth and access to adequate sanitation facilities strongly affect short -and long-run improvements in children anthropometric outcomes