RESUMO
Here we report a new microfluidic paper-based analytical device (mPAD) for quantifying metals in water. Metals represent an important class of water contaminants that come from a variety of sources including mining, transportation, manufacturing, waste management, and energy production. Current technologies for quantifying aquatic metals in water are expensive, relatively slow, tedious, provide inadequate performance, and are difficult to use in a field setting. As a result, a need exists for simple, portable, power-free measurement tools that enable rapid in-field quantification of aquatic metals. The reported metal test cards, referred to as the On-Target Water Chemistry test cards, represent a major improvement over previously reported linear distance-based detection systems comprised of paper. With the On-Target approach, the sample flows outwards radially and reacts with colorimetric complexing agents, significantly reducing assay time. The diameter of the resulting color formation is directly proportional to analyte concentration. The On-Target cards were used for detecting copper, iron, and zinc with detection limits as low as 0.1 ppm in â¼3 min and single ppb in combination with a membrane pre-concentration system.
RESUMO
We show that qubits traveling along closed timelike curves are a resource that a party can exploit to distinguish perfectly any set of quantum states. As a result, an adversary with access to closed timelike curves can break any prepare-and-measure quantum key distribution protocol. Our result also implies that a party with access to closed timelike curves can violate the Holevo bound.
RESUMO
We present a scheme of fault-tolerant quantum computation for a local architecture in two spatial dimensions. The error threshold is 0.75% for each source in an error model with preparation, gate, storage, and measurement errors.
RESUMO
The theoretical existence of photon-number-splitting attacks creates a security loophole for most quantum key distribution (QKD) demonstrations that use a highly attenuated laser source. Using ultralow-noise, high-efficiency transition-edge sensor photodetectors, we have implemented the first version of a decoy-state protocol that incorporates finite statistics without the use of Gaussian approximations in a one-way QKD system, enabling the creation of secure keys immune to photon-number-splitting attacks and highly resistant to Trojan horse attacks over 107 km of optical fiber.