We consider the problem of optimizing the achievable EPR-pair distribution rate between multiple source-destination pairs in a quantum Internet, where the repeaters may perform a probabilistic Bell-state measurement and we may impose a minimum end-to-end fidelity as a requirement. We construct an efficient linear programming (LP) formulation that computes the maximum total achievable entanglement distribution rate, satisfying the end-to-end fidelity constraint in polynomial time (in the number of nodes in the network). Our LP formulation gives the optimal rate for a class of entanglement generation protocols where the repeaters have very short-lived quantum memories. We also propose an efficient algorithm that takes the output of the LP solver as an input and runs in polynomial time (in the number of nodes) to produce the set of paths to be used to achieve the entanglement distribution rate. Moreover, we point out a practical entanglement generation protocol that can achieve those rates.

No abstract

Present study reveals the low concentrations (∼4 ppm) of pesticide sensing vis-à-vis degradation of pesticides with the help of nontoxic zinc oxide quantum dots (QD). In our study, we have taken four different pesticides viz., aldrin, tetradifon, glyphosate, and atrazine, which are widely used in agriculture and have structural dissimilarities/diversity. By using optical sensing techniques such as steady state and time-resolved fluorescence, we have analyzed the detailed exciton dynamics of QD in the presence of different pesticides. It has been found that the pesticide containing good leaving groups (-Cl) can interact with QD promptly and has high binding affinity (∼10 M). The different binding signatures of QD with different pesticides enable us to differentiate between the pesticides. Time resolved fluorescence spectroscopy provides significant variance (∼150-300 ns) for different pesticides. Furthermore, a large variation (10 Ω to 7 × 10 Ω) in the resistance of QD in the presence of different pesticides was revealed by electrochemical sensing technique. Moreover, during the interaction with pesticides, QD can also act as a photocatalyst to degrade pesticides. Present investigation explored the fact that the rate of degradation is positively affected by the binding affinity, i.e., the greater the binding, the greater is the degradation. What is more, both optical and electrochemical measurements of QD, in tandem, as described in our study could be utilized as the pattern recognition sensor for detection of several pesticides.

The DNA metabolic processes often involve single-stranded DNA (ss-DNA) molecules as important intermediates. In the absence of base complementarity, ss-DNAs are more flexible and interact strongly with water in aqueous media. Ss-DNA-water interactions are expected to control the conformational flexibility of the DNA strand, which in turn should influence the properties of the surrounding water molecules. We have performed room temperature molecular dynamics simulation of an aqueous solution containing the ss-DNA dodecamer, 5'-CGCGAATTCGCG-3'. The conformational flexibility of the DNA strand and the microscopic structure and ordering of water molecules around it have been explored. The simulation reveals transformation of the initial base-stacked form of the ss-DNA to a fluctuating collapsed coil-like conformation with the formation of a few non-sequentially stacked base pairs. A preliminary analysis shows further collapse of the DNA conformation in presence of additional salt (NaCl) due to screening of negative charges along the backbone by excess cations. Additionally, higher packing of water molecules within a short distance from the DNA strand is found to be associated with realignment of water molecules by breaking their regular tetrahedral ordering.