Practical high-dimensional quantum key distribution protocol over deployed multicore fiber

Quantum key distribution (QKD) is a secure communication scheme for sharing symmetric cryptographic keys based on the laws of quantum physics, and is considered a key player in the realm of cyber-security. A critical challenge for QKD systems comes from the fact that the ever-increasing rates at which digital data are transmitted require more and more performing sources of quantum keys, primarily in terms of secret key generation rate. High-dimensional QKD based on path encoding has been proposed as a candidate approach to address this challenge. However, while proof-of-principle demonstrations based on lab experiments have been reported in the literature, demonstrations in realistic environments are still missing. Here we report the generation of secret keys in a 4-dimensional hybrid time-path-encoded QKD system over a 52-km deployed multicore fiber link forming by looping back two cores of a 26-km 4-core optical fiber. Our results indicate that robust high-dimensional QKD can be implemented in a realistic environment by combining standard telecom equipment with emerging multicore fiber technology.

Resource-effective quantum key distribution: a field trial in Padua city center

Field trials are of key importance for novel technologies seeking commercialization and widespread adoption. This is also the case for quantum key distribution (QKD), which allows distant parties to distill a secret key with unconditional security. Typically, QKD demonstrations over urban infrastructures require complex stabilization and synchronization systems to maintain a low quantum bit error and high secret key rates over time. Here we present a field trial that exploits low-complexity self-stabilized hardware and a novel synchronization technique, to perform QKD over optical fibers deployed in the city center of Padua, Italy. Two techniques recently introduced by our research group are evaluated in a real-world environment: the iPOGNAC polarization encoder was used for preparation of the quantum states, while temporal synchronization was performed with the Qubit4Sync algorithm. The results here presented demonstrate the validity and robustness of our resource-effective QKD system, which can be easily and rapidly installed in an existing telecommunication infrastructure, thus representing an important step towards mature, efficient, and low-cost QKD systems.

S-15176 reduces the hepatic injury in rats subjected to experimental ischemia and reperfusion

The protective effect of N-[(3, 5-di-tertiobutyl-4-hydroxy-1-thiophenyl)]-3-propyl-N'-(2,3, 4-trimethoxybenzyl)piperazine (S-15176) on liver injury induced by warm ischemia-reperfusion was investigated using a rat model. Animals were subjected to 2 h of ischemia followed by different reperfusion times. Hepatocyte integrity was assessed by measuring plasma alanine and aspartate aminotransferase activities, and by determining reduced and oxidized glutathione in plasma and bile. Hepatocyte function was quantitated by determining bile flow and liver ATP content. Ischemia-reperfusion resulted in severe hepatic injury involving a huge increase in alanine and aspartate aminotransferase activities, a drop in ATP content, and a decrease in bile flow. Plasma and bile reduced (GSH) and oxidized (GSSG) glutathione concentrations were inversely related: plasma levels increased when biliary levels decreased. This was associated with a decrease in animal survival (-34%). S-15176 pretreatment (1.25, 2.5, 5 or 10 mg kg(-1) day(-1)) improved the survival rate and limited tissue damages in a dose-dependent manner. The pretreatment also reduced the aminotransferase leakage from hepatocytes and the increase in plasma glutathione levels. In addition, normalization of the plasma GSSG/GSH ratio, a good index of an oxidative stress, was observed in groups treated with the higher dosage, suggesting that the antioxidant properties demonstrated for the compound in vitro (IC(50)=0.3 microM towards lipid peroxidation) could play a role in its protective effect. S-15176 pretreatment also protected the organ from the drop in ATP levels. At the higher dose, ATP content was maintained at a level almost 86% of the sham-operated group after 60 min of reperfusion. This was associated with a restoration of the biliary flow. These data suggest that S-15176 may be a useful drug in liver surgery to prevent ischemia-reperfusion injury.