The influence of ski helmets on sound perception and sound localisation on the ski slope

Objectives: The aim of the study was to investigate whether a ski helmet interferes with the sound localization and the time of sound perception in the frontal plane. Material and Methods: Twenty-three participants (age 30.7±10.2) were tested on the slope in 2 conditions, with and without wearing the ski helmet, by 6 different spatially distributed sound stimuli per each condition. Each of the subjects had to react when hearing the sound as soon as possible and to signalize the correct side of the sound arrival. Results: The results showed a significant difference in the ability to localize the specific ski sounds; 72.5±15.6% of correct answers without a helmet vs. 61.3±16.2% with a helmet (p < 0.01). However, the performance on this test did not depend on whether they were used to wearing a helmet (p = 0.89). In identifying the timing, at which the sound was firstly perceived, the results were also in favor of the subjects not wearing a helmet. The subjects reported hearing the ski sound clues at 73.4±5.56 m without a helmet vs. 60.29±6.34 m with a helmet (p < 0.001). In that case the results did depend on previously used helmets (p < 0.05), meaning that that regular usage of helmets might help to diminish the attenuation of the sound identification that occurs because of the helmets. Conclusions: Ski helmets might limit the ability of a skier to localize the direction of the sounds of danger and might interfere with the moment, in which the sound is firstly heard

Polarisation Based Entanglement Distribution Quantum Networking

Quantum networks based on entanglement distribution have shown promise for building scalable and fully connected systems that support quantum key distribution. This work aims to go beyond simply implementing quantum key distribution and explore the potential of such networks for implementing quantum photonic interconnects. Our research demonstrates the passive polarization stability of these networks for over a week and highlights the benefits of dynamic reconfiguration to remove redundant resources. We discuss recent advancements in quantum frequency conversion and quantum memory-based networks, and argue that the development of scalable, long-distance interconnects is crucial for advancing quantum technology. Our findings have important implications for the future of quantum networking and highlight the need for entanglement based photonic interconnect networks, such that quantum technology can scale beyond monolithic systems

Towards a Fully Connected Many-User Entanglement Distribution Quantum Network Within Deployed Telecommunications Fibre-Optic Infrastructure

We present developments in entanglement distribution quantum networks towards a fully connected, scalable, many-user network, which is not limited to simple quantum key distribution protocol

Entanglement distribution quantum networking within deployed telecommunications fibre-optic infrastructure

Quantum networks have been shown to connect users with full-mesh topologies without trusted nodes. We present advancements on our scalable polarisation entanglement-based quantum network testbed, which has the ability to perform protocols beyond simple quantum key distribution. Our approach utilises wavelength multiplexing, which is ideal for quantum networks across local metropolitan areas due to the ease of connecting additional users to the network without increasing the resource requirements per user. We show a 10 user fully connected quantum network with metropolitan scale deployed fibre links, demonstrating polarisation stability and the ability to generate secret keys over a period of 10.8 days with a network wide average-effective secret key rate of 3.38 bps

A study of polarization compensation for quantum networks

The information-theoretic unconditional security offered by quantum key distribution has spurred the development of larger quantum communication networks. However, as these networks grow so does the strong need to reduce complexity and overheads. Polarization-based entanglement distribution networks are a promising approach due to their scalability and no need for trusted nodes. Nevertheless, they are only viable if the birefringence of all-optical distribution fibres in the network is compensated to preserve the polarization-based quantum state. The brute force approach would require a few hundred fibre polarization controllers for even a moderately sized network. Instead, we propose and investigate four different realizations of polarization compensation schemes that can be used in quantum networks. We compare them based on the type of reference signals, complexity, effort, level of disruption to network operations and performance on a four-user quantum network.</p