This article describes experimental research studies conducted towards understanding the implementation aspects of high-capacity quantum-secured optical channels in missioncritical metro-scale operational environments based on Quantum Key Distribution (QKD) technology. The test bed for this research study was carefully designed to mimic such environments.To the best of our knowledge, this is the first time that an 800 Gbps quantum-secured optical channel-along with several other Dense Wavelength Division Multiplexed (DWDM) channels on the C-band and multiplexed with the QKD channel on the Oband-was established at distances up to 100 km, with secure-key rates relevant for practical industry use cases. In addition, during the course of these trials, transporting a blockchain application over this established channel was utilized as a demonstration of securing a financial transaction in transit over a quantum-secured optical channel.In a real-world operational environment, deployment of such high-capacity quantum-secured optical channels multiplexed with the quantum channel will inevitably introduce challenges due to their strict requirements, such as high launch powers and polarization fluctuations. Therefore, in the course of this research, experimental studies were conducted on the impact on the system performance-and specifically on the quantum channel-of several degradation factors present in real-world operational environments, including inter-channel interference (due to Raman scattering and nonlinear effects), attenuation, polarization fluctuations and distance dependency. The findings of this research pave the way towards the deployment of QKDsecured optical channels in high-capacity, metro-scale, missioncritical operational environments, such as Inter-Data Center Interconnects.

SUMMARYA high-speed one-to-all broadcasting algorithm is proposed whose performance does not deteriorate much when the number of processors is increased in a massively parallel computer. For the network topology, 3D torus networks are considered. Two methods are discussed for a system which broadcasts by repeating one-to-one communications. One uses paths having a smaller maximum transfer number to reduce the number of transfers, and the other presets the hardware to reduce the overhead of individual one-toone communications. These methods are evaluated using a double loop model which consists of an inner loop for local processing and an outer loop for global communications. When these methods are used, the scalability increases and for a 32K processor system a 4.2 times speedup in program execution can be achieved.

The authors developed an one-to-all broadcasting algorithm which is less dependent on the increase of processors, by reducing the overhead of each communications, and by shortening the message transmission sequence. The result shows that the program which employs this algorithm can achieve a 2.8 times speedup in the case of a 32K processor system.

This article describes experimental research studies conducted towards understanding the implementation aspects of high-capacity quantum-secured optical channels in mission- critical metro-scale operational environments using Quantum Key Distribution (QKD) technology. To the best of our knowledge, this is the first time that an 800 Gbps quantum-secured optical channel — along with several other Dense Wavelength Division Multiplexed (DWDM) channels on the C-band and multiplexed with the QKD channel on the O-band—was established at distances up to 100 km, with secret key-rates relevant for practical industry use cases. In addition, during the course of these trials, transporting a blockchain application over this established channel was utilized as a demonstration of securing a financial transaction in transit over a quantum-secured optical channel. The findings of this research pave the way towards the deployment of QKD-secured optical channels in high-capacity, metro-scale, mission-critical operational environments, such as Inter-Data Center Interconnects.