Optimisation of Optical Network for Continuous-Variable Quantum Key Distribution by Means of Simulation

The unprecedented breakthrough in the field of quantum computing in the last several years is threatening with the exploitation of our current communication systems. To address this issue, researchers are getting more involved in finding methods to protect these systems. Amongst other tools, quantum key distribution could be a potentially applicable way to achieve the desired level of protection. In this paper we are evaluating the physical layer of an optical system realising continuous variable quantum key distribution (CVQKD) with simulations to determine its weak points and suggest methods to improve them. We found that polarisation dependent devices are crucial for proper operation, therefore we determined their most defining parameters from the point of operation and suggested extra optical devices to largely improve transmission quality. We also paid attention to polarisation controlling in these sort of systems. Our findings could be valuable as practical considerations to construct reliable CVQKD optical transmission links

Amplified spontaneous emission based quantum random number generator

There is an increasing need for true random bits, for which true random number generators (TRNG) are absolutely necessary, because the output of pseudo random number generators is deterministically calculated from the previous states. We introduce our quantum number generator (QRNG) based on amplified spontaneous emission (ASE), a truly random quantum physical process. The experimental setup utilizes the randomness of the process. In this system, optical amplifiers (based on ASE) play the major role. The suitable sampling rate is selected in order to build the fastest generator, while avoiding the correlation between consecutive bits. Furthermore, the applied post-processing increases the quality of the random bits. As a results of this, our system generated random bits which successfully passed the NIST tests. Our real-time generation system – which is currently a trial version implemented with cheap equipment – will be available for public use, generating real time random bits using a web page

Integration of QKD Channels to Classical High-speed Optical Communication Networks

Integrating Quantum Key Distribution service with classical high-speed optical data transmission using a dense wavelength division multiplexing technique in a fiber is a cost-effective solution to improve the network's security. In this multichannel system, several noise sources degrade the quality of the quantum channel. The dominant degradation effect is determined by modeling in different cases. Optical filtering cannot decrease spontaneous Raman Scattering caused by the classical optical channels. So this nonlinear optical effect is investigated in detail with different system parameter setups. The optimal channel allocation and the required bandgap between the classical and quantum channels are determined