The purpose of my thesis is to analyze the Earth-satellite quantum communication using a simulation and to examine the feasibility of a global, satellite based quantum key distribution network.
The development of quantum computers effects several fields of the current information technology. In digital communication the data encryption and the distribution of keys used for the encryption rely on computationally secure cryptosystems, which means that cracking the encryption with current technology would take astronomical time. With the arrival of quantum computers, this security will not be enough, the current cryptosystems (e.g., RSA and the relying SSH or SSL/TLS) will be breakable in short time with existing quantum algorithms (e.g., Shor's algorithm).
For this reason, it is expedient to develop and apply cryptosystems as soon as possible, that can withstand quantum mechanical code breaking. One possible solution is the quantum key distribution using optical fiber cables, but because of the physical limitations, this can only be used for nodes with up to 100km between them. If we want to increase this distance, then a possible solution would be a satellite-based, free-space quantum key distribution, which could provide global, information-theoretically secure key distribution between two arbitrary nodes on Earth.
In this work, I analyze the properties of the Earth-satellite quantum communication by simulating a global, satellite based quantum key distribution network, evaluate the results and propose solutions to correct some of the effects that distort the polarization measurement of the photons.