Thermal State Quantum Key Distribution

This thesis covers two separate fields of research, first focusing on quantum key distribution before covering research on atomic clock synchronisation.

Initially, a method of performing thermal state key distribution was analysed. A protocol for radio key distribution inspired by quantum methods which could be performed using easily accessible equipment was known, with some evidence that it could realistically be carried out, but this had yet to be confirmed in testing. In this writing, we first simulate the protocol in Python, and verify that the results of simulation suggests that a practical setup would be reasonable. After confirming that off-the-shelf broadcasting equipment may be used for the protocol, we performed both wired and wireless tests of the protocol and was able to distribute bit strings suitable for key distillation. This provides a method for performing quantum key distribution using only common radio equipment and open-source software -- a procedure which typically requires specialist equipment, is not compatible with current communication setups, and does not currently exist in a widely accessible form for public use.

For clock synchronisation, current accessible methods of wireless synchronisation have poor precision, relying on GPS for timing information. Optical protocols for synchronisation offer far more precise results, but require either line of sight or a fibre connection, which is not always reasonable to implement. This can lead to issues in which accessible methods of synchronisation are not sufficient for parties which require higher precision, such as in market trading. Here, we devise and test a radio-based method of clock synchronisation with commonly-used broadcast protocols based on experimental results observed in the first section of the thesis. From this testing, we find that the protocol is able to reach precision approximately 10^3 times smaller than the minimum advertised by the clocks used, which itself was already more precise than can be reached using GPS synchronisation.

Overall, this represents new methods of solving known problems; producing the security conferred by Quantum Key Distribution (QKD) and clock synchronisation, without requiring specialised equipment which may prevent other potential solutions from being viable in real-world applications. The ability to perform the experiments set up here with off-the-shelf radio equipment and open-source software provides a straightforward way to apply the protocols for any party interested in either of these fields. This will be shown to be especially true in the case of clock synchronisation, in which we find evidence that our protocol outperforms currently used methods by a significant margin while using similar equipment.