Adam Walton

A central broadcast Quantum Key Distribution protocol employs a thermal source to produce a secret key between Alice and Bob in the presence of an eavesdropper, Eve. Intensity correlations arising due to the Hanbury Brown and Twiss effect are used to produce correlated strings of quadrature measurements between each party, which may then be converted into bit strings. Using analytic methods, as well as through Monte Carlo simulations, we find that the correlations survive a series of beam splitters, and that the bit strings produced are suitable for distilling into a shared key. As thermal sources are already regularly used in modern communications equipment, this may allow quantum key distribution to be performed without using specialist equipment, with future work focusing on experimental implementations of the protocol in the microwave region.