Entanglement based quantum key distribution over long distances using hybrid entangled states

In this talk, I will provide a general introduction to entanglement based quantum key distribution (QKD), which so far has only been studied in either fully discrete variable (DV) systems (like polarization of photons) or in fully continuous variable (CV) systems (like squeezed coherent states). I will discuss the advantages and disadvantages of using both systems. After this introduction, I will introduce a scheme which uses the advantages of both DV and CV systems to produce long-distance entanglement, which can then be used for QKD. The key idea is for Alice and Bob to first prepare entanglement between DV and CV systems locally, known as hybrid entanglement (HE). Then, we use the CV part for increasing the transmission distance, while we use the DV part for achieving high key rates. This way it is possible to achieve upto 300 km of transmission distances even with realistic sources of error. Moreover, this also points out that HE states provide a clear advantage for practical long-distance high-rate entanglement.