Fully tested QKD protocols and working hardware solutions exist and are ready for deployment [ED16]. Indeed, commercial QKD systems have been available for some time, but closer scrutiny has revealed security weaknesses caused not by a failure of the protocol itself, but by vulnerabilities of the physical hardware. Hence, in a quest to ameliorate such side-channel attacks and to improve the overall performance, researchers have continued to propose new and sometimes better QKD protocols. A particularly interesting method, named Measurement Device Independent (MDI) QKD [HKL12], completely avoids side-channel attacks on the detectors, which are most vulnerable part of the system. Another important advantage the MDI QKD protocol is that it locates the most challenging tasks and costly hardware elements at a central node (“Charlie”), which allows for a convenient and cost-effective star-type architecture and removes cost and complexity from the users (“Alices”). At the UofC an MDI QKD system has been demonstrated over deployed optical fibres and in another experiment with coexisting classical communication.
In the QCloudLab we are developing a quantum dot based MDI-QKD system in collaboration with the National Research Council of Canada for the fabrication of quantum dots. The NRC quantum dots are based on a InAsP layer embedded in InP nanowires. These quantum dots have shown very large collection efficiencies [GB14] and are currently being integrated with waveguide structures to produce single-photon emitters that could easily be transported and installed in a cryostat. Currently the optimal emission wavelength is at around 900 nm, i.e. not well suited for neither free space or fibre long-distance transmission. Thus, a proof-of-principle demonstration over shorter fibres is a first step. In parallel, quantum dot emission around 1300 nm (telecom O-band) [SH18] will be further studied with the aim of improving the collection efficiency. Finally, we will collaborate on efforts to perform frequency conversion in commercial waveguide-based non-linear crystals [AD18].