Alberto Boaron

To enable the widespread use of Quantum Key distribution, network integration is crucial. We present a case study where we investigate the performance of a 2.5 GHz simplified BB84 implementation using a wavelength of 1310nm multiplexed in a fiber together with 13 classical channels. We found that a secret key exchange at a distance of 95.5km and classical launch power up to 8.9dBm was possible. Further, we compare our results to previous results, both for continuous variable systems using a wavelength of 1550nm and discrete variable systems using either a wavelength of 1550nm or 1310nm. We find that both for long distance and for high power in the classical channels, the discrete variable systems perform better.

We investigate a class of partially device-independent quantum key distribution protocols based on a prepare-and-measure setup which simplifies their implementation. The security of the protocols is based on the assumption that Alice’s prepared states have limited overlaps, but no explicit bound on the Hilbert space dimension is required. The protocols are therefore immune to attacks on Bob’s device, such as blinding attacks. The users can establish a secret key while continuously monitoring the correct functioning of their devices through observed statistics. We report a proof- of-principle demonstration, involving mostly off-the-shelf equipment, as well as a high-efficiency superconducting nanowire detector. A positive key rate is demonstrated over a 4.8km low-loss optical fiber with finite-key analysis. The prospects of implementing these protocols over longer distances is discussed.

We implement 5 GHz clocked polarization-based simplified BB84 protocol. Secret keys can be distributed over 151.5 km of standard telecom fiber at a rate of 54.5 kbps. The high clock frequency might give rise to correlations between the pulses. We characterize the correlations in decoy intensity, polarization and in the phase between the pulses and discuss their impact on the security of the protocol.