Aodhan Corrigan

Quantum Dots can generate on-demand, highly indistinguishable photons for quantum information purposes. We make use of a high performance quantum dot with dynamic polarization modulation in order to experimentally implement the BB84 protocol. State preparation is achieved with a custom built pulse-pattern generator and a 10^5-bit random sequence controlling an electro-optical modulator and an 80 MHz repetition rate. These are then detected in a 4 state polarization analyzer with which we record a QBER of 2.9%. In order to gauge the performance of the protocol, we make use of advanced numerical techniques to compute lower bounds on secure key rates. These techniques allow us to demonstrate the security and performance of this protocol while considering device imperfections such as the source on Alice's side and unequal detection efficiencies on Bob's side. Our detailed analysis of the protocol’s performance including device imperfections is an important step towards practical implementations of QKD.

We examine the performance of three Quantum Key Distribution (QKD) protocols with different classical announcement structures, namely BB84, SARG04 and No Public Announcement of Basis (NPAB) BB84, using numerical security proof techniques. We simulate these protocols in a Weak Coherent Pulse (WCP) implementation in order to characterize their behaviour in a realistic implementation without decoy states. We vary the quantum channel characteristics and compare key rates of the three protocols in asymptotic and finite-size regimes. The three protocols show different relative advantages depending on the channel behaviour. Canonical BB84 shows robustness against errors and depolarization, SARG04 demonstrates resilience against high loss channels and NPAB BB84 shows potential advantages when we introduce physical misalignment between QKD devices.