Scott Johnstun

Decoy state methods improve the feasibility of quantum key distribution (QKD) by enabling the use of simple, robust sources, and techniques have been developed to allow for the use of decoy analysis in the regime where only a finite number of signals are sent. We present an iid security proof for finite-size key rates of prepare-and-measure protocols with probabilistic testing, including decoy state methods, within a composable security framework that allows for future extensions to device imperfections. Additionally, we improve the acceptance set over previous works through the use of entrywise constraints, allowing us to efficiently perform decoy state protocols. Moreover, we introduce a new figure of merit, the expected key rate, to capture the tradeoff between aborting too often and achieving high key rates, which allows for increased practicality of QKD implementations.