Abstract
Memory-assisted quantum key distribution (MA-QKD) systems are among novel promising solutions that can improve the key-rate scaling with channel loss. By using a middle node with quantum storage and measurement functionalities, they offer the same key-rate scaling with distance as a single-node quantum repeater. However, the distance at which they can surpass the nominal key rate of repeaterless systems, in terms of bits per second, is typically long, owing to the efficiency and/or interaction time issues when one deals with quantum memories. This crossover distance can be a few hundred kilometres, for instance, when one relies on the exchange of infinitely many key bits for the key-rate analysis. In a realistic setup, however, we should account for the finite-key effects in our analysis. Here, we show that accounting for such effects would actually favour MA-QKD setups, by reducing the crossover distance to the regime where realistic implementations can take place. We demonstrate this by rigorously analysing a decoy-state version of MA-QKD, in the finite-key regime, using memory parameters already achievable experimentally. This provides us with a better understanding of the advantages and challenges of working with memory-based systems.
Highlights
Quantum key distribution (QKD) has made a lot of progress as part of the solution package for secure communications in the quantum era [1]
We find that Memory-assisted quantum key distribution (MA-QKD) is inherently more resistant to finite-key effects, and it experiences a lower reduction in secret key rate than measurement-device-independent QKD (MDI-QKD)
By borrowing ideas from quantum repeaters, MA-QKD can improve the scaling of repeaterless QKD systems
Summary
Keywords: quantum key distribution, quantum communications, quantum memories, quantum optics, quantum repeaters Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
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