# Long-distance device-independent quantum key distribution

## TL;DR

This paper explores extending the distance of device-independent quantum key distribution by using qubit amplifiers to overcome channel loss limitations, analyzing resource requirements for practical long-distance secure communication.

## Contribution

It investigates the use of qubit amplifiers in photonic DIQKD with finite data, identifying key resource thresholds for feasible long-distance implementation.

## Key findings

- Qubit amplifiers significantly increase achievable DIQKD distance.
- Detection efficiency and entanglement quality are critical resources.
- Finite data analysis provides realistic resource estimates.

## Abstract

Besides being a beautiful idea, device-independent quantum key distribution (DIQKD) is probably the ultimate solution to defeat quantum hacking. To guarantee security, it requires, however, that the fair-sampling loophole is closed, which results in a very limited maximum achievable distance. To overcome this limitation, DIQKD must be furnished with fair-sampling devices like, for instance, qubit amplifiers. These devices can herald the arrival of a photon to the receiver and thus decouple channel loss from the selection of the measurement settings. Consequently, one can safely postselect the heralded events and discard the rest, which results in a significant enhancement of the achievable distance. In this work, we investigate photonic-based DIQKD assisted by two main types of qubit amplifiers in the finite data block size scenario, and study the resources -- particularly, the detection efficiency of the photodetectors and the quality of the entanglement sources -- that would be necessary to achieve long-distance DIQKD within a reasonable time frame of signal transmission.