only using the channel a finite number of times. As such, the burden of demonstrating a quantum repeater is now somewhat relieved in comparison to what was previously thought would be necessary.

From an experimental perspective, it could be of interest to perform a test using the results of our paper in order to demonstrate a working quantum repeater. A convincing approach for doing so would be to conduct an actual secret-key-distillation protocol over some finite number of uses of the channel and determine what secret-key rates can be achieved. [RGRKVRHWE17]{} details methods for determining secret-key rates that are achievable in particular physical setups. For a given rate and number of channel uses, one can then compare the results with our plots (or other plots generated via the same method for different parameter values) to determine if the rate is achieved is larger than the upper bounds in our plots; if it is the case, then one can claim a working quantum repeater, albeit with the understanding that our upper bounds are the normal approximations of the true finite-length upper bounds (as discussed previously). This approach is to be contrasted with those that estimate the quantum bit-error rate from just 