Thanks for this article, the previous description of the experiment I read omitted the 'discard the result unless a measurement show that the entanglement was s

Thanks for this article, the previous description of the experiment I read omitted the 'discard the result unless a measurement show that the entanglement was successful' step, leaving me very confused.. I didn't know that this was possible, that said I still don't have any clue about HOW this is possible.