A quantum repeater hop requires two sources of entangled photon pairs separated by distance L. (infinite symbols in lower inset). One photon from each pair is sent toward a central measurement node(central shaded area in figure), where they are stored in quantum memories. Their partner photons are sent in opposite directions, also stored in quantum memories separated by a distance 2L. A measurement quantifying the indistinguishability of the two photons arriving at the central node, similar to what was demonstrated by Figueroa’s team, can be used to entangle the distantly located photons.