The reversible transfer of quantum states of light into and out of matter constitutes an important building block for future applications of quantum communication: it will allow the synchronization of quantum information

^{1}, and the construction of quantum repeaters

^{2}and quantum networks

^{3}. Much effort has been devoted to the development of such quantum memories

^{1}, the key property of which is the preservation of entanglement during storage. Here we report the reversible transfer of photon–photon entanglement into entanglement between a photon and a collective atomic excitation in a solid-state device. Towards this end, we employ a thulium-doped lithium niobate waveguide in conjunction with a photon-echo quantum memory protocol

^{4}, and increase the spectral acceptance from the current maximum

^{5}of 100 megahertz to 5 gigahertz. We assess the entanglement-preserving nature of our storage device through Bell inequality violations

^{6}and by comparing the amount of entanglement contained in the detected photon pairs before and after the reversible transfer. These measurements show, within statistical error, a perfect mapping process. Our broadband quantum memory complements the family of robust, integrated lithium niobate devices

^{7}. It simplifies frequency-matching of light with matter interfaces in advanced applications of quantum communication, bringing fully quantum-enabled networks a step closer.