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Double slits provide incoming particles with a choice. Those that survive passage through the slits have chosen from two possible paths, which interfere to distribute them in a wave-like manner. Such wave–particle duality continues to be challenged and investigated in a broad range of disciplines with electrons, neutrons, helium atoms, C60 fullerenes, Bose–Einstein condensates and biological molecules. All variants have hitherto involved material constituents. We present a matterless double-slit scenario in which photons generated from virtual electron–positron pair annihilation in head-on collisions of a probe laser field with two ultra-intense laser beams form a double-slit interference pattern. Such electromagnetic fields are predicted to induce material-like behaviour in vacuum, supporting elastic scattering between photons. Our double-slit scenario presents, on the one hand, a realizable method with which to observe photon–photon scattering and, on the other hand, demonstrates the possibility of both controlling light with light and non-locally investigating features of the quantum vacuum structure. [ABSTRACT FROM AUTHOR]