Double-slit experiment at Fermi scale: Coherent photoproduction in heavy-ion collisions

The double-slit experiment has become a classic thought experiment for its clarity in expressing the central puzzle of quantum mechanics—wave-particle complementarity. Such wave-particle duality continues to be challenged and investigated in a broad range of entities with electrons, neutrons, helium atoms, C60 fullerenes, Bose-Einstein condensates, and biological molecules. In this Rapid Communication, we present a double-slit scenario at Fermi scale with new entities—coherent photon products in heavy-ion collisions. Virtual photons from the electromagnetic fields of relativistic heavy ions can fluctuate to quark-antiquark pairs, scatter off a target nucleus, and emerge as vector mesons. The two colliding nuclei can take turns to act as targets, forming a double-slit interference pattern. Furthermore, the “which-way” information can be partially solved using sufficiently-high multiplicity heavy-ion collisions so that the reaction plane can be determined, which demonstrates the complementary principle, a key concept of quantum mechanics.