Pair Production with Ultracold Atoms

Electron-positron pair production in quantum electrodynamics (QED) is predicted to occur at electric field strengths beyond Schwinger’s limit of approximately E=10$^{18}$ V/m. However, fields on this scale are not experimentally accessible, and direct observation of pair production is currently out of reach. The versatility of ultra-cold atomic experiments makes it possible to simulate these quantum phenomena. Here, we exploit the mapping between the Dirac dispersion relation that underlies pair production and the dispersion relation of a 1-D optical lattice at the edge of the Brillouin zone. A linear force applied to the atoms models an electric field, and atoms excited to the second band of the lattice simulate pair production. We load a cloud of $^{87}$Rb into the lowest band of such a lattice and study the number of 'pairs' produced as a function of the force applied or the "rest mass", allowing us to probe Schwinger's limit.