Exceeding the Sauter-Schwinger limit of pair production with a quantum gas A. M. Pi˜ neiro, D. Genkina, Mingwu Lu and I. B. Spielman Joint Quantum Institute, National Institute of Standards and Technology and University of Maryland, Gaithersburg, MD 20899, USA E-mail: pineiro@.umd.edu, ian.spielman@nist.gov Abstract. We quantum-simulated particle-antiparticle pair production with a bosonic quantum gas in an optical lattice by emulating the requisite 1d Dirac equation and uniform electric field. We emulated field strengths far in excess of Sauter- Schwinger’s limit for pair production in quantum electrodynamics, and therefore readily produced particles from “the Dirac vacuum” in quantitative agreement with theory. The observed process is equivalently described by Landau-Zener tunneling familiar in the atomic physics context. The creation of particle-antiparticle pairs from vacuum by a large electric field is a phenomenon arising in quantum electrodynamics (QED) [1, 2, 3, 4], with threshold electric field strength E c ≈ 10 18 V/m first computed by J. Schwinger [5]. Electric fields on this scale are not experimentally accessible; even the largest laboratory fields produced by ultrashort laser pulses [6] fall short, making direct observation of pair production out of reach of current experiments. To experimentally probe this limit with a bosonic quantum gas, we engineered the relativistic 1d Dirac Hamiltonian with mc 2 reduced by 17 orders of magnitude, allowing laboratory scale forces to greatly exceed Sauter-Schwinger’s limit. We readily measured pair production and demonstrated that this high-energy phenomenon is equivalently described by Landau-Zener tunneling [7, 8]. In the Dirac vacuum, the enormous electric field required is E c = m 2 e c 3 /q e , (1) determined by the particle/antiparticle mass m e and charge q e . For an applied electric field E, the pair production rate is governed only by the dimensionless ratio E/E c , allowing our physical system with very different characteristic scales to be used to realize the underlying phenomenon. Our system was well described by the 1d Dirac Hamiltonian [9, 10, 11, 12] ˆ H D = c ˆ pσ z + mc 2 σ x , (2) where ˆ p is the momentum operator and σ x,y,z are the Pauli operators. Starting with m = 0, the 1d Dirac Hamiltonian describes particles with velocities ±c, that are then coupled with strength mc 2 to give the familiar E (p)= ±(p 2 c 2 + m 2 c 4 ) 1/2 dispersion relation for relativistic particles and antiparticles. At zero momentum, this dispersion arXiv:1903.09667v1 [quant-ph] 22 Mar 2019