Manipulation of the Vacuum to Control Its Field-Induced Decay

: It has long been predicted that permanent electron-positron pairs can be created from the quantum vacuum at those spatial regions where an external electric field exceeds a supercritical value. By solving the Dirac equation numerically, we show that the yield of the created positrons at targeted energies can be controlled via a second (subcritical) electric field that is placed far outside the creation zone. This is a clear indication of the nonlocal character of the pair-creation process, as the second field can be placed at distant spatial regions that are never visited by the created positrons. This counterintuitive phenomenon can be understood in terms of a dressing of the vacuum state long before the particles are actually created. We present an analytical expression for the spectrum of the created particles that describes all quantitative features of this dressing and predicts how the second field can be used to increase as well as decrease the electron-positron yield for desired energies.