Tunneling under Coherent Control by Sequences of Unitary Pulses

Ramsey fringes and time-domain multiple-slit interference from vacuum

Sequences of alternating-sign time-dependent electric field pulses lead to coherent interference effects in Schwinger vacuum pair production, producing a Ramsey interferometer, an all-optical time-domain realization of the multiple-slit interference effect, directly from the quantum vacuum. The interference, obeying fermionic quantum statistics, is manifest in the momentum dependence of the number of produced electrons and positrons along the linearly polarized electric field. The central value grows like N(2) for N pulses [i.e., N "slits"], and the functional form is well described by a coherent multiple-slit expression. This behavior is generic for many driven quantum systems.