Fast Generation of 2N‐Photon Fock States using Shortcuts to Adiabaticity and Ultrastrong Light–Matter Coupling

By using shortcuts to adiabatic (STA) method, the proposal is to implement a fast multi‐photon down‐conversion, which can rapidly create 2N photons from the quantum vacuum based on the counter‐rotating effect of an ultrastrong light–matter coupling. The energy for the produced photons is given by a high‐frequency pump field. The STA method is used to design the driving fields to induce a rapid population transfer. Such an accelerated evolution can restrain the influence of decoherence during the evolution, so as to generate Fock states from vacuum with high fidelities. Off‐resonantly driving a three‐level atom can create 2N photons from the vacuum, where the upper two levels of the atom are ultrastrongly coupled to a single‐mode cavity. This can prove that the vacuum of space is not empty but filled with a sea of virtual particles.