A robust extension of stimulated Raman adiabatic passage to N-level systems

Abstract

Summary form only given. We show that the counterintuitive pulse sequence in stimulated Raman adiabatic passage (STIRAP), in which the Stokes pulse precedes the pump, emerges automatically from a variant of optimal control theory we have previously called optimization. Because local optimization is a well-defined, automated computational procedure, this opens the door to automated computation of generalized STIRAP schemes in arbitrarily complicated N-level coupling situations. If the coupling is sequential, a simple qualitative extension of STIRAP emerges: the Stokes pulse precedes the pump as in the three-level system. In addition, spanning both the Stokes and pump pulses are pulses corresponding to the transitions between the N-2 intermediate states with intensities about an order of magnitude greater than those of the Stokes and pump pulses. We call this a straddling STIRAP (or S-STIRAP) pulse sequence. This scheme is amazingly robust, leading to almost 100% population transfer with significantly less population transfer to the N-2 intermediate states than in previously proposed extensions of STIRAP.