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

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 local 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.