Population transfer in a Lambda system induced by detunings

In this paper we propose a new protocol to achieve coherent population transfer between two states in a three-level atom by using two ac fields. It is based on the physics of Stimulated Raman Adiabatic Passage (STIRAP), but it is implemented with the constraint of a reduced control, namely one of the fields cannot be switched off. A combination of frequency chirps is used with resonant fields, allowing to achieve approximate destructive interference, despite of the fact that an exact dark state does not exist. This new chirped STIRAP protocol is tailored for applications to artificial atoms, where architectures with several elementary units can be strongly coupled but where the possibility of switching on and off such couplings is often very limited. Demonstration of this protocol would be a benchmark for the implementation of a class of multilevel advanced control procedures for quantum computation and microwave quantum photonics in artificial atoms.