Coherent states stimulated Raman adiabatic passage

Coherent excitation of quantum systems by external fields is a versatile and powerful tool for application in quantum control. In particular, adiabatic evolution has been widely used to produce population transfer between discrete quantum states. Eor two states the control is by means of a varying detuning (a chirp), while for three states the change is induced, for example, by a pair of pulses, offset in time, that implement stimulated Raman adiabatic passage (STIRAP) [1-3]. STIRAP produces complete population transfer between the two end states 11) and 3) of a chain linked by two fields. In the adiabatic limit, the process places no temporary population in the middle state 2), even though the two driving fields - pump and Stokes-may be on exact resonance with their respective transitions, 1) 2)and... 

Starting with very weakly bound molecules produced by MA, coherent transfer to more deeply bound levels has been achieved in both Rb2 [134] and KRb [135]. The stimulated Raman adiabatic passage (STIRAP) process, incorporating pump and dump pulses in the counterintuitive order (see Figure 5.29), enabled high transfer efficiency. Pulses of cw laser light were used in order for the process to be phase coherent. In this initial work, the final states were not very deeply bound, 600 MHz for Rb2 and 10 GHz for KRb. In more recent work, very deeply bound states have been reached. In Cs2, levels bound by >1000cm have been populated... 

S. Q. Jin, S. Q. Gong, R. X. Li, and Z. Z. Xu. Coherent population transfer and superposition of atomic states via stimulated Raman adiabatic passage using an excited-doublet four-level atom. 

L. Wang, X. L. Song, A. J. Li and et al. Coherence transfer between atomic ground states by the technique of stimulated Raman adiabatic passage. Optics Letters 2008 Oct 15 33(20) 2380-2382. 

With a coherent stimulated Raman process (STIRAP) (see Sect. 7.3), nearly the whole initial population Ni may be transferred into the final level If) [1048]. Here no exact resonance with the intermediate excited level ) is wanted in order to avoid transfer losses by spontaneous emission from level ). The population transfer can be explained by an adiabatic passage between dressed states (that is, states of the molecule plus the radiation field) [1049, 1050]. 

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