Creation of coherent superpositions using Stark-chirped rapid adiabatic passage

We show that the technique of Stark-chirped rapid adiabatic passage (SCRAP), hitherto used for complete population transfer between two quantum states, offers a simple and robust method for creating coherent superpositions of states. SCRAP uses two laser pulses: a strong far off-resonant pulse modifies the transition frequency by inducing ac Stark shifts in the energies of the two states, and an appropriately offset in time, near-resonant and moderately strong pump pulse drives the population between the states via one of the induced diabatic level crossings. The populations in the created superposition are controlled by the detuning of the pump laser from the transition frequency and are insensitive to variations in the intensities of the pump and Stark lasers, as long as these are sufficiently large to allow adiabatic evolution. (C) 2002 Elsevier Science B.V. All rights reserved.