Time evolution of the population of the D3/2 (red dotted line), S1/2 (black dashed line) and D5/2 (dot-dashed blue line) states during an incomplete STIRAP process driven by Gaussian pulses ΩB(t) and ΩR(t) kept constant since t = 40  μs (see equation (6))

Figure 8. Time evolution of the population of the D3/2 (red dotted line), S1/2 (black dashed line) and D5/2 (dot-dashed blue line) states during an incomplete STIRAP process driven by Gaussian pulses ΩB(t) and ΩR(t) kept constant since t = 40  μs (see equation (6)). Laser parameters are τ = Δt = 28  μs, ΩC/2π = 50 MHz, ΔC/2π = 10 MHz, \Omega _B^0/2\pi =400 MHz, ΔB/2π = 100 MHz, \Omega _R^0/2\pi =40 MHz, \Delta _R=\Delta _B-\Delta _C(1+\sqrt{1+4\alpha _C^2})/2.

Abstract

A stimulated Raman adiabatic passage (STIRAP)-like scheme is proposed to exploit a three-photon resonance taking place in alkaline-earth-metal ions. This scheme is designed for state transfer between the two fine structure components of the metastable D-state which are two excited states that can serve as optical or THz qubit. The advantage of a coherent three-photon process compared to a two-photon STIRAP lies in the possibility of exact cancellation of the first-order Doppler shift which opens the way for an application to a sample composed of many ions. The transfer efficiency and its dependence with experimental parameters are analysed by numerical simulations. This efficiency is shown to reach a fidelity as high as (1–8 × 10−5) with realistic parameters. The scheme is also extended to the synthesis of a linear combination of three stable or metastable states.