Non-fidelity 1 − <em>F</em> = 1 − <em>P</em><sub>Q</sub> of the full transfer driven by Gaussian pulses plus weak coupling decay versus pulse duration and delay τ = Δ<em>t</em> (see equation (6))

<p><strong>Figure 4.</strong> Non-fidelity 1 − <em>F</em> = 1 − <em>P</em><sub>Q</sub> of the full transfer driven by Gaussian pulses plus weak coupling decay versus pulse duration and delay τ = Δ<em>t</em> (see equation (<a href="http://iopscience.iop.org/0953-4075/46/14/145502/article#jpb467794eqn06" target="_blank">6</a>)). Laser parameters are \Omega _B^0/2\pi =400 MHz, Δ<sub><em>B</em></sub>/2π = 100 MHz, \Omega _R^0/2\pi =40 MHz and Δ<sub><em>R</em></sub> = Δ<sub><em>B</em></sub> − Δ<sub><em>C</em></sub> − α<sub><em>C</em></sub>Ω<sub><em>C</em></sub>/2. The open red circles on the solid line are for Ω<sub><em>C</em></sub>/2π = 1 MHz, Δ<sub><em>C</em></sub>/2π = 10 MHz, the black crosses on the dash-dotted line are for Ω<sub><em>C</em></sub>/2π = 5 MHz, Δ<sub><em>C</em></sub>/2π = 50 MHz and the full blue squares on the dashed line are for Ω<sub><em>C</em></sub>/2π = 10 MHz, Δ<sub><em>C</em></sub>/2π = 100 MHz.</p> <p><strong>Abstract</strong></p> <p>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 <b>×</b> 10<sup>−5</sup>) with realistic parameters. The scheme is also extended to the synthesis of a linear combination of three stable or metastable states.</p>