Optimum pulse shapes for stimulated Raman adiabatic passage

Stimulated Raman adiabatic passage (STIRAP) driven with pulses of optimum shape and delay has the potential of reaching fidelities high enough to make it suitable for quantum-information processing. The optimum pulse shapes are obtained upon reduction of STIRAP to effective two-state systems. We use the Dykhne-Davis-Pechukas (DDP) method to minimize nonadiabatic transitions and to maximize the fidelity of STIRAP. This results in a particular relation between the pulse shapes of the two fields driving the Raman process. The DDP-optimized version of STIRAP maintains its robustness against variations in the pulse intensities and durations, the single-photon detuning, and possible losses from the intermediate state.

Figure 1

(Color online) Pulse shapes. 1: ideally optimized pulse shapes, which obey the optimization condition (17) for all times $t$; 2: pulse shapes with a hypergaussian mask (23), with $n=3$, $\lambda =4$, and $T_0=2T$; 3: Gaussian pulses (27), with pulse delay $\tau =1.2T$.

Figure 2

(Color online) Deviation (infidelity) from complete population transfer vs the peak Rabi frequency for Gaussian (delay $\tau =1.2T$) and DDP-optimized pulse (23) ($n=3$, $\lambda =4$, $T_0=2T$ and $n=1$, $\lambda =2$, $T_0=2T$).

Figure 3

(Color online) Deviation (infidelity) from complete population transfer vs the peak Rabi frequency for DDP-optimized pulses for different values of the width $T_0$ of the hypergaussian $\left(n=3\right)$ mask $F\left(t\right)$ [Eq. (23)].

Figure 4

(Color online) Line profile as a function of the common detuning $\Delta$ from the intermediate level for DDP-optimized $\left(n=3,\lambda =4,T_0=2T\right)$ and Gaussian pulses (delay $\tau =1.2T$) for a peak Rabi frequency $\Omega =20$.

Figure 5

(Color online) Raman line profile for the DDP-optimized $\left(n=3,\lambda =4T_0=2T\right)$ and Gaussian pulses (delay $\tau =1.2$) for a peak Rabi frequency $\Omega =20$.

Figure 6

(Color online) Transfer efficiency for fractional STIRAP vs the peak Rabi frequency for DDP-optimized pulses (with $n=3$, $\lambda =4$, $T_0=2T$ and $n=1$, $\lambda =2$, $T_0=2T$) and Gaussian pulses (31) (with $\tau =1.4T$).