Rapid population transfer of a two-level system by a polychromatic driving field

Abstract

We propose a simple exact analytical solution for a model consisting of a two-level system and a polychromatic driving field. It helps us to realize a rapid complete population transfer from the ground state to the excited state, and the system can be stable at the excited state for an extremely long time. A combination of the mechanism and the Rydberg atoms successfully prepares the Bell state and multipartite W state, and the experimental feasibility is discussed via the current experimental parameters. Finally, the simple exact analytical solution is generalized into a three-level system, which leads to a significant enhancement of the robustness against dissipation.

Figure 1

The populations of state |e〉 as functions of Ωt with different parameters, where the population is defined as 〈e|ρ(t)|e〉. The dash-dotted lines indicate the situations without symmetrically detuned fields. The initial states are all the ground state. The other relevant parameters of subgraphs are chosen as: (a) N = 2; (b) N = 10; (c) N = 2; (d) Δ = 2Ω and δ = 10Ω; (e) N = 2 and γ = 0.1Ω.

Figure 2

(a,b) Respectively illustrate the populations of |T〉 as functions of Ωt with different Δ. (c,d) exhibit the time evolutions of population for the multipartite W state with $M=\mathrm{3,}\mathrm{\Delta }=2\sqrt{3}\mathrm{\Omega }$ and $M=\mathrm{5,}\mathrm{\Delta }=2\sqrt{5}\mathrm{\Omega }$, respectively. The other relevant parameters are: N = 10 and U_αβ = 400Ω. Solid lines are all governed by the full Hamiltonian and empty circles are governed by the corresponding effective Hamiltonian.

Figure 3

The time evolutions of state |e〉 with different cases for the Λ type atom. N are all set as 10.