Double-excitation transfer in dimer and trimer three-level systems using laser pulses and single photons

We derive and simulate the wavefunctions and double-excitation probabilities for dimer and trimer three-level systems. Perfect state transfer occurs for pulse strengths that are odd multiples of π /2 when the parameter Jt equals odd multiples of π /2 and π /2 for the dimer and trimer, respectively. Near-perfect state transfer with a single photon occurred for photon coupling strength g =2 J when Jt=1.99,19.87 in the dimer and Jt=2.62,25.51 in the trimer. The nature of perfect state transfer is due to localization and transfer of double excitations for given pulse strengths and times.