Yizhu Zhang, Tian-Min Yan, and Y. H. Jiang
https://journals.aps.org/prl/accepted/72070YfeY1813151b83985b6a2b9e1d97a95cc969
A time-resolved spectroscopic protocol exploiting terahertz-assisted photoionization is proposed to reconstruct transient density matrix. Population and coherence elements are effectively mapped onto spectrally separated peaks in photoionization spectra. The beatings of coherence dynamics can be temporally resolved beyond the pulse duration, and the relative phase between involved states is directly readable from the oscillatory spectral distribution. As demonstrated by a photo-excited multilevel open quantum system, the method shows potential applications for sub-femtosecond time-resolved measurements of coherent dynamics with free electron lasers and tabletop laser fields.
Quantum coherence is of potential applications from quantum computation using simple atoms to optimized energy transports in biomolecular complexes. Here, a time-resolved spectroscopic protocol exploiting a terahertz-assisted field locked with the probe pulse is proposed for full observations of the evolution of elements in transient density matrix. Coherence contributions of off-diagonal elements are detectable in the spotlight. The coherence dynamics for photoexcitation of hydrogen atom are explicitly demonstrated with significantly improved temporal resolution beyond the probe pulse duration. Present approach with improving time resolution and highlighting coherence dynamics displays potential applications for sub-femtosecond or attosecond time-resolved measurements in free electron lasers and tabletop laser fields.
