We present an approach,a Terahertz streaking-assisted photoelectron spectrum(THz SAPS),to achieve direct observations of ultrafast coherence dynamics with timescales beyond the pulse duration.Using a 24 fs probe pulse...We present an approach,a Terahertz streaking-assisted photoelectron spectrum(THz SAPS),to achieve direct observations of ultrafast coherence dynamics with timescales beyond the pulse duration.Using a 24 fs probe pulse,the THz SAPS enables us to well visualize Rabi oscillations of 11.76 fs and quantum beats of 2.62 fs between the 5S_(1/2) and 5P_(3/2) in rubidium atoms.The numerical results show that the THz SAPS can simultaneously achieve high resolution in both frequency and time domains without the limitation of Heisenberg uncertainty of the probe pulse.The long probe pulse promises sufficiently high frequency resolution in photoelectron spectroscopy allowing to observe Autler-Townes splittings,whereas the streaking THz field enhances temporal resolution for not only Rabi oscillations but also quantum beats between the ground and excited states.The THz SAPS demonstrates a potential applicability for observation and manipulation of ultrafast coherence processes in frequency and time domains.展开更多
Bichromatic circularly polarized fields provide a useful tool to probe the ionization dynamics.In this work, we compare the photoelectron momentum distribution in few-cycle bichromatic field of different helicities.Th...Bichromatic circularly polarized fields provide a useful tool to probe the ionization dynamics.In this work, we compare the photoelectron momentum distribution in few-cycle bichromatic field of different helicities.The spectral features are analyzed with semiclassical trajectories derived from the strong field approximation.In particular, the interference fringes in momentum distribution are investigated by tracking the ionization time and tunneling exits of released photoelectrons.Different types of trajectories that contribute to the interference fringes are elucidated.展开更多
The characterization of an unknown quantum system requires the Hamiltonian identification. The full access to the system, however, is usually restricted, hindering the direct retrieval of the relevant parameters, and ...The characterization of an unknown quantum system requires the Hamiltonian identification. The full access to the system, however, is usually restricted, hindering the direct retrieval of the relevant parameters, and a reliable indirect estimation is usually required. In this work, based on the reformulated form of the original algorithm of Burgarth et al.[Phys. Rev. A 79 020305(2009)], the robustness of the estimation scheme against numerous sources of errors during the actual measurement is analyzed. The scheme is numerically studied for sites with a chain structure, exploring its applicability against observational errors including the limited signal-noise ratio and the finite spectral width. The spectral distribution of the end site is shown to determine the applicability of the method, and reducing the influence from truncated spectral components is critical to realize the robust reconstruction of the coupling strengths.展开更多
The origin of terahertz(THz)generation in a gas-phase medium is still in controversy,although the THz sources have been applied across many disciplines.Herein,the THz generation in a dual color field is investigated e...The origin of terahertz(THz)generation in a gas-phase medium is still in controversy,although the THz sources have been applied across many disciplines.Herein,the THz generation in a dual color field is investigated experimentally by precisely controlling the relative phase and polarization of dual-color lasers,where the accompanying third-harmonic generation is employed for in situ determination of the relative phase up to sub-wavelength accuracy.Joint studies with the strong approximation(SFA)theory reveal that the continuum-continuum(CC)transition within an escaped electron wave packet in the single atom gives birth to THz emission,without the necessity of considering the plasma effect.Meanwhile,we develop the analytic form from SFA-based CC description,which is able to reproduce and decompose the classical photocurrent model from the viewpoint of microscopic quantum theory,establishing the quantum-lassical correspondence and bringing a novel insight into the mechanism of THz generation.Present studies leave open the possibility for probing the ultrafast dynamics of continuum electrons and a new dimension for the study of THz-related science and methodology.展开更多
基金Supported by the National Natural Science Foundation of China(Grant Nos.11827806,11874368 and 61675213).
文摘We present an approach,a Terahertz streaking-assisted photoelectron spectrum(THz SAPS),to achieve direct observations of ultrafast coherence dynamics with timescales beyond the pulse duration.Using a 24 fs probe pulse,the THz SAPS enables us to well visualize Rabi oscillations of 11.76 fs and quantum beats of 2.62 fs between the 5S_(1/2) and 5P_(3/2) in rubidium atoms.The numerical results show that the THz SAPS can simultaneously achieve high resolution in both frequency and time domains without the limitation of Heisenberg uncertainty of the probe pulse.The long probe pulse promises sufficiently high frequency resolution in photoelectron spectroscopy allowing to observe Autler-Townes splittings,whereas the streaking THz field enhances temporal resolution for not only Rabi oscillations but also quantum beats between the ground and excited states.The THz SAPS demonstrates a potential applicability for observation and manipulation of ultrafast coherence processes in frequency and time domains.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11420101003,11604347,11827806,11874368,61675213,and 91636105)
文摘Bichromatic circularly polarized fields provide a useful tool to probe the ionization dynamics.In this work, we compare the photoelectron momentum distribution in few-cycle bichromatic field of different helicities.The spectral features are analyzed with semiclassical trajectories derived from the strong field approximation.In particular, the interference fringes in momentum distribution are investigated by tracking the ionization time and tunneling exits of released photoelectrons.Different types of trajectories that contribute to the interference fringes are elucidated.
基金Project supported by Shanghai Sailing Program,China(Grant No.16YF1412600)the National Natural Science Foundation of China(Grant Nos.11420101003,11604347,11827806,11874368,and 91636105)。
文摘The characterization of an unknown quantum system requires the Hamiltonian identification. The full access to the system, however, is usually restricted, hindering the direct retrieval of the relevant parameters, and a reliable indirect estimation is usually required. In this work, based on the reformulated form of the original algorithm of Burgarth et al.[Phys. Rev. A 79 020305(2009)], the robustness of the estimation scheme against numerous sources of errors during the actual measurement is analyzed. The scheme is numerically studied for sites with a chain structure, exploring its applicability against observational errors including the limited signal-noise ratio and the finite spectral width. The spectral distribution of the end site is shown to determine the applicability of the method, and reducing the influence from truncated spectral components is critical to realize the robust reconstruction of the coupling strengths.
基金National Natural Science Foundation of China(11827806,11874368,61675213).
文摘The origin of terahertz(THz)generation in a gas-phase medium is still in controversy,although the THz sources have been applied across many disciplines.Herein,the THz generation in a dual color field is investigated experimentally by precisely controlling the relative phase and polarization of dual-color lasers,where the accompanying third-harmonic generation is employed for in situ determination of the relative phase up to sub-wavelength accuracy.Joint studies with the strong approximation(SFA)theory reveal that the continuum-continuum(CC)transition within an escaped electron wave packet in the single atom gives birth to THz emission,without the necessity of considering the plasma effect.Meanwhile,we develop the analytic form from SFA-based CC description,which is able to reproduce and decompose the classical photocurrent model from the viewpoint of microscopic quantum theory,establishing the quantum-lassical correspondence and bringing a novel insight into the mechanism of THz generation.Present studies leave open the possibility for probing the ultrafast dynamics of continuum electrons and a new dimension for the study of THz-related science and methodology.