Photonic Molecule, also called Photonic Dimer, is a quantum bound state of two photons. A photonic bound state has a specific entanglement of a Lorentzian anti-correlation in frequency space and two photons are in proximity due to its binding nature.Such signatures of a photonic molecule illuminates a potential tool that increases the two-photon microscopy efficiency to orders of magnitude higher. Here we numerically and analytically demonstrate the two-photon excitation efficiency between photonic molecules, long uncorrelated light pulses and ultrashort light pulses. The high excitation efficiency of a photonic molecule enables a saturation of fluorophores, such that the linear dependence of two-photon excitation crosssection does not necessarily hold. Also, we exhibits two possible methods to obtain the photonic molecules, as a fundamental possibility for a continuous photonic molecule source.
We study computationally the 3-photon molecule generation through coherent scattering process in nonlinear quantum nanophotonics. Specifically, the molecule signature is confirmed with an imprinted π conditional phase shift by examining the wave function in both real- and frequency-space representation, and correlation functions <i>g</i><sup>(3)</sup> and <i>g</i><sup>(2)</sup>. Moreover, we show that the correlation metrics for the three- and two-photon Fock state scattering also apply to a weak-coherent optical input, which describe well the recent experimental results in ultra-cold atomic gas. Our work opens up a new research direction of computational study for correlated three-photon scattering and transport processes. Generations of 3-photon molecule may tremendously enhance the three-photon fluorescence microscopy efficiency and facilitate the realization of deterministic quantum logic gates.
In a waveguide-QED system, under certain condition, the spontaneous emission rate of an atom cloud with a single excitation can be enhanced. Single-photon superradiance refers to the case when the enhancement attains its maximum. We show that an atom cloud exhibiting single-photon superradiance can be described by an effective two-level system. We also adopt a real space numerical approach to validate the understanding of single-photon superradiance using such an effective mapping picture. We further numerically investigate the spontaneous emission of superradiant state and dark state.
We present a computational study of two-photon scattering process in an atom-ring resonator-waveguide QED system. By properly manipulating the operating frequency of incoming photons, we show that two-photon bound state and photon antibunching statistics are generated through resonator-mediated atom-photon interactions. Numerically, we find that mild backscattering and dissipation enhance the quality of generated photonic correlations. In addition, we also report the quantum photonic halo effect and the dissipation-induced photonic correlation transition phenomenon.
In order to correct the atmospheric disturbance around the main mirror and the error caused by wind, the calibration frequency must reach 10 Hz in the active optics system. Therefore, the force actuator must have good dynamic response and high-precision positioning. A new scheme of force actuator, in which linear voice coil motor is used as the driver and linear grating is used as the displacement sensor, is proposed in this paper. With using the deadbeat control theory, the force actuator could achieve fast response, no steady-state error, small overshoot, rapid recovery, and high-resolution which cannot be deeply improved by the traditional PID control method. Finally, the calibration frequency can reach 20 Hz which has met system design requirements. Simulation and experiment demonstrates that this kind of control method can effectively improve the performance of the force actuator.