Enantio-conversion of chiral mixtures via optical pumping

Photon pumping in a weakly-driven quantum cavity-spin system

We investigate the photon pumping effect in a topological model consisting of a periodically driven spin-1/2 coupled to a quantum cavity mode out of the adiabatic limit. In the strong-drive adiabatic limit, a quantized frequency conversion of photons is expected as the temporal analog of the Hall current. We numerically establish a novel photon pumping phenomenon in the experimentally accessible nonadiabatic driving regime for a broad region of the parameter space. The photon frequency conversion efficiency exhibits strong fluctuations and high efficiency that can reach up 80% of the quantized…

Triplet-singlet conversion by broadband optical pumping

We demonstrate the conversion of cold Cs_{2} molecules initially distributed over several vibrational levels of the lowest triplet state a^{3}Σ_{u}^{+} into the singlet ground state X^{1}Σ_{g}^{+}. This conversion is realized by a broadband laser exciting the molecules to a well-chosen state from which they may decay to the singlet state throug\textcolor{black}{h two sequential single-photon emission steps: Th}e first photon populates levels with mixed triplet-singlet character, making possible a second spontaneous emission down to several vibrational levels of the X^{1}Σ_{g}^{+} states. By ad…

Spontaneous topological pumping in non-Hermitian systems

We introduce modulational instability in non-Hermitian systems to study state conversion of topological edge states. We show that state conversion in non-Hermitian systems leads to topological pumping, which is a way of transferring topological edge state from one edge to the opposite edge. In contrast to Hermitian systems, topological pumping can occur spontaneously in non-Hermitian systems.

Photon-number entangled states generation model with stimulated parametric down conversion

We address the process of generation of the photon-number entangled states of light in the stimulated nonlinear parametric down conversion process and build the simple model describing the generation, not involving the traditional parametric approximation. The motion equations for the system of pumping and two-mode outgoing field are solved for the case of the strong correlation between two modes, the evolution of the state parameters of the generated modes is obtained. The solution is briefly analyzed for particular types of photon-number entangled states.

Upconversion of optical signals with multi-longitudinal-mode pump lasers

Multi-longitudinal-mode lasers have been believed to be good candidates as pump sources for optical frequency conversion. However, we present a semi-classical model for frequency conversion of optical signals with a multimode pump laser, which shows that fluctuations of the instantaneous pump power limit the conversion efficiency. In an experiment, we upconverted a 1550 nm optical signal in a periodically poled lithium niobate waveguide using with a multi-longitudinal-mode laser, an observed a maximum conversion efficiency of 70%, in good agreement with our theoretical model. Compared to singl…

Interferometric autocorrelation in the ultra-violet utilizing spontaneous parametric down-conversion

Autocorrelation is a common method to estimate the duration of ultra-short laser pulses. In the ultra-violet (UV) regime it is increasingly challenging to employ the standard process of second harmonic generation, most prominently due to absorption in nonlinear crystals at very short wavelengths. Here we show how to utilize spontaneous parametric down-conversion (SPDC) to generate an autocorrelation signal for UV pulses in the infrared. Our method utilizes the $n^{\text{th}}$ order emission of the SPDC process, which occurs for low pumping powers proportional to the $n^{\text{th}}$ power of th…

Observation of Multiphoton Frequency Conversion in Superconducting Circuits

Multiphoton up/down conversion in a transmon circuit, driven by a pair of microwaves tuned near and far off the qubit resonance, has been observed. The experimental realization of these high order non-linear processes is accomplished in the three-photon regime, when the transmon is coupled to weak bichromatic microwave fields with the same Rabi frequencies. A many-mode Floquet formalism, with longitudinal coupling, is used to simulate the quantum interferences in the absorption spectrum that manifest the multiphoton pumping processes in the transmon qubit. An intuitive graph theoretic approach…

混合光学谐振腔系统中的多通道量子噪声抑制与相位敏感调制

Multi-channel quantum noise suppression and phase-sensitive modulation in a hybrid optical resonant cavity system

本文理论研究了混合光学谐振腔系统中真空场和压缩场的多通道量子噪声抑制与相位敏感调制，观察到多个类EIT暗窗口，在泵浦光功率为6.5 Beta_th时实现高达13.9 dB的噪声抑制，并提出了填补压缩场正交振幅多通道抑制空白的相位敏感调制方案。

基于自发参量下转换的单光子源多模特性表征

Characterization of the multimode nature of single-photon sources based on spontaneous parametric down conversion

该研究针对自发参量下转换预示单光子源，建立了基于精确Bogoliubov处理的多模描述及微扰有效方法，解析估计成功概率与纯度，并揭示短泵浦下单模描述准确、长泵浦或连续泵浦下需多模描述，为量子信息协议设计提供指导。

Transient Dynamics in Molecular Junctions: Coherent Bichromophoric Molecular Electron Pumps

The possibility of using single molecule junctions as electron pumps for energy conversion and storage is considered. It is argued that the small dimensions of these systems enable to make use of unique intra-molecular quantum coherences in order to pump electrons between two leads and to overcome relaxation processes which tend to suppress the pumping efficiency. In particular, we demonstrate that a selective transient excitation of one chromophore in a bi-chromophoric donor-bridge-acceptor molecular junction model yields currents which transfer charge (electron and holes) unevenly to the two…

自旋与电荷泵浦及其在太赫兹自旋电子学中产生辐射的量子-经典方法：以超快光驱动Weyl反铁磁体Mn$_3$Sn为例

Quantum-classical approach to spin and charge pumping and the ensuing radiation in THz spintronics: Example of ultrafast-light-driven Weyl antiferromagnet Mn$_3$Sn

本研究提出量子-经典多尺度方法（QME+LLG+Jefimenko），揭示飞秒光驱动Mn$_3$Sn双层中自旋与电荷泵浦产生太赫兹辐射的机制，发现局域磁化电荷泵浦贡献最大。