Large-tuning-range frequency stabilization of an ultraviolet laser by an open-loop piezoelectric ceramic controlled Fabry-Pérot cavity.

We demonstrate a laser frequency stabilization method with large tuning range to stabilize a UV laser by installing piezoelectric ceramic actuators into a Fabry-Pérot cavity with an ultra-low expansion spacer. To suppress piezoelectric drift, a two-layer symmetrical structure is adopted for the piezoelectric actuator, and a 14.7 GHz tuning range is achieved. The short-term drift of the piezoelectric ceramics caused by temperature and creep is eliminated, and the long-term drift is 0.268 MHz/h when the Fabry-Pérot cavity is sealed in a chamber without a vacuum environment. The long-term frequency drift is mainly caused by stress release and is eliminated by compensating the cavity voltage with an open loop. Without the need for an external reference or a vacuum environment, the laser frequency stabilization system is greatly simplified, and it can be extended to wavelengths ranging from ultraviolet to infrared. Owing to its simplicity, stability, and large tuning range, it is applicable in cold atom and trapped ion experiments.

Quantum frequency conversion from ultraviolet to visible band through waveguides in a period-poled MgO:LiTaO3 crystal.

In research on hybrid quantum networks, visible or near-infrared frequency conversion has been realized. However, technical limitations mean that there have been few studies involving the ultraviolet band, and unfortunately the wavelengths of the rare-earth or alkaline-earth metal atoms or ions that are used widely in research on quantum information are often in the UV band. Therefore, frequency conversion of the ultraviolet band is very important. In this paper, we demonstrate a quantum frequency conversion between ultraviolet and visible wavelengths by fabricating waveguides in a period-poled MgO:LiTaO3 crystal with a laser writing system, which will be used to connect the wavelength of the dipole transition of 171Yb+ at 369.5 nm and the absorption wavelength of Eu3+ at 580 nm in a solid-state quantum memory system. An external conversion efficiency of 0.85% and a signal-to-noise ratio of greater than 500 are realized with a pumping power of 3.28 W at 1018 nm. Furthermore, we complete frequency conversion of the classical polarization state by means of a symmetric optical setup based on the fabricated waveguide, and the process fidelity of the conversion is (96.13 ± 0.021)%. This converter paves the way for constructing a hybrid quantum network and realizing a quantum router in the ultraviolet band in the future.

Super-resolved Imaging of a Single Cold Atom on a Nanosecond Timescale.

In cold atomic systems, fast and high-resolution microscopy of individual atoms is crucial, since it can provide direct information on the dynamics and correlations of the system. Here, we demonstrate nanosecond-scale two-dimensional stroboscopic pictures of a single trapped ion beyond the optical diffraction limit, by combining the main idea of ground-state depletion microscopy with quantum-state transition control in cold atoms. We achieve a spatial resolution up to 175 nm using a NA=0.1 objective in the experiment, which represents a more than tenfold improvement compared with direct fluorescence imaging. To show the potential of this method, we apply it to observe the secular motion of the trapped ion; we demonstrate a temporal resolution up to 50 ns with a displacement detection sensitivity of 10 nm. Our method provides a powerful tool for probing particle positions, momenta, and correlations, as well as their dynamics in cold atomic systems.

An efficient one-pot synthesis of functionalized chromeno[4,3-b]pyridine derivatives under catalyst-free conditions.

A concise, efficient one-pot synthesis of functionalized chromeno[4,3-b]pyridine derivatives via a three-component reaction of 4-oxo-4H-chromene-3-carbaldehydes, malononitrile or cyanoacetates, and aromatic amines under catalyst-free conditions in an environmentally friendly medium (ethanol-water, 3:1 v/v) is described. This synthesis involves a group-assisted purification process, which avoids traditional recrystallization and chromatographic purification methods.

Microwave-Assisted Regioselective Synthesis of 3-Functionalized Indole Derivatives via Three-Component Domino Reaction.

A microwave-assisted regioselective synthesis of 3-functionalized indole derivatives via a three-component domino reaction of anilines, arylglyoxal monohydrates, and cyclic 1,3-dicarbonyl compounds is described. The main advantages of this protocol are short reaction times, practical simplicity, its metal-free nature, the availability of starting materials, green solvents, and high regioselectivity.

Elucidation of the pharmacophore of echinocystic acid, a new lead for blocking HCV entry.

To elucidate the pharmacophore of echinocystic acid (EA), an oleanane-type triterpene displaying substantial inhibitory activity on HCV entry, two microbial strains, Rhizopus chinensis CICC 3043 and Alternaria alternata AS 3.4578, were utilized to modify the chemical structure of EA. Eight new metabolites with regio- and stereo-selective introduction of hydroxyl and lactone groups at various inert carbon positions were obtained. The anti-HCV entry activity of the metabolites 2-13, along with their parental compound EA and other analogs 14-15, were evaluated. Most of the metabolites showed no improvement but detrimental effect on potency except compound 5 and 6, which showed similar and even a litter higher anti-HCV entry activity than that of EA. The results demonstrated that ring A, B, C and the left side of ring E of EA are highly conserved, while ring D and the right side of ring E of EA are flexible. Introduction of a hydroxyl group at C-16 enhanced the triterpene potency. Further analysis indicated that the hemolytic effect of EA disappeared upon such modifications.