[en] Ensemble simulations, which use multiple short independent trajectories from dispersive initial conformations, rather than a single long trajectory as used in traditional simulations, are expected to sample complex systems such as biomolecules much more efficiently. The re-weighted ensemble dynamics (RED) is designed to combine these short trajectories to reconstruct the global equilibrium distribution. In the RED, a number of conformational functions, named as basis functions, are applied to relate these trajectories to each other, then a detailed-balance-based linear equation is built, whose solution provides the weights of these trajectories in equilibrium distribution. Thus, the sufficient and efficient selection of basis functions is critical to the practical application of RED. Here, we review and present a few possible ways to generally construct basis functions for applying the RED in complex molecular systems. Especially, for systems with less priori knowledge, we could generally use the root mean squared deviation (RMSD) among conformations to split the whole conformational space into a set of cells, then use the RMSD-based-cell functions as basis functions. We demonstrate the application of the RED in typical systems, including a two-dimensional toy model, the lattice Potts model, and a short peptide system. The results indicate that the RED with the constructions of basis functions not only more efficiently sample the complex systems, but also provide a general way to understand the metastable structure of conformational space. (paper)

[en] Nanofibers have many promising applications because of their advantages of high power density and ultralow saturated light intensity. We present here a Zeeman shift of the Doppler-broadened cesium D ₂ transition using a tapered optical nanofiber in the presence of a magnetic field. When a weak magnetic field is parallel to the propagating light in the nanofiber, the Zeeman shift rates for different circularly polarized spectra are observed. For the σ ⁺ component, the typical linear Zeeman shift rates of F = 3 and F = 4 ground-state cesium atoms are measured to be 3.10(±0.19) MHz/G and 3.91(±0.16) MHz/G. For the σ ⁻ component, the values are measured to be −2.81(±0.25) MHz/G, and −0.78(±0.28) MHz/G. The Zeeman shift using the tapered nanofiber can help to develop magnetometers to measure the magnetic field at the narrow local region and the dispersive signal to lock laser frequency. (paper)

[en] We introduce a novel scheme which combines conventional Doppler dichroic atomic vapor laser lock (DAVLL) and nanofiber techniques for realizing frequency stabilization with sub-nanowatt laser power. The dependences of DAVLL signal on the total incident power of probe light and the quantification magnetic field amplitude indicate that the power for frequency stabilization could be minimized to only 15 pW. To evaluate the frequency stability of the locked laser, we calculate the Allan standard deviation, which shows that the relative frequency stability could reach 10⁻¹⁰ level at 10 s. This frequency stabilization scheme paves the road for future quantum optical device integration. (paper)