两个真空光悬浮纳米粒子间的光诱导偶极相互作用

光悬浮微纳米粒子系统是研究多体物理的重要平台,但是以往相关研究大多集中在液体环境中。真空光悬浮由于其显著的优势,近年来受到了广泛关注。本文利用两个紧聚焦光场单独捕获两个纳米粒子,在真空环境下,实验研究了粒子间由于散射光诱导的偶极相互作用。在不同捕获光偏振条件下,通过调控两个粒子质心运动（或扭摆运动）在频率简并附近的相对频率,测量了光诱导偶极相互作用强度。实验表明,粒子间光诱导偶极散射对扭摆运动影响很小,未观察到粒子间扭摆运动的相互作用;而质心运动在两束捕获光偏振都垂直于粒子间连线时,产生较强耦合,在两粒子间距为2.91μm时,得到沿捕获光传播方向质心运动在简并点处的耦合强度为1.6 kHz。     

Feshbach resonances in an ultracold mixture of 87Rb and 40K

We report the experimental preparations of the absolute ground states of ⁸⁷Rb and ⁴⁰K atoms (| F=1, m_F=1,〉+ |F=9/2, m_F=-9/2,〉) by means of the radio-frequency and microwave adiabatic rapid passages, and the observation of magnetic Feshbach resonances in an ultracold mixture of bosonic ⁸⁷Rb and fermionic ⁴⁰K atoms between 0 T and 6.0 × 10^-2 T, including 7 homonuclear and 4 heteronuclear Feshbach resonances. The resonances are identified by the abrupt trap loss of atoms induced by the strong inelastic three-body collisions. These Feshbach resonances should enable the experimental control of interspecies interactions.     

Simulation of the Weakly Nonlinear Rayleigh–Taylor Instability in Spherical Geometry

The Rayleigh-Taylor instability at the weakly nonlinear(WN) stage in spherical geometry is studied by numerical simulation.The mode coupling processes are revealed.The results are consistent with the WN model based on parameter expansion,while higher order effects are found to be non-negligible.For Legendre mode perturbation Pn(cos B),the nonlinear saturation amplitude(NS A) of the fundamental mode decreases with the mode number n.When n is large,the spherical NSA is lower than the corresponding...     

线性色散理论描述内腔EIT介质的正交模式分裂

正交模分裂(或真空Rabi分裂)是原子与光学腔构成的复合系统实现强相互作用的一个典型现象.本文理论研究了三能级原子介质与腔构成的复合系统,利用线性色散理论将腔内三能级原子自感应透明(EIT)介质的吸收和色散引入光学腔透射公式,非常直观清晰得到腔透射谱的三个分裂峰,它是由腔内EIT介质的吸收和色散特性使一个共振腔模分裂为三个腔模.该方法可以推广到腔内含有任意色散和吸收的介质.     

Active Learning Approach to Optimization of Experimental Control

We present a general machine learning based scheme to optimize experimental control.The method utilizes the neural network to learn the relation between the control parameters and the control goal, with which the optimal control parameters can be obtained.The main challenge of this approach is that the labeled data obtained from experiments are not abundant.The central idea of our scheme is to use the active learning to overcome this difficulty.As a demonstration example, we apply our method to ...     

Interface Width Effect on the Weakly Nonlinear Rayleigh–Taylor Instability in Spherical Geometry

Interface width effect on the spherical Rayleigh–Taylor instability in the weakly nonlinear regime is studied by numerical simulations.For Legendre perturbation mode P_n with wave number K_n and interface half-width L,the commonly adopted empirical linear growth rate formula γ_n^em(L)=γn/√1 + K_nL is found to be sufficient in spherical geometry.At the weakly nonlinear stage,the interface width affects the mode coupling processes.The development o...     

39K-87Rb双组分|F=1,mF=-1>态玻色-爱因斯坦凝聚体的实验制备

本文在³⁹K-⁸⁷Rb混合气体的|F=1,mF=-1>态上获得了双组分玻色-爱因斯坦凝聚体(Bose-Einstein condensates,BECs)。由于³⁹K原子气体的背景散射长度是负值,必须利用磁场调节Feshbach共振技术来操控其散射长度,从而实现³⁹K原子气体的有效蒸发冷却。在0～200 G磁场强度范围内,我们分别测量了³⁹K-⁸⁷Rb混合气体的同核和异核Feshbach共振,并确定了它们在|1,-1>态中的散射长度与磁场的对应关系。通过优化³⁹K-⁸⁷Rb混合气体中原子种内和种间的相互作用,进一步比较了在不同磁场区域³⁹K-⁸⁷Rb混合气体的协同蒸发冷却效率。最后,实验上制备出³⁹K-⁸⁷Rb混合气体|1,-1>态的双组分BECs,同时为接下来进一步研究量子液滴等相互作用体系提供了理想的平台...     

Evaporative cooling of 87Rb atoms into Bose-Einstein condensate in an optical dipole trap

We create a Bose-Einstein condensate(BEC) of 87Rb atoms by runaway evaporative cooling in an optical trap.Two crossed infrared laser beams with a wavelength of 1064 nm are used to form an optical dipole trap.After precooling the atom samples in a quadrupole-Ioffe configuration(QUIC) trap under 1.5 μK by radio-frequency(RF) evaporative cooling,the samples are transferred into the center of the glass cell,then loaded into the optical dipole trap with 800 ms.The pure condensate with up to 1.5×105 atoms is obtained over 1.17 s by lowering the power of the trap beams.     

褐藻糖胶的提取纯化及其抗凝血活性的研究

从海带中提取出的水溶性提取物，经超滤，醇析获得褐藻糖胶粗多糖，以DEAE-Sephrose Fast Flow离子交换层析分离纯化，得到了F1，F2和F3三个级分，这三个级分具有明显的抗凝血作用。尤其是F3级分，能显地延长激活部分凝血活酶时间和凝血酶时间。     

An Enriched ^40K Source for Atomic Cooling

We have developed an enriched ⁴⁰K source used in ⁴⁰K--⁸⁷Rb atomic mixture cooling experiment. The enriched ⁴⁰K source is a home-made dispenser which releases ⁴⁰K atoms by the redox reaction between ⁴⁰K enriched KCl and calcium. It is efficient and easy to be made and used. We collect 10⁷ ～10^{8 40}K atoms in collection magneto-optical trap. With this dispenser, we perform a quantum degenerate Fermi gas experiment.