It is shown that a superposition of static and rapidly oscillating electric {\it monopole} (source) fields is capable of trapping particles with a permanent electric dipole moment. Thus, the new trapping mechanism differs fundamentally from saddle-point traps that use static and oscillating higher-multipole fields. An analytical stability analysis together with detailed molecular dynamics trajectory calculations prove that the trap is stable. Thin rods of barium titanate (BaTiO$_3$) provide an illustrative example for the working principle of the new trap. The effects of gravity are considered. The existence of a bifurcation regime is predicted. A particular strength of the new trap is that it also works for zero orbital angular momentum with respect to the field-generating electrodes.
We demonstrate loading of SrF molecules into an optical dipole trap (ODT) via in-trap $Λ$-cooling. We find that this cooling can be optimized by a proper choice of relative ODT and $Λ$ beam polarizations. In this optimized configuration, we observe molecules with temperatures as low as 14(1) $μ$K in traps with depths up to 570 $μ$K. With optimized parameters, we transfer $\!\sim\!5$% of molecules from our radio-frequency magneto-optical trap into the ODT, at a density of $\sim\!2\times 10^{9}$ cm$^{-3}$, a phase space density of $\sim\!2\times 10^{-7}$, and with a trap lifetime of $\!\sim\!1$ …
Highly excited Rydberg states are usually extremely polarizable and exceedingly sensitive to electric fields. Because of this Rydberg ions confined in electric fields have state-dependent trapping potentials. We engineer a Rydberg state that is insensitive to electric fields by coupling two Rydberg states with static polarizabilities of opposite sign, in this way we achieve state-independent magic trapping. We show that the magically-trapped ion can be coherently excited to the Rydberg state without the need for control of the ion's motion.
External field control of spin-dependent rotational decoherence of ultracold polar molecules
我们确定超冷极性分子的捕获条件，其中对内部状态经历相同的捕获电位。这样的条件可以确保显著降低超冷样品中不可避免的不均匀性的有害影响。特别是，我们调查的内部旋转和超精细量子态的超冷费米子基态$^{40}$ K $^{87}$ Rb极性分子，当静磁场，静电场，和陷阱激光场同时施加。理解改变这三个场的相对取向或偏振的效果对于从两个或更多个旋转振动态构建无退相干子空间至关重要。此外，我们评估在这些领域的存在下，这将允许控制分子之间的相互作用在不同的网站的光晶格和研究的相互作用各向异性的影响的能力，纠缠极性分子的诱导偶极矩的分子。
We have experimentally demonstrated that magnetic-field-insensitive coherent-population-trapping (CPT) resonances are generated between the ground hyperfine levels on the $D_1$ line of $^{133}$Cs using a two-photon $Λ$ scheme excited by lin || lin polarizations. The frequency shift of the CPT resonance is 0.04 Hz for the deviation of 1 $μ$T at a "magic" magnetic field of 139 $μ$T and is 50 times smaller than that of the conventional clock transition at a typical bias magnetic field for the clock operation. The amplitude of the CPT spectrum excited by lin || lin polarizations is enhanced as the…
Modeling magneto-optical trapping of CaF molecules
分子的磁光俘获力远弱于碱金属原子，因为当存在多个基态时，光子散射率会降低，并且因为光泵入暗态。当上态的塞曼分裂比下态小得多时，力进一步减小。我们使用速率模型来估计CaF分子的磁光阱（MOT）中的捕获力和阻尼力的强度，使用A $^{2}Π_{1/2}$ - X $^{2}Σ^{+}$跃迁或B $^{2}Σ^{+}$ - X $^{2}Σ^{+}$跃迁。我们确定了一个新的机制时，出现的磁光捕获，在每一个光束的MOT，两个激光组件具有相反的偏振和不同的失谐地址相同的过渡。这种机制产生一个强大的捕获力，即使在上层状态有很少或没有塞曼分裂。当使用A $^{2}Π_{1/2}$ - X $^{2}Σ^{+}$转变时，它是负责捕获力的主要机制。
We experimentally investigate $σ^+$-$σ^-$ polarization gradient cooling~(PGC) of a single $^{87}$Rb atom in a tightly focused dipole trap and show that the cooling limit strongly depends on the polarization of the trapping field. For optimized cooling light power, the temperature of the atom reaches~$10.4(6)\,μ$K in a linearly polarized trap, approximately five times lower than in a circularly polarized trap. The inhibition of PGC is qualitatively explained by the fictitious magnetic fields induced by the trapping field. We further demonstrate that switching the trap polarization from linear t…
From the study of long-range-interacting systems to the simulation of gauge fields, open-shell Lanthanide atoms with their large magnetic moment and narrow optical transitions open novel directions in the field of ultracold quantum gases. As for other atomic species, the magneto-optical trap (MOT) is the working horse of experiments but its operation is challenging, due to the large electronic spin of the atoms. Here we present an experimental study of narrow-line Dysprosium MOTs. We show that the combination of radiation pressure and gravitational forces leads to a spontaneous polarization of…
Usually the influence of the quadratic Stark effect on an ion's trapping potential is minuscule and only needs to be considered in atomic clock experiments. In this work we excite a trapped ion to a Rydberg state with polarizability $\sim$~eight orders of magnitude higher than a low-lying electronic state; we find that the highly-polarizable ion experiences a vastly different trapping potential owing to the Stark effect. We observe changes in trap stiffness, equilibrium position and minimum potential, which can be tuned using the trapping electric fields. These effects lie at the heart of prop…
We investigate the effect of far-off-resonant trapping light on ultracold bosonic RbCs molecules. We use kHz-precision microwave spectroscopy to measure the differential AC Stark shifts between the ground and first excited rotational levels of the molecule with hyperfine-state resolution. We demonstrate through both experiment and theory that coupling between neighboring hyperfine states manifests in rich structure with many avoided crossings. This coupling may be tuned by rotating the polarization of the linearly polarized trapping light. A combination of spectroscopic and parametric heating …
Superpositions of rotational states in polar molecules induce strong, long-range dipolar interactions. Here we extend the rotational coherence by nearly one order of magnitude to 8.7(6) ms in a dilute gas of polar $^{23}$Na$^{40}$K molecules in an optical trap. We demonstrate spin-decoupled magic trapping, which cancels first-order and reduces second-order differential light shifts. The latter is achieved with a dc electric field that decouples nuclear spin, rotation and trapping light field. We observe density-dependent coherence times, which can be explained by dipolar interactions in the bu…
Magneto-electrostatic trapping of ground state OH molecules
我们报道了在密度为$\sim3\times10^{3}$ cm $^{-3}$和温度为$\sim$ 30 mK的中性、基态羟基自由基（OH）的磁约束。一个可调节的电场的大小足以抑制OH是叠加在陷阱中的四极或均匀场的几何形状。OH被限制在一个整体的潜力，建立通过分子状态混合诱导的组合电场和磁场作用于分子的电偶极子和磁偶极矩，分别。构造了一个包含斯塔克项和塞曼项的有效分子哈密顿量来描述阱内的单分子动力学。使用该哈密顿量的蒙特卡罗模拟精确地模拟了在各种陷阱配置中观察到的陷阱动力学。将冷极性分子限制在磁阱中，留下大的、可调节的电场进行控制，是研究低能偶极-偶极碰撞的重要一步。
Inhomogeneous mass trap for dark-state polaritons in atomic media
National Central University（中央大学）；National Tsing Hua University（清华大学）；National Center for Excellence in Quantum Information Science and Engineering, National Tsing Hua University（国家量子信息科学与工程卓越中心）；Physics Division, National Center for Theoretical Sciences（理论科学国家中心物理部）；Quantum Technology Center, National Central University（量子技术中心）
Hybrid quantum systems that unite laser-cooled trapped ions and ultracold quantum gases in a single experimental setup have opened a rapidly advancing field of study, including Quantum chemistry, polaron physics, quantum information processing and quantum simulations. We present a fully developed and tested ion trap chip and propose a flat chip trap that can be placed beneath the ion trap. This design substantially addresses the difficulties specific to hybrid traps and features well-aligned chips that allow for independent adjustment of the depth of the atomic trap and the confinement and pos…
Tightly focused optical dipole traps induce vector light shifts ("fictitious magnetic fields") which complicate their use for single-atom trapping and manipulation. The problem can be mitigated by adding a larger, real magnetic field, but this solution is not always applicable; in particular, it precludes fast switching to a field-free configuration. Here we show that this issue can be addressed elegantly by deliberately adding a small elliptical polarization component to the dipole beam. In our experiments with single $^{87}$Rb atoms in a chopped trap, we observe improvements up to a factor 1…
Optical metasurfaces of subwavelength pillars have provided new capabilities for the versatile definition of the amplitude, phase, and polarization of light. In this work, we demonstrate that an efficient dielectric metasurface lens can be used to trap and image single neutral atoms with a long working distance from the lens of 3 mm. We characterize the high-numerical-aperture optical tweezers using the trapped atoms and compare with numerical computations of the metasurface lens performance. We predict that future metasurfaces for atom trapping will be able to leverage multiple ongoing develo…
We propose to control light trapping in a large ensemble of cold atoms by an external, static magnetic field. For an appropriate choice of frequency and polarization of the exciting pulse, the field is expected to speed up the fluorescence of a dilute atomic system. In a dense ensemble, the field does not affect the early-time superradiant signal but amplifies intensity fluctuations at intermediate times and induces a very slow, nonexponential long-time decay. The slowing down of fluorescence is due to the excitation of spatially localized collective atomic states that appear only under a stro…
