Ole Steuernagel
Superpositions of paraxial laser beam modes to generate atom-optical lenses based on the optical dipole force are investigated theoretically. Thin, wide, parabolic, cylindrical and circular atom lenses with numerical apertures much greater than those reported in the literature to date can be synthesized. This superposition approach promises to make high quality atom beam imaging and nano-deposition feasible.
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Recent efforts to define microscopic solid-immersion-lenses (SIL) by focused ion beam milling into diamond substrates that are registered to a preselected single photon emitter are summarized. We show how we determine the position of a single emitter with at least 100 nm lateral and 500 nm axial accuracy, and how the milling procedure is optimized. The characteristics of a single emitter, a Nitrogen Vacancy (NV) center in diamond, are measured before and after producing the SIL and compared with each other. A count rate of 1.0 million counts per second is achieved with a $[111]$ oriented NV ce…
We propose and discuss `quantum spin lenses', where quantum states of delocalized spin excitations in an atomic medium are `focused' in space in a coherent quantum process down to (essentially) single atoms. These can be employed to create controlled interactions in a quantum light-matter interface, where photonic qubits stored in an atomic ensemble are mapped to a quantum register represented by single atoms. We propose Hamiltonians for quantum spin lenses as inhomogeneous spin models on lattices, which can be realized with Rydberg atoms in 1D, 2D and 3D, and with strings of trapped ions. We …
Scalar theory of quantum electron beam optics, at the single-particle level, derived from the Dirac equation using a Foldy-Wouthuysen-like transformation technique is considered. Round magnetic electron lenses with Glaser and power law models for the axial magnetic field $B(z)$ are studied. Paraxial quantum propagator for the Glaser model lens is obtained in terms of the well known fundamental solutions of its paraxial equation of motion. In the case of lenses with the power law model for $B(z)$ the well known fundamental solutions of the paraxial equations, obtained by solving the differentia…
We present an optical setup with focus-tunable lenses to dynamically control the waist and focus position of a laser beam, in which we transport a trapped ultracold cloud of 87-Rb over a distance of 28 cm. The scheme allows us to shift the focus position at constant waist, providing uniform trapping conditions over the full transport length. The fraction of atoms that are transported over the entire distance comes near to unity, while the heating of the cloud is in the range of a few microkelvin. We characterize the position stability of the focus and show that residual drift rates in focus po…
A model for a new electron vortex beam production method is proposed and experimentally demonstrated. The technique calls on the controlled manipulation of the degrees of freedom of the lens aberrations to achieve a helical phase front. These degrees of freedom are accessible by using the corrector lenses of a transmission electron microscope. The vortex beam is produced through a particular alignment of these lenses into a specifically designed astigmatic state and applying an annular aperture in the condensor plane. Experimental results are found to be in good agreement with simulations.
General guidelines for constructing a quantum theory of charged-particle beam optics starting ab initio from the basic equations of quantum mechanics, appropriate to the situation under study. In the context of spin-1/2 particles, these guidelines are used starting with the Dirac equation. The spinor theory just constructed is used to obtain the transfer maps for normal and skew magnetic quadrupoles respectively. As expected the traditional transfer maps get modified by the quantum contributions. The classical limit of the quantum formalism presented, reproduces the well-known Lie algebraic fo…
Correcting astigmatism and ellipticity in Gaussian beams using a cylindrical lens pair with tunable focal lengths
提出一种基于三柱透镜（含可调双轴透镜对）的无源方法，通过调整透镜相对角度使像散光束束腰重叠，将像散椭圆光束转换为无像散圆形高斯光束，兼具高灵活性、低成本与紧凑性。
Superresolution technique beyond the diffraction limit under a structured beam via different optical nanostructures
本文提出利用不同纳米结构（如金字塔形纳米透镜）结合高阶高斯光束（Hermite-Gauss模式）实现约27 nm分辨率的近场聚焦，超越衍射极限，适用于量子技术等领域的超分辨成像。
We demonstrate the use of cylindrical vector beams - beams with spatially varying polarization - for detecting and preparing the spin of a warm rubidium vapor in a spatially dependent manner. We show that a modified probe vector beam can serve as an atomic spin analyzer for an optically pumped medium, which spatially modulates absorption of the beam. We also demonstrate space-variant atomic spin by optical pumping with the vector beams. The beams are thus beneficial for making singleshot polarization-dependent measurements, as well as for providing a means of preparing samples with position-de…
A diffractive optical element (DOE) has been fabricated for creating blue detuned atomic bottle beam traps. The DOE integrates several diffractive lenses for trap creation and imaging of atomic fluorescence. We characterize the performance of the DOE and demonstrate trapping of cold Cesium atoms inside a bottle beam.
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We investigate topological aspects of sub-nm electron vortex beams upon elastic propagation through atomic scattering potentials. Two main aspects can be distinguished: (i) Significantly reduced delocalization compared to a similar non-vortex beam if the beam centers on an atomic column and (ii) site symmetry dependent splitting of higher-order vortex beams. Furthermore, the results provide insight into the complex vortex line fabric within the elastically scattered wave containing characteristic vortex loops predominantly attached to atomic columns and characteristic twists of vortex lines ar…
An integrated photonic platform is proposed for strong interactions between atomic beams and annealing-free high-quality-factor (Q) microresonators. We fabricated a thin-film, air-clad SiN microresonator with a loaded Q of $1.55\times10^6$ around the optical transition of $^{87}$Rb at $~780$ nm. This Q is achieved without annealing the devices at high temperatures, enabling future fully integrated platforms containing optoelectronic circuitry as well. The estimated single-photon Rabi frequency (2g) is ${2\boldsymbolπ}\times$64 MHz at a height of 100 nm above the resonator. Our simulation resul…
We study two-photon scattering of a tightly focused weak light beam from a small atomic ensemble of two-level atoms (2LAs). This is similar to the scattering of photons from an atomic ensemble in a one-dimensional waveguide. The scaling of two-photon nonlinearity at single-photon resonance shows a non-monotonic behaviour with an increasing number of few identical 2LAs. The two-photon nonlinearity decays monotonically with an increasing number of atoms for incident photons detuned from single-photon resonance. Single-photon transport in two 2LAs is similar to that in a single V-type three-level…
Atomic magnetometry using a metasurface polarizing beamsplitter in silicon on sapphire
本文首次将蓝宝石上硅超表面偏振分束器用于铷原子磁力测量，实现亚纳特斯拉灵敏度，为小型化高灵敏原子传感器奠定基础。
Quantum trajectory simulations of a cavity QED system comprising an atomic beam traversing a standing-wave cavity are carried out. The delayed photon coincident rate for forwards scattering is computed and compared with the measurements of Rempe et al. [Phys. Rev. Lett. 67, 1727 (1991)] and Foster et al. [Phys. Rev. A 61, 053821 (2000)]. It is shown that a moderate atomic beam misalignment can account for the degradation of the predicted correlation. Fits to the experimental data are made in the weak-field limit with a single adjustable parameter--the atomic beam tilt from perpendicular to the…
We study the generation of atom vortex beams in the case where an atomic wave-packet, moving in free space, is diffracted from a properly tailored light mask with a spiral transverse profile. We show how such a diffraction scheme could lead to the production of an atomic Ferris wheel beam.
We propose and demonstrate an experimental implementation for the observation of magnetic fields from spatial features of absorption profiles in a warm atomic vapor. A radially polarized vector beam that traverses an atomic vapor will generate an absorption pattern with petal-like structure by the mediation of a transverse magnetic field (TMF). The spatial absorption pattern rotates when the azimuthal angle of the TMF is changed, while its contrast decreases when the longitudinal component of the magnetic field increases. By analyzing the intensity distribution of the transmitted pattern we ca…
We propose and investigate a protocol for Gaussification of quantum states of traveling light beams in an atomic quantum memory that couples to light via quantum non-demolition interaction. The protocol relies on a periodic switching between two different QND couplings and the total coupling strength scales only logarithmically with number of Gaussified light modes. The present scheme can be used to prepare entangled states of two distant atomic ensembles and to purify and Gaussify noisy non-Gaussian entangled states of light while simultaneously storing the purified state in atomic memories.
Trapping of single ultracold atoms is an important tool for applications ranging from quantum computation and communication to sensing. However, most experimental setups, while very precise and versatile, can only be operated in specialized laboratory environments due to their large size, complexity and high cost. Here, we introduce a new trapping concept for ultracold atoms in optical tweezers based on micrometer-scale lenses that are 3D printed onto the tip of standard optical fibers. The unique properties of these lenses make them suitable for both trapping individual atoms and capturing th…
We propose and analyze a scheme for generating entangled atomic beams out of a Bose-Einstein condensate using spin-exchanging collisions. In particular, we show how to create both atomic squeezed states and entangled states of pairs of atoms.
The influence of photon-momentum recoil on adiabatic population transfer in an atomic three-level lambda system is studied. It is shown that the Doppler frequency shifts, due to atomic motion can play an important role in adiabatic population transfer processes of atomic internal states by a pair of laser fields. For the limiting case of slow atoms ( Doppler shift much smaller than the photon recoil energy) the atoms occupy the same target state regardless of the order of switching of laser fields, while for the case of fast atoms interacting with the intuitive sequence of pulses, the target s…
We propose a simplest detector of harmonic vibrations with micro amplitudes and low frequencies, i.e. the detector consisting of one atomic beam. Here the atomic beam is induced by a plane harmonic wave and has a classical collective harmonic vibrations, which vibrant directions are perpendicular to the wave vectors of atomic beam. Compared with the detector consisting of atomic Mach-Zehnder interferometer, the new detector has two advantages: (1) it is suitable for the detection of the harmonic vibrations induced either by a longitudinal plane harmonic wave or by a transverse plane harmonic w…
We report on theoretical and numerical study of propagation of atomic beams crossing a detuned standing-wave laser beam in the geometric optics limit. The interplay between external and internal atomic degrees of freedom is used to manipulate the atomic motion along the optical axis by light. By adjusting the atom-laser detuning, we demonstrate how to focus, split and scatter atomic beams in a real experiment. The novel effect of chaotic scattering of atoms at a regular near-resonant standing wave is found numerically and explained qualitatively. Some applications of the effects found are disc…
We propose a scheme to split a cloud of cold non-interacting neutral atoms based on their dipole interaction with a single structured light beam which exhibits parabolic cylindrical symmetry. Using semiclassical numerical simulations, we establish a direct relationship between the general properties of the light beam and the relevant geometric and kinematic properties acquired by the atomic cloud as its passes through the beam.
A natural approach to measure the time of arrival of an atom at a spatial region is to illuminate this region with a laser and detect the first fluorescence photons produced by the excitation of the atom and subsequent decay. We investigate the actual physical content of such a measurement in terms of atomic dynamical variables, taking into account the finite width of the laser beam. Different operation regimes are identified, in particular the ones in which the quantum current density may be obtained.
We present a protocol for increasing the entanglement between two atomic ensembles based on applying an approximate atom-light beamsplitter transformation to both ensembles. The effective asymmetric atom-light beamsplitter is created via a double-pass quantum non-demolition interaction between polarized light and a spin polarized atomic ensemble, derived from the linearised dipole interaction. The entanglement concentration protocol itself uses the procrustean method, similar to that first devised for light by Browne et al [2003 Phys Rev A 67 062320] and includes photon counting after the inte…
Faraday-Ramsey rotation measurement in a thin cell as an analogy to an atomic beam
本研究针对原子束装置庞大难以小型化的问题，利用微米级薄铷蒸气盒的几何速度滤波模拟原子束行为，通过空间位移泵浦-探测方案和磁场扫描获得清晰拉姆齐条纹，为原子束系统提供紧凑替代方案，支撑可扩展传感器与频率标准。
A chip-scale atomic beam source for non-classical light
本研究将芯片级铷原子束源与高精细度腔量子电动力学系统集成，成功产生非经典光，为分布式非经典光源开辟新途径，并为提升芯片级磁力计和原子钟性能奠定基础。
We have demonstrated an atom-optical lens, with the advantage of a small scale and flexible adjustment of the parameters, realized by a far red-detuned Gaussian laser beam perpendicular to the propagation direction of the cold atomic cloud. The one-dimensional transverse focusing effect of cold atomic clouds at the temperature order of 1 $μ$K freely falling through the atom-optical lens on the micron scale have been studied theoretically and then verified experimentally. It is found that theory and experiment are in good agreement.
Miniature atomic beams can provide new functionalities for atom based sensing instruments such as atomic clocks and interferometers. We recently demonstrated a planar silicon device for generating well-collimated thermal atomic beams [Nat Commun 10, 1831 (2019)]. Here, we present a near-source fluorescence spectroscopy (NSFS) technique that can fully characterize such miniature beams even when measured only a few millimeters from the nozzle exit. We also present a recipe for predicting the fluorescence spectrum, and therefore, the source angular distribution, even under conditions of strong la…
We study the fidelity of single qubit quantum gates performed with two-frequency laser fields that have a Gaussian or super Gaussian spatial mode. Numerical simulations are used to account for imperfections arising from atomic motion in an optical trap, spatially varying Stark shifts of the trapping and control beams, and transverse and axial misalignment of the control beams. Numerical results that account for the three dimensional distribution of control light show that a super Gaussian mode with intensity $I\sim e^{-2(r/w_0)^n}$ provides reduced sensitivity to atomic motion and beam misalig…
We study the collective emission of a beam of atomic dipoles into an optical cavity. Our focus lies on the effect of a finite detuning between the atomic transition frequency and the cavity resonance frequency. By developing a theoretical description of the coupled atom-cavity dynamics we analyze the stationary atomic configurations including a superradiant phase where the atoms undergo continuous monochromatic collective emission. In addition, we derive an analytical formula for the cavity pulling coefficient which characterizes the displacement of the emission frequency towards the cavity fr…
We demonstrate an atomic Faraday dichroic beam splitter suitable to spatially separate signal and idler fields from pump degenerate four-wave mixing in an atomic source. By rotating the plane of polarization of one mode $90^{\circ}$ with respect to the other, a subsequent polarizing beam splitter separates the two frequencies, which differ by only 13.6 GHz, and achieves a suppression of $(-26.3\pm0.1)$ and $(-21.2\pm0.1)$ dB in the two outputs, with a corresponding transmission of 97 and 99 %. This technique avoids the need to use spatial separation of four-wave mixing modes and thus opens the…
Hyperfine and Zeeman Optical Pumping and Transverse Laser Cooling of a Thermal Atomic Beam of Dysprosium Using a Single 421 nm Laser
利用单个421 nm激光对热镝原子束进行超精细和塞曼光学泵浦及横向激光冷却，用于基础物理实验中的宇称违反测量。
Polariton formalism is applied for studying the propagation of a probe field of light in a cloud of cold atoms influenced by two control laser beams of larger intensity. The laser beams couple resonantly three hyperfine atomic ground states to a common excited state thus forming a tripod configuration of the atomic energy levels involved. The first control beam can have an optical vortex with the intensity of the beam going to zero at the vortex core. The second control beam without a vortex ensures the loseless (adiabatic) propagation of the probe beam at a vortex core of the first control la…
We demonstrate the fast accumulation of Cr atoms in a conservative potential from a magnetically guided atomic beam. Without laser cooling on a cycling transition, a single dissipative step realized by optical pumping allows to load atoms at a rate of 2*10^7 1/s in the trap. Within less than 100 ms we reach the collisionally dense regime, from which we directly produce a Bose-Einstein condensate with subsequent evaporative cooling. This constitutes a new approach to degeneracy where, provided a slow beam of particles can be produced by some means, Bose-Einstein condensation can be reached for …
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