Optical Nanofibers for Manipulating and Probing Single-Atom Fluorescence

Tapered optical fibers as tools for probing magneto-optical trap characteristics

We present a novel technique for measuring the characteristics of a magneto-optical trap for cold atoms by monitoring the spontaneous emission from trapped atoms coupled into the guided mode of a tapered optical nanofiber. We show that the nanofiber is highly sensitive to very small numbers of atoms close to its surface. The size and shape of the MOT, determined by translating the cold atom cloud across the tapered fiber, is in excellent agreement with measurements obtained using the conventional method of fluorescence imaging using a CCD camera. The coupling of atomic fluorescence into the ta…

基于光学纳米纤维的多于100个可单独寻址原子的量子接口

Fiber-optic quantum interface with an array of more than 100 individually addressable atoms on an optical nanofiber

本文提出一种结合光学镊子单原子阵列可扩展性和纳米光子波导高效光物质接口的量子接口，实现了310nm光学纳米纤维引导光子与平均155个可单独寻址原子的接口，通过光子相关性测量验证了单原子陷阱的特性。

Real-time observation of single atoms trapped and interfaced to a nanofiber cavity

We demonstrate an optical tweezer based single atom trapping on an optical nanofiber cavity. We show that the fluorescence of single atoms trapped on the nanofiber cavity can be readily observed in real-time through the fiber guided modes. The photon correlation measurements further clarify the atom number and the dynamics of the trap. The trap lifetime is measured to be 52$\pm$5 ms. From the photon statistics measured for different cavity decay rates, the effective coupling rate of the atom-cavity interface is estimated to be 34$\pm$2 MHz. This yields a cooperativity of 5.4$\pm$0.6 and a cavi…

Imaging and localizing individual atoms interfaced with a nanophotonic waveguide

Single particle-resolved fluorescence imaging is an enabling technology in cold-atom physics. However, so far, this technique was not available for nanophotonic atom-light interfaces. Here, we image single atoms that are trapped and optically interfaced using an optical nanofiber. Near-resonant light is scattered off the atoms and imaged while counteracting heating mechanisms via degenerate Raman cooling. We detect trapped atoms within 150 ms and record image sequences of given atoms. Building on our technique, we perform two experiments which are conditioned on the number and position of the …

Optical nanofibers and spectroscopy

We review our recent progress in the production and characterization of tapered optical fibers with a sub-wavelength diameter waist. Such fibers exhibit a pronounced evanescent field and are therefore a useful tool for highly sensitive evanescent wave spectroscopy of adsorbates on the fiber waist or of the medium surrounding. We use a carefully designed flame pulling process that allows us to realize preset fiber diameter profiles. In order to determine the waist diameter and to verify the fiber profile, we employ scanning electron microscope measurements and a novel accurate in situ optical m…

Probing Surface-Bound Atoms with Quantum Nanophotonics

Quantum control of atoms at ultrashort distances from surfaces would open a new paradigm in quantum optics and offer a novel tool for the investigation of near-surface physics. Here, we investigate the motional states of atoms that are bound weakly to the surface of a hot optical nanofiber. We theoretically demonstrate that with optimized mechanical properties of the nanofiber these states are quantized despite phonon-induced decoherence. We further show that it is possible to influence their properties with additional nanofiber-guided light fields and suggest heterodyne fluorescence spectrosc…

Projective measurement of a single nuclear spin qubit by using two-mode cavity QED

We report the implementation of projective measurement on a single 1/2 nuclear spin of the 171Yb atom by measuring the polarization of cavity-enhanced fluorescence. To obtain cavity-enhanced fluorescence having a nuclear-spin-dependent polarization, we construct a two-mode cavity QED system, in which two cyclic transitions are independently coupled to each of the orthogonally polarized cavity modes, by manipulating the energy level of 171Yb. This system can associate the nuclear spin degrees of freedom with the polarization of photons, which will facilitate the development of hybrid quantum sy…

Fictitious magnetic field gradients in optical microtraps as an experimental tool for interrogating and manipulating cold atoms

Optical microtraps provide a strong spatial confinement for laser-cooled atoms. They can, e.g., be realized with strongly focused trapping light beams or the optical near fields of nano-scale waveguides and photonic nanostructures. Atoms in such traps often experience strongly spatially varying AC Stark shifts which are proportional to the magnetic quantum number of the respective energy level. These inhomogeneous fictitious magnetic fields can cause a displacement of the trapping potential that depends on the Zeeman state. Hitherto, this effect was mainly perceived as detrimental. However, it…

Near-ground-state cooling of atoms optically trapped 300nm away from a hot surface

Laser-cooled atoms coupled to nanophotonic structures constitute a powerful research platform for the exploration of new regimes of light-matter interaction. While the initialization of the atomic internal degrees of freedom in these systems has been achieved, a full preparation of the atomic quantum state also requires controlling the center of mass motion of the atoms at the quantum level. Obtaining such control is not straightforward, due to the close vicinity of the atoms to the photonic system that is at ambient temperature. Here, we demonstrate cooling of individual neutral Cesium atoms,…

捕获、操控与探测超冷原子：量子技术教程

Trapping, manipulating and probing ultracold atoms: a quantum technologies tutorial

本教程综述超冷原子的捕获、操控与探测关键技术，涵盖激光冷却、光镊、干涉测量及多种成像方法，旨在为初学者提供实验工具包的全面概览。

基于单像素纳米结构的透镜效应与增强型单原子探测

Lensing and enhanced single atom detection via a single-pixel nanostructure

该研究提出基于单纳米结构相位梯度的纳米级透镜机制，以单原子为量子探针验证效应，使单原子探测效率提升4倍，确立片上纳米结构为多功能量子光学平台，为量子应用提供新机遇。

用于量子模拟的单个锶原子在光学镊子阵列中

Single Sr Atoms in Optical Tweezer Arrays for Quantum Simulation

该研究实现了用于量子模拟的单个锶原子在光学镊子阵列中的高效捕获、冷却和高保真度检测，为可扩展的量子模拟和信息处理奠定了基础。