We report on the experimental realization of a standing-wave atom tweezer (SWAT) by aligning tightly focused dipole laser beams from a commercial objective lens and a metalens on a chip. By independently tuning the laser intensities of the two beams, we demonstrate the controlled loading of multiple atoms into the SWAT. We systematically investigate the influence of the standing-wave potential modulation depth on single-atom loading dynamics and quantitatively estimate the number of atoms in the SWAT by calculating the fluorescence of trapped atoms. Our results show that the SWAT can trap a chain of more than 20 atoms with significantly suppressed atom collisions, exhibiting a lifetime exceeding 1 second. Our work presents a versatile platform for investigating atom dynamics in 1D optical lattices, enabling the study of collective atom-photon interactions and many-body physics in a highly controllable system.
We report on the experimental realization of a standing-wave atom tweezer (SWAT) by aligning tightly focused dipole laser beams from a commercial objective lens and a metalens on a chip. By independently tuning the laser intensities of the two beams, we demonstrate the controlled loading of multiple atoms into the SWAT. We systematically investigate the influence of the standing-wave potential modulation depth on single-atom loading dynamics and quantitatively estimate the number of atoms in the SWAT by calculating the fluorescence of trapped atoms. Our results show that the SWAT can trap a chain of more than 20 atoms with significantly suppressed atom collisions, exhibiting a lifetime exceeding 1 second. Our work presents a versatile platform for investigating atom dynamics in 1D optical lattices, enabling the study of collective atom-photon interactions and many-body physics in a highly controllable system.
Single atoms are promising candidates for physically implementing quantum bits, the fundamental unit of quantum information. We have built an apparatus for cooling, trapping and imaging single rubidium atoms in microscopic optical tweezers. The traps are formed from a tightly focused off-resonant laser beam, which traps atoms using the optical dipole force. The traps have a diameter of ~1 μm and a depth of ~1 mK. The novelty of our approach is the use a digital mirror device (DMD) to generate multiple independently movable tweezers from a single laser beam. The DMD consists of an array of micro-mirrors that can be switched on and off, thus acting as a binary amplitude modulator. We use the DMD to imprint a computer-generated hologram on the laser beam, which is converted in to the desired arrangement of traps in the focal plane of a lens. We have developed fast algorithms for calculating binary holograms suitable for the DMD. In addition, we use this method to measure and correct for errors in the phase of the wavefront caused by optical aberrations, which is necessary for producing diffraction-limited focal spots. Using this apparatus, we have trapped arrays of up to 20 atoms with arbitrary geometrical arrangements. We exploit light-assisted collisions between atoms to ensure there is at most one atom per trapping site. We measure the temperature of the atoms in the traps to be 12 μK, and their lifetime to be 1.4 s. Finally, we demonstrate the ability to select individual atoms from an array and transport them over a distance of 14μm with laser cooling, and 5 μm without.
A small known number of cesium atoms is loaded from a magneto-optical trap into a far detuned, standing wave optical dipole trap. This trap is made of two counter-propagating Nd:YAG laser beams (/spl lambda/= 1064 nm) which give rise to a chain of potential wells with a depth of about 1 mK and an axial spacing of 532 nm. By fitting the axial intensity distribution with a Gaussian function, the positions of the individual atoms are determined automatically with a precision of 100 nm rms, mainly limited by photon statistics.
Atoms can be individually captured and guided by light through optical dipole-trapping. However, applying this to many atoms simultaneously has been difficult due to the low inertia of atoms. Recently dynamically-controlled laser beams achieved such demonstrations, enabling a bottom-up approach to form arbitrary atom lattices, deterministic atom loading, atom-sorting, and even single-atom-level machinery. Here we report the latest improvements of the single-atom-level dynamic holographic optical tweezers. With the hardware and software upgrades to be explained in the text, the overall performance has improved to form arbitrary 2D lattices of a size about N=20, with success probability exceeding 50%.
Optical tweezer arrays of neutral atoms have emerged as a versatile and powerful platform for quantum simulation and quantum information processing. In this thesis, I present the realization of an experimental platform for quantum simulation based on individually trapped strontium atoms in optical tweezer arrays. The experiment combines precise laser cooling, optical control, and high-resolution imaging to enable the manipulation and high fidelity detection of single atoms. I developed and optimized a two-stage three-dimensional magneto-optical trap (3D-MOT) that produces cold and dense samples of strontium atoms from a thermal beam. In the f irst stage, atoms are captured and precooled using the dipole-allowed 1S0 → 1P1 transition at 461nm (which has a linewidth of !=2ω ↑ 32MHz). The second stage employs the 1S0 → 3P1 narrow intercombination transition at 689nm (with a linewidth of !=2ω ↑7.5kHz) to further cool and compress the atomic cloud. By optimizing the trapping parameters, I achieved clouds with temperatures around 5μK and densities above 1010cm→3, providing ideal initial conditions for e!cient loading into optical tweezers. A 3↑3 array of 360μK deep optical tweezers is generated by spatially modulating an 813.4nm laser beam using two crossed acousto-optic deflectors. The deflected beams are relayed and focused into the science chamber using a high–numericalaperture objective, which simultaneously serves as the collection optics for atomic f luorescence. The fluorescence light emitted by the atoms is imaged onto a scientific qCMOS camera, enabling site-resolved detection of individual atoms. I implemented and optimized the in-trap cooling dynamics to prevent atom loss during imaging and to minimize residual thermal motion. In addition, by precisely tuning lightassisted collisions, multiple atoms occupancies are removed from the traps and a single-atom regime is reached in the array, with a filling fraction of about 50%. I have demonstrated a single-atom detection fidelity of 99,986(1)% and a survival probability of 97(2)% between subsequent image acquisition, comparable to other current state-of-the-art experiments. To characterize the platform, I carried out release-and-recapture experiments, from which it is possible to measure a temperature for the individually trapped atoms of 12.95(5)μK. These results demonstrate the successful implementation of a robust and high-fidelity platform for optical trapping and imaging of single strontium atoms. The apparatus provides the foundation for future quantum simulation experiments with alkalineearth atoms excited to the Rydberg state, o"ering precise control over individual particles and the ability to scale towards larger, programmable atomic arrays.
Microscopically controlled neutral atoms in optical tweezers and lattices have led to exciting advances in the study of quantum information and quantum many-body systems. The light shifts of atomic levels from the trapping potential in these systems can result in detrimental effects such as fluctuating dipole force heating, inhomogeneous detunings, and inhibition of laser cooling, which limits the atomic species that can be manipulated. In particular, these light shifts can be large enough to prevent loading into optical tweezers directly from a magneto-optical trap. We implement a general solution to these limitations by loading, as well as cooling and imaging the atoms with temporally alternating beams, and present an analysis of the role of heating and required cooling for single atom tweezer loading. Because this technique does not depend on any specific spectral properties, it should enable the optical tweezer platform to be extended to nearly any atomic or molecular species that can be laser cooled and optically trapped.
We present an optical system designed to capture and observe a single neutral atom in an optical dipole trap, created by focusing a laser beam using a large-numerical-aperture (NA=0.5) aspheric lens. We experimentally evaluate the performance of the optical system and show that it is diffraction limited over a broad spectral range $(\ensuremath{\sim}200\phantom{\rule{0.3em}{0ex}}\mathrm{nm})$ with a large transverse field $(\ifmmode\pm\else\textpm\fi{}25\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{m})$. The optical tweezer created at the focal point of the lens is able to trap single atoms of 87Rb and to detect them individually with a large collection efficiency. We measure the oscillation frequency of the atom in the dipole trap and use this value as an independent determination of the waist of the optical tweezer. Finally, we produce with the same lens two dipole traps separated by $2.2\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{m}$ and show that the imaging system can resolve the two atoms.