Optical setup for a two-dimensional tweezer array with independently adjustable columns for neutral atom quantum computing
Martin Adams, Martin Traub, Hans-Dieter Hoffmann, Florian Meinert, P. Ilzhöfer, Thomas Westphalen, Kersten Ludwig, Jiachen Zhao, A. Scholz, Govind Unnikrishnan, Ratnesh Kumar Gupta, Tilman Pfau, C. Haefner
We present an optical design concept to create a two-dimensional tweezer array for neutral atom quantum computing. The first part of the setup splits the four input laser beams into 20 individual beam lines that correspond to the columns of the tweezer array. A combination of an acousto-optic deflector (AOD) and a suitable imaging lens for each beam line creates a magnified image of the one-dimensional columns in the tweezer array with a spacing of less than 200 μm. The spacing between the 20 columns is reduced to this value as well to achieve a spot array with an equidistant spacing in both axes. This is done successively in four steps by using a combination of one discrete mirror cascade and three mirror cascades integrated into monolithic mirror arrays. The final tweezer array with a spacing of 3.5 μm is then created by a two-stage telecentric demagnifying lens group. Unlike other approaches to create a two-dimensional tweezer array (e.g. crossed AODs), the use of a separate AOD for each column allows for an independent adjustment of the spacings within each column and thus a flexible adjustment of the local interaction of neighboring atoms. A raytracing analysis demonstrates that the whole setup produces a telecentric and diffraction-limited image of 20 × 100 spots in the following vacuum chamber.
We present an optical design concept to create a two-dimensional tweezer array for neutral atom quantum computing. The first part of the setup splits the four input laser beams into 20 individual beam lines that correspond to the columns of the tweezer array. A combination of an acousto-optic deflector (AOD) and a suitable imaging lens for each beam line creates a magnified image of the one-dimensional columns in the tweezer array with a spacing of less than 200 μm. The spacing between the 20 columns is reduced to this value as well to achieve a spot array with an equidistant spacing in both axes. This is done successively in four steps by using a combination of one discrete mirror cascade and three mirror cascades integrated into monolithic mirror arrays. The final tweezer array with a spacing of 3.5 μm is then created by a two-stage telecentric demagnifying lens group. Unlike other approaches to create a two-dimensional tweezer array (e.g. crossed AODs), the use of a separate AOD for each column allows for an independent adjustment of the spacings within each column and thus a flexible adjustment of the local interaction of neighboring atoms. A raytracing analysis demonstrates that the whole setup produces a telecentric and diffraction-limited image of 20 × 100 spots in the following vacuum chamber.
We present a novel acousto-optic lens (AOL) design for neutral atom quantum computing. This approach enhances atom rearrangement in optical tweezer arrays and addresses the speed limitations imposed by the cylindrical lensing effect of acousto-optic deflectors (AODs). By combining a double-pass AOD configuration for dynamic focal tuning with a standard pair of crossed AODs for transverse beam steering, our design enables the generation of arbitrary focal point trajectories. This configuration enables shuttling of atoms in 3D space, thereby helping to realise fully connected two-qubit gates and mid-circuit measurements. We detail the optical implementation, characterize its performance, and discuss its applications in scalable quantum computing architectures.
Reconfigurable arrays of neutral atoms are a leading platform for quantum computing, quantum simulation, and quantum metrology. The most common method for atom reconfiguration using optical tweezers relies on frequency chirping of acousto-optic deflectors (AODs). However, chirp-induced acoustic lensing limits the speed of atom transport by deformation of the tweezer profile and warping of the tweezer trajectory. We use a three-dimensional acousto-optic deflector lens (3D-AODL) to mitigate both effects, a design predicted to halve current state-of-the-art long-range transport times. Additionally, we introduce fading-Shepard waveforms that bypass the finite AOD bandwidth and thus enable sustained axial displacement. We demonstrate unrestricted 3D motion within a cuboid volume of at least 200 μm × 200 μm × 136 μm, with tweezer velocities exceeding 4.2 m/s. The ability to move optical tweezers along arbitrary trajectories in 3D should enable rapid in-plane and out-of-plane rearrangement of atoms in 2D or 3D tweezer arrays and optical lattices, as well as omnidirectional trajectories and dynamical engineering of optical potentials. This technology has the potential to advance quantum control and atom manipulation in current atom-array quantum computers, boosting clock rates and enabling rapid sorting in geometries scalable to millions of qubits.
Optical tweezer arrays of neutral atoms have emerged as a promising platform for studying quantum physics. These individual atoms can be carefully prepared in single quantum states, and easily manipulated with microwaves and lasers. MHz scale interactions are accessible at several micron scale distances by exciting these atoms to Rydberg states. These arrays can also be created in arbitrary 2D geometries with the use of a spatial light modulator. Adding the capability of a second species opens new possibilities in non-destructive measurement and quantum simulation of bipartite systems with widely tunable parameters. In this thesis, we describe our efforts to build a flexible platform for studying quantum phenomena utilizing two species of atoms, sodium and cesium. In particular, we discuss the laser technology and setups required to create dual species optical tweezer arrays. These arrays are made defect-free with real-time rearrangement of atoms using a separate set of tweezers created with acousto-optical deflectors. We then describe how to excite these atoms coherently to the Rydberg state with coherence times in Cs as long as 20 microseconds. With these techniques established, we are able to probe an Ising critical point in 1D and 2D systems with up to 81 atoms. In particular, we measure and confirm the value of the universal critical exponent, η, via adiabatic preparation of the ground state at the critical point. Then, we measure the interactions between sodium and cesium atoms setting the stage for future experiments. Lastly, a theoretical proposal is presented where Rydberg atoms can be used to enhance the interaction rates of ultracold polar molecules, as well as measure their states non-destructively.
Neutral atoms for quantum computing applications show promise in terms of scalability and connectivity. We demonstrate the realization of a versatile apparatus capable of stochastically loading a 5x5 array of optical tweezers with single 88Sr atoms featuring flexible magnetic field control and excellent optical access. A custom-designed oven, spin-flip Zeeman slower, and deflection stage produce a controlled flux of Sr directed to the science chamber. In the science chamber, featuring a vacuum pressure of 3×10−11 mbar, the Sr is cooled using two laser cooling stages, resulting in ∼3×105 atoms at a temperature of 5(1) μK. The optical tweezers feature a 1/e2 waist of 0.81(2) μm, and loaded atoms can be imaged with a fidelity of ∼0.997 and a survival probability of 0.99−0.02+0.01. The atomic array presented here forms the core of a full-stack quantum computing processor targeted for quantum chemistry computational problems.
In this work we present the results of studies of one-dimensional (1D) and twodimensional (2D) optical lattices on a chip.We have developed a method to create 1D and 2D optical lattices above an optical waveguide.The method is based on the destructive interference of the evanescent waves of two modes of the waveguide, resulting in a periodic array of nodes above the waveguide surface.For blue-detuned light, this constitutes an array of optical dipole traps for neutral atoms.One pair of modes coupled into a ridge waveguide creates a 1D array of nodes in this manner, and two orthogonal pairs of modes in a slab waveguide result in a 2D array of nodes.Computational analysis of our method showed that these optical atom chips may be suitable for use as a quantum register, and for studies of atom-surface interactions between the trapped atoms and the waveguide surface.Using realistic waveguide materials and laboratory laser parameters we found that for a laser power of ~100 mW nodes can be created ~100 nm above the waveguide surface.The nodes constitute atom traps that are ~1mK deep, and have trap frequencies ~1MHz and ground state sizes of ~10 nm.The spacing between traps is ~1 µm enabling individual addressing with a focused laser beam.iii With the implementation of two-qubit gates in mind, initial investigations of extensions of the basic 2D optical lattice were conducted.Computational results for a counter-propagating 2D optical lattice with very close trap spacing (~λ/4) in one dimension, and for a 2D optical lattice with adjustable spacing between pairs of traps in one dimension are presented.An experimental setup for the realization of the proposed 2D optical lattices on a chip was designed and built.Several cooling and trapping steps necessary to prepare a cold atom sample for loading of the 2D optical lattice have been implemented successfully.In the course of previous studies of atom-surface interactions, a novel surfaceionization detector for 2D imaging of neutral atom samples was built and characterized.We find a detection efficiency ~50 %, a spatial resolution of 20 µm and a time response < 1/30 s. iv To my family.v ACKNOWLEDGMENTS First and foremost I would like to thank my advisor Greg Lafyatis for everything that he taught me.I also want to thank Frank DeLucia for always being there with his advice when I needed it.I appreciate Eric Herbst and Junko Shigemitsu for being willing to serve on
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.