Bulletin of the American Physical Society
52nd Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 66, Number 6
Monday–Friday, May 31–June 4 2021; Virtual; Time Zone: Central Daylight Time, USA
Session Z05: New Techniques in Laser CoolingLive
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Chair: Seth Aubin, William and Mary |
Friday, June 4, 2021 10:30AM - 10:42AM Live |
Z05.00001: Atom Cloud Detection and Segmentation Using a Deep Neural Network Lucas Hofer, Milan Krstajić, Peter Juhász, Anna Marchant, Robert Smith We use a deep neural network to detect and place region-of-interest boxes around ultracold atom clouds in absorption and fluorescence images—with the ability to identify and bound multiple clouds within a single image. The neural network also outputs segmentation masks that identify the size, shape and orientation of each cloud from which we extract the clouds' Gaussian parameters. This allows 2D Gaussian fits to be reliably seeded thereby enabling fully automatic image processing. The method developed performs significantly better than a more conventional method based on a standardized image analysis library (Scikit-image) both for identifying regions-of-interest and extracting Gaussian parameters. |
Friday, June 4, 2021 10:42AM - 10:54AM Live |
Z05.00002: Employing deep neural networks in the analysis of visual data in ultracold atoms experiments Anastasiya Vainbaum, Gal Ness, Yoav Sagi, Constantine Shkedrov, Yanay Florshaim, Meny Menashes Deep learning reconstruction models enable the analysis of noisy physical data with unparalleled accuracy. These tools prove to be extremely useful when analyzing absorption imaging signals that suffer from structural structured noise due to slow changes in the illumination. Most of this noise can be removed by taking two successive exposures. Even then, some noise remains. Here we demonstrate the powerful advantage of deep learning in removing structured noise without a need for a second exposure. Specifically, we present an analysis of condensate fraction measurements taken with a superfluid Fermi gas, which is especially sensitive to background noise. The denoising of the spatial distribution obtained by absorption imaging uncovers an intriguing dynamical behavior of a periodically driven gas. To distill the data from the noise, we have developed a method that relies on a single exposure and an image-completion autoencoder neural network. The autoencoder is trained to reconstruct the noise from the information in the area surrounding the data, thus generating an ideal reference frame. Subtraction of this reference image provides a clean signal and thus higher accuracy, which enables deeper insight into the underlying physics. |
Friday, June 4, 2021 10:54AM - 11:06AM Live |
Z05.00003: Machine learning estimation of optimal resolved sideband cooling strategies Alexander Rasmusson, Marissa D'Onofrio, Yuanheng Xie, Jiafeng Cui, Philip Richerme Ground state preparation of trapped ions through resolved sideband cooling is an integral technique to trapped ion experiments and technologies. Despite its prevalence, the optimal cooling strategy given an initial ion temperature, a target temperature, and trap parameters is currently unknown. We present a methodic search for the fastest cooling strategies over a wide range of experimental parameters. By varying the laser pulse duration and number of pulses, and by including the possibility of higher-order sidebands, we determine potential candidates for optimal cooling strategies. Since the space of cooling strategies scales exponentially both in the number of pulses and the number of higher-order sidebands applied, brute-force computation proves impractical if not impossible. Instead, we numerically estimate optimal cooling strategies by employing a support-vector machine trained on Monte Carlo estimators. We find that traditional sequential pi pulse strategies are far from optimal, especially for initially "hot" ions and/or ions not deep within the Lamb-Dicke regime, and propose more efficient pulse sequences for achieving faster near-ground-state cooling. |
Friday, June 4, 2021 11:06AM - 11:18AM Live |
Z05.00004: Continuous slowing of a gadolinium atomic beam Andrés Chavarría, Andre Araya-Olmedo, Óscar Andrey Herrera-Sancho The article presents the development of a new and innovative experimental method to fully characterize a solenoidal ''spin-flip" Zeeman slower (ZS) using a Quartz Crystal μ-balance (QCM) as a kinetic energy sensor. In this experiment, we focus a 447.1 nm laser into a counter-propagating beam of gadolinium (Gd) atoms in order to drive the dipole transition between ground 9D02 state and 9D3 excited state. The changes in the velocity of the beam were measured using a QCM during this process, as a novel and alternative method to characterize the efficiency of a 1 m-long spin-flip Zeeman slower. The QCM, normally used in solid-state physics, is continuously and carefully monitored to determine the change in its natural frequency of oscillation. These changes reveal a direct relation with changes in the deposition rate and the momentum exchanged between the QCM and Gd atoms. Hence, in terms of ultracold atom physics, it might be used to study the time-evolution of the velocity distribution of the atoms during the cooling process. By this method, we obtain a maximum atom average velocity reduction of (43.5 ± 6.4)% produced by our apparatus. Moreover, we estimate an experimental lifetime of τe= 8.2 ns for the used electronic transition, and then we compared it with the reported lifetime for 443.06 nm and 451.96 nm electronic transitions of Gd. These results confirm that the QCM offers an accessible and simple solution to take into account for laser cooling experiments. Therefore, a novel and innovative technique can be available for future experiments. |
Friday, June 4, 2021 11:18AM - 11:30AM Live |
Z05.00005: Centilitre-scale vacuum chamber with integrated grating magneto-optical trap optics for compact ultracold quantum technologies Oliver Burrow, Aidan S Arnold, Paul F Griffin, Erling Riis A key enabling component for cold atom technologies are compact ultra-high vacuum systems, which facilitate high precision quantum sensing applications. Whilst there has been progress towards portable compact vacuum systems, their size, weight and power usage can be prohibitively large. Here, we present a centilitre-scale ceramic vacuum chamber with He-impermeable viewports and an integrated diffractive optic, allowing simple and robust laser cooling from a single circularly-polarised laser beam. A demonstration of a portable cold atom source based on this vacuum system delivers 107 laser-cooled 87Rb atoms per second. Pressure measurement from magneto-optical trap loading curves gauges the pressure to be below 10-7 mbar under active pumping. The pressure under passive pumping stabilizes to 3 x 10-6 mbar with a 17 day time constant - which has already been verified for a year without active pumping. The passive pumping vacuum lifetime is estimated to be several years, from short-term He throughput measurements, and there are many foreseeable improvements. This technology is a key step towards realising wide-ranging mobilization of ultracold quantum sensing. [see also arxiv:2101.07851] |
Friday, June 4, 2021 11:30AM - 11:42AM Live |
Z05.00006: PyLCP: A python package for laser cooling physics Stephen P Eckel, Daniel S Barker, eric Norrgard, Julia Scherschligt We present a python object-oriented computer program for simulating laser cooling physics. Our software is designed to be both easy to use and adaptable, allowing the user to specify the level structure, magnetic field profile, and the laser beams' geometry, detuning, and intensity. The program contains three levels of approximation for the motion of the atom, applicable in different regimes offering cross checks for calculations and computational efficiency depending on the physical situation. We test the software by reproducing well-known phenomena, such as damped Rabi flopping, electromagnetically induced transparency, stimulated Raman adiabatic passage, and optical molasses. We also use our software package to quantitatively simulate recoil-limited magneto-optical traps, like those formed on the narrow $^1$S$_0\rightarrow ^3$P$_1$ transition in $^{88}$Sr and $^{87}$Sr. |
Friday, June 4, 2021 11:42AM - 11:54AM Live |
Z05.00007: A Compact Strontium 2D Magneto-Optical Trap for Programmable Atom Arrays Minho Kwon, Aaron Holman, Weijun Yuan, Max Aalto, Quan Gan, Sebastian Will We report on the design and implementation of a new apparatus for the creation of strontium optical tweezer arrays. In particular, we have developed a novel 2D magneto-optical trap as a source for cold strontium atoms. Typically, sources for strontium experiments rely on an effusive oven combined with a Zeeman slower, which tends to lead to large and expensive setups. Here, we demonstrate a 2D MOT that is directly loaded from dispensers. Our design has a compact footprint, a simple optical setup and enables good optical access. The initial characterization demonstrates robust performance. In addition, we discuss our approach towards creating arbitrary optical tweezer arrays of strontium atoms for fundamental quantum optics experiments and quantum simulation. |
Friday, June 4, 2021 11:54AM - 12:06PM Live |
Z05.00008: Circumventing AC Tweezers With Single Sodium Atoms Mohammad Mujahid Aliyu, Xiu Quan Quek, Krishna Chaitanya Yellapragada, Luheng Zhao, Huanqian Loh Optical trapping and manipulation of individual neutral atoms in tweezer arrays have proved central to recent advances in studies of many-body physics, precision measurement, and metrology. Trapping and imaging of single atoms require efficient cooling of the atoms into the tweezer trap while scattering photons during imaging. This can be challenging for atoms like sodium, where the excited states can become anti-trapping in red-detuned light, so to date, single sodium atoms have only been trapped by temporally alternating between the cooling light and tweezer light. Such an "AC tweezer" method, however, increases demands on the optical tweezer power per trap and limits the total number of tweezer traps in an array. Here, we report the demonstration of DC trapping and imaging of a tweezer array of sodium atoms, thereby circumventing the need for AC tweezers and increasing the scalability of atom arrays. |
Friday, June 4, 2021 12:06PM - 12:18PM Live |
Z05.00009: Progress towards deep-ultraviolet laser cooling of AlCl Jamie Shaw, Joseph Schnaubelt, Daniel McCarron Laser-cooled molecules promise access to a diverse range of research directions from ultracold chemistry to improved precision measurements. However, inefficient trap loading remains the key barrier preventing molecular magneto-optical traps (MOTs) from realizing large, dense samples of ultracold molecules with properties similar to their atomic counterparts. Our experiment aims to remove this barrier by realizing bright quasi-continuous beams of cold molecules [1] and by selecting a molecular species susceptible to large optical forces via photon scattering. Our molecule of choice, aluminum monochloride (AlCl), is projected to have favorable properties for laser cooling and efficient MOT loading, including a lack of spin-rotation structure and a strong optical transition in the deep-ultraviolet. This talk will present an update on experimental progress, including our tunable laser system capable of >1.8 W at 261.5 nm and our recent work using this light to characterize and manipulate a beam of AlCl from our cryogenic source. |
Friday, June 4, 2021 12:18PM - 12:30PM Live |
Z05.00010: High density and loading rate MOT of K atoms using a buffer-gas beam source Maryam M Hiradfar, Zack Lasner, Debayan Mitra, Sridhar Prabhu, Lawrence W Cheuk, Benjamin Augenbraun, Eunice Lee, John M Doyle Whereas AMO experiments with alkali atoms typically rely on dispenser- or oven-based sources of gas-phase atoms, cold radical molecules are more commonly generated from a cryogenic buffer gas beam (CBGB). Building on previous proof-of-principle work that demonstrated efficient loading of lanthanide-series atoms into a magneto-optical trap (MOT), we achieve an exceptionally dense MOT of potassium atoms using the D2 line, with a loading time of only ~10 ms. This method could be applied to any cold atom experiment, and would be especially useful when very high initial atomic MOT densities or <<100 ms loading times are required. Explorations of high repetition rates will also be discussed. |
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