Bulletin of the American Physical Society
50th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics APS Meeting
Volume 64, Number 4
Monday–Friday, May 27–31, 2019; Milwaukee, Wisconsin
Session D05: Laser Cooling and Trapping |
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Chair: Trey Porto, Joint Quantum Institute, NIST/UMD Room: Wisconsin Center 102C |
Tuesday, May 28, 2019 2:00PM - 2:12PM |
D05.00001: Torsional and rotational optomechanics of an optically trapped nanoparticle in vacuum Tongcang Li An optically levitated nanoparticle in vacuum is excellent for precision measurements. Recently, we optically levitated pure silica nanodumbbells in high vacuum. With a circularly polarized laser, we drove it to rotate beyond 1 GHz [Phys. Rev. Lett., 121, 033603 (2018)]. With a linearly-polarized laser, we observed its torsional vibration. A nanodumbbell levitated by a linearly polarized laser in vacuum will be a novel torsion balance with a torque detection sensitivity on the order of $10^{-28} Nm/\sqrt{Hz}$. This will be sufficient to detect the Casimir torque due to the angular momentum of quantum vacuum fluctuations. This system can also be used to study the nonadiabatic dynamics and geometric phase of a fast rotating electron spin [arXiv:1811.01641]. With a levitated nanoparticle under drive, we also tested the differential fluctuation theorem and a generalized Jarzynski equality that is valid for arbitrary initial states [Phys. Rev. Lett. 120, 080602 (2018)]. [Preview Abstract] |
Tuesday, May 28, 2019 2:12PM - 2:24PM |
D05.00002: Grey-molasses based optical-tweezer loading: Controlling collisions for scaling up atom-array assembly Mark Brown, Tobias Thiele, Christopher Kiehl, Ting-Wei Hsu, Cindy Regal An array of single neutral atoms trapped in tightly-confined optical tweezers has proven to be a powerful platform for quantum computation and quantum simulation. However, the $\sim 50\% $ single-atom loading probability inherent in the typical approach complicates the assembly of defect-free atomic configurations. Here, I present our recent work in developing a new loading technique to address this long-standing problem. By utilizing lambda-enhanced grey molasses, we exercise an unprecedented amount of control over light-assisted atomic collisions to achieve an enhanced single-atom loading rate of 90{\%} in particularly shallow optical tweezers. We also demonstrate how combining this novel loading scheme with new rearranging techniques will be key to scaling up atom-array assembly. [Preview Abstract] |
Tuesday, May 28, 2019 2:24PM - 2:36PM |
D05.00003: Sisyphus Optical Lattice Decelerator ChunChia Chen, Shayne Bennetts, Rodrigo González Escudero, Florian Schreck, Benjamin Pasquiou We demonstrate a new deceleration scheme that slows and cools atoms without using radiation pressure [1]. This scheme is adapted from proposals originally aimed at laser cooling (anti)hydrogen [2]. In our implementation, atoms are selectively excited to an electronic state whose energy is spatially modulated by an optical lattice. Atoms decelerate only through climbing the potential hill created by the lattice. The ensuing spontaneous decay completes one Sisyphus cooling cycle. We characterize the cooling efficiency of this technique on a continuous beam of Sr, and compare it with radiation pressure based laser cooling. We demonstrate that this technique not only eliminates many of the constraints and limitations of traditional radiation pressure based approaches, it does so while delivering a similar atom number with lower final temperatures. It can also be instrumental in bringing new exotic species and molecules to the ultracold regime. [1] C.-C. Chen \textit{et al.,} arXiv:1810.07157 (2018). [2] S. Wu \textit{et al.}, Phys. Rev. Lett. 106, 213001 (2011). [Preview Abstract] |
Tuesday, May 28, 2019 2:36PM - 2:48PM |
D05.00004: ABSTRACT WITHDRAWN |
Tuesday, May 28, 2019 2:48PM - 3:00PM |
D05.00005: Progress toward a chipscale MOT Kaitlin Moore, James McGilligan, Rodolphe Boudot, John Kitching We report on progress toward forming a magneto-optical trap (MOT) in a passively-pumped, chipscale MEMS-fabricable package. This work is an essential step in integrating cold atoms into mass-producible, portable instruments\footnote{J Kitching, et al. \textbf{J. Phys: Conf. Ser.} 723, 1 (2016)}$^,$\footnote{JA Rushton, et al. \textbf{Rev. of Sci. Instr.} 85, 12 (2014)}. One major challenge is preserving ultra-high vacuum levels in anodically-bonded MEMS cells without the use of an active pump. Ultra-high vacuum levels are critical to forming a vapor-loaded MOT\footnote{T Arpornthip, et al. \textbf{PRA} 85, 033420 (2012)}$^,$\footnote{E Cornell, et al. In Collected Papers Of Carl Wieman, pp. 533-584, Sec. 2.8.4, (2008)} and attaining commercially-relevant cell lifetimes. Here, we report on experimentally-tested solutions to mitigating gas evolution in the 1-cc-volume MEMS cell during and after the fabrication process, as well as controlling rubidium-vapor content. We report on testing performed in our actively-pumped MEMS-cell MOT systems and outline remaining steps toward achieving a true chipscale MOT. [Preview Abstract] |
Tuesday, May 28, 2019 3:00PM - 3:12PM |
D05.00006: Magneto-optical trapping of lithium using a nanofabricated diffraction grating D. S. Barker, E. B. Norrgard, N. N. Klimov, J. A. Fedchak, J. Scherschligt, S. Eckel We demonstrate a compact system for laser cooling and trapping atoms from a heated dispenser source. Our system uses a nanofabricated diffraction grating to generate a magneto-optical trap (MOT) using a single input laser beam. An aperture in the grating allows atoms from the dispenser to be loaded from behind the grating chip, increasing the interaction distance of atoms with the cooling light. To take full advantage of the increased cooling distance, we extend the magnetic field gradient of the MOT into the region behind the chip to create a Zeeman slower. The MOT traps approximately $10^6$ $^7$Li atoms emitted from an effusive source with loading rates greater than $10^6~\text{s}^{-1}$. A model of the MOT loading dynamics agrees with the experimental data and suggests several improvements to the apparatus. Our design is portable to a variety of atomic and molecular species and could be a principal component of miniaturized cold-atom-based technologies. [Preview Abstract] |
Tuesday, May 28, 2019 3:12PM - 3:24PM |
D05.00007: Feedback control of evaporative cooling through continuous nondestructive measurement Julian Wolf, Jonathan Kohler, Johannes Zeiher, Dan Stamper-Kurn Dispersive coupling of an ultracold atomic ensemble to a high-finesse optical cavity enables continuous readout of the number of atoms present in the ensemble. Real-time feedback based on this measurement allows for experimental parameters to be varied depending on the instantaneous atom number. I will present recent experiments in which we have implemented such a feedback loop during evaporative cooling of a cloud of ultracold ${}^{87}$Rb, informing the cutoff time of the evaporation. This procedure has the potential to reduce fluctuations in final atom number to below the shot-noise limit. Further, by tuning closer to the strong-coupling regime, the dispersive atom number readout could be made sensitive to single-atom evaporation events, offering a microscopic probe of the evaporation process. In addition to providing a novel technique for improved preparation of atomic ensembles in a broad range of experiments, this work paves the way toward the observation and characterization of the microscopic processes involved in the evaporation of atomic ensembles. [Preview Abstract] |
Tuesday, May 28, 2019 3:24PM - 3:36PM |
D05.00008: Optical trapping and manipulations for single airborne particle studies Chuji Wang, ZHIYONG GONG, Gorden Videen, Yong-Le Pan The first demonstration of optical trapping (OT) was done in 1970 by Arthur Ashkin. Single airborne particles can be levitated, trapped, and transported in air using light force under appropriate arrangements. Most airborne particles are nontransparent, therefore both radiation pressure force and photophoretic force account for the status of motion of the particles, which is often further compounded by many other factors, such as drag force, air turbulence, particle properties as well their changes overtime. This nature makes the single airborne particle study a challenging yet attractive topic. When a single airborne particle is trapped in air, its time-dependent physical and chemical properties reveal exact particle dynamics without surface interferences. We can examine a single particle layer-by-layer, its chemical phase separation, morphology, up-take and evaporation, photochemical processes, fluorescence, using OT-Raman spectroscopy, cavity ringdown spectroscopy (CRDS), light-scattering techniques, or their combination. We can even now look at chemical compositions point-by-point within a single particle. Significant strides have been made in single particle studies using OT and manipulations to date, yet many more challenges have not been addressed. This talk will discuss current status and future perspectives in single airborne particle studies using OT and manipulations. [Preview Abstract] |
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