Bulletin of the American Physical Society
54th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 68, Number 7
Monday–Friday, June 5–9, 2023; Spokane, Washington
Session Z08: Controlling and Interfacing Trapped Ions |
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Chair: Timko Dubielzig, Leibniz University Hannover Room: 206 C |
Friday, June 9, 2023 10:30AM - 10:42AM |
Z08.00001: Photon-mediated entanglement of co-trapped atomic barium ions Jameson O'Reilly, George Toh, Mikhail Shalaev, Allison L Carter, Andrew Risinger, Sagnik Saha, Isabella Goetting, Tingguang Li, Christopher Monroe Long chains of trapped ions are a leading platform for quantum information processing, but their control suffers from spectral crowding and excess motional heating when chains grow too long. One proposal to access larger Hilbert spaces and thus more computational power is to entangle ions in separate traps via photonic interconnects. Previous demonstrations have used objectives with 0.6 numerical aperture (NA) to entangle ytterbium [1] and strontium [2] ions or optical cavities to entangle calcium ions [3]. Here, we use an RF Paul trap with two in-vacuo 0.8 NA aspheric lenses to entangle co-trapped barium ions. The higher NA increases the efficiency of our photonic interconnects and the presence of two high-NA imaging systems in a single vacuum chamber will allow this system to be integrated as the middle node in a three-node quantum network. |
Friday, June 9, 2023 10:42AM - 10:54AM |
Z08.00002: Progress toward quantum networking with 40Ca+ ions in a cryogenic surface-electrode trap with integrated fiber cavity Margie Bruff, Katie David, Lindsay Sonderhouse, Jules M Stuart, Andrew C Wilson, Daniel H Slichter, Dietrich Leibfried Quantum networks are a promising new infrastructure to accelerate scalability in quantum computing, remotely share entanglement, improve secure communication, and propel a wide range of distributed sensing applications. Trapped ions are nearly ideal stationary qubits in quantum network nodes because of their long coherence time, precise state preparation and control, and reconfigurable interconnectivity, while telecom-wavelength photons are an optimal choice for non-stationary qubits travelling between nodes with low loss. Here we show progress toward long-distance entanglement distribution between ion qubits in separate network nodes. We aim to integrate a fiber Fabry-Perot optical cavity into a surface-electrode ion trap to generate high-fidelity, high-rate entanglement between Ca+ ions and 854 nm photons, which are then coherently converted to 1550 nm photons by difference frequency generation. I will present our progress in evaluating and addressing the challenges of coherently controlling a trapped ion in an integrated ion trap/microcavity system at cryogenic temperatures. |
Friday, June 9, 2023 10:54AM - 11:06AM |
Z08.00003: High-fidelity trapped-ion qubit operations with scalable photonic modulators Craig Hogle, Daniel Dominguez, Andrew Leenheer, Hayden J McGuinness, Brandon P Ruzic, Matt Eichenfield, Daniel L Stick Quantum information processors and atomic clocks based on trapped ions continue to scale towards greater I/O, size, and power requirements. These demands motivate the replacement of external optical conditioning elements, such as amplitude, phase, and frequency modulators, with integrated versions on the same chip. Here we present the design, fabrication, and implementation of a monolithically integrated piezo-optomechanical Mach-Zehnder modulator compatible with microfabricated surface ion traps[1-3]. We demonstrate quantum operations with these modulators, testing directly on a trapped ion apparatus, measuring single qubit gate fidelities better that 99.7% |
Friday, June 9, 2023 11:06AM - 11:18AM |
Z08.00004: Multi-tone RF generation for parallel trapped-ion control Martin Stadler, Michael Nydegger, Roland Matt, Robin Oswald, Jeremy B Flannery, Luca Huber, Utku Altunkaya, Ilia Sergachev, Çagri Önal, Vlad Negnevitsky, Peter Clements, Jonathan Home I present the latest development cycle of our control system designed to address the demands of state-of-the-art quantum computing experiments with trapped ions. Long coherence times and parallel ion control together with optimised gate implementations and low-latency feedback push the limits of what our previous system can do in terms of channel count and multi-frequency generation. Our new platform can efficiently synthesize up to 4 parametrised sine outputs per channel on up to 96 phase-coherent channels and can act as an AWG for parts of the channels. |
Friday, June 9, 2023 11:18AM - 11:30AM |
Z08.00005: Addressing Trapped Ions with Semiconductor Optical Waveguides Clayton L Craft, P. M Alsing, Nicholas J Barton, A. Brownell, Vekatesh Deenadayalan, M. L Fanto, Gregory A Howland, D. Hucul, Andrew Klug, Michael Macalik, Evan Manfreda-Schulz, G. Percevault, N. Porto, Stefan F Preble, A. J Rizzo, Kenneth Scalzi, James Schneeloch, Erin Sheridan, Vijay Soorya Shunmuga Sundaram, A. M Smith, Z. S Smith, Christopher C Tison, Kathy-Anne Brickman Soderberg Quantum computing (QC) is theorized to solve certain important problems much faster than classical computers. However, the current state of QC, the noisy intermediate-scale quantum (NISQ) era, is limited in the scope of problems it can solve, largely due to the quantity of reliable qubits available to universal quantum operations. And while all available quantum computing systems have their advantages, ion-based systems have been shown to be a reliable option with low infidelity and a capability for universal gating procedure. These advantages are dependent on achieving low crosstalk when addressing ions, a vital challenge for this QC system, particularly when using only bulk optic systems. Here we show a microfabricated planar waveguide which can selectively interact in free space with 8 trapped Ba+ ions. The imaged light is characterized by a spatial scan of the chip and PMT counts from the fluorescence of Ba+ ions from the intended mode of operation with low crosstalk measured by both methods. This performance meets or exceeds that of similar waveguides couple to trapped ion systems and shows a reliable method to selectively interact with ions bound by a Paul Trap using imaged waveguide outputs |
Friday, June 9, 2023 11:30AM - 11:42AM |
Z08.00006: Laser cooling of trapped ions via an analog of velocity-selective coherent population trapping Muhammad Miskeen Khan, Bhuvanesh Sundar, Ana M Rey We theoretically study a ground-state cooling scheme that efficiently cools the phonon modes in generic trapped ion arrays. Our scheme employs a pair of highly detuned Raman lasers that couples the electronic spins with the motion of the ions. The same Raman beams drive the spin into a dark state that is tunable by the laser parameters. At appropriate resonances, ions can escape the dark state by absorbing phonons while cooling their motion, in a way that emulates the velocity-selective coherent population trapping scheme in atomic gases. We show that the relevant heating mechanisms are suppressed in this setting allowing the ions to reach their motional ground state with high fidelity. The proposed scheme can be implemented in current trapped ion experiments such as a two-dimensional ion crystal in a Penning trap where the rotation of the ions complicates more standard cooling schemes. For this system, we discuss the currently accessible parameter regimes in which the cooling is operational. |
Friday, June 9, 2023 11:42AM - 11:54AM |
Z08.00007: Laser Cooling of Trapped Ions in the High-Temperature Regime John P Bartolotta, Christopher Gilbreth, David Hayes We employ a semiclassical framework to explore the motional dynamics of trapped ion crystals with arbitrarily high energy, including the effects of laser cooling. There are two major benefits to this approach: (1) it is non-perturbative, and hence captures dynamics beyond the Lamb-Dicke regime, and (2) it reduces the computational complexity by tracking a small number of phase space coordinates instead of several high-dimensional Fock spaces. This allows us to accurately and efficiently model a variety of exotic phenomena, such as the recrystallization of ion clouds which have been imparted with thousands of motional quanta due to collisions with background particles, a potentially limiting factor of trapped ion quantum computers. We show that this approach quantitatively agrees with the familiar quantum rate equation method when operating in the Lamb-Dicke regime, but also predicts non-exponential cooling and capture ranges for EIT cooling. |
Friday, June 9, 2023 11:54AM - 12:06PM |
Z08.00008: Mitigating electric field noise from Aluminum surfaces in close proximity to trapped ions Matthew P Roychowdhury, David L Reens, Colin D Bruzewicz, Kyle Debry, May E Kim, Robert McConnell, John Chiaverini Electrical noise from surfaces can be a challenge for quantum sensing and high-fidelity quantum information processing in atomic systems. In the trapped-ion context, the origin of this noise is unknown, but its characteristics appear dependent on the surface material. Previous work has demonstrated that the temperature dependence of the noise can be altered, and sometimes reduced, by energetic ion bombardment, or "ion milling" of trapping electrodes. The effectiveness of ex-situ ion milling in removing oxides and the subsequent effect on noise has been studied on Nb and Au. Here, we present temperature dependence of noise measurements using individual ions trapped near electrodes made from Al, a widely-used microelectronics material, before and after repeated rounds of ion milling; we also present measurements of the material removal rate of the milling treatments. These results demonstrate both noise reduction and variation in the effect of milling across various materials, suggesting a need to investigate the effect of milling on a material-by-material basis. |
Friday, June 9, 2023 12:06PM - 12:18PM |
Z08.00009: Optimized pulsed sideband cooling vs continuous sideband cooling on an electric quadrupole transition Evan C Reed, Lu Qi, Kenneth R Brown Trapped-ion quantum computers rely on two-qubit gates that achieve optimal performance when the ions are near the ground state of motion. Ion cooling takes up a significant amount of the time required to prepare the qubit register, and as the computer scales, cooling the ions in the middle of the algorithm becomes more critical. Therefore, cooling can be a significant source of latency in the algorithm. Recently, a graph theoretic method for determining the optimal set of sideband cooling (SBC) pulses for a given trapped ion system has been proposed and experimentally demonstrated [1]. Here, we investigate the difference in efficiency of optimized pulsed SBC versus continuous SBC [2] for optical qubits and compare numerical simulation with experimental results using 40Ca+ ions. |
Friday, June 9, 2023 12:18PM - 12:30PM |
Z08.00010: Laser Cooling Planar Motion of a 2D Ion Crystal with a Strong Rotating Wall Wes Johnson, John Zaris, John J Bollinger, Athreya Shankar, Scott E Parker 2D planar ion crystals stored in Penning traps offer an attractive platform for quantum sensing and simulation protocols on hundreds of qubits1. However, to realize these applications, the crystal must be cooled to milli-Kelvin temperatures. The motion of the crystal consists of three mode branches: out of plane axial modes (along B-field) and in plane cyclotron and magnetron like modes (perpendicular to B-field)2. Conventional doppler laser cooling techniques on axial and cyclotron modes reliably reach milli-Kelvin temperatures, however, a nonuniform beam intensity is required to begin cooling the potential energy dominated magnetron modes3. Recent work indicates that magnetron modes are not cooled below 10mK in experiment. Uncooled magnetron modes broaden the axial mode spectra, limiting the performance of quantum protocols4. Our full-dynamics simulations5 suggest that magnetron modes can be cooled to milli-Kelvin temperatures by raising the strength of an oscillating rf quadrupolar field (rotating wall) and utilizing a narrower beam width. In tandem, a stronger rotating wall overcomes torques from the nonuniform planar beam, and the narrower beam width increases the intensity gradient that cools magnetron modes. Furthermore, we present simulation and theoretical work characterizing the disparate planar cooling rates of the rapidly cooled (millisecond) cyclotron mode branch and slowly cooled (hundred millisecond) magnetron mode branch. |
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