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 C10: Quantum Gates, Algorithms, and Architectures ILive
|
Hide Abstracts |
Chair: Christie Chiu, Princeton University |
Tuesday, June 1, 2021 10:30AM - 10:42AM Live |
C10.00001: Next-generation trapped-ion quantum computing system Lei Feng, Alexander Kozhanov, Marko Cetina, Crystal Noel, Debopriyo Biswas, Laird Egan, Daiwei Zhu, Andrew Risinger, Christopher Monroe The first generation of a trapped ion-based integrated quantum processor, constructed in a collaboration between universities and industrial partners, was used to perform quantum algorithms with high-fidelity on 12 qubits, and high-fidelity quantum gates with up to 23 qubits. We are now building a second-generation system with an improved design benefiting from the building and operating the current system. The new system has a capacity of 32 qubits and parallel addressing capability using an RF-on-a-chip system. This work presents the recent progress in constructing the system with the upgraded optical design and the new-generation micro-fabricated surface ion trap from Sandia National Laboratories. |
Tuesday, June 1, 2021 10:42AM - 10:54AM Live |
C10.00002: Entanglement from tensor networks on a trapped-ion QCCD quantum computer Michael S Foss-Feig, Steve Ragole, Andrew C Potter, Joan Dreiling, Caroline Figgatt, John Gaebler, Steven A Moses, Juan Pino, Ben Spaun, David Hayes The ability to selectively measure, initialize, and reuse qubits during a quantum circuit is a crucial ingredient in scalable (error-corrected) quantum computation. Recently, it has been realized that these tools also enable "holographic" algorithms that map the spatial structure of certain tensor-network states onto the dynamics of a quantum circuit, thereby achieving dramatic resource savings when using a quantum computer to simulate many-body systems with limited entanglement. Here we explore another significant benefit of the holographic approach to quantum simulation: The entanglement structure of an infinite system, specifically the half-chain entanglement spectrum, can be extracted from a data-compressed register of "bond qubits" encoding a matrix-product state. We demonstrate this idea experimentally on a trapped-ion QCCD quantum computer by computing the near-critical entanglement entropy of the transverse-field Ising model directly in the thermodynamic limit, and show that the phase transition becomes very quickly resolved upon expanding the bond qubit register. |
Tuesday, June 1, 2021 10:54AM - 11:06AM Live |
C10.00003: Demonstration of Interactive Protocols for Classically-Verifiable Quantum Advantage Daiwei Zhu, Crystal Noel, Andrew Risinger, Laird Egan, Debopriyo Biswas, Qingfeng Wang, Yunseong Nam, Gregory D Meyer, Umesh Vazirani, Norman Y Yao, Alexandru Gheorghiu, Laura Lewis, Thomas Vidick, Marko Cetina, Christopher R Monroe
|
Tuesday, June 1, 2021 11:06AM - 11:18AM Live |
C10.00004: Towards Max-Cut QAOA with Trapped Ion Crystals Joel Rajakumar, Jai Moondra, Bryan T Gard, Swati Gupta, Creston D Herold Applications of near-term quantum computing hardware like the quantum approximate optimization algorithm (QAOA) motivate a desire to map application-specific coupling graphs to the native coupling graph between physical qubits. We show that a pairwise all-to-all entangling operator naturally realized with trapped ion crystals can be leveraged to produce the cost function for any Max-Cut graph of interest. We describe a novel 'union-of-stars' construction method and compare the required resources to Max-Cut QAOA constructions on other quantum hardware. Finally, we present initial progress towards realizing this scheme in the laboratory. |
Tuesday, June 1, 2021 11:18AM - 11:30AM Live |
C10.00005: experimental measurement of out-of-time-order correlators at finite temperature on a trapped ion quantum computer Alaina Green, Bhuvanesh Sundar, Andreas Elben, Lata Kh Joshi, Torsten Zache, Norbert M Linke
|
Tuesday, June 1, 2021 11:30AM - 11:42AM Live |
C10.00006: Using 'protected' modes in trapped ions to enable mid-algorithm measurements for CVQC Jeremy Metzner, Colin D Bruzewicz, Isamm Moore, Alexander Quinn, David J Wineland, John Chiaverini, David Allcock Measurements of the motional states of trapped ions require coupling the motion to the ions’ internal spin states. These measurements, however, require detection of spin-dependent fluorescence. Photon scattering, giving rise to fluorescence, causes the ion to recoil, which generally decoheres the ions’ motional modes. This decoherence prevents mid-algorithm measurements, which are necessary for processes that require classical feedback. Overcoming this challenge is likely necessary for the viability of practical continuous variable quantum computing (CVQC) in trapped ions. To address this issue, we are investigating the use of ‘protected’ modes within chains consisting of an odd number of ions, where the center ion has zero displacement (3(N-2) protected modes with N ions). As a demonstration we use a dual-species three-ion chain (88Sr+ -40Ca+ - 88Sr+), which allows us to simply address the center ion with global laser fields. We perform measurements of the heating rate and coherence time, via Ramsey interferometry, of these protected modes, to determine how much the decohering effects of photon scattering are suppressed. We are also developing models to minimize the effects of symmetry breaking due to radiation pressure, and non-linear coupling between modes, on the coherence time of the protected modes. |
Tuesday, June 1, 2021 11:42AM - 11:54AM Live |
C10.00007: Efficient, stabilized entangling gates on a trapped-ion chain Nhung Nguyen, Reinhold Blumel, Nikodem Grzesiak, Alaina Green, Ming Li, Andrii Maksymov, Norbert M Linke, Yunseong Nam Two-qubit gates are an important building block of a universal quantum computer. On trapped-ions, two-qubit gates with high fidelity, short gate times and/or robustness against parameter drifts have been demonstrated. However, maintaining their performance while scaling to larger system sizes is challenging. Here, we present and demonstrate two scalable methods to find optimal solutions for M\o lmer-S\o rensen gates, a standard scheme to entangle trapped-ion qubits. Our methods are linear, thus allowing us to circumvent the need for non-linear optimization routines. Furthermore, with these methods, trade-offs between laser power, gate time, qubit-connectivity and robustness can be made systematically. We experimentally verify the performance of calculated pulses on a seven-ion system and find good agreement with theoretical predictions. |
Tuesday, June 1, 2021 11:54AM - 12:06PM Live |
C10.00008: Spontaneous scattering errors from Raman transitions in metastable trapped-ion qubits Isam D Moore, David J Wineland, David T Allcock Trapped-ion quantum information processing (QIP) often makes use of coherent stimulated-Raman transitions to perform logic gates on the qubits. Spontaneous photon scattering during this process is an important source of errors; therefore, characterization of such errors is important for calculating limits to logic gate fidelity. These errors have been well-studied for qubits encoded in the S1/2 ground state; here, we present calculations of scattering probabilities for hyperfine qubits stored in the metastable D5/2 manifold of Ca+, Sr+, or Ba+. Additionally, we consider some effects which have been (reasonably) assumed to be negligible in studies of ground state qubits but cannot be ignored here: the detuning dependence of the scattered photon frequency and the Lamb-Dicke parameter, scattering from higher levels, and contributions from a second Feynman diagram. We conclude that detuning and power requirements for a given error are generally higher in the metastable qubits than in ground state qubits, but the ultimate limits on achievable error may be lower in some cases. Additionally, the required wavelengths are convenient for high-power solid-state lasers and offer better compatibility with integrated optics approaches. |
Tuesday, June 1, 2021 12:06PM - 12:18PM Live |
C10.00009: Motional squeezing for trapped ion transport and separation Robert T Sutherland, Shaun C Burd, Daniel H Slichter, Stephen B Libby, Dietrich Leibfried Transport, separation, and merging of trapped ion crystals are essential operations for most large-scale quantum computing architectures. In this work, we develop a theoretical framework that describes the dynamics of ions in time-varying potentials with a motional squeeze operator, followed by a motional displacement operator. Using this framework, we develop a new, general protocol for trapped ion transport, separation, and merging. We show that motional squeezing can prepare an ion wave packet to enable faster shuttling from the ground state of one trapping potential to another. The framework and protocol are applicable if the potential is harmonic over the extent of the ion wave packets at all times. As illustrations, we discuss two specific operations: changing the strength of the confining potential for a single ion, and separating same-species ions with their mutual Coulomb force. Both of these operations are, ideally, free of residual motional excitation. |
Tuesday, June 1, 2021 12:18PM - 12:30PM Live |
C10.00010: Correcting Time-dependent Errors in the Qubit Control Pulses with Composite Pulses. Qile Su, Robijn F Bruinsma, Wes Campbell Qubit operations are typically vulnerable to imperfections in the underlying control pulses. The existing composite pulses (CPs) usually rely on the constancy of the error over time to mitigate systematic errors in the rabi frequency and in the detuning of the control pulses. Here we extend this technique to correct slow-varying, time-dependent errors by regarding the errors as superpositions of power-law drifts whose first-order effects on the qubit add linearly. We present several new CPs obtained with this technique, compare their simulated performance under time-dependent errors to available CPs, and provide a way to categorize them according to the suppressed power-law drifts and their ability to suppress higher-order effects. |
Tuesday, June 1, 2021 12:30PM - 12:42PM Live |
C10.00011: Quantum computing with a 2D array of Cs atom qubits Trent Graham, Jacob Scott, Yunheung Song, Kais Jooya, Preston Huft, Matthew Gillette, Jonathan Gilbert, Josh Cherek, Matthew Ebert, Thomas Noel, Mark Saffman We present recent progress on circuit model quantum computing with a 2D array of atomic qubits. Atoms are loaded into blue-detuned optical lattices constructed from cross-hatched lines, each of a different frequency, which form optical traps, as well as other methods. We examine and compare various methods for loading, cooling, and detecting atoms. These techniques include creating a MOT using cooling on the second excited state transition (7p3/2), lambda grey molasses cooling, and cooling on a quadrupole line. We also demonstrate atomic rearrangement using optical tweezers to create defect-free atomic arrays. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700