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 Q09: Quantum Gates, Algorithms, and Architectures IILive
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Chair: Alaina Green, JQI |
Thursday, June 3, 2021 8:00AM - 8:12AM Live |
Q09.00001: Phonon Tomography with Ancillary Modes in Trapped Ion System Wentao Chen Boson tomography is a fundamental physical problem that has the capacity to show the power of quantum computation. While it has been considered mostly for linear optical systems with photons, phonons for trapped ions are also a good candidate to realize the full tomography of their quantum states. A recent proposal by L.Banchi et al. (PRL 121, 250402 (2018)) shows that with ancillary vacuum modes, the number of measurement settings required for the experiment can be reduced. Here, we demonstrate, for the first time, a full phonon tomography of a two-mode number-restricted input phonon state with a beam splitter operation and projective measurements. Then we use up to two ancillary vacuum modes to realize the reduction of settings for the tomography of this two-mode input state. Our experiment demonstrates a new way to realize boson tomography with minimal resources for a trapped ion system which can be generalized to other physical systems. |
Thursday, June 3, 2021 8:12AM - 8:24AM Live |
Q09.00002: Calculating the phase shift of a scattering process on a trapped-ion quantum computer Yingyue Zhu, Erik J Gustafson, Patrick Dreher, Yannick L Meurice, Norbert M Linke Simulating real-time evolution for lattice quantum chromodynamics (QCD) on a large Hilbert space is unfeasible with current classical methods. Quantum computers offer an alternative approach to solve this problem. Estimating the phase shift of a scattering process in the quantum Ising model on quantum computers forms a tentative first step towards this goal. However, gate errors and decoherence limit the evolution depth that can be realized on near-term quantum devices. We demonstrate a method to extract the phase shift using information obtained in the early stages of the scattering event. We implement real-time evolution of a one-dimensional scattering process for the quantum mechanics limit with two qubits and the field theory formulation with four qubits on a trapped-ion quantum computer. |
Thursday, June 3, 2021 8:24AM - 8:36AM Live |
Q09.00003: Experimental realization of a two-qubit entangling transport gate with trapped ions Holly Tinkey, Brian Sawyer, Craig R Clark, Kenton R Brown We perform a two-qubit entangling Mølmer-Sørensen gate by transporting two trapped 40Ca+ ions through a stationary, global laser beam. Waveform resampling dynamically compensates for observed nonuniformities in velocity to produce a constant qubit-frequency Doppler shift during transport. We analyze two different methods for Stark shift compensation: (1) applying a constant frequency offset to the gate beams or (2) finely adjusting the transport waveform sampling so that the associated Doppler shifts dynamically cancel the Stark shifts. We compare the performance of this gate to stationary gates performed in the same system and show that the transport gate provides a natural Gaussian intensity ramp which should minimize off-resonant coupling. This represents the first demonstration of a two-ion entangling gate mediated with ion transport rather than via optical switching, and it could relax the requirements on optical-pulse timing precision and on the optical power needed for parallel gate operations. |
Thursday, June 3, 2021 8:36AM - 8:48AM Live |
Q09.00004: High-fidelity laser-free universal control of two trapped ion qubits Raghavendra Srinivas, Shaun C Burd, Hannah M Knaack, Robert T Sutherland, Alex Kwiatkowski, Scott Glancy, Emanuel Knill, David J Wineland, Dietrich Leibfried, Andrew C Wilson, David T Allcock, Daniel H Slichter Universal control of multiple qubits -- the ability to entangle qubits and to perform arbitrary individual qubit operations -- is a fundamental resource for quantum computation, simulation, and networking. Here, we implement a new laser-free scheme for universal control of trapped ion qubits based on microwave magnetic fields and radiofrequency magnetic field gradients. We demonstrate high-fidelity entanglement and individual control by creating symmetric and antisymmetric two-qubit maximally entangled states with fidelities in the intervals [0.9983, 1] and [0.9964, 0.9988], respectively, at 68% confidence, corrected for state initialization error. This technique is robust against multiple sources of decoherence, usable with essentially any trapped ion species, and has the potential to perform simultaneous entangling operations on many pairs of ions without increasing control signal power or complexity. |
Thursday, June 3, 2021 8:48AM - 9:00AM Live |
Q09.00005: Demonstration of a Wavelength-Insensitive Entangling Gate for Group-2 Atomic Ions Kenton R Brown, Craig R Clark, Holly Tinkey, Brian Sawyer, Karl Burkhardt, Adam Meier, Christopher M Seck, Chris Shappert, Nicholas D Guise, Harley Hayden, Wade Rellergert, Curtis Volin Entanglement generation in trapped-ion systems has thus far relied on two distinct but related two-qubit geometric phase gate techniques: Mølmer-Sørensen (MS) and light-shift (LS) gates. In both schemes, normal modes of ion motion are employed as a “quantum bus” whereby an internal-state-dependent force excites ion motion to induce entanglement between internal (i.e. spin) and external (i.e. motion) degrees of freedom. We have recently proposed a variant of the LS scheme where the qubit levels are separated by an optical frequency [1]. Some advantages of this optical transition dipole force (OTDF) gate include: a broad range of feasible entangling laser wavelengths (including visible and infrared wavelengths), two-qubit photon scattering error <10-4 in some wavelength regimes, and straightforward extension to multispecies co-trapped group-2 ions. We report an experimental demonstration of the OTDF gate using a co-trapped pair of 40Ca+ ions in a cryogenic surface-electrode ion trap. We measure a two-qubit entanglement infidelity of 8(4)×10-4 obtained directly from Bell state parity analysis without subtraction of state preparation, measurement, or one-qubit gate errors. To our knowledge, this represents the highest laser-based two-qubit entanglement fidelity yet reported in a surface trap, and it establishes the OTDF scheme as competitive with typical LS and MS schemes. |
Thursday, June 3, 2021 9:00AM - 9:12AM Live |
Q09.00006: Trapped-Ion Quantum Information with Metastable Qubits Susanna Todaro, Kyle DeBry, Felix W Knollmann, Gabriel Mintzer, Xiaoyang Shi, Jasmine Sinanan-Singh, Jules M Stuart, Colin D Bruzewicz, Jeremy Sage, John Chiaverini, Isaac Chuang Most quantum information experiments with trapped ions rely on encoding the qubit in two Zeeman or hyperfine sublevels of the ground electronic state or between the ground state and a long-lived metastable state. We report work investigating another category of qubits: the metastable qubit, in which the qubit is encoded in sublevels of a long-lived metastable state. Qubits in this metastable manifold would be largely insensitive to scattered laser light addressing a neighboring qubit in the ground state manifold and vice versa. This could enable quasi-dual species operation, in which many of the applications of dual-species ion trapping, such as sympathetic cooling or ancilla qubits in quantum error correcting codes, could be implemented in a chain of identical ions. This would improve the vibrational mode structure and potentially reduce experimental complexity. We present experimental progress towards metastable qubit operations using 88Sr+ and 133Ba+ ions, which have accessible visible and infrared transition wavelengths and an appropriate atomic structure for encoding quantum information in a metastable qubit. |
Thursday, June 3, 2021 9:12AM - 9:24AM Live |
Q09.00007: Chip Integrated Detectors for Trapped Ions David L Reens, Robert McConnell, John Chiaverini, Colin D Bruzewicz, Brian Aull, Joe Ciampi, Kevan Donlon, Kevin Ryu, Dave Kharas Integrated technologies greatly enhance the prospects for practical quantum devices based on trapped ions. Photonic integration of the laser light necessary for manipulating trapped ions constitutes an important step, and recent progress in this direction has garnered much enthusiasm. High-fidelity and rapid state detection is also important, not only at the conclusion of computations, but also along the way. Quantum sensors or computers which intend to leverage error correction schemes will need to perform targeted measurements and implement actions based on their results. In light of this, integrated detectors can offer advantages for system portability and can also greatly facilitate parallelism if a separate detector can be incorporated at each ion-trapping location. Here we demonstrate ion detection utilizing avalanche photodiodes (APDs) integrated directly into the substrate of silicon ion trapping chips. While less sensitive than superconducting nanowires, which have also been successfully demonstrated with trapped ions, APDs offer the significant advantage of room temperature operability. Using ^{88}Sr^+ ions and detecting their fluorescence along the 5^2P_{1/2} to 5^2S_{1/2} transition with integrated APDs, we report key figures of merit pertaining to their performance. |
Thursday, June 3, 2021 9:24AM - 9:36AM Live |
Q09.00008: Towards a Radioactive Barium Atomic Source for an Open-access Trapped Ion Quantum Information Processor noah greenberg, Brendan White, Nikolay N Videnov, Richard W Rademacher, Ali Binai-Motlagh, Matthew L Day, Rajibul Islam, Crystal Senko Trapped ions for quantum information processing has been an area of intense study in the past twenty years due to the extraordinarily high-fidelity operations that have been achieved experimentally, and the recent microfabricated traps that offer a potential path to scaling the technology. Specifically, the Barium-133 trapped ion has been shown to have some of the highest fidelity operations of any qubit. Barium-133 is readily available as a salt, which can be ablated by a low pulse-energy ($<$ 1 mJ) 532 nm nanosecond laser. We present progress towards a method for preparing and testing barium salt atomic sources that will be used for loading different barium isotopes. The impact of different heat treatments applied to the ablation targets are investigated and the efficiency and longevity of the source are estimated by collecting barium neutral atom fluorescence from the ablation plume after nanosecond pulses. Furthermore, a mechanical design is presented, which will produce a highly collimated atomic beam, reducing contamination on current chip-trap architectures. |
Thursday, June 3, 2021 9:36AM - 9:48AM Live |
Q09.00009: A system for coherent site-resolved control of an array of neutral-atom qubits, part III Jonathan P King, Stanimir Kondov, Albert Ryou, Tsung-Yao Wu, Nicole Crisosto, Brian J Lester, Krish Kotru, Mickey P McDonald, Remy P Notermans, Kayleigh Cassella, Lucas Peng, Eli Megidish, Peter Battaglino, Sandeep Narayanaswami, Ciro Nishiguchi, Raul Atkinson, Emme Yarwood, Joseph Lauigan, Robin Coxe, Benjamin Bloom Individually-trapped neutral atoms are a promising technology for scalable quantum computation. Such systems offer high readout fidelity, control over excursions to Rydberg states for qubit interactions, and spatial manipulation of many-atom arrays. Here we present methods for achieving multi-qubit control over neutral atom strontium qubits confined in arrays of optical tweezers. We characterize and demonstrate coherent control of Rydberg states and show progress towards their use in multi-qubit gates. |
Thursday, June 3, 2021 9:48AM - 10:00AM Live |
Q09.00010: Programming a general purpose trapped-ion quantum computer Virginia Frey, Richard W Rademacher, Elijah Durso-Sabina, Ruhi Shah, Ria Chakraborty, Matthew L Day, Noah Greenberg, Nikolay N Videnov, Ali Binai-Motlagh, Rajibul Islam, Crystal Senko Over the past few years we have seen an explosion of new programming libraries and tools to program quantum computers that allow users to define quantum programs at the level of hardware-agnostic quantum circuits and gates that are applicable to different physical realizations of quantum computers. However, approaching quantum computing exclusively on the circuit level provides a limited perspective on the full stack of operations that physical quantum computers can perform, and is insufficient to program the entire experimental apparatus. A general purpose language, that describes both circuit-level operations as well as low-level, time-dependent hardware instructions in a cohesive manner is lacking, and experimentalists are left to write their own control system code. |
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