Bulletin of the American Physical Society
53rd Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 67, Number 7
Monday–Friday, May 30–June 3 2022; Orlando, Florida
Session Q07: New Frontiers for Quantum Computing with Trapped IonsRecordings Available
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Chair: Raghavendra Srinivas, University of Oxford Room: Salon 5/6 |
Thursday, June 2, 2022 8:00AM - 8:12AM |
Q07.00001: Revealing quantum correlation functions with zero measurement back-action Pengfei Wang, Hyukjoon Kwon, Chunyang Luan, Myungshik Kim, Kihwan Kim Exploring the joint probability distribution of a quantum system in sequential measurements is an important issue in quantum thermodynamics. A straightforward way to achieve this task is to let the system interacts with an ancilla qubit and then measure the ancilla qubit with the projection measurements. However, projection measurements disturb the quantum state thus influencing the subsequent measurement statistics, often referred to as the back-action of the quantum measurement. Alternatively, one can experimentally obtain the real and imaginary parts of the correlation function without the back-action but needs an explicit knowledge of the system's dynamics. In this work, we propose and experimentally verify that the quantum correlation functions can be reconstructed from ancilla-assisted measurements without measurement back-action, where the measurement setup is independent of the system dynamics. During the measurement protocol, POVM (positive operator-valued measure) other than projection measurements are performed on the ancilla qubit. We demonstrate this protocol in a trapped 171Yb+-138Ba+ ion system, where 171Yb+ ion and 138Ba+ ion role as the system qubit and the ancilla qubit, respectively. The hybrid system enables us to reconstruct quantum statistics unaffected by the measurement back-action. The Mølmer-Sørensen (M-S) gate is adopted to generate entanglement between two ions. Two-point and three-point correlation functions are experimentally demonstrated, which shows that our protocol can be extended to multi-point correlation measurements straightforwardly. |
Thursday, June 2, 2022 8:12AM - 8:24AM |
Q07.00002: Implementation of interactive proofs for quantum advantage on an ion-trap quantum computer Daiwei Zhu, Gregory Kahanamoku-Meyer, Laura Lewis, Crystal Noel, Or Katz, Bahaar Harraz, Qingfeng Wang, Andrew Risinger, Feng Lei, Debopriyo Biswas, Laird Egan, Alexandru Gheorghiu, Yunseong Nam, Thomas Vidick, Umesh Vazirani, Norman Y Yao, Marko Cetina, Christopher Monroe An interactive proof of quantum advantage enables a classical verifier to determine the quantumness of a prover via the real-time exchange of messages. The verifier can rule out a broad range of cheating strategies by checking for inconsistencies in the claims of the quantum prover. Such interactive protocols require the ability for quantum systems to perform mid-circuit measurements, followed by continued coherent evolution. In this talk, we will apply a split-and-shuttle approach to realize multiple rounds of mid-circuit measurements on different subsets of qubits in an ion-trap quantum computer. We then implement two interactive protocols of quantum advantage on our system and show that for both protocols, the fidelities exceed the asymptotic bound for classical behavior. Looking forward, the ability to perform mid-circuit measurements also enables the exploration of a broad range of topics ranging from measurement-induced phase transitions to novel error correction protocols. |
Thursday, June 2, 2022 8:24AM - 8:36AM |
Q07.00003: Provable quantum advantage in Bell-type nonlocal games with the cyclic cluster state Yingyue Zhu, Austin K Daniel, Cinthia Huerta Alderete, Vikas Buchemmavari, Alaina Green, Nhung H Nguyen, Tyler G Thurtell, Andrew Zhao, Norbert M Linke, Akimasa Miyake We propose two Bell-type nonlocal games and perform proof-of-principle demonstrations on a trapped-ion quantum computer. These games can be used to prove quantum computational advantage in an objective and hardware-agnostic manner, as well as offer a practical and scalable set of quantitative benchmarks for quantum computers in the pre-fault-tolerant regime. The experimental result surpasses the conventional depth-0 classical bounds by a significant margin for the cubic Boolean function games, and is on the cusp of demonstrating advantage against the more difficult depth-1 classical bounds in the stabilizer submeasurement games. |
Thursday, June 2, 2022 8:36AM - 8:48AM |
Q07.00004: Measurement of MaxCut QAOA solution quality with increasing $p$-depth Kevin D Battles, Bryan T Gard, Creston D Herold We solve MaxCut problems using the Quantum Approximate Optimization Algorithm (QAOA) with up to ten trapped $^{171}$Yb$^+$ ions. |
Thursday, June 2, 2022 8:48AM - 9:00AM |
Q07.00005: Data-Driven Quantum Approximate Optimization Algorithm (QAOA) for Max-Cut Problems Hang Jing, Ye Wang, Yan Li We present a data-driven QAOA for the Max-Cut problem over generic weighted graphs, which can avoid the expensive optimization effort for its quantum circuit parameters. In data-driven QAOA, a parameter transfer strategy based on graph density can provide quasi-optimal parameters from previous instances with similar properties in a database prepared in advance. The quasi-optimal parameters can be directly used to obtain a good cut or be a good initial guess for significantly saving optimization time. Moreover, as running cases increase, the database grows and can provide more effective parameters. We numerically verified the strategy on 1710 random instances on IBM simulators with perfect quantum gates. We also simulated the algorithm on 3 practical graphs in the power system with a realistic noise model and observed good approximation results on the Max-Cut problem. It is encouraging that, without any parameter optimization, the proposed data-driven QAOA is competitive with the famous classical algorithm, the Goemans-Williamson algorithm. |
Thursday, June 2, 2022 9:00AM - 9:12AM |
Q07.00006: Individual qubit addressing of rotating ion crystals in a Penning trap Anthony M Polloreno, Ana Maria Rey, John J Bollinger Trapped ions boast long coherence times, and excellent gate fidelities, making them a useful platform for quantum information processing. Scaling to larger numbers of ion qubits in RF Paul traps demands great effort. Another technique for trapping ions is via a Penning trap where a 2D crystal of hundreds of ions is formed by controlling the rotation of the ions in the presence of a strong magnetic field. However, the rotation of the ion crystal makes single ion addressability a significant challenge. We propose a protocol that takes advantage of a deformable mirror to introduce AC Stark shift patterns that are static in the rotating frame of the crystal. Through numerical simulations we validate the potential of this protocol to perform high-fidelity single ion gates in traps of hundreds of ions. |
Thursday, June 2, 2022 9:12AM - 9:24AM |
Q07.00007: Comparing Two-Qubit and Multi-Qubit Gates within the Toric Code David Schwerdt, Yotam Shapira, Tom Manovitz, Roee Ozeri Quantum error correction (QEC) is a necessary component for any long-term realization of a quantum computer. So far, QEC works seem to consider only standard gate sets involving two-qubit entangling gates. However in several quantum computing architectures, such as trapped ion systems, it is possible to exceed this regime by entangling many qubits in a single operation. Stabilizer measurements can then be implemented using a single multi-qubit gate instead of several two-qubit gates. |
Thursday, June 2, 2022 9:24AM - 9:36AM |
Q07.00008: Real-time capable CCD-based individual trapped-ion qubit measurement Sebastian Halama, Timko Dubielzig, Niklas Orlowski, Celeste Torkzaban, Christian Ospelkaus We report on the individual detection of 9Be+ qubit states undergoing coherent excitation using an EMCCD camera. The ions are trapped in a cryogenic surface-electrode ion trap with integrated microwave conductors [1] for near-field quantum control. This kind of trap promises good scalability to a higher number of qubits [2]. Together with the individual real-time detection this is a key requirement for many-body quantum simulation and also error-correction protocols in quantum information processing [3]. We discuss known error sources during state preparation and measurement in the order of 0.5% and comment on the sources and the amount of crosstalk in our detection system. We briefly present the used imaging system and compare the qubit state detection performance of the EMCCD camera with a PMT. |
Thursday, June 2, 2022 9:36AM - 9:48AM |
Q07.00009: Realizing coherently convertible dual-type qubits with the same ion species Jianyu Ma, Haoxiang Yang, Yukai Wu, Ye Wang, Yuanyuan Huang, Zichao Zhou, Luming Duan, Lu Feng, Mingming Cao, Weixuan Guo For large-scale ion-trap based quantum computers and networks, it is critical to have two types of qubits, one for computation and storage, while the other for auxiliary operations like runtime qubit detection, sympathetic cooling, et al. Dual-type qubits have previously been realized in hybrid systems using two ion species, which, however, introduces significant experimental challenges for laser setup, gate operations as well as the control of the fraction and positioning of each qubit type within an ion crystal. Here we solve these problems by implementing two coherently-convertible qubit types using the same ion species. We encode the qubits into two pairs of clock states of the 171Yb+ ions, and achieve fast and high-fidelity (about 99.5%) conversion between the two types using narrow-band lasers. We further demonstrate that operations on one qubit type, including sympathetic cooling, gates and qubit detection, have crosstalk errors less than 0.06% on the other type. |
Thursday, June 2, 2022 9:48AM - 10:00AM |
Q07.00010: Increasing transport speeds in the trapped-ion quantum CCD computer architecture Steven A Moses, Maya Fabrikant, Ivaylo Madjarov, Adam Reed, Matthew Swallows, Gabriel Price In a recent demonstration of the quantum charge coupled device (QCCD) trapped ion architecture [1], transport operations and cooling comprise the majority of the circuit time. Cooling is required due to excitation arising from nonideal transport operations. To mitigate this requirement and decrease circuit times, there is significant interest in achieving fast transport operations resulting in low excitation. A complication of the work of Ref. [1] is that in order to sympathetically cool during circuits, multi-species ion crystals are used. As a result, there are more ion crystal modes that can be excited by transport operations. Designing transport operations that have low intrinsic excitation is the goal. However, in practice, any residual coherent excitation can be removed by a suitably applied coherent force. Previous work has demonstrated fast transport of single ions or multiple ions of the same species, while deexciting the resulting coherent motion [2,3]. Here, we report progress on applying coherent deexcitation and other techniques to improve the transport speed in our QCCD system. |
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