SESSION 13: Ions for quantum computing and simulation

Chair: (Hartmut Haeffner (University of California, Berkeley))
3:00pm - 3:30pmRoee Ozeri, Weizmann Institute of Science
Theory of robust multi-qubit non-adiabatic gates for trapped-ions
Abstract. Entanglement gates are essential building blocks of quantum computers. Such two-qubit gates have been demonstrated in trapped-ions systems with outstanding fidelities. However retaining the gate’s performance in a large qubit register remains a major challenge in the realization of a quantum computer. Here we propose and investigate multi-qubit entanglement gates for trapped-ions in ion-chain configurations. Our gates purposefully utilize all the normal-modes of motion of the ion-chain allowing for the operation of our gates outside of the adiabatic regime. The coupling to the different normal-modes of motion is used to form all-to-all entangling gates, e.g gates that rotate the ground state to a GHZ state, and to generate spin-Hamiltonian interactions such as nearest-neighbor Ising model or the Su-Schriefer-Heeger topological Hamiltonian. Our gates use a multi-tone laser field, which couples uniformly to all ions, i.e there is no need to individually address the different ions. Thus, our method is simple to implement and natural to most trapped-ion architectures. Furthermore, we endow our gate with robustness properties, which make them resilient to various sources of system noise and imperfections.
3:30pm - 4:00pmRaghavendra Srinivas, National Institute of Standards and Technology, Boulder
Laser-free trapped-ion entangling gates
Abstract. Trapped-ion entangling gates are usually performed using laser-induced coupling of the ions’ internal spin states to their motion. Laser-free methods, which eliminate photon scattering errors and offer benefits for scalability have been proposed and demonstrated using static magnetic field gradients or magnetic field gradients oscillating at GHz frequencies [1-4]. We demonstrate a recently proposed method for trapped-ion entangling gates [5] implemented using an oscillating magnetic field gradient at radio frequency in addition to two microwave magnetic fields symmetrically detuned about the qubit frequency. This implementation offers important technical advantages over other laser-free techniques, while also enabling laser-free entangling gates with reduced sensitivity to qubit frequency errors. These experiments are performed in a surface-electrode trap that incorporates current-carrying electrodes to generate the microwave fields and the oscillating magnetic field gradient. Currently, we achieve a Bell-state fidelity of 0.996(2) with ground-state-cooled ions and 0.991(3) for ions cooled to the Doppler limit (nbar=2). [1] Mintert and Wunderlich PRL 87, 257904 (2001) [2] Weidt et al. PRL 117, 220501 (2016) [3] Ospelkaus et al. Nature 476, 181 (2011) [4] Harty et al. PRL 117, 140501 (2016) [5] Sutherland et al. NJP 21, 033033 (2019)
4:00pm - 4:30pmCraig Hogle, Sandia National Laboratories
Logical cooling for robust analogue quantum simulation
Abstract. Analogue quantum simulation is arguably the most promising near-term application of quantum computing. However, it is unknown how noise may limit analogue simulators’ computational power. Using a technique to remove errors in the computational basis of the system, without resorting to a full error correcting scheme, we look to both measure and increase an analogue quantum simulator’s robustness to noise, using a chain of trapped ions in a state-of-the-art microfabricated surface electrode trap. SNL is managed and operated by NTESS, LLC, a subsidiary of Honeywell International, Inc., for the US DOE NNSA under contract DE-NA0003525.The views expressed here do not necessarily represent the views of the DOE or the U.S. Government. SAND2019-13560 A
4:30pm - 5:00pmCrystal Noel, University of Maryland Joint Quantum Institute
A universal quantum computer based on long chains of ions
Abstract. We present the system design and architecture of a trapped ion universal quantum processor with high-fidelity quantum gates and addressing of up to 32 qubits. Our approach takes advantage of individual optical addressing to achieve simultaneous high-fidelity operations on a long chain of 171Yb+ ions, resulting in one of the largest academic general-purpose quantum computers. Under the IARPA Logical Qubit (LogiQ) program, we aim to demonstrate a logical qubit using the Bacon-Shor [[9,1,3]] subsystem code. The Bacon-Shor code consists of 9 data qubits, encoding 1 logical qubit, with stabilizer circuits mapped to 4 ancilla qubits capable of correcting any single qubit error. In this talk, we report on the experimental progress made towards implementation of quantum error correction, including the encoding of the logical qubit and stabilizer readout. Additionally, we report progress towards achieving multiple rounds of error correction using added capabilities of sympathetic cooling on long chains and individual ancilla readout.

SQuInT Chief Organizer
Akimasa Miyake, Associate Professor

SQuInT Co-Organizer
Brian Smith, Associate Professor UO

SQuInT Program Committee
Postdoctoral Fellows:
Markus Allgaier (UO OMQ)
Sayonee Ray (UNM CQuIC)
Pablo Poggi (UNM CQuIC)
Valerian Thiel (UO OMQ)

SQuInT Event Co-Organizers (Oregon)
Jorjie Arden
Holly Lynn

SQuInT Event Administrator (Oregon)
Brandy Todd

SQuInT Administrator (CQuIC)
Gloria Cordova
505 277-1850

SQuInT Founder
Ivan Deutsch, Regents' Professor, CQuIC Director

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