Bulletin of the American Physical Society
APS March Meeting 2018
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session C26: Quantum Annealing: ArchitecturesFocus

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Sponsoring Units: DQI Chair: Roman Caudillo, Intel Corporation Room: LACC 404A 
Monday, March 5, 2018 2:30PM  3:06PM 
C26.00001: Design and simulation of complex superconducting circuits for advanced quantum annealing hardware Invited Speaker: Andrew Kerman The hardware characteristics likely to maximize the computational potential of quantum annealing machines almost certainly include: (i) high spin coherence; (ii) complex and highconnectivity Ising interactions between spins; and (iii) multispin, nonstoquastic quantum fluctuations. In this talk, I will describe our work at MITLL on the design and simulation of superconducting circuits with the potential to achieve some or all of these characteristics. Specifically, I will present a new type of superconducting flux qubit, uniquely suited to emulating a quantum spin, called the Josephson phaseslip qubit, and the architecture in which we plan to embed it, based on paramagnetic coupler trees. In addition, I will discuss possible circuits for implementing quantum error suppression using these qubits, and for engineering the multiqubit interactions needed to exploit them. Finally, I will describe the simulation methodology which allows us to capture the lowenergy physics of these complex circuits. 
Monday, March 5, 2018 3:06PM  3:18PM 
C26.00002: Finding optimal quantum annealer architectures Zoe Gonzalez Izquierdo Quantum annealing is a promising method for finding the global minimum of a given cost function with many instances, particularly useful for search spaces with a large number of local minima, like the energy of a spin glass.\\ 
Monday, March 5, 2018 3:18PM  3:30PM 
C26.00003: Qubits Coupling via Lamped Element Resonators toward Quantum Annealing on Superconducting Circuit Hiroto Mukai, Akiyoshi Tomonaga, Yu Zhou, JawShen Tsai We propose a coupling method of superconducting qubits for a novel quantum annealing circuit. In order to derive the capability of the quantum annealing system, a qubit is desirable to be coupled not only with adjacent qubits but also with other qubits located far apart. In this talk, we show a circuit that uses a lumped element resonator coupled with one qubit. The resonatorqubit units are coupled by SQUIDbase couplers. Unlike the coplanar type resonator, the lumped element resonator can realize a uniform coupling strength independent of the position of the coupling. Therefore, it is possible to integrate circuits in a small space. By using rf  SQUID as a nonlinear inductor for coupling between resonators, it is possible to achieve ON / OFF and positive / negative intensity. Combining the unit and the nonlinear inductance is a new kind of scalable circuit scheme. Moreover, by strengthening the coupling between the resonator and the qubit, it is considered that the effective coupling strength between the qubits could be set to several hundred MHz. 
Monday, March 5, 2018 3:30PM  3:42PM 
C26.00004: Multispin couplers in superconducting quantum annealers – analysis based on perturbation theory Yongchao Tang, Denis Melanson, Antonio Martinez, Huichen Sun, Muhammet Ali Yurtalan, Adrian Lupascu Multiqubit interactions are important for many applications in quantum annealing, including the implementation of logical qubits for error correction and K^{th} order optimization problems with K > 2. One approach to the implementation of multiqubit coupling is to use perturbative gadgets. We analyzed the properties of the couplers by the perturbative gadgets. We discuss the design of couplers optimized in the context of superconducting circuits, including gadgets based on ancilla qubits and other more general superconducting circuits. Critical problems in the design of perturbative gadgets with superconducting circuits are addressed. 
Monday, March 5, 2018 3:42PM  3:54PM 
C26.00005: New circuit method using superconducting lumped element resonator for Quantum Annealing machine Akiyoshi Tomonaga, Hiroto Mukai, Makoto Hasegawa, Yu Zhou, Jaw Shen Tsai We propose correlating all spins on a spin glass as a quantum annealer by coupling quantum bits through superconducting lumped element resonators. Unlike the conventional type coplanar wave guide resonator, the lumped element resonator does not need to consider the waveform when qubits couple to each other. It is possible to couple many qubits with in a small space. Currently DWave systems Inc. released the world’s first commercial quantum annealing machine. However, there are a lot of challenges yet to be solved to fulfill the dream of a quantum annealing machine which is useful for human society. One of them is circuit scaling. It is necessary to increase the number of qubits and their coupling for mapping practical problem. It can be greatly improved with the circuit that consist of our lumped element resonator with a long edge coupled line. We use Al flux qubits with long quantum coherence time and Nb lumped element resonators. This experiment suggests that the new type of lumped element resonator can strongly couple to many qubits with in a small space for quantum annealing machine. 
Monday, March 5, 2018 3:54PM  4:06PM 
C26.00006: Tunable ZZZ Coupler for Quantum Annealing with Superconducting Flux Qubits Denis Melanson, Antonio Martinez, Huichen Sun, Muhammet Ali Yurtalan, Yongchao Tang, Adrian Lupascu Implementations of quantum annealing with superconducting qubits rely on tunable twobody interactions. Having higher order interactions, such as ZZZ coupling, can enable more efficient embedding of hard problems and error suppression schemes. We designed a coupler for highcoherence superconducting flux qubits that mediates a strong tunable ZZZ coupling. We use both the BornOppenheimer approximation and exact simulations to understand the interactions mediated by the coupler. We discuss plans for the implementation of this coupler in a quantum annealer. The research is based upon work partially supported by the Office of the Director of National Intelligence (ODNI), Intelligence Advanced Research Projects Activity (IARPA), via the U.S. Army Research Office contract W911NF17C0050. The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of the ODNI, IARPA, or the U.S. Government. The U.S. Government is authorized to reproduce and distribute reprints for Governmental purposes notwithstanding any copyright annotation thereon. 
Monday, March 5, 2018 4:06PM  4:18PM 
C26.00007: Four Body Local Interactions in a Superconducting Flux Qubit Coupling Architecture Marius Schöndorf, Frank Wilhelm Quantum annealing is a promising candidate to realize quantum computation and break the limit of classical computers. 
Monday, March 5, 2018 4:18PM  4:30PM 
C26.00008: Progress Towards Quantum Annealer v2.0 I: Hardware Yu Chen, Chris Quintana, Dvir Kafri, Ben Chiaro, Andrew Dunsworth, Brooks Foxen, James Wenner, John Martinis, Hartmut Neven We report on Google Quantum A.I. Lab’s progress in building a quantum annealer. Our annealer architecture is constructed from CPWbased flux qubits, integrated with airbridge crossovers and flip chip technology. With individual components such as qubits and tunable couplers fully characterized, we demonstrate efficient implementation of smallsized graphs consisting of multiple qubits. We investigate the dependence of system performance on various aspects such as graph topology, annealing trajectories, etc. In particular, we report on a small scale demonstration of how reduced dissipation and optimized annealing schedules can improve annealer performance. 
Monday, March 5, 2018 4:30PM  4:42PM 
C26.00009: Progress Towards Quantum Annealer v2.0 II: Theory Dvir Kafri, Chris Quintana, Yu Chen, John Martinis, Hartmut Neven

Monday, March 5, 2018 4:42PM  4:54PM 
C26.00010: Analyzing MisSpecification and Noise in Superconducting FluxQubit Quantum Annealers Antonio Martinez, Denis Melanson, Huichen Sun, Muhammet Ali Yurtalan, YongChao Tang, Adrian Lupascu Quantum annealers are a promising architecture for near term applications of quantum computing. In quantum annealing, one encodes a problem in an Isingtype Hamiltonian, with spin biases and couplings chosen so that the ground state encodes the solution. However, in a real system this ideal picture is complicated by hardware variance and environmental noise, and these uncertainties cause errors during the annealing process. To understand these errors, we developed models of hardware variance and environmental noise, and created methods to predict errors. Our work allows realistic levels of uncertainty to be accounted for during the process of annealer design. The research is based upon work partially supported by the Office of the Director of National Intelligence (ODNI), Intelligence Advanced Research Projects Activity (IARPA), via the U.S. Army Research Office contract W911NF17C0050. The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of the ODNI, IARPA, or the U.S. Government. The U.S. Government is authorized to reproduce and distribute reprints for Governmental purposes notwithstanding any copyright annotation thereon. 
Monday, March 5, 2018 4:54PM  5:06PM 
C26.00011: Modeling and Characterizing Noise in Quantum Annealers via ARMA Models Gregory Quiroz, Kevin Schultz Accurate characterization of noise processes in quantum hardware is key to understanding device dynamics and building precise noise models. Thus far, noise modeling efforts for quantum annealing hardware haven been solely limited to the adiabatic Markovian master equation. Here, we examine an alternative approach for building noise models of quantum annealers based on autoregressive moving average (ARMA) models, a classic technique from time series analysis that models time correlations in data. This approach, known as Schroedinger Wave ARMA (SchWARMA), adapts ARMA modeling to the tanget space of a matrix manifold on which a family of probability distributions on the space of completely positive trace preserving (CPTP) maps yields the average CPTP maps as a sufficient statistic. We investigate the applicability and extension of SchWARMA to modeling and characterizing noise in quantum annealers using measurements of the average energy of the system as a function of (1) discrete times throughout the quantum annealing evolution and (2) the total annealing time. Considering a range of ARMA models, we discuss the viability of SchWARMA for experimental characterization of quantum annealers and potential pitfalls. 
Monday, March 5, 2018 5:06PM  5:18PM 
C26.00012: Renormalization of MultiQubit Bath Coupling Tobias Chasseur, Frank Wilhelm While perfectly implemented quantum bits promise an exponential speedup compared to classical computation, the physical realization has proven to be a challenging field of research as a physical two level system can never be engineered to be completely decoupled from its environment. Whether this coupling is sought to be suppressed to increase gate fidelities or used for adiabatic quantum computing, it is essential to understand the inevitable effects of the environment. 
Monday, March 5, 2018 5:18PM  5:30PM 
C26.00013: Multispin measurements for quantum annealing Adrian Lupascu, Denis Melanson, Antonio Martinez, Huichen Sun, Muhammet Ali Yurtalan, YongChao Tang Measurements of multispin operators are expected to play an important role for quantum annealing, in applications including verification of entanglement, probing noise, and operation with feedback. We discuss the implementation of multispin measurements, with focus on annealing based on superconducting flux qubits. We identify a connection between multispin interactions and measurements, which helps designing the latter. We present in detail implementations of ZZ and ZZZ measurements, and comment on other types of measurements. We discuss also the prospects for integration and operation of multispin readout in a functional quantum annealer. The research is based upon work (partially) supported by the Office of the Director of National Intelligence (ODNI), Intelligence Advanced Research Projects Activity (IARPA), via the U.S. Army Research Office contract W911NF17C0050. The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of the ODNI, IARPA, or the U.S. Government. The U.S. Government is authorized to reproduce and distribute reprints for Governmental purposes notwithstanding any copyright annotation thereon. 
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