Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session B27: Superconducting Circuits: Quantum Simulations and ManyBody Physics 
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Sponsoring Units: DQI Chair: Inanc Adagideli, Sabanci University Room: BCEC 160C 
Monday, March 4, 2019 11:15AM  11:27AM 
B27.00001: Probing remote entanglement in a localized system with a superconducting qubit quantum simulator. Ben Chiaro, Brooks Foxen, Matthew McEwen, John M Martinis

Monday, March 4, 2019 11:27AM  11:39AM 
B27.00002: A dissipatively stabilized Mottinsulator of photons Brendan Saxberg, Ruichao Ma, Clai Owens, Jonathan Simon, David Schuster

Monday, March 4, 2019 11:39AM  11:51AM 
B27.00003: A transmon based fivequtrit processor for simulations in high energy physics Machiel Blok, Vinay Ramasesh, Dar Dahlen, Kevin P. O'Brien, John Mark Kreikebaum, Norman Yao, Irfan Siddiqi Encoding quantum information in the higher energy levels of the transmon circuit provides a hardware efficient way to harness a larger Hilbert space in existing quantum processors while also increasing their connectivity. Furthermore, a network of qutrits (threelevel systems) is naturally suited to experimentally demonstrate recently identified connections between high energy physics and quantum information, such as holographic quantum error correction codes and the physics of scrambling. Here we report on the control of a fivequtrit processor and our progress toward characterizing the scrambling of quantum information. We implement a circuit to measure the decay of outoftime ordered correlators, a hallmark of scrambling, in a method that distinguishes between decoherence and scrambling. The same circuit can be viewed as a teleportation protocol where quantum information is scrambled by a black hole and then decoded through measurement of emitted Hawking photons. 
Monday, March 4, 2019 11:51AM  12:03PM 
B27.00004: Band Engineering for Quantum Simulation in Circuit QED Alicia Kollar, Mattias Fitzpatrick, Peter Sarnak, Andrew Houck The field of circuit QED has emerged as a rich platform for both quantum com putation and quantum simulation. Lattices of coplanar waveguide (CPW) resonators realize artificial photonic materials in the tightbinding limit. In combination with qubitmediated photonphoton interactions, these systems can be used to study dynamical phase transitions and manybody phenomena in drivendissipative systems. In this talk, we will show how graphtheory and graphlevel operations can be used to tailor the singleparticle band structures of such systems. In particular, we will show that the process of taking a line graph produces controllably gapped flat bands at −2 and that subdividing all graph edges produces Dirac cones from formerly quadratic band edges and chiral flat bands at zero energy. 
Monday, March 4, 2019 12:03PM  12:15PM 
B27.00005: Tunableprofile qubitphoton bound state interactions with superconducting circuits Basil Smitham, Neereja Sundaresan, Przemyslaw Bienias, Rex Lundgren, Alexey V Gorshkov, Andrew Houck Strongly coupling qubits to the band edge of a photonic crystal results in the formation of qubitphoton dressed bound states. The photonic components of these bound states are exponentially localized around the qubit positions and represent the interbound state interaction profiles. Tunability of the exponential localization length of bound state interactions has been experimentally demonstrated in superconducting circuits of two transmons coupled to a microwave photonic crystal [1]. To expand the range of 1D quantum models that can be probed with qubits coupled to photonic crystals, proposals have been put forth to engineer nonexponential interaction profiles by further dressing the systems with external driving fields [2]. We present experimental progress towards characterizing the effective bound states of transmons coupled to photonic crystals driven by auxiliary microwave tones. By driving the photonic crystal with multiple tones we aim to engineer nonexponential effective interactions, with the goal of accessing a broader class of tunable spin models. 
Monday, March 4, 2019 12:15PM  12:27PM 
B27.00006: Emulating Majorana Fermions Using Transmon Qubits with Application to Topological Quantum Computing Alireza NajafiYazdi Majorana Fermions are fermionic modes with nonabelian dynamics and are of significant interest to realize topologically protected quantum processors. There have been signifcant efforts by the community to realize the Majorana modes in solidstate devices. Despite significant progress, fabricating and operating a Majorana qubit has proven to be extremely challenging. 
(Author Not Attending)

B27.00007: High coherence quantum simulation of coherent backscattering in an effective twolevel system composed of two superconducting qubits Ana Gramajo, Dan Campbell, Bharath Kannan, David K Kim, Alexander Melville, Bethany M Niedzielski, Jonilyn L Yoder, Daniel Domínguez, María José Sánchez, Simon Gustavsson, William D Oliver In a recent experiment by Gustavsson et al. [1], a superconducting flux qubit was used to model scattering events using multiple LandauZener transitions by driving the qubit periodically back and forth through an avoided crossing. In highly coherent systems, timereversal symmetry in the driving field should give rise to a dip in the average transition rate (averaged over many quantum trajectories), by analogy with weak localization in condensed matter systems. We experimentally emulate the scattering events with multiple LandauZener transitions in an effective twolevel system, seeking to demonstrate the theoretically predicted weak localization phenomenon in this system, Ferrón et al. [2]. The effects of systembath coupling are accurately simulated by a FloquetMarkov master equation. 
Monday, March 4, 2019 12:39PM  12:51PM 
B27.00008: Demonstration of a nonstoquastic Hamiltonian in coupled superconducting flux qubits Isil Ozfidan, Chunqing Deng, Mohammad Amin, Anatoly Smirnov, Trevor Lanting Currently available quantum annealers (QA) provide solutions to the transverse field Ising model with thousands of magnetically coupled qubits. To achieve a nonstoquastic Hamiltonian with QA, coupling via two canonically conjugate (orthogonal) degrees of freedom is necessary. Furthermore this orthogonal coupling can potentially enhance the performance of QA processors and enable an extended range of quantum simulations. Here we present one and twoqubit microwave spectroscopy as well as time evolution measurements on two superconducting flux qubits coupled via two orthogonal degrees of freedom, charge and flux. We show that the electrostatic interaction, realized through a coupling capacitor, produces \sigma_y\sigma_y coupling in the computational basis and leads to broken gauge invariance. We also observe emergence of \sigma_x\sigma_x coupling through higher energy states of each rfSQUID. Finally, we show that the reduced two qubit Hamiltonian is nonstoquastic across a wide range of parameters. 
Monday, March 4, 2019 12:51PM  1:03PM 
B27.00009: Metamaterial SlowLight Waveguide for Finite Range Interactions and NonMarkovian Dynamics with Superconducting Qubits Vinicius Ferreira, Jash Banker, Mohammad Mirhosseini, Alp Sipahigil, Oskar Painter The ability to engineer the dispersion of light through subwavelength patterning of bulk materials has been a powerful tool for studying the influence of novel electromagnetic environments on lightmatter interactions. Here, we present the experimental realization of an onchip superconducting metamaterial waveguide composed of an array of coupled resonators of subwavelength size and negligible frequency disorder. By matching the array boundaries to 50Ω coplanar waveguides, our design achieves an 80MHz bandwidth photonic channel with nearly constant group index of ~650, as well as extinction of more than 70dB outside of the passband. Coupling transmon qubits to this metamaterial allows us to study nonMarkovian dynamics of a single qubit’s interaction with the photonic bath, as well as collective nonMarkovian dynamics of multiple qubits. Moreover, far from the passband, we can dynamically measure finiterange qubitqubit interactions that extend beyond nearest neighbor and depend on detuning from the bandedge. We thus establish our metamaterial design as an attractive platform for studying photonmediated nonMarkovian dynamics and quantum manybody physics. 
Monday, March 4, 2019 1:03PM  1:15PM 
B27.00010: Roadmap to a superconducting quantum many body simulator Yariv Yanay, Daniel Campbell, Jochen Braumüller, William D Oliver, Charles Tahan A superconducting circuit constructed from a repeating pattern of identical unit cells comprising qubits or resonators can be used to simulate a quantum many body system of spins or bosons. While single or few qubit systems have been repeatedly demonstrated in the last few years, the majority of those require tuning each individual qubit frequency through individual control lines. Here, we propose how a larger twodimensionsal system can be realized with far fewer control lines by focusing on qubit designs that can be uniformly fabricated, with deviation from the design frequency acting as disorder. We examine the operating regimes for such a system and the required fabrication accuracy, as well as readout and control schemes. We discuss how a such a superconducting system could be prepared in nonthermal states in different parts of the manybody spectrum, and consider what observables could be accessed and whether they could be used to test assumptions on entanglement entropy and eigenstate thermalization in 2D systems. 
Monday, March 4, 2019 1:15PM  1:27PM 
B27.00011: Synthetic quantum materials in superconducting circuits Ruichao Ma, Brendan Saxberg, Clai Owens, Jonathan Simon, David Schuster Superconducting circuits have emerged as a competitive platform for quantum computation, satisfying the challenges of controllability, long coherence and strong interactions. Here we apply this toolbox to the exploration of strongly correlated quantum matter, building a BoseHubbard lattice for photons in the strongly interacting regime. We develop a versatile recipe for the dissipative preparation of incompressible manybody phases through reservoir engineering and apply it in our system to realize the first Mott insulator of photons. Site and timeresolved readout of the lattice allows microscopic observation of the lattice dynamics. The low entropy Mott state can serve as a starting point for studying other strongly correlated phases, e.g. a TonksGirardeau gas of interacting defects. The dissipative preparation demonstrated in this work also enable future exploration of elusive interacting topological phases. 
Monday, March 4, 2019 1:27PM  1:39PM 
B27.00012: TimeResolved Measurements of Energy Transport in a System of Coupled Superconducting Qubits Inspired by Simulations of Photosynthetic Processes Graham J. Norris, Anton Potočnik, Michele Collodo, Abdulkadir Akin, Simone Gasparinetti, Christopher Eichler, Andreas Wallraff Engineered quantum systems have recently found application as a testbed for answering open questions about energy transport in complex open quantum systems such as photosynthetic systems. Using a circuit incorporating three superconducting transmon qubits, we simulate energy transport with electronphonon interactions, where we emulate longitudinal coupling to different types of phononic baths by applying engineered flux noise to the qubits. Previously, we considered the effects of noise on energy transport efficiency in steadystate measurements under continuous driving [1]. To study the transport of single photons, we now switch to pulsed excitations and timeresolved measurements. We verify the quantum nature of the excitations transported through the system in antibunching measurements, showing secondorder correlation functions with g^{(2)}(0) < 0.05, observe coherent oscillations of the emitted power indicative of static coherence, and study the efficiency of transport as a function of noise type. 
Monday, March 4, 2019 1:39PM  1:51PM 
B27.00013: Quantum impurity in a 1D photonic crystal Andrei Vrajitoarea, Rex Lundgren, Yidan Wang, Przemyslaw Bienias, Alexey Gorshkov, Andrew Houck Quantum impurity problems are described in terms of a single quantummechanical degree of freedom interacting with a dissipative reservoir. Superconducting circuits offer an ideal platform for studying the quantum dynamics of artificial atoms embedded in the electromagnetic continuum of a onedimensional waveguide, reaching nonperturbative coupling regimes in the spinboson model for an ohmic bath. Parallel experiments have explored transmon qubits strongly coupled to a photonic crystal, where the impurity hybridizes with the band structure resulting in a photonic bound state inside the gap. In this talk we present recent efforts in further pushing the coupling strength with the stepped impedance microwave crystal, using an artificial atom with a large magnetic moment, the fluxonium circuit. The goal of this experiment is to explore how photon scattering inside the waveguide is influenced by the significance of counterrotating coupling terms and by the nonlinear photon dispersion in the crystal. 
Monday, March 4, 2019 1:51PM  2:03PM 
B27.00014: Quantum impurity physics simulation with superconducting circuits I: perturbative regime Nitish Jitendrakumar Mehta, Roman Kuzmin, Nicholas Grabon, Ray Mencia, Vladimir Manucharyan We report our progress in the field of quantum impurity simulations with superconducting circuits. Our simulator consists of a split Josephson junction terminating a highimpedance transmission line, which is made of a linear chain of up to 40,000 junctions [1,2]. In part I, we start with a relatively large area splitjunction, such that its quartic anharmonicity can be treated as a perturbation. In this regime, the system is welldescribed by a CaldeiraLeggett model of a quantum degree of freedom interacting with an Ohmic bath. The interaction effects are revealed through the measurement of the frequency shifts of over 100 discrete modes of the bath. In part II, we explore smallarea impurity junction where the nonlinearity is nonperturbative. Now the system can be described by a boundary sineGordon quantum impurity model. It is expected that inelastic scattering of single photons becomes the dominant photon loss mechanism, with the loss frequency dependence containing information on the manybody correlation functions. We will present the measurements at various line impedances and impurity parameters. 
Monday, March 4, 2019 2:03PM  2:15PM 
B27.00015: Quantum impurity physics simulation with superconducting circuits II: manybody regime Roman Kuzmin, Nitish Jitendrakumar Mehta, Nicholas Grabon, Ray Mencia, Vladimir Manucharyan We report our progress in the field of quantum impurity simulations with superconducting circuits. Our simulator consists of a split Josephson junction terminating a highimpedance transmission line, which is made of a linear chain of up to 40,000 junctions [1,2]. In part I, we start with a relatively large area splitjunction, such that its quartic anharmonicity can be treated as a perturbation. In this regime, the system is welldescribed by a CaldeiraLeggett model of a quantum degree of freedom interacting with an Ohmic bath. The interaction effects are revealed through the measurement of the frequency shifts of over 100 discrete modes of the bath. In part II, we explore smallarea impurity junction where the nonlinearity is nonperturbative. Now the system can be described by a boundary sineGordon quantum impurity model. It is expected that inelastic scattering of single photons becomes the dominant photon loss mechanism, with the loss frequency dependence containing information on the manybody correlation functions. We will present the measurements at various line impedances and impurity parameters. 
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