Bulletin of the American Physical Society
APS March Meeting 2016
Volume 61, Number 2
Monday–Friday, March 14–18, 2016; Baltimore, Maryland
Session A48: Quantum Computing and Quantum Simulations with Superconducting Circuits |
Hide Abstracts |
Sponsoring Units: GQI Chair: David Schuster, University of Chicago Room: 349 |
Monday, March 14, 2016 8:00AM - 8:12AM |
A48.00001: Digitized adiabatic quantum computing with a superconducting circuit, part I: Theory L. Lamata, R. Barends, A. Shabani, J. Kelly, A. Mezzacapo, U. Las Heras, R. Babbush, A. G. Fowler, B. Campbell, Yu Chen, Z. Chen, B. Chiaro, A. Dunsworth, E. Jeffrey, E. Lucero, A. Megrant, J. Y. Mutus, M. Neeley, C. Neill, P. J. J. O’Malley, C. Quintana, P. Roushan, E. Solano, H. Neven, John M. Martinis Adiabatic quantum computing (AQC) is a general-purpose optimization algorithm that in contrast to circuit-model quantum algorithms can be applied to a large set of computational problems. An analog physical realization of AQC has certain limitations that we propose can be overcome by a gate-model equivalence of the AQC. In this talk we discuss the hardware advantages of digitized AQC in particular arbitrary interactions, precision, and coherence. We could experimentally realize the principles of digitized AQC on a chain of nine qubits, and highlight the physics of adiabatic evolutions as well as the Kibble-Zurek mechanism. [Preview Abstract] |
Monday, March 14, 2016 8:12AM - 8:24AM |
A48.00002: Digitized adiabatic quantum computing with a superconducting circuit, part II: Experiment R. Barends, A. Shabani, L. Lamata, J. Kelly, A. Mezzacapo, U. Las Heras, R. Babbush, A.G. Fowler, B. Campbell, Y. Chen, Z. Chen, B. Chiaro, A. Dunsworth, E. Jeffrey, E. Lucero, A. Megrant, J. Mutus, M. Neeley, C. Neill, P. O'Malley, C. Quintana, P. Roushan, E. Solano, H. Neven, J. Martinis A major challenge in quantum computing is to solve general problems with limited physical hardware. We implement digitized adiabatic quantum computing, combining the generality of the adiabatic algorithm with the universality of the digital approach, using a superconducting circuit with nine qubits. We probe the adiabatic evolutions, explore the scaling of errors with system size, and quantify the success of the algorithm for random spin problems. We find that the system can approximate the solutions to both frustrated Ising problems and non-stoquastic problem Hamiltonians with a performance that is comparable. [Preview Abstract] |
Monday, March 14, 2016 8:24AM - 8:36AM |
A48.00003: Digital quantum simulations with superconducting circuits Urtzi Las Heras, Laura Garcia-Alvarez, Lucas Lamata, Enrique Solano Superconducting circuits are a promising quantum technology for the implementation of quantum information protocols. In particular, digital quantum simulations are an efficient method for reproducing dynamics that are not produced naturally in the simulating system. We propose a method for simulating efficiently the dynamics of prototypical spin and fermionic models in circuit quantum electrodynamics architectures with either qubit-qubit pairwise interactions or resonators acting as quantum buses. We show how to implement Ising and Heisenberg spin models, and the Fermi-Hubbard model, making use of the Jordan-Wigner mapping and M\o lmer-S\o rensen gates. [Preview Abstract] |
Monday, March 14, 2016 8:36AM - 8:48AM |
A48.00004: Quantum simulation of micro and macro frustrated quantum magnetism with superconducting circuits. Joydip Ghosh, Barry C. Sanders We devise a scalable scheme for simulating a quantum phase transition from paramagnetism to frustrated magnetism in a superconducting flux-qubit network, and show how to characterize this system experimentally both macroscopically and microscopically. The proposed macroscopic characterization of the quantum phase transition is based on the transition of the probability distribution for the spin-network net magnetic moment with this transition quantified by the difference between the Kullback-Leibler divergences of the distributions corresponding to the paramagnetic and frustrated magnetic phases with respect to the probability distribution at a given time during the transition. Microscopic characterization of the quantum phase transition is performed using the standard local-entanglement-witness approach. Simultaneous macro and micro characterizations of quantum phase transitions would serve to verify in two ways a quantum phase transition and provide empirical data for revisiting the foundational emergentist-reductionist debate regarding reconciliation of macroscopic thermodynamics with microscopic statistical mechanics especially in the quantum realm for the classically intractable case of frustrated quantum magnetism. [Preview Abstract] |
Monday, March 14, 2016 8:48AM - 9:00AM |
A48.00005: Engineering artificial Hamiltonians with parametric superconducting circuits Yao Lu, Srivatsan Chakram, Nelson Leung, Ravi Naik, Nathan Earnest, Peter Groszkowski, Jens Koch, Eliot Kapit, David Schuster One major challenge in building a large scale quantum computer is to generate and manipulate interactions between its many qubits. One promising approach is to use parametric flux or voltage modulation to realize effective interactions between different components of superconducting circuits, generating artificial Hamiltonians that are suitable for various quantum computation tasks, which might be difficult to achieve through other means. We propose a parametric superconducting circuit where transmon qubits and resonators are coupled to a flux-modulated parametric coupler. We show that with this device, arbitrary pairs of qubits or resonators in the circuit can be selectively and simultaneously brought into resonance with each other and swap excitations at a controllable rate. This allows for the creation of various artificial circuit Hamiltonians that are suitable for a number of applications such as single qubit state stablization, parametric qubit state readout, autonomous error correction and so on. [Preview Abstract] |
Monday, March 14, 2016 9:00AM - 9:12AM |
A48.00006: Strongly interacting photons in a synthetic magnetic field Pedram roushan, C. Neill, A. Megrant, Y. Chen, R. Barends, B. Cambell, Z. Chen, B. Chiaro, A. Dunsworth, A. Fowler, E. Jeffrey, J. Kelly, E. Lucero, J. Mutus, P. O'Malley, M. Neeley, C. Quintana, D. Sank, A. Vainsencher, J. Wenner, T. White, E. Kapit, J. Martinis Interacting electrons in the presence of magnetic fields exhibit some of the most fascinating phases in condensed matter systems. Realizing these phases in an engineered platform could provide deeper insight into their. Using three superconducting qubits, we synthesize artificial magnetic fields by modulating the inter-qubit coupling. In the closed loop formed by the qubits, we observe the directional circulation of a microwave photon as well as chiral groundstate currents, the signatures of broken time-reversal symmetry. The existence of strong interactions in our system is seen via the creation of photon vacancies, or "holes", which circulate in the opposite direction from the photons. Our work demonstrates an experimental approach for engineering quantum phases of strongly interacting bosons. [Preview Abstract] |
Monday, March 14, 2016 9:12AM - 9:24AM |
A48.00007: Emulating the 1-Dimensional Fermi-Hubbard Model with Superconducting Qubits Jan-Michael Reiner, Michael Marthaler, Gerd Schön A chain of qubits with both $ZZ$ and $XX$ couplings is described by a Hamiltonian which coincides with the Fermi-Hubbard model in one dimension. The qubit system can thus be used to study the quantum properties of this model. We investigate the specific implementation of such an analog quantum simulator by a chain of tunable Transmon qubits, where the $ZZ$ interaction arises due to an inductive coupling and the $XX$ interaction due to a capacitive coupling. [Preview Abstract] |
Monday, March 14, 2016 9:24AM - 9:36AM |
A48.00008: Cavity-assisted cooling of Bose-Hubbard model simulator with superconducting circuits Xiuhao Deng, Chunjing Jia Interesting progress have been made in using superconducting circuits to simulate Bose-Hubbard model (BHM). However, studying ground state feature of BHM calls for effective cooling process, where the cooling mechanism must preserve total number of simulated bosons and cooling rate has to be much stronger than decay rate. Here, we propose a cooling scheme that satisfies these two conditions by coupling an array of transmission line resonators with an assisted cavity. The quantum simulator we modelled here can be used to study generic BHM, which include both repulsive and attractive on-site interaction and hopping strength. We evaluate the cooling rate in all these regime analytically. And numerical simulation in time domain gives further supports. Our results present a promising cooling scheme for experiments. [Preview Abstract] |
Monday, March 14, 2016 9:36AM - 9:48AM |
A48.00009: Simulating chemical energies to high precision with fully-scalable quantum algorithms on superconducting qubits Peter O'Malley, Ryan Babbush, Ian Kivlichan, Jhonathan Romero, Jarrod McClean, Andrew Tranter, Rami Barends, Julian Kelly, Yu Chen, Zijun Chen, Evan Jeffrey, Austin Fowler, Anthony Megrant, Josh Mutus, Charles Neill, Christopher Quintana, Pedram Roushan, Daniel Sank, Amit Vainsencher, James Wenner, Theodore White, Peter Love, Alan Aspuru-Guzik, Hartmut Neven, John Martinis Quantum simulations of molecules have the potential to calculate industrially-important chemical parameters beyond the reach of classical methods with relatively modest quantum resources. Recent years have seen dramatic progress both superconducting qubits and quantum chemistry algorithms. Here, we present experimental demonstrations of two fully-scalable algorithms for finding the dissociation energy of hydrogen: the variational quantum eigensolver and iterative phase estimation. This represents the first calculation of a dissociation energy to chemical accuracy with a non-precompiled algorithm. These results show the promise of chemistry as the ``killer app" for quantum computers, even before the advent of full error-correction. [Preview Abstract] |
Monday, March 14, 2016 9:48AM - 10:00AM |
A48.00010: Hybrid Quantum-Classical Approach to Molecular Excited States On Superconducting Qubits Jarrod McClean, Mollie Schwartz, Chris Macklin, Irfan Siddiqi, Jonathan Carter, Wibe de Jong Quantum computers promise to dramatically advance our understanding of correlated quantum systems. Unfortunately, many proposed algorithms have resource requirements not yet suitable for near-term quantum devices. The variational quantum eigensolver (VQE) is a recently proposed hybrid quantum-classical method for solving eigenvalue problems and more generic minimizations on a quantum device leveraging classical resources to minimize coherence time requirements. However, this algorithm has so far focused only on the quantum ground state and has almost exclusively been studied in ideal closed system conditions. We briefly review the original VQE approach and introduce a simple extension requiring no additional coherence time to approximate excited states. Moreover, we show how the same method can be used to mitigate the effects of noise in a real system and how this algorithm can be applied in practice on a superconducting qubit architecture. [Preview Abstract] |
Monday, March 14, 2016 10:00AM - 10:12AM |
A48.00011: Implementation of a Quantum Variational Eigensolver in Superconducting Qubits Mollie Schwartz, Jarrod McClean, Chris Macklin, Jonathan Carter, Wibe Albert de Jong, Irfan Siddiqi The quantum variational eigensolver (QVE) represents an efficient implementation of quantum simulation that relies on a synergy between classical and quantum computing components. In this approach, a classical computer is used to map the target Hamiltonian onto a fermionic Hilbert space and to perform a variational update of the estimated ground state. This test state is then prepared in the quantum system, enabling an efficient estimation of the expectation value of the Hamiltonian and reducing the requirements for coherent qubit evolution. We present experimental progress toward implementing a QVE in superconducting qubits, capitalizing on the flexibility and scalability of the transmon cQED architecture. [Preview Abstract] |
Monday, March 14, 2016 10:12AM - 10:24AM |
A48.00012: Cavity-assisted dynamical quantum phase transition in superconducting quantum simulators Lin Tian Coupling a quantum many-body system to a cavity can create bifurcation points in the phase diagram, where the many-body system switches between different phases. Here I will discuss the dynamical quantum phase transitions at the bifurcation points of a one-dimensional transverse field Ising model coupled to a cavity. The Ising model can be emulated with various types of superconducting qubits connected in a chain. With a time-dependent Bogoliubov method, we show that an infinitesimal quench of the driving field can cause gradual evolution of the transverse field on the Ising spins to pass through the quantum critical point. Our calculation shows that the cavity-induced nonlinearity plays an important role in the dynamics of this system. Quasiparticles can be excited in the Ising chain during this process, which results in the deviation of the system from its adiabatic ground state. [Preview Abstract] |
Monday, March 14, 2016 10:24AM - 10:36AM |
A48.00013: Visualizing singularities of a groundstate landscape using superconducting circuits Erik Lucero, A. Dunsworth, P. roushan, A. Megrant, C. Neill, T. Souza, M. Tomka, M. Kolodrubetz, Y. Chen, R. Barends, B. Campbell, Z. Chen, B. Chiaro, E. Jeffrey, J. Kelly, J. Mutus, P. O'Malley, C. Quintana, D. Sank, J. Wenner, T. White, A. Polkovnikov, J. Martinis The defining properties of condensed matter phases are set by their groundstate wavefunctions. The adiabatic theorem provides an experimental approach for realizing such states. However, a general protocol for applying this theorem is experimentally unexplored, in particular when the energy gap is small. Using two superconducting qubits, we adiabatically prepare the entire groundstate manifold in a region of the parameter-space where degeneracies are present. We prepare these states by varying the Hamiltonian along 'geodesics' in parameter-space, obtained by minimizing the local non-adiabatic error. From the measured total magnetization of the final state, we compute the Berry curvature, where degeneracies appear as singular points, allowing us to directly visualize the degeneracies in the groundstate landscape. [Preview Abstract] |
Monday, March 14, 2016 10:36AM - 10:48AM |
A48.00014: Observation of the correspondence between Landau-Zener transition and Kibble-Zurek mechanism with a superconducting qubit system Ming Gong, Dong Lan, Yuhao Liu, Xinsheng Tan, Haifeng Yu, Yang Yu, Shiliang Zhu, Guozhu Sun, Yu Zhou, Yunyi Fan, Peiheng Wu, Xueda Wen, Danwei Zhang, Siyuan Han We present a direct experimental observation of the correspondence between Landau-Zener transition and Kibble-Zurek mechanism with a superconducting qubit system. We develop a time resolved approach to study quantum dynamics of the Landau-Zener transition. By using this method, we observe the key features of the correspondence between Landau-Zener transition and Kibble-Zurek mechanism, e.g., the boundary between the adiabatic and impulse regions, the freeze out phenomenon in the impulse region. Remarkably, the scaling behavior of the population in the excited state, an analogical phenomenon originally predicted in Kibble-Zurek mechanism, is also observed in the Landau-Zener transition. [Preview Abstract] |
Monday, March 14, 2016 10:48AM - 11:00AM |
A48.00015: Artificial Quantum Thermal Bath Alireza Shabani, Hartmut Neven In this talk, we present a theory for engineering the temperature of a quantum system different from its ambient temperature, that is basically an analog version of the quantum metropolis algorithm. We define criteria for an engineered quantum bath that, when couples to a quantum system with Hamiltonian $H$, drives the system to the equilibrium state $\frac{e^{-H/T}}{{{\rm{Tr}}}(e^{-H/T})}$ with a tunable parameter $T$. For a system of superconducting qubits, we propose a circuit-QED approximate realization of such an engineered thermal bath consisting of driven lossy resonators. We consider an artificial thermal bath as a simulator for many-body physics or a controllable temperature knob for a hybrid quantum-thermal annealer. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700