Bulletin of the American Physical Society
41st Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 55, Number 5
Tuesday–Saturday, May 25–29, 2010; Houston, Texas
Session W2: Focus Session: Quantum Simulation and Complexity |
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Chair: Carl Williams, National Institute of Standards and Technology Room: Imperial Center |
Saturday, May 29, 2010 8:00AM - 8:30AM |
W2.00001: Quantum computation for quantum chemistry Invited Speaker: Numerically exact simulation of quantum systems on classical computers is in general, an intractable computational problem. Computational chemists have made progress in the development of approximate methods to tackle complex chemical problems. The downside of these approximate methods is that their failure for certain important cases such as long-range charge transfer states in the case of traditional density functional theory. In 1982, Richard Feynman suggested that a quantum device should be able to simulate quantum systems (in our case, molecules) exactly using quantum computers in a tractable fashion. Our group has been working in the development of quantum chemistry algorithms for quantum devices. In this talk, I will describe how quantum computers can be employed to carry out numerically exact quantum chemistry and chemical reaction dynamics calculations, as well as molecular properties. Finally, I will describe our recent experimental quantum computation of the energy of the hydrogen molecule using an optical quantum computer. [Preview Abstract] |
Saturday, May 29, 2010 8:30AM - 9:00AM |
W2.00002: Stroboscopic Generation of Topological Protection Invited Speaker: An exciting prospect for quantum simulation is the possibility of generating and studying systems whose ground states possess topological order and which can be used to robustly store and process quantum information. The Hamiltonians governing these phases frequently require more-than-2-body interactions that are hard or even impossible to realize naturally. We present a dynamic emulation approach for realization of such a Hamiltonian with $n$-body ($n > 2$) interactions on a set of neutral atoms trapped in an addressable optical lattice, using only 1- and 2-body physical operations together with a dissipative protocol that allows thermalization to finite temperature or cooling to the ground state. Based on a stroboscopic approach to time evolution, the method allows generation of time evolution of states under the Hamiltonian, in addition to generation of the ground state. It also allows for finite temperature simulation and hence for study of topological protection as a function of system size and temperature. We demonstrate the approach with application to dynamic simulation of the toric code Hamiltonian, ground states of which can be used to robustly store quantum information when coupled to a low temperature reservoir. [Preview Abstract] |
Saturday, May 29, 2010 9:00AM - 9:12AM |
W2.00003: Exploring the phase diagram of the transverse-field Ising model using trapped ions K.R. Islam, S. Korenblit, K. Kim, M.-S. Chang, E.E. Edwards, C. Monroe, G.-D. Lin, L.-M. Duan, J. Freericks We explore the phase diagram of transverse-field long range Ising model using a linear chain of $^{171}$Yb+ ions with two hyperfine energy levels of each ion mapped to the two spin-1/2 states. The system is prepared close to the ground state of an initial Hamiltonian with transverse field much larger than the tunable spin-spin interaction and the field is then adiabatically lowered to a value where the probabilities of different magnetic orders are measured. The phase diagram contains interesting features such as quantum phase transitions and first order transitions due to frustration $i.e$., competition between spin-spin couplings. This work is supported by the Army Research Office (ARO) with funds from the DARPA Optical Lattice Emulator (OLE) Program, IARPA under ARO contract, the NSF Physics at the Information Frontier Program, and the NSF Physics Frontier Center at JQI. [Preview Abstract] |
Saturday, May 29, 2010 9:12AM - 9:24AM |
W2.00004: Quantum simulation of arbitrary Hamiltonians with superconducting circuits C. Benjamin, E.J. Pritchett, M.R. Geller, A. Galiautdinov, A.T. Sornborger, P.C. Stancil, J. Martinis While advances are continually being made in the computational treatment of atomic and molecular scattering on classical computers, the computational costs grow exponentially with system size. As a consequence, collision complexes involving 5 particles are at the fore-front of modern research with exact treatment of larger systems currently intractable. It has been proposed that quantum computers using quantum logic gates could treat such problems as the computation expense would scale polynomially. However, such digital quantum simulation would require hundreds of qubits and gate operations to treat the simplest 3-atom reactive scattering problem. In contrast, we have developed an analog quantum simulation(AQS) approach in which the scattering (or any arbitrary) Hamiltonian is directly mapped to the Hamiltonian of the quantum simulation device. Physically interesting collision problems could be mapped to just 2 or 3 coupled qubits. We illustrate such mappings and discuss how such an approach can be realized on a system of coupled Josephson junctions(JJs). Previous experiments with quantum circuits consisting of pairs of JJs have demonstrated highly accurate control and readout making them especially well suited for AQS. [Preview Abstract] |
Saturday, May 29, 2010 9:24AM - 9:36AM |
W2.00005: The Dicke Quantum Phase Transition in a Superfluid Gas Coupled to an Optical Cavity Ferdinand Brennecke, Kristian Baumann, Christine Guerlin, Silvan Leinss, Rafael Mottl, Tilman Esslinger A fundamental concept to describe the collective matter-light interaction is the Dicke model which has been predicted to how an intriguing quantum phase transition. We have realize d the Dicke quantum phase transition in an open system formed by a Bose-Einstein condensate coupled to an optical cavity, and observed the emergence of a self-organized supersolid phase. The phase transition is driven by infinitely long-ranged interactions between the condensed atoms. We show that the phase transition is described by the Dicke Hamiltonian, including counter-rotating coupling terms, and that the supersolid phase is associated with a spontaneously broken spatial symmetry. The boundary of the phase transition is mapped out in quantitative agreement with the Dicke model. [Preview Abstract] |
Saturday, May 29, 2010 9:36AM - 9:48AM |
W2.00006: Probing the Kondo Lattice Model with Alkaline Earth Atoms Michael Foss-Feig, Michael Hermele, Victor Gurarie, Ana Maria Rey It has recently been proposed that alkaline-earth atoms can be used to simulate condensed matter Hamiltonians with both spin and orbital electronic degrees of freedom[1]. For example, it is possible to create two independent optical lattices for trapping the 1S0 and 3P0 clock states, which we then associate with two orbital degrees of freedom[2]. Such a system is particularly well suited to simulation of the Kondo Lattice Model (KLM): by placing one clock state in a deep lattice and the other in a shallow lattice it is possible to mimic the interaction of localized spins with a band of conduction electrons. We suggest simple dynamical probes of the KLM phase diagram that can be implemented with current experimental techniques. In particular, we show how Kondo physics at strong coupling, low density, and in the heavy fermion phase is manifest in the dipole oscillations of the conduction band upon sudden displacement of a parabolic trapping potential. [1] A V Gorshkov et al. arXiv:0905.2610v2 [cond-mat.quant-gas], Jan 2009. [2] A Daley, M Boyd, J Ye, and P Zoller. Phys. Rev. Lett. 101, 170504 (2008). [Preview Abstract] |
Saturday, May 29, 2010 9:48AM - 10:00AM |
W2.00007: Singlet-triplet oscillations with pairs of neutral atoms in an optical superlattice Stefan Trotzky, Yu-Ao Chen, Ute Schnorrberger, Patrick Cheinet, Simon F\"olling, Immanuel Bloch We show the creation, detection and manipulation of effective-spin triplet and singlet pairs with ultracold $^{87}$ Rb atoms in an optical superlattice. Starting from two atoms on a lattice site being in different Zeeman states labeled by $|\!\!\uparrow\rangle$ and $|\!\!\downarrow\rangle$, we split the sites into symmetric double-wells to form delocalized spin triplets $|\!\!\uparrow,\downarrow\rangle + |\!\!\downarrow,\uparrow\rangle$. We use a magnetic field gradient to achieve a coherent coupling between the triplet and the corresponding singlet state. The detection of the emerging oscillations relies on measuring the parity of the spatial two-body wavefunction after merging the double-wells. A superexchange coupling between adjacent double-wells realizes a ${\rm SWAP}$ operation that stretches the entangled pairs over more than one lattice spacing. Our method provides a tool to detect short-range spin correlations e.g. emerging in Fermi-Hubbard type systems close to the Neel temperature. The ${\rm SWAP}$ operation realizes an important step towards the creation of robust multiparticle entangled states suitable for one-way quantum computing. [Preview Abstract] |
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