Bulletin of the American Physical Society
43rd Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 57, Number 5
Monday–Friday, June 4–8, 2012; Orange County, California
Session H7: Quantum Computing I |
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Chair: Chris Monroe, University of Maryland and JQI Room: Terrace |
Wednesday, June 6, 2012 10:30AM - 10:42AM |
H7.00001: Quantum simulation of the transverse field antiferromagnetic Ising model with trapped ions Simcha Korenblit, Wes Campbell, Emily Edwards, Zhexuan Gong, Dvir Kafri, Kihwan Kim, Rajibul Islam, Aaron Lee, Jacob Smith, Joseph Wang, Luming Duan, Jim Freericks, Jungsang Kim, Chris Monroe We simulate a long range quantum Ising model with a chain of Yb-171+ ions, with two ground states in the hyperfine manifold representing the spin-1/2 states. The Ising interactions are generated by phonon mediated stimulated Raman excitations, and can be tuned in strength and sign by selectively controlling the coupling to various vibrational normal modes. We have recently observed emergence of a quantum phase transition and ferromagnetism due to the interplay of Ising interactions and an effective transverse magnetic field. In our current effort, we simulate long range antiferromagnetic couplings which potentially lead to spin frustration, and investigate the nature of spin ordering as we vary the range of the interaction. We are also investigating the generation of more exotic Ising graphs, even in 2D, by controlling the spectrum of the Raman lasers. [Preview Abstract] |
Wednesday, June 6, 2012 10:42AM - 10:54AM |
H7.00002: Engineering 2D Ising Interactions in a Large (N$>$100) Ensemble of Trapped Ions Brian Sawyer, Joseph Britton, Adam Keith, Joseph Wang, James Freericks, Hermann Uys, Michael Biercuk, John Bollinger Experimental progress in atomic, molecular, and optical physics has enabled exquisite control over ensembles of cold trapped ions. We have recently engineered long-range Ising interactions in a two-dimensional, 1-mK Coulomb crystal of hundreds of $^{9}$Be$^{+}$ ions confined within a Penning trap. Interactions between the $^{9}$Be$^{+}$ valence spins are mediated via spin-dependent optical dipole forces (ODFs) coupling to transverse motional modes of the planar crystal. A continuous range of inverse power-law spin-spin interactions from infinite (1/r$^{0})$ to dipolar (1/r$^{3})$ are accessible by varying the ODF drive frequency relative to the transverse modes. The ions naturally form a triangular lattice structure within the planar array, allowing for simulation of spin frustration using our generated antiferromagnetic couplings. We report progress toward simulating the ferromagnetic/antiferromagnetic transverse quantum Ising Hamiltonians in this large ensemble. We also report spectroscopy, thermometry, and sensitive displacement detection ($\sim $100 pm) via entanglement of valence spin and drumhead oscillations. [Preview Abstract] |
Wednesday, June 6, 2012 10:54AM - 11:06AM |
H7.00003: Theory for adiabatic state evolution of a transverse field Ising model simulated in a Penning trap James Freericks, Adam Keith, C.-C. Joseph Wang We discuss the equilibrium positions and phonon modes of Be$^{9+}$ ions trapped in the NIST Penning trap and how one can use a laser-induced spin-dependent dipole force to generate a transverse field Ising model. Recent experiments have benchmarked the accuracy of the theory by measuring the average Ising spin-spin interaction and the transverse phonon mode frequencies and effective temperatures. Here we will discuss details about how one calculates the equilibrium positions, the phonon normal modes, and the theory behind the phonon mode thermometry. We will also discuss how a laser dipole force can be used to generate effective Ising spin-spin interactions and compare them to measurements in the case of weak coupling. Finally, we will discuss interesting prospects for new experiments both in analog quantum simulation and in phonon-spin entanglement. [Preview Abstract] |
Wednesday, June 6, 2012 11:06AM - 11:18AM |
H7.00004: A quantum phase transition in a quantum external field: The formation of a Schrodinger magnet Bogdan Damski, Marek Rams, Michael Zwolak Recent developments in manipulations of trapped ions allow for simulation of various spin models in ion chains (S. Korenblit et al., e-print arXiv:1201.0776). This motivates our work on novel types of quantum phase transitions, whose experimental studies could not have been performed in traditional condensed matter systems due to insufficient level of control. We focus on an Ising lattice undergoing a quantum phase transition in a quantum magnetic field. Such a field can be emulated by coupling the lattice to a central spin initially in a superposition state. We show that, by adiabatically driving such a system, one can prepare a quantum superposition of any two ground states of the Ising lattice. In particular, one can end up with the Ising lattice in a superposition of ferromagnetic and paramagnetic phases, a scenario with no analogue in prior studies of quantum phase transitions. Remarkably, the resulting magnetization of the lattice encodes the position of the critical point and universal critical exponents, as well as the ground state fidelity. The model that we study can be emulated in an ion chain. This research is summarized in M.M. Rams, M. Zwolak, and B. Damski, arXiv:1201.1932 (2012). [Preview Abstract] |
Wednesday, June 6, 2012 11:18AM - 11:30AM |
H7.00005: Ion-photon entanglement and state mapping in an optical cavity Tracy E. Northup, Andreas Stute, Bernardo Casabone, Birgit Brandst\"atter, Konstantin Friebe, Rainer Blatt Quantum networks require a coherent interface between quantum states of light and matter. In order to realize such an interface, we couple a single calcium ion to two orthogonal polarization modes of a high-finesse optical resonator. Trapped ions have the advantage of well-developed techniques for coherent state manipulation and readout, while the cavity setting enables an efficient mapping process. We demonstrate on-demand, high-fidelity entanglement between an ion and a photon. Both amplitude and phase of the entangled state are fully tunable due to the use of a bichromatic Raman field. In contrast to previous work, the phase of the entangled state is independent of the photon detection time. In a second step toward cavity-based quantum networks, an ion is prepared in a superposition state, and this state is mapped coherently onto a photon, with characterization via process tomography. Finally, prospects for single-ion strong coupling are discussed. [Preview Abstract] |
Wednesday, June 6, 2012 11:30AM - 11:42AM |
H7.00006: Integrated Cavity QED in a linear Ion Trap Chip for Enhanced Light Collection Francisco Benito, Sterk Jonathan, Tabakov Boyan, Raymond Haltli, Chris Tigges, Daniel Stick, Matthew Balin, David Moehring Realizing a scalable trapped-ion quantum information processor may require integration of tools to manipulate qubits into trapping devices. We present efforts towards integrating a 1 mm optical cavity into a microfabricated surface ion trap to efficiently connect nodes in a quantum network. The cavity is formed by a concave mirror and a flat coated silicon mirror around a linear trap where ytterbium ions can be shuttled in and out of the cavity mode. By utilizing the Purcell effect to increase the rate of spontaneous emission into the cavity mode, we expect to collect up to 13{\%} of the emitted photons. This work was supported by Sandia's Laboratory Directed Research and Development (LDRD) and the Intelligence Advanced Research Projects Activity (IARPA). Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the US Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. [Preview Abstract] |
Wednesday, June 6, 2012 11:42AM - 11:54AM |
H7.00007: Ultrafast spin-motion entanglement and interferometry in single atomic qubits Crystal Senko, Jonathan Mizrahi, Wesley C. Campbell, Kale G. Johnson, Charles W.S. Conover, Christopher Monroe We report entanglement between the hyperfine spin state and motional dynamics of a single atom on a timescale of 15 ns. We extract single pulses from a picosecond mode-locked laser and split them into short pulse trains tailored to create the desired spectrum by tuning the relative delays and frequency shifts appropriately. The resulting interaction imparts a momentum transfer of $2\hbar k$ to each of the two spin states in opposite directions. We apply pairs of momentum kicks to create an interferometer and probe the collapse and revival of spin coherence as the motional wavepacket is split and recombined. This technique holds promise for applications such as interferometry [1] and scalable entangling gates [2,3]. \\[4pt] [1] J.F. Poyatos et al., PRA 54, 1532 (1996)\\[0pt] [2] J.J. Garcia-Ripoll et al., PRL 91, 157901 (2003)\\[0pt] [3] L.-M. Duan, PRL 93, 100502 (2004). [Preview Abstract] |
Wednesday, June 6, 2012 11:54AM - 12:06PM |
H7.00008: Multi-pulse compensation sequences for quantum information processing with trapped ions S. Charles Doret, True Merrill, Kenneth Brown, Alexa Harter Now that the basic components of a trapped ion quantum information processor have all been demonstrated, many recent experiments have focused on scaling systems to larger numbers of qubits to permit the execution of classically intractable quantum algorithms/simulations. Microfabricated surface electrode ion traps offer one avenue for scaling to more qubits, allowing for the stable trapping of long chains of many ions. However, the small spacing between ions required for strong coupling makes the single-qubit laser addressing needed for arbitrary gate operations extremely challenging. Although such addressing is possible using tightly focused lasers, focusing requires cumbersome multi-element lenses and is highly sensitive to pointing instabilities. Transporting the target ion away from its neighbors is another option but is time consuming and may cause motional heating. Multi-pulse passband compensation sequences offer an appealing alternative that can simultaneously correct for errors in pulse amplitude and duration while reducing the effects of laser bleed-through on to neighboring ions. Here we report on experimental progress toward the use of such pulse sequences for individual addressing of $^{40}$Ca$^{+}$ ions without the use of complicated optics. [Preview Abstract] |
Wednesday, June 6, 2012 12:06PM - 12:18PM |
H7.00009: Trapping ions in a segmented ring trap B.P. Tabakov, J.D. Sterk, F. Benito, R. Haltli, C.P. Tigges, D. Stick, M.G. Blain, D.L. Moehring We demonstrate robust trapping in an ion trap which has a ring shaped RF node. Ions are back-side loaded through a small $10~\mu m$ diameter loading hole and we have demonstrated thousands of complete circuits around the trap. Each circuit passes through 44 trapping zones; the trap has 89 independent DC control electrodes. Measurements of the tangential secular frequency indicate a weak dependence on the RF and the loading hole. The ion trap is fabricated using four metal layers, allowing for the inner islanded electrodes to be electrically routed underneath the trap with negligible effects on the trapped ions. \\[4pt] This work was supported by the Intelligence Advanced Research Projects Activity (IARPA). Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the US Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. [Preview Abstract] |
Wednesday, June 6, 2012 12:18PM - 12:30PM |
H7.00010: ABSTRACT WITHDRAWN |
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