Bulletin of the American Physical Society
2007 APS March Meeting
Volume 52, Number 1
Monday–Friday, March 5–9, 2007; Denver, Colorado
Session D2: Ion Traps for Scalable Quantum Computation |
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Sponsoring Units: GQI Chair: Lorenza Viola, Dartmouth College Room: Colorado Convention Center Four Seasons 4 |
Monday, March 5, 2007 2:30PM - 3:06PM |
D2.00001: Architectural Design Issues for Reliable Trapped Ion Quantum Computers Invited Speaker: Central to the design of large-scale quantum computers is the fact that reliable quantum systems must explicitly and actively deal with relatively large component failure rates during operation. A quantum computing system must thus attain reliability by encoding operations with unreliable components such that faults can be detected and corrected, despite occasional failures induced by ubiquitous quantum noise. Accomplishing this requires more than just high gate fidelities, however, as two recent interesting results highlight. First, universal quantum computation on standard stabilizer quantum codes is impossible using only transversal gates, those which limit error propagation; it turns out non-transversal steps such as teleportation are necessary. Second, the overall reliability of trapped ion and other quantum computing schemes will ultimately be limited not by gate or measurement fidelities, but very likely, by the fidelity of movement and waiting operations, due to the necessity of non-transversal gates. These results are presented, together with implications for architectural design requirements. [Preview Abstract] |
Monday, March 5, 2007 3:06PM - 3:42PM |
D2.00002: Quantum information processing and quantum-limited metrology using trapped ions at NIST. Invited Speaker: With the use of atomic ions confined in a multi-zone array, we implement simple quantum algorithms and study the problems in scaling such a device to tens of qubits [1]. Current work is devoted to better control of classical parameters such as laser intensity, suppression of heating from ambient fluctuating electric fields, and studying limitations caused by more fundamental sources of decoherence, such as spontaneous emission. Along with other groups, we are studying ways to increase the number of trap zones; in particular, we concentrate on a surface-electrode multi-zone geometry. Although a general purpose quantum computer appears to be a distant goal, simple applications of quantum information processing methods enable new techniques for spectroscopy and efficient quantum detection. [1] Current research in collaboration with D. Leibfried, J. Amini, J. C. Bergquist, R. B. Blakestad, J. J. Bollinger, J. Britton, K. Brown, R. J. Epstein, D. B. Hume, W. M. Itano, J. D. Jost, E. Knill, C. Langer, R. Ozeri, T. Rosenband, S. Seidelin, N. Shiga, and J. H. Wesenberg. [Preview Abstract] |
Monday, March 5, 2007 3:42PM - 4:18PM |
D2.00003: Ion Trap Quantum Networks Invited Speaker: Trapped atomic ions are among the most promising candidates for a future quantum information processor, with each ion storing a single quantum bit (qubit) of information.~ Trapped ion qubits enjoy an unrivaled level of quantum coherence, and small numbers of ions can be entangled through a suitable interaction with optical fields.~ The next generation experiments will transport and distribute trapped ion qubits to generate truly large-scale entangled quantum states.~ Several approaches for networking trapped ion qubits will be discussed, along with state-of-the-art experimental progress.~ This includes the use of phonons between ions in a Coulomb crystal, the physical shuttling of ions throughout complex and microfabricated ion trap structures, the coupling of remotely-located ions through a photonic coupling, and perhaps even the use of a cold (neutral) atomic gas. [Preview Abstract] |
Monday, March 5, 2007 4:18PM - 4:54PM |
D2.00004: Scalable Designs for Planar Ion Trap Arrays Invited Speaker: Recent progress in quantum operations with trapped ion qubits has been spectacular for qubit counts up to approximately ten ions. Two qubit quantum gates, quantum error correction, simple quantum algorithms and entanglement of up to 8 qubits have been demonstrated by groups including those at NIST, University of Michigan, University of Innsbruck and Oxford. Interesting problems in quantum information processing including quantum simulations of condensed matter systems and quantum repeaters for long distance quantum communication systems require hundreds or thousands of qubits. Initial designs for an ion trap ``Quantum CCD'' using spatially multiplexed planar ion traps\footnote{D. Kielpinski, C. Monroe, and D.J. Wineland, ``Architecture for a large-scale ion-trap quantum computer,'' Nature, Vol.417, pp.709--711, (2002).} as well as initial experiments\footnote{S. Seidelin, J. Chiaverini, R. Reicle, J. J. Bollinger, D. Leibfried, J. Briton, J. H. Wesenberg, R. B. Blakestad, R. J. Epstein, D. B. Hume, J. D. Jost, C. Langer, R. Ozeri, N. Shiga, and D. J. Wineland, ``Amicrofabricated surface-electrode ion trap for scalable quantum informtion processing,'' quant-ph/0601173, (2006).} using planar ion traps are promising routes to scaling up the number of trapped ions to more interesting levels. We describe designs\footnote{J. Kim, S. Pau, Z. Ma, H.R. McLellan, J.V. Gates, A. Kornblit, and R.E. Slusher, ``System design for large-scale ion trap quantum information processor,'' Quantum Inf. Comput., Vol 5, pp 515--537, (2005).} for planar ion traps fabricated using silicon VLSI techniques. This approach allows the control voltages required for the moving and positioning the ions in the array to be connected vertically through the silicon substrate to underlying CMOS electronics. We have developed techniques that allow the ion trap structures to be fabricated monolithically on top of the CMOS electronics. The planar traps have much weaker trapping depths than the more conventional multi-level traps. However, the trap depths are still adequate for trapping hot ions from many ion sources. The planar traps also involve more complex configurations for laser cooling and micromotion control. Initial solutions to these problems will be presented. Laser access to the ions can be provided by laser beams grazing the trap surface or by using vertical slots through the trap chip. We will also discuss limits imposed by power dissipation and ion transport through trap junctions (e.g. crosses and Ys). We have fabricated these VLSI based traps in a number of configurations. Initial fabrication and packaging challenges will be discussed. [Preview Abstract] |
Monday, March 5, 2007 4:54PM - 5:30PM |
D2.00005: Quantum Simulations in Ion Traps Invited Speaker: When Richard Feynman famously proposed a quantum computer, his intended application was to simulate quantum dynamical systems. This is a hard problem because as the number of elements of a quantum system linearly increases, the complexity of the equations modeling it grows exponentially. Feynman's proposed solution to this problem was to simulate one quantum mechanical system with another. Such quantum simulators can solve only a limited set of problems, but building one would represent an important milestone in the road to universal quantum computation.~ At LANL we use an array of strontium ions confined in a linear rf trap to build a multi-body quantum simulator. Each ion simulates a single spin system, while Coulomb and optical forces simulate spin-spin interactions and magnetic fields. This system can simulate the most basic models of condensed matter physics, the Ising model and the Heisenberg XY model, in addition to more complex physical systems. We have modeled the basic interactions in this system and are starting to demonstrate the interactions central to the simulations. [Preview Abstract] |
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