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 J7: Quantum Computing II |
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Chair: Patricia Lee, Army Research Laboratory Room: Terrace |
Wednesday, June 6, 2012 2:00PM - 2:12PM |
J7.00001: Entanglement of ions in a uniformly-spaced chain using individual addressing and pulse shaping S. Debnath, T.A. Manning, T. Choi, B. Fields, C. Monroe We present progress towards entanglement of subsets of $^{171}$Yb$^{+}$ ions in a single uniformly-spaced chain using individual optical addressing and simple laser pulse shaping. A pulsed 355~nm laser drives Raman transitions to create a spin-dependent force on individual ions in the chain, where the collective ion motion facilitates the entanglement of the ions' spin states. By coupling to transverse phonon modes instead of axial modes, we will be less sensitive to thermal motion and ion heating, resulting in comparatively higher gate fidelities. Additionally, faster gate speeds are achievable by applying sequences of a few laser pulses at optimized intensities and detuning that couple to multiple modes of motion~[1,2]. \\[4pt] [1] G.-D. Lin, \textit{et al.} \emph{Europhys. Lett.} \textbf{86}, 60004 (2009)\\[0pt] [2] S-L Zhu, \textit{et al.}, \emph{Europhys. Lett.} \textbf{73}, 485-491 (2006) [Preview Abstract] |
Wednesday, June 6, 2012 2:12PM - 2:24PM |
J7.00002: Quantum Information Processing with Ytterbium Ions and a Frequency Comb in a Surface Trap Emily Mount, So-Young Baek, Daniel Gaultney, Stephen Crain, Rachel Noek, Peter Maunz, Jungsang Kim Microfabricated surface ion traps are one of the key components for building a trapped ion quantum information processor.These multi-segmented traps are fabricated using existing silicon processing technology and can provide the fields to store a chain of ions and shuttle ions within the trap structure. Using a surface trap microfabricated by Sandia National Laboratories [1] we trap individual Yb-171 ions and demonstrate fundamental quantum information processing primitives. Low light scatter from the trap and the use of photon arrival times during fluorescence state detection enables a state detection fidelity of 98\%. High fidelity rotations of the hyperfine clock state qubit have been performed using a resonant microwave field. Furthermore, we have realized single qubit rotations using Raman transitions driven by a repetition-rate stabilized frequency comb, a prerequisite for realizing motional gates with frequency combs [2]. Microelectromechanical systems (MEMS) mirrors will be used to focus Raman laser beams on individual ions in a chain to perform single qubit gates. MEMS beam steering systems can easily be scaled to multiple beams to realize two-ion gates between arbitrary ions in the chain.\\[4pt] [1] D Stick et al., arXiv:1008.0990v2 2010\\[0pt] [2] D Hayes et al., PRL 104(14)2010 [Preview Abstract] |
Wednesday, June 6, 2012 2:24PM - 2:36PM |
J7.00003: ABSTRACT WITHDRAWN |
Wednesday, June 6, 2012 2:36PM - 2:48PM |
J7.00004: ABSTRACT WITHDRAWN |
Wednesday, June 6, 2012 2:48PM - 3:00PM |
J7.00005: Adiabatic Quantum Computing with Neutral Atoms Aaron Hankin, Grant Biedermann, George Burns, Yuan-Yu Jau, Cort Johnson, Shanalyn Kemme, Andrew Landahl, Michael Mangan, L. Paul Parazzoli, Peter Schwindt, Darrell Armstrong We are developing, both theoretically and experimentally, a neutral atom qubit approach to adiabatic quantum computation. Using our microfabricated diffractive optical elements, we plan to implement an array of optical traps for cesium atoms and use Rydberg-dressed ground states to provide a controlled atom-atom interaction. We will develop this experimental capability to generate a two-qubit adiabatic evolution aimed specifically toward demonstrating the two-qubit quadratic unconstrained binary optimization (QUBO) routine. [Preview Abstract] |
Wednesday, June 6, 2012 3:00PM - 3:12PM |
J7.00006: Adiabatic Quantum Computing via the Rydberg Blockade Tyler Keating, Krittika Goyal, Ivan Deutsch We study an architecture for implementing adiabatic quantum computation with trapped neutral atoms. Ground state atoms are dressed by laser fields in a manner conditional on the Rydberg blockade mechanism, thereby providing the requisite entangling interactions. As a benchmark we study the performance of a Quadratic Unconstrained Binary Optimization (QUBO) problem whose solution is found in the ground state spin configuration of an Ising-like model. We model a realistic architecture, including the effects of magnetic level structure, with qubits encoded into the clock states of $^{133}$Cs, effective B-fields implemented through microwaves and light shifts, and atom-atom coupling achieved by excitation to a high-lying Rydberg level. Including the fundamental effects of photon scattering we find a high fidelity for the two-qubit implementation. [Preview Abstract] |
Wednesday, June 6, 2012 3:12PM - 3:24PM |
J7.00007: State Mapping and Unitary Transformations in the Cesium Hyperfine Ground Manifold Hector Sosa Martinez, Aaron Smith, Brian Anderson, Poul Jessen, Carlos Riofrio, Ivan Deutsch Quantum systems with Hilbert space dimension greater than two (qudits) provide an alternative to qubits as carriers of quantum information, and may prove advantageous for quantum information tasks if good laboratory tools for qudit manipulation and readout can be developed. We have successfully implemented a protocol for arbitrary quantum state-to-state mapping in the 16 dimensional hyperfine ground manifold of Cesium 133 atoms using only DC, rf and microwave magnetic fields to drive the atomic evolution. Experimentally we achieve a state-to-state average mapping fidelity of better than 99\%, averaged over a sample of randomly chosen initial and target states. Current work involves designing and implementing unitary transformations. We have successfully used the GRAPE algorithm to design unitary operators that can be implemented with the same experimental framework as state mapping. [Preview Abstract] |
Wednesday, June 6, 2012 3:24PM - 3:36PM |
J7.00008: Utilizing Doubly Excited States of Barium for Quantum Computation and Improved Quantum Control John Papaioannou, Chris H. Greene The existence of doubly excited perturbers in the alkali-earth atoms provides a rich spectrum of states with possible applications for quantum information storage. Using the framework of multichannel quantum defect theory, the bound state spectra with total angular momenta up to J=5 were calculated. Due to configuration mixing, these doubly excited perturbers can have significant Rydberg character to their wavefunctions. By tuning electric fields it is possible to induce transitions between perturbers and excited Rydberg states with higher orbital angular momenta. This not only allows the possibility of improved control in exciting to high-l Rydberg states but may also be utilized as possible qubit candidates. [Preview Abstract] |
Wednesday, June 6, 2012 3:36PM - 3:48PM |
J7.00009: Single qubit gates in a 3D array of neutral atoms Theodore A. Corcovilos, Yang Wang, Xiao Li, David S. Weiss, Jungsang Kim We present an approach to quantum computing using single Cs atoms in a cubic 5-$\mu$m spaced 3D optical lattice. After cooling the atoms to near their vibrational ground state (76\% ground state occupancy) using projection sideband cooling, we manipulate the state of individual atoms using the AC Stark shift induced by intersecting lasers and microwave pulses that are only resonant with the shifted atom. Here we demonstrate Rabi oscillations of a single atom in the center of the array and progress towards steering the beams to address the other atoms. Rapid steering of the lasers using micromirrors allows single-atom gates of $\sim$10 $\mu$s. This single-site addressing along with lattice polarization rotation will enable us to fill voids in the central region of the atom array by selectively moving individual atoms. Future work will couple adjacent qubits via the Rydberg blockade mechanism with expected two-qubit gate times of $\sim$100 ns. [Preview Abstract] |
Wednesday, June 6, 2012 3:48PM - 4:00PM |
J7.00010: Geometric quantum gates for an electron-spin qubit in a quantum dot Vladimir Malinovsky, Sergey Rudin A scheme to perform arbitrary unitary operations on a single electron-spin qubit in a quantum dot is proposed. The design is based on the geometrical phase acquired after a cyclic evolution by the qubit state. The scheme is utilizing ultrafast linearly-chirped pulses providing adiabatic excitation of the qubit states and the geometric phase is fully controlled by the relative phase between pulses. The analytic expression of the evolution operator for the electron spin in a quantum dot, which provides a clear geometrical interpretation of the qubit dynamics, is obtained. Using parameters of InGAN/GaN, GaN/AlN quantum dots we provide an estimate for the time scale of the qubit rotations and parameters of the external fields. Robustness of the proposed scheme against external noise is also discussed. [Preview Abstract] |
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