Bulletin of the American Physical Society
APS March Meeting 2011
Volume 56, Number 1
Monday–Friday, March 21–25, 2011; Dallas, Texas
Session B29: Advances in Ion Trap Quantum Computation |
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Sponsoring Units: GQI Chair: Jungsang Kim, Duke University Room: C148 |
Monday, March 21, 2011 11:15AM - 11:51AM |
B29.00001: Trapped ion arrays for quantum simulation Invited Speaker: Trapped ions have been used to demonstrate a broad range of quantum information processes with high fidelity\footnote{D. Leibfried, D. J. Wineland, R. B. Blakestad, J. J. Bollinger, J. Britton, J. Chiaverini, R. J. Epstein, W. M. Itano, J. D. Jost, E. Knill, C. Langer, R. Ozeri, R. Reichle, S. Seidelin, N. Shiga, and J. H. Wesenberg, Hyperfine Interactions \textbf{174}, 1 - 7 (2007). Proc. 4th Int. Conf. Trapped Charged Particles and Fundamental Physics (TCP 2006), Parksville, Canada 3-8 Sept. 2006.} and are an obvious choice for quantum simulations. Several quantum simulations have already been demonstrated with ions.\footnote{K. Kim, M.-S. Chang, S. Korenblit, R. Islam, E. E. Edwards, J. K. Freericks, G.-D. Lin, L.-M. Duan, and C. Monroe, \textit{Nature} \textbf{465}, 590 (2010).}$^,$\footnote{E. E. Edwards, S. Korenblit, K. Kim, R. Islam, M.-S. Chang, J. K. Freericks, G.-D. Lin, L.-M. Duan, and C. Monroe, Phys. Rev. \textbf{B 82}, 060412 (2010).} The present goal is to simulate quantum systems that cannot be achieved with classical computation using more than 20 ions. It is challenging to assemble more than 20 ions in suitable arrays for quantum simulation of arbitrary model systems. Present ion trap based quantum simulations with up to 20 ions are now in progress. This talk describes ion trap micro-fabrication techniques and designs that have the potential to increase the number of coupled ions to the range between 50 and 100 ions. High precision ion traps are fabricated using silicon VLSI techniques on silicon wafers with aluminum electrodes.\footnote{D.R. Leibrandt, J. Labaziewicz, R.J. Clark, I.L. Chuang, R.J. Epstein, C. Ospelkaus, J.H. Wesenberg, J.H. Bollinger, D. Leibfried, D. Wineland, D. Stick, J. Sterk, C. Monroe, C.-S. Pai, Y. Low, R. Frahm, and R.E. Slusher, Quant. Inf. Comp. \textbf{9}, 901 (2009)} At the Georgia Tech Research Institute we are designing, fabricating and testing ion trap arrays that will contain and accurately control at least 50 ions in linear chains of equally spaced ions. Large numbers of equally spaced ions have recently been shown\footnote{G.-D. Lin, S.-L. Zhu, R. Islam, K. Kim, M.-S. Chang, S. Korenblit, C. Monroe, and L.-M. Duan, Europhys. Lett. \textbf{86}, 60004 (2009).} to be stable in anharmonic trap potentials that are easily obtained in the micro-fabricated traps. The limits on quantum simulation accuracy due to errors in the ion trap parameters will be discussed. [Preview Abstract] |
Monday, March 21, 2011 11:51AM - 12:03PM |
B29.00002: Laser-induced charging of microfabricated ion traps Guang Hao Low, Shannon X. Wang, Nathan Lachenmyer, Yufei Ge, Peter Herskind, Isaac L. Chuang Microfabricated ion traps are promising candidates for realizing large-scale quantum computers, but small trap sizes leads to increased sensitivity of the trapped ions to surface effects, including localized charging of the trap electrodes. Laser-induced charging on microfabricated ion traps is studied by monitoring the ion micromotion over a period of up to 20 minutes that a laser is incident on the trap. The ion is trapped 100~$\mu$m above the metal surface and the trap is operated at 6K. The lasers used are at 405, 460, and 674 nm, which are relevant atomic transitions in Sr+ ions, and the typical intensity at the trap is 10$^{35}$ photons/sec. The ion's micromotion signal is related to the number of charges created on the trap. A wavelength and material dependence of the charging behavior is observed: lasers at lower wavelengths cause more charging, and aluminum exhibits more charging than copper or gold. We describe the charging dynamic based on a rate equation approach. [Preview Abstract] |
Monday, March 21, 2011 12:03PM - 12:15PM |
B29.00003: Superconducting microfabricated ion traps Shannon X. Wang, Yufei Ge, Jaroslaw Labaziewicz, Eric Dauler, Karl Berggren, Isaac L. Chuang We fabricate superconducting ion traps with niobium and niobium nitride and trap single $^{88}$Sr ions at cryogenic temperatures. The superconducting transition is verified and characterized by measuring the resistance and critical current using a 4-wire measurement on the trap structure, and observing change in the rf reflection. The lowest observed heating rate is 2.1(3) quanta/sec at 800~kHz at 6~K and shows no significant change across the superconducting transition, suggesting that anomalous heating is primarily caused by noise sources on the surface. This demonstration of superconducting ion traps opens up possibilities for integrating trapped ions and molecular ions with superconducting devices. [Preview Abstract] |
Monday, March 21, 2011 12:15PM - 12:27PM |
B29.00004: Microfabricated surface trap for scalable ion-photon interfaces Peter Herskind, Shannon Wang, Molu Shi, Yufei Ge, Marko Cetina, Isaac Chuang The combination of high-finesse optical mirrors and ion traps is attractive for quantum light-matter interfaces, which represents an enabling resource for large-scale quantum information processing. We report on a scalable approach to ion-photon interfaces based on a surface electrode ion trap microfabricated on top of a highly reflective mirror. An aperture in the central electrode, directly below the ion, allows the mirror to interact with the ion. The integration of such mirrors is scalable as several mirror apertures may be added with no additional overhead for fabrication. Furthermore, the design provides a path for reaching the strong coupling regime of Cavity QED, where an ion-cavity system can be realized by adding a small concave mirror above the trap mirror. The quality of the mirror is not significantly compromised in the course of fabrication and we have measured an increase in losses for light at 422~nm at the level of 100~ppm. The functionality of the mirror has also been verified by light collection from, and imaging of, the ion $169\pm 4~\mu$m above the mirror. Despite its proximity, we find that the presence of the mirror does not perturb the trap. Trapping is stable with laser cooled ion lifetimes of several hours and we observe only minimal sensitivity to laser-induced charging. Furthermore, through operation of the trap in a cryostat at 15~K the heating rate of the ion is a the level of only 0.1~quanta/ms. [Preview Abstract] |
Monday, March 21, 2011 12:27PM - 12:39PM |
B29.00005: Ion crystal transducer for strong coupling between single ions and single photons Lucas Lamata, David Leibrandt, Isaac Chuang, Ignacio Cirac, Mikhail Lukin, Vladan Vuletic, Susanne Yelin A quantum interface between single photons and single ions in an ion crystal is proposed. The coupling between single photon and single particle is collectively enhanced via a collective internal ion state and a phonon state. Applications for this scheme include single-photon generation, a memory for a quantum repeater, and a deterministic photon-photon or photon-ion entangler. [Preview Abstract] |
Monday, March 21, 2011 12:39PM - 12:51PM |
B29.00006: Temperature driven structural phase transition for trapped ions Zhe-Xuan Gong, Guin-Dar Lin, Lu-Ming Duan A Wigner crystal formed with trapped ion can undergo structural phase transition, which is determined only by the mechanical conditions on a classical level. Instead of this classical result, we show that through consideration of quantum and thermal fluctuation, a structural phase transition can be solely driven by change of the system's temperature. We determine a finite-temperature phase diagram for trapped ions using the renormalization group method and the path integral formalism, and propose an experimental scheme to observe the predicted temperature-driven structural phase transition, which is well within the reach of the current ion trap technology. [Preview Abstract] |
Monday, March 21, 2011 12:51PM - 1:03PM |
B29.00007: Differential Stark shift measurement of clock states of Yb+ using an optical frequency comb Qudsia Quraishi*, David Hayes, David Hucul, Dzmitry Matsukevich, Shantanu Debnath, Susan Clark, Chris Monroe Quantum information processing with trapped ions has traditionally involved state preparation, manipulation (eg. quantum gates) and detection using CW lasers. Quantum gates implemented with ions typically involve optical Raman transitions between two atomic levels. An optical frequency comb, emitted by a pulsed laser, is an excellent tool for bridging atomic frequency differences. Previously, we demonstrated quantum gates and separately, ultrafast spin manipulation, using pulsed lasers [1,2]. Unlike the CW case, employing pulsed lasers has the marked advantage of both low spontaneous emission and low AC Stark shifts, because the high powers available from pulsed lasers allow for larger detunings from optical resonance. Here, we show both experimentally and theoretically the scaling of the differential Stark shift with detuning (6 THz to 20 THz) of the Raman fields, achieving values of 10$^{-3}$ of the Rabi frequency. [1] D. Hayes, et al., Phys. Rev. Lett. 104, 140501 (2010) [2] W. C. Campbell, et al., Phys. Rev. Lett. 105, 090502 (2010).~ *Currently NRC postdoc with SEDD, ARL, Adelphi, MD. Support: DARPA OLE under ARO contract, IARPA under ARO contract, NSF PIF Program, NSF PFC at JQI and *IC Postdoc administered by the NGA. [Preview Abstract] |
Monday, March 21, 2011 1:03PM - 1:15PM |
B29.00008: ``Tack'' ion trap for efficient photon collection. Chen-Kuan Chou, Gang Shu, Nathan Kurz, Thomas Noel, John Wright, Boris Blinov Trapped, laser-cooled atoms and ions produce intense fluorescence of the order 10$^{7}$ -- 10$^{8}$ photons per second. Detection of this fluorescence enables the efficient measurement of the quantum state of qubit based on the trapped atoms. Thus, it is desirable to collect a large fraction of the (isotropically emitted) photons to make the detection faster and more reliable. Additionally, efficient fluorescence collection can improve the speed and fidelity of remote ion entanglement and quantum gates. Refractive and reflective optics, as well as optical cavities, and, recently, bare multimode optical fibers have all been used to collect the trapped ion fluorescence with up to 10{\%} efficiency. Here we show a novel ion trap design that incorporates a high numerical aperture metallic spherical mirror as the integral part of the trap itself (the RF electrode) which enables up to 35{\%} solid angle collection of trapped ion fluorescence. The movable central needle-shaped electrode of this ``tack'' trap allows precise placement of the ion at the focus of the spherical mirror. We also study the properties of the images formed by the spherical mirror and comment on possible methods for aberration correction. Owning to the simplicity of its design, this trap structure can be adapted for mircofabrication and integration into more complex trap architectures. [Preview Abstract] |
Monday, March 21, 2011 1:15PM - 1:27PM |
B29.00009: Towards laser cooling of a LC-resonator via trapped ions Soenke Moeller, Nikos Daniilidis, Boyan Tabakov, Aaron Bradley, Hartmut Haeffner We will discuss our experimental progress towards coupling strings of trapped ions to an LC-resonator. The goal of our experiments is to cool the resonant mode of a superconducting high-quality resonant circuit to ultra-low temperatures. By continuously laser cooling a crystal of ions coupled to the circuit, energy is removed from the resonator. For quality factors on the order of 10$^5$, the time-scale of the environment-to-mode coupling, i.e. the time for the resonant mode of the LC-resonator to thermally equilibrate, can be on the order of a second. Thus, engineering an ion-resonator coupling of 10$\sim $kHz results in a reduction of the electronic temperature by four orders of magnitude as compared to the ambient temperature of the resonator. The expected temperatures below 1mK are extremely low approaching even the vibrational ground state of the oscillator mode, enabling novel quantum electronics applications in the solid state. [Preview Abstract] |
Monday, March 21, 2011 1:27PM - 1:39PM |
B29.00010: Micro-Fabricated Surface Electrode Y-Junction Ion Traps David Moehring, Matthew Blain, Robert Cook, Kevin Fortier, Raymond Haltli, Clark Highstrete, Daniel Stick, Chris Tigges We will present results of the design, operation, and performance of two different Y-Junction surface ion micro-traps fabricated at Sandia. Recent progress in the testing of the micro-traps will be highlighted, including the successful shuttling of single and multiple ions, ion-chain splitting and recombination, and the validation of simulations with experiments. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. [Preview Abstract] |
Monday, March 21, 2011 1:39PM - 1:51PM |
B29.00011: Emergent effective spin models in ion-trap-based quantum simulators Cheng-Ching Joseph Wang We show how effective spin models emerge from the interaction of laser light with the ions in a linear Paul trap. It has been shown that quantum Ising models can be studied by adiabatic state evolution in a transverse magnetic field which is ramped from large to small values. The standard proof involves and adiabatic elimination of the phonons in the Lamb-Dicke regime. We discuss here that such an elimination can be problematic due to the inherent entanglement between the spins and the phonons. If the magnetic field is ramped sufficiently fast, one can show that all quantum state probabilities measured along the Ising field axis are independent of the phonons. But if the field is ramped more slowly, then the phonons and spins become entangled. Nevertheless, the main effects are to change the spin entanglement of the quantum states rather than the probabilities of the different states in the wavefunction. We present numerical evidence to illustrate these points. [Preview Abstract] |
Monday, March 21, 2011 1:51PM - 2:03PM |
B29.00012: Individual addressing of trapped ions using a MEMS beam steering system Taehyun Kim, Caleb Knoernschild, Emily Mount, Stephen Crain, Rachel Noek, Daniel Gaultney, Peter Maunz, Jungsang Kim Implementation of single-qubit and two-qubit quantum gates in a long linear chain of trapped ions generally requires the manipulation of qubits stored in individual ions using a set of laser beams. Individual addressing has been demonstrated with acousto-optic and electro-optic deflectors, by using the Zeeman shift due to a magnetic field gradient, and by separating the ions. Microelectromechanical system (MEMS) technology offers an alternative approach using micromirrors to focus laser beams on individual ions. Advantages of this approach are its broadband optical performance and scalability to more beams and multiple dimensions. We report progress towards integrating a MEMS beam steering system with an Yb ion trap experiment. The MEMS system will direct an ultraviolet beam with waist of $\sim $1.5$\mu$m at the ions across a 20$\mu$m range. For a designed ion separation of 4um this allows addressing up to 5 ions. The far-detuned laser will induce an AC Stark shift on a single ion in the chain, and the induced phase shift can be measured by Ramsey spectroscopy. [Preview Abstract] |
Monday, March 21, 2011 2:03PM - 2:15PM |
B29.00013: Scalable micro-scale optics for planar ion traps True Merrill, Harley Hayden, Chien-Shing Pai, Rachel Noek, Jungsang Kim, Curtis Volin Efficient collection of fluorescence from atomic ions is required for fast high-fidelity measurement in ion trap quantum information processing. Conventional multi-element lens stacks can achieve photon collection efficiencies as high as 5\%, however these systems typically have restricted field-of-view and are not generally scalable to image large arrays of ions. We report the development and fabrication of planar traps with integrated micro-scale spherical mirrors with an expected 15\% collection efficiency. The mirror shape is controlled with a combination of silicon wet-processing and polishing techniques while maintaining a surface roughness below $\sigma_{RMS} < 10$ nm. The design allows for multiple integrated mirrors in a single chip allowing for the simultaneous measurement of many ions over a 10 mm object space. [Preview Abstract] |
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