Bulletin of the American Physical Society
46th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 60, Number 7
Monday–Friday, June 8–12, 2015; Columbus, Ohio
Session H7: Focus Session: Mircrowave Control and Trap Design for Ion Trap Quantum Computation |
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Chair: Steven Olmschenk, Denison University Room: Delaware CD |
Wednesday, June 10, 2015 10:30AM - 11:00AM |
H7.00001: Adjustable Spin-Spin Interaction with $^{171}$Yb$^+$ ions and Addressing of a Quantum Byte Invited Speaker: Christof Wunderlich Trapped atomic ions are a well-advanced physical system for investigating fundamental questions of quantum physics and for quantum information science and its applications. When contemplating the scalability of trapped ions for quantum information science one notes that the use of laser light for coherent operations gives rise to technical and also physical issues that can be remedied by replacing laser light by microwave (MW) and radio-frequency (RF) radiation employing suitably modified ion traps. Magnetic gradient induced coupling (MAGIC) makes it possible to coherently manipulate trapped ions using exclusively MW and RF radiation. After introducing the general concept of MAGIC, I shall report on recent experimental progress using $^{171}$Yb$^+$ ions, confined in a suitable Paul trap, as effective spin-1/2 systems interacting via MAGIC. Entangling gates between non-neighbouring ions will be presented. The spin-spin coupling strength is variable and can be adjusted by variation of the secular trap frequency. In general, executing a quantum gate with a single qubit, or a subset of qubits, affects the quantum states of all other qubits. This reduced fidelity of the whole quantum register may preclude scalability. We demonstrate addressing of individual qubits within a quantum byte (eight qubits interacting via MAGIC) using MW radiation and measure the error induced in all non-addressed qubits (cross-talk) associated with the application of single-qubit gates. The measured cross-talk is on the order $10^{-5}$ and therefore below the threshold commonly agreed sufficient to efficiently realize fault-tolerant quantum computing. Furthermore, experimental results on continuous and pulsed dynamical decoupling (DD) for protecting quantum memories and quantum gates against decoherence will be briefly discussed. Finally, I report on using continuous DD to realize a broadband ultrasensitive single-atom magnetometer. [Preview Abstract] |
Wednesday, June 10, 2015 11:00AM - 11:30AM |
H7.00002: Implementation of microwave quantum logic towards developing a large scale ion trap quantum computer Invited Speaker: Winfried Hensinger To this point, entanglement operations on ion qubits have predominantly been performed using lasers. When scaling to larger qubit numbers however this becomes problematic due to the challenging engineering that might be required. The use of microwaves combined with a static magnetic field gradient overcomes this problem. I will present our work towards implementing high-fidelity entanglement gates using microwave radiation including the experimental demonstration of spin-motion entanglement, the demonstration of ground-state cooling using long-wavelength radiation and the first realization of driving motional sideband transitions with microwave dressed states. I will present a vision to scale this scheme to build a large scale quantum computer and present results concerning the development of ion microchips that can be used for this purpose. [Preview Abstract] |
Wednesday, June 10, 2015 11:30AM - 11:42AM |
H7.00003: Field-free junctions for surface electrode ion traps Robert Jordens, R. Schmied, M.G. Blain, D. Leibfried, D. Wineland Intersections between transport guides in a network of RF ion traps are a key ingredient to many implementations of scalable quantum information processing with trapped ions. Several junction architectures demonstrated so far are limited by varying radial secular frequencies, a reduced trap depth, or a non-vanishing RF field along the transport channel. We report on the design and progress in implementing a configurable microfabricated surface electrode Y-junction that employs switchable RF electrodes. An essentially RF-field-free pseudopotential guide between any two legs of the junction can be established by applying RF potential to a suitable pair of electrodes. The transport channel's height above the electrodes, its depth and radial curvature are constant to within 15\%. [Preview Abstract] |
Wednesday, June 10, 2015 11:42AM - 11:54AM |
H7.00004: Shortcuts to Adiabaticity in Transport of a Single Trapped Ion Shuoming An, Dingshun Lv, Adolfo del Campo, Kihwan Kim We report an experimental study on shortcuts to adiabaticity in the transport of a single 171Yb$+$ ion trapped in a harmonic potential. In these driving schemes, the application of a force induces a nonadiabatic dynamics in which excitations are tailored so as to preserve the ion motional state in the ground state upon completion of the process. We experimentally apply the laser induced force and realize three different protocols: (1) a transitionless driving with a counterdiabatic term out of phase with the displacement force [1], (2) a classical protocol assisted by counterdiabatic fields in phase with the main force [2], (3) and an engineered transport protocol based on the Fourier transform of the trap acceleration [3]. We experimentally compare and discuss the robustness of these protocols under given experimental limitations such as trap frequency drifts. \\[4pt] [1] M. V. Berry, J. Phys. A: Math. Theor. 42 (2009).\\[0pt] [2] S. Deffner, C. Jarzynski, A. Campo, Phys. Rev. X 4, 021013 (2014).\\[0pt] [3] D. Gu\'ery-Odelin and J. G. Muga, Phys. Rev. A, 90, 063425 (2014). [Preview Abstract] |
Wednesday, June 10, 2015 11:54AM - 12:06PM |
H7.00005: Motional Ion Heating Rate Measurements over a Range of Trap Frequencies and Temperatures Colin Bruzewicz, Robert McConnell, Jeremy Sage, John Chiaverini Anomalous motional heating limits high-fidelity two-qubit gate operations in large-scale trapped-ion quantum computation. To examine the possible mechanisms driving this process, we present detailed measurements of the heating rate of a single trapped ion over a range of trap frequencies and temperatures. We compare these results to predictions given by available theoretical electric-field noise models and constrain a subset of these models based on the observed trap frequency and temperature scaling interdependence. Additionally, we report on recent efforts to mitigate motional state heating with electrode surface treatments, such as \textit{in situ} local trap chip baking and plasma cleaning. [Preview Abstract] |
Wednesday, June 10, 2015 12:06PM - 12:18PM |
H7.00006: Nonlinear dynamics in a surface-electrode multipole ion trap Robert Clark, Mark Maurice, Dylan Green The surface electrode multipole ion trap (Appl. Phys. B \textbf{113} 171 (2013)) allows one to realize a highly symmetric, yet anharmonic, confining potential for a single charged particle. We present a detailed model of such a trap, and measurements demonstrating the nonlinear character of the trap through the observation of frequency upconversion in the (classical) motion of a single trapped sugar particle. We will discuss extending these measurements to atomic-scale systems, as well as possible applications to mass spectrometry, quantum chaos, and quantum information science. [Preview Abstract] |
Wednesday, June 10, 2015 12:18PM - 12:30PM |
H7.00007: A hybrid ion trap in a three-dimensional geometry Ye Wang, Dahyun Yum, Kuan Zhang, Shuoming An, Kihwan Kim We develop a three-dimensional (3D) monolithic ion trap that has the advantages of both 3D geometry, i.e., having a deep confining potential and surface trap, i.e., containing multiple zones for scaling up, no uncertainty between design and manufacture. The trap is fabricated by gold coating on a single layer of alumina plate sculpted by laser-machining technology. The axial trap frequencies are in the range from 230 kHz to 850 kHz with the average dc voltages from 20 V to 75V and the radial frequencies lie in 3 MHz with 3.5W input power of 40 MHz radio-frequency, which is well in agreement with numerical simulations. We successfully load Yb and Ba ions together and report the progress of the hybrid quantum operation with them. [Preview Abstract] |
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