Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session M34: Focus Session: AMO Quantum Information Processing: Ion Trapping Technologies |
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Sponsoring Units: GQI DAMOP Chair: L. Paul Parazzoli, Sandia National Laboratories Room: 704 |
Wednesday, March 5, 2014 11:15AM - 11:51AM |
M34.00001: Reducing Motional Decoherence in Ion Traps with Surface Science Methods Invited Speaker: Hartmut Haeffner Many trapped ions experiments ask for low motional heating rates while trapping the ions close to trapping electrodes. However, in practice small ion-electrode distances lead to unexpected high heating rates. While the mechanisms for the heating is still unclear, it is now evident that surface contamination of the metallic electrodes is at least partially responsible for the elevated heating rates. I will discuss heating rate measurements in a microfabricated surface trap complemented with basic surface science studies. We monitor the elemental surface composition of the Cu-Al alloy trap with an Auger spectrometer. After bake-out, we find a strong Carbon and Oxygen contamination and heating rates of 200 quanta/s at 1 MHz trap frequency. After removing most of the Carbon and Oxygen with Ar-Ion sputtering, the heating rates drop to 4 quanta/s. Interestingly, we still measure the decreased heating rate even after the surface oxidized from the background gas throughout a 40-day waiting time in UHV. [Preview Abstract] |
Wednesday, March 5, 2014 11:51AM - 12:03PM |
M34.00002: Multiparicle Entanglement in one step Tarun Dutta In this presentation, I will show how the linear ramp dynamics of phonons in a one-dimensional trapped ion system can be used for both generating multiparticle entangled states and motional state cooling of a string of trapped ions where all the trapped ions are prepared in a state of transverse motional mode. These phonons are well known to be described by an effective Bose Hubbard model where the onsite potential of this model is induced by an optical dipole potential which can be created by an off-resonant standing wave to individual ion. I will present a specific ramping protocol which involves a site specific dynamical tuning of the onsite potential of the model leads to generate entangled state and to achieve transverse motional state cooling without involving electronic states of the ions.\\[4pt] [1] T. Dutta, M. Mukherjee and K. Sengupta, Phys. Rev. Lett {\bf 111},170406 (2013).\\[0pt] [2] T. Dutta, M. Mukherjee and K. Sengupta, Phys. Rev. A {\bf 85}, 063401 (2012).\\[0pt] [3] D. Porras and J.I. Cirac, Phys. Rev. Lett.{\bf 92}, 207901 (2004). [Preview Abstract] |
Wednesday, March 5, 2014 12:03PM - 12:15PM |
M34.00003: Ion Motion Control and Heating Measurements in a Y Junction Surface Electrode Trap Gang Shu, Grahame Vittorini, Curtis Volin, Kenneth Brown Trapped atomic ions have demonstrated all the basic quantum operations necessary to implement quantum computation. Micro-fabricated surface electrode ion traps are a promising tool for implementing the scalable Kielpinski-Monroe-Wineland (KMW) architecture [1]. In the KMW scheme, trapped ions are held in small chains and communication between chains is performed by shuttling ions. Here we present our measurements of shuttling operations on a Sandia Y-junction trap [2] over a two year period. We have measured the ion heating after an adiabatic linear shuttling and after transport through the junction. The low linear shuttling heating is consistent with adiabatic motion. The high heating after crossing the junction indicates that sympathetic cooling will be required to perform high-fidelity two qubit operations. [1] D. Kielpinski, C. Monroe, and D. J. Wineland, Nature \textbf{417}, 709, (2002) [2] D. L. Moehring, C. Highstrete, D. Stick, K. M. Fortier, R. Haltli, C. Tigges, and M. G. Blain, New J. Phys. \textbf{13}, 075018, (2011) [Preview Abstract] |
Wednesday, March 5, 2014 12:15PM - 12:27PM |
M34.00004: Microwave quantum logic spectroscopy and control of molecular ions Molu Shi, Peter Herskind, Michael Drewsen, Isaac Chuang A general method for rotational microwave spectroscopy and control of polar molecular ions via direct microwave addressing is considered. Our method makes use of spatially varying ac Stark shifts, induced by far off-resonant, focused laser beams to achieve an effective coupling between the rotational state of a molecular ion and the electronic state of an atomic ion. In this setting, the atomic ion is used for read-out of the molecular ion state, in a manner analogous to quantum logic spectroscopy based on Raman transitions. In addition to high-precision spectroscopy, this setting allows for rotational ground state cooling, and can be considered as a candidate for the quantum information processing with polar molecular ions. All elements of our proposal can be realized with currently available technology. [Preview Abstract] |
Wednesday, March 5, 2014 12:27PM - 12:39PM |
M34.00005: Entangling spin-spin interactions of ions in individually controlled potential wells Andrew Wilson, Yves Colombe, Kenton Brown, Emanuel Knill, Dietrich Leibfried, David Wineland Physical systems that cannot be modeled with classical computers appear in many different branches of science, including condensed-matter physics, statistical mechanics, high-energy physics, atomic physics and quantum chemistry. Despite impressive progress on the control and manipulation of various quantum systems, implementation of scalable devices for quantum simulation remains a formidable challenge. As one approach to scalability in simulation, here we demonstrate an elementary building-block of a configurable quantum simulator based on atomic ions. Two ions are trapped in separate potential wells that can individually be tailored to emulate a number of different spin-spin couplings mediated by the ions' Coulomb interaction together with classical laser and microwave fields. We demonstrate deterministic tuning of this interaction by independent control of the local wells and emulate a particular spin-spin interaction to entangle the internal states of the two ions with 0.81(2) fidelity. Extension of the building-block demonstrated here to a 2D-network, which ion-trap micro-fabrication processes enable, may provide a new quantum simulator architecture with broad flexibility in designing and scaling the arrangement of ions and their mutual interactions. [Preview Abstract] |
Wednesday, March 5, 2014 12:39PM - 12:51PM |
M34.00006: A Graphene-Coated Ion Trap for Electric Field Noise Suppression Amira Eltony, Hyesung Park, Shannon Wang, Jing Kong, Isaac Chuang Trapped ions have proven to be effective quantum bits; but increasing electric field noise as traps are miniaturized limits gate fidelity and progress towards a large-scale quantum computer. Removing contamination from surfaces is important for noise suppression; but cleaning techniques like argon ion bombardment are difficult to integrate with current systems and are too harsh for traps incorporating optical devices. We investigate an alternative solution: a protective coating against surface contamination. We fabricate copper traps with a graphene passivation layer and characterize them with single ions. Surprisingly, we find worse noise performance than for an uncoated metal trap. [Preview Abstract] |
Wednesday, March 5, 2014 12:51PM - 1:03PM |
M34.00007: Measurement Scheme with 171Yb+ Chains in a Microfabricated Ion Trap Daniel Gaultney, Rachel Noek, Geert Vrijsen, Emily Mount, Stephen Crain, Soyoung Baek, Jungsang Kim Trapped ions are promising candidates for implementing a scalable quantum computing system. We consider a quantum information processor implemented in an ion chain, where a multi-qubit gate between ions is executed using the transverse modes of ion motion. Quantum error correction requires that the states of data qubits be maintained during the initialization and readout of ancilla qubits. Such procedures require the ability to collect light from individual fluorescing ions without resonantly exciting other ions in the system. We describe an ion measurement protocol that uses shuttling to separate the ions being detected from the rest of the chain in order to decrease the resonant crosstalk between measured and unmeasured qubits. We will discuss experimental progress towards the implementation of this scheme in a microfabricated surface trap where scattered photons are collected using a high numerical aperture lens, and characterize the impact of resonant scattering from the measured qubits on the remaining qubits in the ion chain. A similar isolation scheme is required for the generation of heralded entanglement between two ion chains. [Preview Abstract] |
Wednesday, March 5, 2014 1:03PM - 1:15PM |
M34.00008: Photon extraction and conversion for scalable ion-trap quantum computing Susan Clark, Francisco Benito, Hayden McGuinness, Daniel Stick Trapped ions represent one of the most mature and promising systems for quantum information processing. They have high-fidelity one- and two-qubit gates, long coherence times, and their qubit states can be reliably prepared and detected. Taking advantage of these inherent qualities in a system with many ions requires a means of entangling spatially separated ion qubits. One architecture achieves this entanglement through the use of emitted photons to distribute quantum information - a favorable strategy if photon extraction can be made efficient and reliable. Here I present results for photon extraction from an ion in a cavity formed by integrated optics on a surface trap, as well as results in frequency converting extracted photons for long distance transmission or interfering with photons from other types of optically active qubits. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U. S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. [Preview Abstract] |
Wednesday, March 5, 2014 1:15PM - 1:27PM |
M34.00009: Operation of a planar-electrode ion trap array with adjustable RF electrodes Muir Kumph, Philip Holz, Kirsten Langer, Michael Niedermayr, Kirill Lakhmanskiy, Michael Brownnutt, Rainer Blatt One path to scaling-up trapped atomic ions for large-scale quantum computing and simulation is to create a two-dimensional array of ion traps in close proximity to each other. A method to control the interactions between nearest neighboring ions is demonstrated and characterized here using an adjustable radio-frequency (RF) electrode between trapping sites. A printed circuit board planar-electrode ion trap is demonstrated, trapping laser-cooled $^{40}$Ca$^+$\, ions. RF shuttling and secular-frequency adjustment are shown as a function of the power applied to the addressed RF electrode. The trapped ion's heating rate is measured via a fluorescence recooling method. [Preview Abstract] |
Wednesday, March 5, 2014 1:27PM - 1:39PM |
M34.00010: Microfabricated Surface Trap and Cavity Integration for High Fidelity State Detection and Photon Collection from Trapped Ions. Andre Van Rynbach, Geert Vrijsen, Dan Gaultney, Jungsang Kim Atomic ions trapped in microfabricated traps can provide a useful resource for quantum information processing. Traditional approaches to qubit state detection using state dependent fluorescence utilize refractive lenses or reflective optics to direct scattered photons to the detector. Here we show progress towards a new method which can drastically enhance the fidelity and speed of qubit state detection by using the interaction between a trapped ion and an optical field in a cavity. Our experiment uses a concentric cavity geometry with a surface trap fabricated on a mirror which is highly reflective at UV wavelengths for $^{171}$Yb$^+$ ions. Using this system, we show that it is feasible to reduce the qubit measurement time to that comparable to single qubit gate times (~1$\mu$s), and the measurement errors down to the $10^{-5}$ range. Furthermore, this system can be used for enhanced photon collection and remote ion entanglement. We describe the design and fabrication of the traps used in the cavity system, and report the experimental progress towards the cavity realization. [Preview Abstract] |
Wednesday, March 5, 2014 1:39PM - 1:51PM |
M34.00011: Measurement of the magnetic interaction between two electrons Shlomi Kotler, Nitzan Akerman, Nir Navon, Yinnon Glickman, Roee Ozeri In this talk we will report on the first measurement of the magnetic interaction between two electronic spins. While the dipolar magnetic interactions between different spin systems, such as an electron and its nucleus or several multi-electron spin complexes, were experimentally studied, the magnetic interaction between two isolated electronic spins was never observed. We will explain why columb exchange forces on the one hand, and magnetic field noise on the other hand, make the electron-electron magnetic interaction measurement a challenging one. This challenge was resolved by the use of Quantum Information techniques. In our experiment, we used the ground state valence electrons of two $^{88}Sr^+$ ions, co-trapped in an electric Paul trap and separated by more than two micrometers. We measured a weak, millihertz scale, magnetic interaction between their electronic spins, in the presence of magnetic noise that was six orders of magnitude larger than the respective magnetic fields the electrons apply on each other. Spin dynamics was restricted to a Decoherence Free Subspace where a coherent evolution of 15 s led to spin-entanglement. Finally, by varying the separation between the two ions, we were able to recover the cubic distance dependence of the interaction [Preview Abstract] |
Wednesday, March 5, 2014 1:51PM - 2:03PM |
M34.00012: Dissipative production of a maximally entangled steady state Yiheng Lin, John Gaebler, Florentin Reiter, Ting Rei Tan, Ryan Bowler, Anders S{\O}rensen, Dietrich Leibfried, Dave Wineland We combine unitary processes with engineered dissipation into a zero-temperature bath to deterministically produce and stabilize an approximate Bell state of two trapped-ion qubits independent of their initial state [arXiv:1307.4443]. We implement the process on a $^9$Be$^+$-$^{24}$Mg$^+$-$^{24}$Mg$^+$-$^9$Be$^+$ four-ion chain in a linear radio-frequency Paul trap. The two $^9$Be$^+$\% ions serve as qubit ions while the two $^{24}$Mg$^+$ ions are used for sympathetic cooling as the zero-temperature bath. We simultaneously apply a combination of a unitary process consists of microwave and laser fields on $^9$Be$^+$ ions, and dissipative processes of optical pumping on $^9$Be$^+$\% ions and sympathetic cooling on $^{24}$Mg$^+$ ions. We realize maximally entangled steady states with a fidelity of F = 0.75(3). We also demonstrate that a sequential stepwise application of unitary and dissipative process can speed up the dynamics of the scheme and achieve a fidelity of F = 0.89(2) after approximately 30 repetitions. In both cases, the errors can be attributed to known experimental imperfections. [Preview Abstract] |
Wednesday, March 5, 2014 2:03PM - 2:15PM |
M34.00013: Quantum synchronization of quantum van der Pol oscillators with trapped ions Tony Lee, Hossein Sadeghpour Van der Pol oscillators are prototypical driven-dissipative oscillators that have been used to study synchronization phenomena in classical systems. We study the van der Pol oscillator in the quantum limit, when the oscillator is near the quantum ground state, and the behavior is sensitive to the quantization of energy levels. We consider four scenarios: one oscillator with and without an external drive, two coupled oscillators, and an infinite number of oscillators with global coupling. We find that phase-locking is much more robust in the quantum model than in the equivalent classical model. Trapped-ion experiments are ideally suited to simulate van der Pol oscillators in the quantum regime via sideband heating and cooling of motional modes. Phys. Rev. Lett. (in press), arXiv:1306.6359 [Preview Abstract] |
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