Bulletin of the American Physical Society
51st Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 65, Number 4
Monday–Friday, June 1–5, 2020; Portland, Oregon
Session N08: Trapped ion quantum control beyond the beaten pathInvited Live
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Sponsoring Units: DQI Chair: David Wineland, University of Oregon Room: Portland 255 |
Thursday, June 4, 2020 10:30AM - 11:00AM Live |
N08.00001: Controlling trapped ions without lasers Invited Speaker: Daniel Slichter Quantum computing using trapped atomic ions relies on manipulation of the ions’ quantum states and the creation of entanglement between ions, both of which are typically accomplished using laser beams. However, there are drawbacks to this approach, including errors due to photon scattering and the complexity of the required laser sources. Our group performs quantum state control using oscillating rf and microwave-frequency magnetic and electric fields, and their near-field gradients, instead of laser beams. We use low-power resonant laser beams for cooling, optical pumping, and readout. A critical element is the use of a microfabricated surface-electrode ion trap, which holds the ions roughly 30 $\mu$m above the electrodes generating the control fields. I will describe several of our recent results, including the creation of high-fidelity entangled states of two ions using only microwave and rf control fields, and the use of rf electric fields to generate squeezed states of ion motion for sensing applications and to amplify phonon-mediated ion-ion interactions. [Preview Abstract] |
Thursday, June 4, 2020 11:00AM - 11:30AM Live |
N08.00002: When precision matters: quantum gates and metrology with $^{171}$Yb$^+$ ions Invited Speaker: Christof Wunderlich Continuous or pulsed dynamical decoupling (DD) has been successfully used to extend the coherence time of qubits, for example in trapped atomic ions. We report on the experimental realization of a recently proposed, novel DD sequence \footnote{I. Arrazola, J. Casanova, J.S. Pedernales, Z.Y. Wang, E. Solano, M.B. Plenio, Phys. Rev. A {\bf 97}, 052312 (2018)} that not only extends the coherence time, but also results in a tunable two-qubit phase gate with high fidelity. Using both axial motional modes of a two-ion crystal, it allows for higher gate speeds than comparable single-mode gates. We have realized a $\frac{\pi}{4}$-gate with a fringe contrast up to 99(+1-2)\%, applying this sequence to two $^{171}$Yb$^+$ ions in a linear Paul trap using a hyperfine qubit driven by radio frequency radiation. The interaction between motional and internal qubit states necessary for conditional quantum logic is provided by magnetic gradient induced coupling (MAGIC) \footnote{T. Sriarunothai et al., Quantum Sci. Technol. {\bf 4} (2019) 015014}. We use this DD sequence for Controlled-NOT operations and the creation of Bell states. We investigate the robustness of such conditional quantum gates against typical error sources present when using trapped ion qubits. These include variations of the Rabi frequency ($\leq 30$ \%), the secular frequency ($\leq 4$ \%), and of the mean vibrational excitation $\bar{n}$ of the center-of-mass mode ($\approx 0.3 \leq \bar{n} \leq \approx 100$). The opticlock consortium (www.opticlock.de) develops a compact transportable optical clock for non-specialist users with a projected uncertainty of order $10^{-16}$. This clock, based on the 2S$_{1/2}$ - 2D$_{3/2}$ resonance with wavelength near 436 nm in a single $^{171}$Yb$^+$ ion, could be further improved using a frequency standard based on multiple ions. For this purpose, a segmented four layer ion trap for confining a linear Coulomb crystal of $^{171}$Yb$^+$ ions \footnote{M. Brinkmann, A.Didier, T. Mehlst\"aubler, Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany} and a compact vacuum interface, allowing for excellent optical access, is used. Here, we will focus on the design aspects and construction process of the new setup and give details regarding optical \footnote{S. Brakhane, D. Meschede, Institut f\"ur Angewandte Physik der Universit\"at Bonn, Wegelerstr. 8, 53115 Bonn, Germany}, electrical and vacuum aspects and present the experimental status of the linear trap project. [Preview Abstract] |
Thursday, June 4, 2020 11:30AM - 12:00PM Live |
N08.00003: Sub-microsecond entangling gates between trapped ions via Rydberg interaction Invited Speaker: Markus Hennrich Trapped Rydberg ions are a novel system for quantum computation and quantum simulation. They combine the key strengths of Rydberg atoms and trapped ion quantum processors in one technology. From Rydberg atoms they inherit the strong dipolar interaction, with trapped ions they share the full quantum information toolbox [1]. This technology has the potential to speed up trapped ion entanglement operations and make them available in large ion crystals. Here, we report on our progress in manipulating the quantum state of trapped Rydberg ions. We have coherently excited trapped ions to Rydberg states [2] and recently we have realized a sub-microsecond entanglement gate between trapped ions via Rydberg interaction [3]. These are important steps towards realizing a fast quantum processor or quantum simulator with trapped Rydberg ions. References: [1] M. M\"{u}ller, et al., Trapped Rydberg ions: from spin chains to fast quantum gates, New J. Phys. 10, 093009 (2008). [2] G. Higgins, et al., Coherent Control of a Single Trapped Rydberg Ion, Phys. Rev. Lett. 119, 220501 (2017). [3] C. Zhang, et al., Sub-microsecond entangling gate between trapped ions via Rydberg interaction, arXiv:1908.11284. [Preview Abstract] |
Thursday, June 4, 2020 12:00PM - 12:30PM Live |
N08.00004: High-rate, high-fidelity entanglement of qubits across an elementary quantum network Invited Speaker: David Lucas We demonstrate remote entanglement of trapped-ion qubits via a quantum-optical fibre link with fidelity and rate approaching those of local (intra-trap) operations. Two $^{\mathrm{88}}$Sr$^{\mathrm{+}}$ qubits are entangled via the polarization degree of freedom of two 422nm photons, which are coupled by high-numerical-aperture lenses into single-mode optical fibres and interfere on a beamsplitter. A novel geometry allows high-efficiency photon collection while maintaining unit fidelity for ion-photon entanglement. We generate heralded Bell pairs with fidelity 94{\%} at an average rate 182 per second (success probability 0.022{\%}). Heralded entanglement of remote qubits with fidelity above 90{\%} has not previously been reported for any physical systems with better than sub-Hz rates. The combination of high rate and high fidelity can enable a variety of networking applications, such as device-independent quantum key distribution and entanglement distillation at practical speeds. [Preview Abstract] |
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