Bulletin of the American Physical Society
49th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics APS Meeting
Volume 63, Number 5
Monday–Friday, May 28–June 1 2018; Ft. Lauderdale, Florida
Session H09: Quantum Gates |
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Chair: John Bollinger, NIST Room: Grand H |
Wednesday, May 30, 2018 8:00AM - 8:12AM |
H09.00001: Robust entanglement of trapped ion qubits Yotam Shapira, Ravid Shaniv, Tom Manovitz, Nitzan Akerman, Roee Ozeri Two-qubit entangling gates are central to quantum information processing. High fidelity two-qubit entangling gates have been demonstrated in several trapped ions systems. A common choice for such entangling gates is the well-known bi-chromatic Mølmer-Sørensen (MS) gate, which ideally allows for deterministic two-qubit entanglement. However, calibration errors such as gate-timing errors or drifts of the normal-mode harmonic frequency result in a, temperature-sensitive, reduced gate fidelity. Furthermore, the gate is constrained to act slower than the trapping frequency due to off-resonance direct carrier coupling. Here, we generalize the MS gate by driving the ions with a multi-chromatic drive, the different components of the drive are then treated as additional degrees of freedom that allow for reducing or eliminating different error mechanisms leading to robust entanglement. Specifically we implement our robust entanglement scheme on two trapped $^{88}\text{Sr}^{+}$ ions. We explicitly measure the increased robustness to gate-timing errors, normal-mode frequency errors and off-resonance carrier coupling. [Preview Abstract] |
Wednesday, May 30, 2018 8:12AM - 8:24AM |
H09.00002: Entanglement between two species of atomic ions and the loophole-free test of quantum contextuality Pengfei Wang, Junhua Zhang, Mark Um, Ye Wang, Tian Xie, Naijun Jin, Jing-Ning Zhang, Kihwan Kim We report the entanglement between $^{171}$Yb$^+$ ion and $^{138}$Ba$^+$ ion. First, we prepare all the motional state to near the ground-state by the three-stage cooling of Doppler, the EIT and the sideband cooling on Ba$^+$ ion. Then, we apply the Raman laser beams of 355 nm for Yb$^+$ and 532 nm for Ba$^+$ and create the entanglement of the two ions through a M$\o$lmer-S$\o$rensen interaction. We detect the quantum states of $^{171}$Yb$^+$ and $^{138}$Ba$^+$ by the standard fluorescence scheme. For the $^{138}$Ba$^+$ ion, we shelve an electronic state in S$_{1/2}$ to a state in D$_{5/2}$ by applying a narrow-linewidth laser of 1762 nm. With the entanglement between two species of atomic ions, we can experimentally verify the quantum contexuality without the major loopholes of detection and compatibility. In our experimental realization, it is naturally free of the detection loophole, since the detection efficiencies of both ions are over 98 $\%$. It is also free of the compatibility loophole, since we measure the pairs of the joint observables simultaneously instead of the sequential measurements with totally different wavelength of laser beams for each ion. [Preview Abstract] |
Wednesday, May 30, 2018 8:24AM - 8:36AM |
H09.00003: Entangling Ions through Multiple Transverse Modes on an Ion-Chain Kuan Zhang, Yao Lu, Shuaining Zhang, Yangchao Shen, Wentao Chen, Jing-Ning Zhang, Kihwan Kim A Greenberger-Horne-Zeilinger (GHZ) state of up to 14 ions has been created by applying a single operation of M\o{}lmer-S\o{}rensen (MS) gate~[1,2]. In their gate, it is essential to use only the center-mass (CM) mode along the axial direction, therefore, requiring well isolation of the mode from all the other motional modes. However, it is difficult to maintain the requirement when the number of ions further increases in a linear ion-chain with reasonable trap frequencies. Here, we present a scalable multi-qubit gate, which entangles ions by using multiple transverse modes instead of a single CM mode. Our gate considers the influence of all the motional modes, and creates entanglement among arbitrary number of selected ions in the ion-chain by simultaneously applying laser beams to them. Our multi-qubit gate provides an efficient and scalable solution for trapped-ion quantum computation and simulation. [1] Anders S\o{}rensen and Klaus M\o{}lmer. Phys.~Rev.~Lett. 62, 022311 (2000). [2] Thomas~Monz, et al., Phys.~Rev.~Lett. 106, 130506 (2011). [Preview Abstract] |
Wednesday, May 30, 2018 8:36AM - 8:48AM |
H09.00004: Parallel 2-Qubit Operations on a Programmable Ion Trap Quantum Computer Caroline Figgatt, Aaron Ostrander, Norbert Linke, Kevin Landsman, Daiwei Zhu, Dmitri Maslov, Christopher Monroe Performing parallel operations will be a powerful capability as deeper circuits on larger, more complex quantum computers present new challenges. We present experimental results for a pair of 2-qubit gates performed simultaneously in a single chain of trapped ions. The system used is a programmable quantum computer consisting of a linear chain of five trapped $^{171}$Yb$^+$ atomic clock ions with long coherence times. We employ a pulse shaping scheme that modulates the phase and amplitude of the Raman transitions to drive programmable high-fidelity 2-qubit XX gates in parallel by coupling to the collective modes of motion of the ion chain. Ensuring the interaction produced yields only spin-spin interactions between the desired pairs with neither residual spin-motion entanglement nor “crosstalk” spin-spin entanglement is a nonlinear constraint problem, and pulse solutions are found using optimization techniques. As an application, we demonstrate the quantum full adder [1] using a depth-4 circuit requiring the use of parallel 2-qubit operations [2] as well as modular 1- and 2-qubit operations previously demonstrated on this system [3]. [1] Opt. News, 11, 11–20 (1985), [2] IEEE Trans. Comput.-Aided Design Integr. Circuits Syst., 27(3):436-444 (2008), [3] Nature 536, 63 (2016). [Preview Abstract] |
Wednesday, May 30, 2018 8:48AM - 9:00AM |
H09.00005: Entanglement of trapped ions using low-frequency magnetic field gradients Shaun C. Burd, David T. C. Allcock, Raghavendra Srinivas, Daniel H. Slichter, Andrew Wilson, Dietrich Leibfried, David Wineland Entangled states of trapped ions are typically generated using laser-induced spin-motion coupling. Spin-motion coupling with hyperfine qubits has also been demonstrated with microwave magnetic fields instead of lasers, thus eliminating photon scattering errors and offering potential benefits for scalability. These experiments have relied on either static magnetic field gradients or oscillating magnetic field gradients at GHz frequencies[1-4]. We present a method of spin-motion coupling using a magnetic field gradient oscillating at MHz frequencies. We describe progress in using this method to perform one- and two-qubit manipulations of $^{25}$Mg$^{+}$ ions in a cryogenic microfabricated surface-electrode trap. This implementation offers important technical advantages over both the static-gradient and GHz-gradient techniques. [1] Mintert and Wunderlich PRL 87, 257904 (2001) [2] Weidt et al. PRL 117, 220501 (2016) [3] Ospelkaus et al. Nature 476, 181 (2011) [4] Harty et al. PRL 117, 140501 (2016) [Preview Abstract] |
Wednesday, May 30, 2018 9:00AM - 9:12AM |
H09.00006: Trapped ion-inspired entangling gate for superconducting qubits Sydney Schreppler, Marie Lu, Lukas Buchmann, Felix Motzoi, Irfan Siddiqi Quantum simulators of analog and digital varieties rely on the ability to entangle constituent particles with high fidelity. The M{\o}lmer-S{\o}rensen gate underlies much of the success of trapped-ion qubits, allowing for two-qubit entanglement with fidelity greater than 99{\%} and for simultaneous multi-qubit operations. For the ions, qubit-qubit entanglement is achieved via stimulated Raman transitions and through their interaction with a shared phonon mode. We describe the development of a M{\o}lmer-S{\o}rensen inspired gate for superconducting qubits, employing an analogous shared photon mode and a bichromatic driving field to engineer multi-qubit entanglement. This new functionality encourages development of hybrid analog-digital approaches to quantum simulations with superconducting qubit systems. [Preview Abstract] |
Wednesday, May 30, 2018 9:12AM - 9:24AM |
H09.00007: Photon-mediated universal quantum gate between two neutral atoms in an optical cavity Stephan Welte, Bastian Hacker, Severin Daiss, Stephan Ritter, Lin Li, Gerhard Rempe Optical high-finesse resonators provide an efficient interface between flying photonic qubits and stationary matter qubits [1] in a future quantum network for secure quantum communication and distributed quantum computing. A prerequisite for the construction of a scalable network is that each node contains several qubits that are connected through universal quantum gate operations. We experimentally realized [2] such a gate [3] between two neutral Rubidium atoms strongly coupled to an optical resonator. The gate is mediated by one optical photon propagating in the network channel defined by the resonator mode. The reflection of the photon from the resonator creates an interaction that is independent of the inter-atomic distance. We demonstrate the functionality of our gate as a CNOT as well as its ability to maximally entangle two atoms. The presented gate mechanism has the potential to serve in an entanglement swapping protocol to generate entanglement over large distances in a quantum repeater. [1] A. Reiserer, G. Rempe, Rev. Mod. Phys. 87, 1379 (2015). [2] S. Welte, B. Hacker, S. Daiss, S. Ritter, G. Rempe, arXiv 1801.05980 (2018). [3] L.-M. Duan, B. Wang, H. J. Kimble, Phys. Rev. A 72, 032333 (2005). [Preview Abstract] |
Wednesday, May 30, 2018 9:24AM - 9:36AM |
H09.00008: Quantum compilation optimized for experiments with multi-qubit gates Liangyu Ding, Xiang Zhang, Qiuxin Zhang, Danna Shen, Xiran Sun, Wei Zhang There is increasing interest in implementing quantum algorithms via simpler and shorter experimental operations for building universal quantum computers. Here, we present a general quantum computation compiler, which maps arbitrary quantum algorithm to an optimal quantum circuit consisting of a sequential set of universal gates which is feasible to operate directly in experiment with atomic qubits by lasers. We implement several methods, including matrix elementary decomposition, cosine-sine decomposition, quantum Shannon decomposition and Cartan's KAK decomposition, to transform the quantum algorithm into a series of one-bit gates and specific two-bit or multi-bit gates. The compiler optimizes experimental gate sequence by heuristically applying mirroring and merging tricks. Moreover, we use algebraic decomposition and numerical optimization method to compile unitaries using native multi-bit gates, i.e., Ising gates, which significantly reduce gate numbers. The compilation technique is practically favorable and will be used in our following trapped ions experiment. [Preview Abstract] |
Wednesday, May 30, 2018 9:36AM - 9:48AM |
H09.00009: A Photon-Photon Quantum Gate Based on Rydberg Polaritons Steffen Schmidt-Eberle, Daniel Tiarks, Thomas Stolz, Stephan Duerr, Gerhard Rempe Rydberg polaritons offer a unique way to create strong interactions for photons. We utilize these interactions to demonstrate a photon-photon quantum gate. To achieve this, a photonic control qubit is stored in a quantum memory consisting of a superposition of a ground state and a Rydberg state in an ultracold atomic gas. This qubit interacts with a photonic target qubit in the form of a propagating Rydberg polariton to generate a conditional pi phase shift.\footnote{D. Tiarks et al., Science Advances 2, 1600036 (2016)} Finally, the control photon is retrieved. We measure two controlled-NOT truth tables and the two-photon state after an entangling-gate operation. This work is an important step toward applications in optical quantum information processing, such as deterministic photonic Bell-state detection which is crucial for quantum repeaters. [Preview Abstract] |
Wednesday, May 30, 2018 9:48AM - 10:00AM |
H09.00010: ABSTRACT WITHDRAWN |
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