Bulletin of the American Physical Society
47th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 61, Number 8
Monday–Friday, May 23–27, 2016; Providence, Rhode Island
Session P4: Quantum Gates and Computation |
Hide Abstracts |
Chair: Martin Lichtman, Joint Quantum Institute, University of Maryland-College Park Room: 554AB |
Thursday, May 26, 2016 2:00PM - 2:12PM |
P4.00001: Universal gates based on targeted phase shifts in a 3D neutral atom array Aishwarya Kumar, Yang Wang, Tsung-Yao Wu, David Weiss We demonstrate a new approach to making targeted single qubit gates using Cesium atoms in a 5x5x5 3D neutral atom array. It combines targeted AC Zeeman phase shifts with global microwave pulses to produce arbitrary single qubit gates. Non-targeted atoms are left virtually untouched by the gates. We have addressed 48 sites, targeted individually, in a 40{\%} full array. We have also performed Randomized Benchmarking to characterize the fidelity and crosstalk errors of this gate. These gates are highly insensitive to addressing beam imperfections and can be applied to other systems and geometries. [Preview Abstract] |
Thursday, May 26, 2016 2:12PM - 2:24PM |
P4.00002: High-Fidelity Two-Qubit Gates in a Surface Ion Trap Daniel Lobser, Matthew Blain, Robin Blume-Kohout, Kevin Fortier, Jonathan Mizrahi, Erik Nielsen, Kenneth Rudinger, Jonathan Sterk, Daniel Stick, Peter Maunz Microfabricated surface traps are capable of supporting a variety of exotic trapping geometries and provide a scalable system for trapped ion Quantum Information Processing (QIP). However, the feasibility of using surface traps for QIP has long been a point of contention because the close proximity of the ions to trap electrodes increases heating rates and might lead to laser-induced charging of the trap. As surface traps continue to evolve at a remarkable rate, their performance is rapidly approaching that of macroscopic electrode traps. Using Sandia's High-Optical-Access surface trap, we demonstrate robust single-qubit gates, both laser- and microwave-based. Our gates are accurately characterized by Gate Set Tomography (GST) and we report the first diamond norm measurements near the fault-tolerance threshold\footnote{P. Aliferis and A. W. Cross, Phys. Rev. Lett. 98, 220502 (2007)}. Extending these techniques, we've realized a M{\o}lmer-S{\o}rensen two-qubit gate\footnote{A. S{\o}rensen and K. M{\o}lmer, Phys. Rev. Lett. 82, 1971 (1999)} that is stable for several hours. This stability has allowed us to perform the first GST measurements of a two-qubit gate, yielding a \textit{process} fidelity of 99.58(6){\%}. [Preview Abstract] |
Thursday, May 26, 2016 2:24PM - 2:36PM |
P4.00003: Ultrafast Interferometry and Gates with Trapped Ions Kale Johnson, David Wong-Campos, Brian Neyenhuis, Jonathan Mizrahi, Christopher Monroe We sense the motion of a trapped atomic ion using a sequence of state-dependent ultrafast momentum kicks. We use this atom interferometer to characterize a nearly-pure quantum state with $n=1$ phonon and accurately measure thermal states ranging from near the zero-point energy to \(\bar{n}\sim 10^4\), with the possibility of extending at least 100 times higher in energy. The complete energy range of this method spans from the ground state to far outside of the Lamb-Dicke regime, where atomic motion is greater than the optical wavelength. Apart from thermometry, these interferometric techniques are useful for quantum information purposes, and we discuss the outlook for ultrafast entangling gates between multiple trapped ions. [Preview Abstract] |
Thursday, May 26, 2016 2:36PM - 2:48PM |
P4.00004: Implementing Quantum Algorithms with Modular Gates in a Trapped Ion Chain Caroline Figgatt, Shantanu Debnath, Norbert Linke, Kevin Landsman, Ken Wright, Chris Monroe We present experimental results on quantum algorithms performed using fully modular one- and two-qubit gates in a linear chain of 5 Yb$+$ ions. This is accomplished through arbitrary qubit addressing and manipulation from stimulated Raman transitions driven by a beat note between counter-propagating beams from a pulsed laser[1]. The Raman beam pairs consist of one global beam and a set of counter-propagating individual addressing beams, one for each ion. This provides arbitrary single-qubit rotations as well as arbitrary selection of ion pairs for a fully-connected system of two-qubit modular XX-entangling gates implemented using a pulse-segmentation scheme[2]. We execute controlled-NOT gates with an average fidelity of 97.0{\%} for all 10 possible pairs. Programming arbitrary sequences of gates allows us to construct any quantum algorithm, making this system a universal quantum computer. As an example, we present experimental results for the Bernstein-Vazirani algorithm using 4 control qubits and 1 ancilla, performed with concatenated gates that can be reconfigured to construct all 16 possible oracles, and obtain a process fidelity of 90.3{\%}. [1] PRL 104, 140501 (2010), [2] PRL 112, 19502 (2014) [Preview Abstract] |
Thursday, May 26, 2016 2:48PM - 3:00PM |
P4.00005: Realization of a scalable coherent quantum Fourier transform Shantanu Debnath, Norbert Linke, Caroline Figgatt, Kevin Landsman, Ken Wright, Chris Monroe The exponential speed-up in some quantum algorithms is a direct result of parallel function-evaluation paths that interfere through a quantum Fourier transform (QFT)[1]. We report the implementation of a fully coherent QFT on five trapped $Yb^+$ atomic qubits using sequences of fundamental quantum logic gates[2]. These modular gates can be used to program arbitrary sequences nearly independent of system size and distance between qubits. We use this capability to first perform a Deutsch-Jozsa algorithm where several instances of three-qubit balanced and constant functions are implemented and then examined using single qubit QFTs. Secondly, we apply a fully coherent five-qubit QFT as a part of a quantum phase estimation protocol. Here, the QFT operates on a five-qubit superposition state with a particular phase modulation of its coefficients and directly produces the corresponding phase to five-bit precision. Finally, we examine the performance of the QFT in the period finding problem in the context of Shor's factorization algorithm. [1] R. Cleve et al. Proc. R. Soc. Lond. A, 454, 339-354(1998). [2] S. Debnath et al., In preparation. [Preview Abstract] |
Thursday, May 26, 2016 3:00PM - 3:12PM |
P4.00006: Individual Optical Addressing of Atomic Clock Qubits With Stark Shifts Aaron Lee, Jacob Smith, Phillip Richerme, Brian Neyenhuis, Paul Hess, Jiehang Zhang, Chris Monroe In recent years, trapped ions have proven to be a versatile quantum information platform, enabled by their long lifetimes and high gate fidelities. Some of the most promising trapped ion systems take advantage of groundstate hyperfine “clock” qubits, which are insensitive to background fields to first order. This same insensitivity also makes $\sigma_z$ manipulations of the qubit impractical, eliminating whole classes of operations. We prove there exists a fourth-order light shift, or four-photon Stark shift, of the clock states derived from two coherent laser beams whose beatnote is close to the qubit splitting. Using a mode-locked source generates a large light shift with only modest laser powers, making it a practical $\sigma_z$ operation on a clock qubit. We experimentally verify and measure the four-photon Stark shift and demonstrate its use to coherently individually address qubits in a chain of 10 Yb 171 ions with low crosstalk. We use this individual addressing to prepare arbitrary product states with high fidelity and also to apply independent $\sigma_z$ terms transverse to an Ising Hamiltonian. [Preview Abstract] |
Thursday, May 26, 2016 3:12PM - 3:24PM |
P4.00007: The use of ${}^{133}$Ba${}^+$ as a new candidate for trapped atomic ion qubits David Hucul, Justin Christiansen, Wesley Campbell, Eric Hudson Trapped atomic ions are qubit standards in quantum information science because of their long coherence times and high fidelity entangling gates. Many different atomic ions have been used as qubits, each with strengths and weaknesses dictated by its atomic structure. We propose to use ${}^{133}$Ba$^+$ as an atomic qubit. ${}^{133}$Ba$^+$ is a nearly ideal, all-purpose candidate by combining many of the strengths of different workhorse atomic ions. ${}^{133}$Ba$^+$, like ${}^{171}$Yb$^+$, has a nuclear spin 1/2, allowing for a robust hyperfine qubit with simple state preparation and readout via differential fluorescence. The lack of a low-lying F-state, like in Ca$^+$, simplifies high-fidelity qubit state detection that relies on shelving a qubit level to a meta-stable excited state. In addition, ${}^{133}$Ba$^+$ can be used for background-free qubit state detection where the wavelength of the qubit detection light differs from all excitation light by at least 50 THz. Unlike all other ions in use, the optical transitions of barium are in the visible spectrum, enabling the use of high power lasers, low-loss fibers, high quantum efficiency detectors, and other technologies developed for visible wavelengths of light to ease some requirements toward scaling a quantum system. [Preview Abstract] |
Thursday, May 26, 2016 3:24PM - 3:36PM |
P4.00008: Implementation of Quantum Plug and Play Protocol in a Trapped Ion System Kuan Zhang, Xiang Zhang, Yangchao Shen, Yao Lu, Shuaining Zhang, Jiajun Ma, Kihwan Kim, Mile Gu, Jayne Thompson, Vlatko Vedral For the large-scale computer programing, it is important to modularize the program into many small parts, which are called as module. To integrate the modules in the program, all that we need to know is the relation between inputs and outputs not the specific details of the physical implementation. However, such modularity is generically impossible to be adapted in quantum computing [1]. It was discussed with the example of deterministic quantum computing with one qubit (DQC1), which efficiently computes the trace of a unitary matrix U. The authors in Ref. [1] pointed that if we compute $|Tr(U)|$ instead of $Tr(U)$, the whole process can be modularized. We implement the proposed quantum plug and play protocol in the simplest situation in our trapped ion system. In the protocol, we begin with 1 pure control qubit and 2 completely mixed registers, which are swapped on a state of the control qubit. The $|Tr(U)|$ is computed for any arbitrary unitary operation performed on the one of the register. [1] Jayne Thompson, et al., arXiv:1310.2927v5 (2013). [Preview Abstract] |
Thursday, May 26, 2016 3:36PM - 3:48PM |
P4.00009: Rapid, Site-Selective Loading of a Scalable Array of Trapped Ions Colin Bruzewicz, Robert McConnell, John Chiaverini, Jeremy Sage Rapid trap reloading is a requirement for any scalable quantum information processor based on trapped-ion qubits. Even cryogenic systems with trap lifetimes in excess of 10 hours will require loading rates of approximately 100 s$^{-1}$ to maintain arrays of millions of ions. Further, the reloading process should not introduce unacceptable levels of decoherence into other ions within the array. Here, we demonstrate rapid, site-selective, random-access loading of a 2x2 array of trapped ions that satisfies the major criteria for scalable quantum processing. This scheme uses a continuous flux of pre-cooled strontium atoms and a pair of orthogonal photo-ionization lasers to load surface-electrode point Paul traps at average rates greater than 400 s$^{-1}$. Additionally, we have conducted a series of Ramsey experiments to measure the effects of loading on the coherence of nearby trapped ions. C. D. Bruzewicz, R. McConnell, J. Chiaverini, and J. M. Sage, arXiv:1511.03293 (2015). [Preview Abstract] |
Thursday, May 26, 2016 3:48PM - 4:00PM |
P4.00010: Integrated Diffractive Optics for Surface Ion Traps Erik Streed, Moji Ghadimi, Valdis Blums, Benjamin Norton, Paul Connor, Jason Amini, Curtis Volin, Mirko Lobino, David Kielpinski Photonic interconnects are a bottleneck to achieving large-scale trapped ion quantum computing. We have modified a Georgia Tech Research Institute microwave chip trap by using e-beam lithography to write reflective diffractive collimating optics (80 $\mu$m x 127 $\mu$m, f=58.6 $\mu$m, $\lambda$=369.5nm) on the center electrode. The optics have an NA of 0.55 x 0.73, capturing 13.2% of the solid angle. To evaluate the optics 174Yb+ was loaded by isotope selective photo-ionization from a thermal oven and then shuttled to imaging sites. Near diffraction limited sub-wavelength ion images were obtained with an observed spot sized FWHM of 338 nm x 268 nm vs. a diffraction limit of 336 nm x 257 nm. The total photon collection efficiency was measured to be 5.2±1.2%. Coupling into a single mode fiber of up to 2.0±0.6% was observed, limited by mismatch in the coupling optics. Image mode quality indicates coupling up to ~4% may be possible. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700