Bulletin of the American Physical Society
2010 Annual Meeting of the California-Nevada Section of the APS
Volume 55, Number 12
Friday–Saturday, October 29–30, 2010; Pasadena, California
Session C4: Atomic and Molecular Physics I |
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Chair: Yohannes Abate, California State University, Long Beach Room: Building 47, Downs Laboratory of Physics, Classroom 107 |
Friday, October 29, 2010 2:00PM - 2:12PM |
C4.00001: Combining Dynamical Decoupling with Optimal Control for Improved Quantum Information Processing Matthew D. Grace, Wayne M. Witzel, Malcolm S. Carroll, Jason Dominy Constructing high-fidelity control pulses that are robust to control and system/environment fluctuations is a crucial objective for quantum information processing (QIP). We combine dynamical decoupling (DD) with optimal control (OC) to identify control pulses that achieve this objective numerically. Previous DD work has shown that general errors up to (but not including) third order can be removed from $\pi$- and $\pi/2$-pulses without concatenation. By systematically integrating DD and OC, we are able to increase pulse fidelity beyond this limit. Our hybrid method of quantum control incorporates a newly-developed algorithm for robust OC, providing a nested DD-OC approach to generate robust controls. Motivated by solid-state QIP, we also incorporate relevant experimental constraints into this DD-OC formalism. To demonstrate the advantage of our approach, the resulting quantum controls are compared to previous DD results in open and uncertain model systems. This work was supported by the Laboratory Directed Research and Development program at Sandia National Laboratories. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000. [Preview Abstract] |
Friday, October 29, 2010 2:12PM - 2:24PM |
C4.00002: Haunted Quantum Entanglement: A New Scenario Douglas Snyder A haunted quantum entanglement scenario is proposed that is very close to Greenberger and YaSin's haunted measurement in that: 1) the entity that is developing as a which-way marker is effectively restored to its state prior to its developing as a which-way marker, and 2) the entity for which the developing which-way marker provides information enters the state it would have had if the development of the which-way marker had never begun. In the hqe scenario, the loss of developing which-way information through 1 relies on the loss of a developing entanglement. The photon initially emitted in one of two micromaser cavities and developing into a which-way marker is effectively lost through the injection of classical microwave radiation into both of the microwave cavities: 1) after the atom initially emits the photon into one of the micromaser cavities and exits the cavity system, and 2) before this atom reaches the 2 slit screen. The atom enters the state it would have had if the atom had never emitted the photon into one of the micromaser cavities because of the injection of classical microwave radiation into both of the microwave cavities and the presence of an rf coil situated at the exit of the micromaser cavity system. [Preview Abstract] |
Friday, October 29, 2010 2:24PM - 2:36PM |
C4.00003: General Symbolic Quantum Mechanics for SymPy Matt Curry, Addison Cugini, Brian Granger SymPy is an open-source symbolic mathematics library for the Python programming language. In this talk we describe the general symbolic quantum mechanics capabilities that we have added to SymPy. This enables SymPy to handle the Dirac notation symbolically and includes objects that represent bras, kets, operators, inner/outer/tensor products, commutators, basis sets and Hilbert spaces. The goal of this work is to build an open-source foundation that allows a wide variety of quantum mechanical systems to be treated symbolically, from basic textbook quantum systems and atomic/molecular Hamiltonians to interacting quantum field theories and quantum computing. We will describe the different objects in the framework and how they can be combined to build and manipulate general symbolic quantum expressions. This will include examples ranging from basic states and operators to more complex usage cases involving basis sets and representations. We will briefly describe how the framework is being used to develop symbolic quantum computing and quantum many body capabilities in SymPy. Finally, we will describe some of the challenges in implementing the full Dirac notation in a symbolic computation. [Preview Abstract] |
Friday, October 29, 2010 2:36PM - 2:48PM |
C4.00004: Symbolic Quantum Computation Simulation in SymPy Addison Cugini, Matt Curry, Brian Granger Quantum computing is an emerging field which aims to use quantum mechanics to solve difficult computational problems with greater efficiency than on a classical computer. There is a need to create software that i) helps newcomers to learn the field, ii) enables practitioners to design and simulate quantum circuits and iii) provides an open foundation for further research in the field. Towards these ends we have created a package, in the open-source symbolic computation library SymPy, that simulates the quantum circuit model of quantum computation using Dirac notation. This framework builds on the extant powerful symbolic capabilities of SymPy to preform its simulations in a fully symbolic manner. We use object oriented design to abstract circuits as ordered collections of quantum gate and qbit objects. The gate objects can either be applied directly to the qbit objects or be represented as matrices in different bases. The package is also capable of performing the quantum Fourier transform and Shor's algorithm. A notion of measurement is made possible through the use of a non-commutative gate object. In this talk, we describe the software and show examples of quantum circuits on single and multi qbit states that involve common algorithms, gates and measurements. [Preview Abstract] |
Friday, October 29, 2010 2:48PM - 3:00PM |
C4.00005: Classical and Quantum Resource Analysis for the Quantum Linear Systems Algorithm Jon Inouye Recently (2009) a quantum algorithm for solving a system of linear equations has been proposed. The algorithm by Harrow, Hassidim, and Lloyd has attracted considerable attention in the quantum algorithms community, due to the broad potential applications of a rapid linear equations solver. The contribution of this presentation is to analyze the classical and quantum resources required for implementation. The presentation has two major tasks. We first summarize the field of quantum algorithms. The papers which established this field (e.g., Feynman and Deutsch) to recent works are briefly surveyed. For the second task, we focus on the algorithm by Harrow, Hassidim, and Lloyd. The advantages of the algorithm are an exponential performance gain over classical algorithms (under conditions of sparse operator matrices and few selected measurements from the solution set), and fewer data registers. We study the classical resources required for implementation of the algorithm. Since classical resources can determine the ultimate efficiency of the quantum algorithm, the optimal use of classical resources is mandatory. This work can therefore contribute to the design of efficient quantum algorithms. [Preview Abstract] |
Friday, October 29, 2010 3:00PM - 3:12PM |
C4.00006: Comparing the Random Phase Approximation to Full Configuration-Interaction Calculations of Atomic Structure Micah Schuster, Calvin Johnson We compute the binding energies for helium through neon, comparing the random phase approximation (RPA) against full configuration-interaction diagonalization. RPA gives a reasonable approximation for the full numerical answer and might be useful for efficient determination of basis set parameters. [Preview Abstract] |
Friday, October 29, 2010 3:12PM - 3:24PM |
C4.00007: Frequency-stabilized cavity ring-down spectroscopy David A. Long, Daniel K. Havey, Mitchio Okumura, Charles E. Miller, Joseph T. Hodges Frequency-stabilized cavity ring-down spectroscopy (FS-CRDS) is an ultrasensitive variant of traditional cw-CRDS whereby the optical cavity length is actively stabilized to an external frequency reference. This in turn stabilizes the cavity's free spectral range which provides an extremely stable, linear, and accurate frequency axis for our spectra. FS-CRDS is particularly well-suited to molecular lineshape studies. We have recently applied FS-CRDS to O$_{2}$ and CO$_{2}$ transitions in the near-infrared which are of great importance in remote sensing. Spectral signal-to-noise ratios as high as 28,000:1 have been achieved, allowing for observation of subtle lineshape effects, such as speed-dependence and collisional narrowing, and measurement of spectral parameters to the 0.1{\%}-level. In the O$_{2} A$-band we have also observed ultraweak electric quadrupole transitions as well as hyperfine structure (for the $^{17}$O-containing isotopologues). [Preview Abstract] |
Friday, October 29, 2010 3:24PM - 3:36PM |
C4.00008: Progress toward a search for anomalous spin-mass couplings with a dual-isotope rubidium magnetometer Julian Valdez, Ian Lacey, Rodrigo Peregrinaramirez, Delyana Delcheva, L.R. Jacome, Derek Kimball A coupling between spin and mass can arise from new spin-0 or spin-1 force-mediating particles or in non-standard gravity with scalar or vector components in addition to the usual tensor interaction. We report on progress toward a search for anomalous couplings between the mass of the earth and Rb spins. In the experiment, a natural isotopic mixture of Rb atoms is contained in an antirelaxation-coated cell. The atomic spins are polarized via laser optical pumping and spin precession is measured in both isotopes using optical rotation. The experiment is particularly sensitive to spin-mass interactions of the proton. We discuss the sensitivity of our experimental scheme and strategies for control of several important systematic effects such as differential light shifts, collisional frequency shifts, and frequency shifts due to the rotation of the earth. [Preview Abstract] |
Friday, October 29, 2010 3:36PM - 3:48PM |
C4.00009: Sensitivity Optimization of a Dual Isotope Rubidium Magnetometer Rodrigo Peregrinaramirez, Ian Lacey, Julian Valdez, Delyana Delcheva, L.R. Jacome, Derek Kimball We report progress on optimization of a dual-isotope Rb magnetometer to be used in experiments searching for anomalous spin-dependent interactions of the proton with the earth's gravitational field. Rubidium atoms are contained in an antirelaxation-coated cell mounted inside a five-layer magnetic shield system. A system of six coils allows precise control of the magnetic environment experienced by the atoms, and atomic spin precession is measured using a pump-probe setup. The ratio of the difference and the sum of the spin precession frequencies of the two Rb isotopes is insensitive to magnetic field fluctuations but highly sensitive to anomalous interactions of the proton spin. We discuss optimization of the optical pumping and probing of the Rb spins and the projected sensitivity of the dual-isotope magnetometer. [Preview Abstract] |
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