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Physics

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Displaying 1726 - 1750 of 2493

Zero-energy modes and gate-tunable gap in graphene on hexagonal boron nitride

September 13, 2012
Author(s)
Markus Kindermann, Bruno Uchoa, David L. Miller
In this article, we derive an effective theory of graphene on a hexagonal boron nitride (h-BN) substrate. We show that the h-BN substrate generically opens a spectral gap in graphene despite the lattice mismatch. The origin of that gap is particularly

100-Fold Reduction of Electric-Field Noise in an Ion Trap Cleanded with In Situ Argon-Ion-Beam Bombardment

September 7, 2012
Author(s)
Dustin Hite, Yves Colombe, Andrew C. Wilson, Kenton R. Brown, Ulrich J. Warring, Robert Jordens, John D. Jost, David P. Pappas, Dietrich Leibfried, David J. Wineland, Kyle McKay
Anomalous heating of trapped atomic ions is a major obstacle to their use as quantum bits in scalable quantum computers. The physical origin of this electric field noise is not fully understood, but experimental evidence suggests that it emanates from the

Ultrafast manetization enhancement in metallic multilayers driven by superdiffusive spin current

September 4, 2012
Author(s)
Thomas J. Silva, Justin M. Shaw, Hans T. Nembach, Dennis Rudolf, Chan La-O-Vorakiat, Marco Battiato, Roman Adam, Emrah Turgut, Stefan Mathias, Margaret M. Murnane, Henry C. Kapteyn, Claus M. Schneider
Uncovering the physical mechanisms that govern ultrafast charge and spin dynamics is crucial for understanding correlated matter as well as the fundamental limits of ultrafast spin-based electronics. Spin dynamics in magnetic materials can be driven by

A Sub-Sampling Digital PM/AM Noise Measurement System

September 1, 2012
Author(s)
Craig W. Nelson, David A. Howe
A digital phase/amplitude modulation (PM/AM) noise measurement systems (DNMS) implementing field progammable gate array (FPGA) based digital down converters (DDCs), and 250 MHz analog to digital converters (ADCs) is reported. Measurements in the first

Simulating Quantum Magnetism with Correlated Non-Neutral Ion Plasmas

August 27, 2012
Author(s)
John J. Bollinger, Joseph W. Britton, Brian C. Sawyer
By employing forces which depend on the internal atomic state (or spin) of an atomic ion, the Coulomb potential energy of a strongly coupled array of ions can be modified in a spin-dependent way to mimic effective quantum spin Hamiltonians. Both

Coherent Diabatic Ion Transport and Separation in a Multizone Trap Array

August 24, 2012
Author(s)
Ryan S. Bowler, John P. Gaebler, Yiheng Lin, Ting Rei Tan, David Hanneke, John D. Jost, J. Home, Dietrich G. Leibfried, David J. Wineland
We investigate ion motion dynamics during the transport between and separation into spatially distinct trap locations in a multi-zone trap array. We laser-cool a single $\ensuremath{^{9}{\rm {Be}^{+}}}$ ion held in a linear Paul trap to near its ground

Optical isolator using an atomic vapor in the hyperfine Paschen-Back regime

August 15, 2012
Author(s)
Svenja A. Knappe, L. Weller, K.S. Kleinbach, M.A. Zentile, I.G. Hughes, C.S. Adams
A light, compact optical isolator using an atomic vapor in the hyperfine Paschen-Back regime is presented. Absolute transmission spectra for experiment and theory through an isotopically pure 87Rb vapor cell show excellent agreement for fields of 0.6 T. We

Scintillation Yield and Time Dependence from Electronic and Nuclear Recoils in Liquid Neon

August 13, 2012
Author(s)
Kevin J. Coakley, W. H. Lippincott, D. Gastler, E. Kearns, D. N. McKinsey, J. A. Nikkel
We have performed measurements of scintillation light in liquid neon, observing a signal yield in our detector as high as (3.5 +/- 0.04) photoelectrons/keV. We measure pulse shape discrimination between electronic and nuclear recoils in liquid neon between

Mid-infrared virtually imaged phased array spectrometer for rapid and broadband trace gas detection

August 1, 2012
Author(s)
Lora L. Nugent-Glandorf, Tyler W. Neely, Florian B. Adler, Adam J. Fleisher, Kevin C. Cossel, Bryce Bjork, Tim P. Dinneen, Chris S. Wood, Jun Ye, Scott A. Diddams
We present and analyze a 2-D imaging spectrometer based on a virtually imaged phased array (VIPA) disperser for rapid, high-resolution molecular detection using mid-infrared (MIR) frequency combs. A broad bandwidth, MIR laser source centered at ~3.1 υm

Calibration uncertainty for the NIST PM/AM noise standards

July 31, 2012
Author(s)
Archita Hati, Craig W. Nelson, Neil Ashby, David A. Howe
NIST provides an on-site calibration service of the accuracy of phase modulation (PM) noise, amplitude modulation (AM) noise and noise floor of the measurement systems at a customer's site using one or more portable PM/AM secondary noise standards. In this

Non-statistical population distributions for hydrogen beam in fusion plasmas

July 27, 2012
Author(s)
O. Marchuk, Yuri Ralchenko, D. R. Schultz
Most atomic models for a neutral hydrogen beam in fusion plasmas assume statistical (Boltzmann) distribution of populations for excited states with the same principal quantum number n. Here we analyze population distributions for the excited magnetic

Determination of graphene work function and graphene-insulator-semiconductor band alignment by internal photoemission spectroscopy

July 11, 2012
Author(s)
Rusen Yan, Qin Zhang, Wei Li, Irene G. Calizo, Tian T. Shen, Curt A. Richter, Angela R. Hight Walker, Xuelei X. Liang, David J. Gundlach, Nhan Van Nguyen, Huili G. Xing, Alan Seabaugh
We determined the band alignment of a graphene-oxide-silicon structure using internal photoemission spectroscopy. From the flatband voltage and Dirac voltage we infer a 4.3  10e11 cm-2 negative extrinsic charge present on the graphene surface. Also, we

Propagation of Vortex Electron Wave Functions in a Magnetic Field

July 5, 2012
Author(s)
Gregg M. Gallatin, Benjamin McMorran
The physics of coherent beams of photons carrying axial orbital angular momentum (OAM) is well understood and such beams, sometimes known as vortex beams, have found applications in optics and microscopy. Recently electron beams carrying very large values

100 Years of Superconductivity

July 2, 2012
Author(s)
Richard L. Kautz
The 100th anniversary of the discovery of superconudctivity by Heike Kamerlingh Onnes was celebrated in 2011 at the Superconductivity Centennial Conference held in The Hague. 100 Years of Superconductivity is a product of that celebration, but it's far

In-situ Polarized 3He system for the Magnetism Reflectometer at the Spallation Neutron Source

July 2, 2012
Author(s)
Thomas R. Gentile, X Tong, C Y. Jiang, V Lauter, H. Ambaye, D. Brown, L Crow, R J. Goyette, W-T Lee, A. Parizzi
We report on the in-situ polarized 3He neutron polarization analyzer developed for the time-of-flight Magnetism Reflectometer (MAGICS) at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL). Using the spin exchange optical pumping

International time and frequency comparisons in real time: recent results

July 2, 2012
Author(s)
Michael A. Lombardi, J. Mauricio Lopez-Romero, Nelida Diaz-Munoz, Eduardo de Carlos Lopez
Within the Sistema Interamericano de Metrologia (SIM) region, a time comparison network, SIMTN, has been developed. The SIMTN continuously compares the time scales of SIM members and publishes measurement results in near real-time. The measurements are

Randomized Benchmarking of Multiqubit Gates

June 29, 2012
Author(s)
John P. Gaebler, Adam M. Meier, Ting Rei Tan, Ryan S. Bowler, Yiheng Lin, David Hanneke, John D. Jost, Jonathan Home, Emanuel H. Knill, Dietrich G. Leibfried, David J. Wineland
As experimental platforms for quantum information processing continue to mature, characterization of the quality of unitary gates that can be applied to their quantum bits (qubits) becomes essential. Eventually, the quality must be sufficiently high to

Ancilla assisted calibration of a measuring apparatus

June 19, 2012
Author(s)
Alan L. Migdall, Giorgio Brida, L. Ciavarella, Ivo P. Degiovanni, Marco Genovese, M. G. Mingolla, M. G. A. Paris, Fabrizio Piacentini, Sergey Polyakov
The rapid development of quantum systems has enabled a wide range of novel and innovative technologies, from quantum information processing to quantum etrology and imaging [113], mainly based on optical systems. Precise characterization techniques of

Generation of a 6602100 nm laser frequency comb based on an erbium fiber laser

June 15, 2012
Author(s)
Gabriel G. Ycas, Steve Osterman, Scott A. Diddams
We present a laser frequency comb based upon a 250 MHz mode-locked erbium fiber-laser that spans more than 300 terahertz of bandwidth, from 660 nm to 2000 nm. Broad bandwidth is achieved by making use of Er:fiber and Yb:fiber amplifiers and supercontinuum

Correlation effects on transition probabilities in Mo vi

June 13, 2012
Author(s)
Charlotte F. Fischer
The effect of correlation on transitions in Mo vi from 4p64d 2D and 4p65s 2S to 4p64f, 4p65p, 4p65f, 4p54d2 with J = 1/2 - 7/2 is investigated. Non-relativistic correlation studies show the near degeneracy of 4p54d2(3F) 2Fo and 4p54d2(1G) 2Fo configuration
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