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Entangling-gate error from coherently displaced motional modes of trapped ions

Physical Review A

Ruzic, Brandon; Barrick, T.A.; Hunker, J.D.; Law, Ryan; Mcfarland, Brian; Mcguinness, Hayden J.E.; Parazzoli, L.P.; Sterk, Jonathan D.; Van Der Wall, Jay W.; Stick, Daniel L.

Entangling gates in trapped-ion quantum computers are most often applied to stationary ions with initial motional distributions that are thermal and close to the ground state, while those demonstrations that involve transport generally use sympathetic cooling to reinitialize the motional state prior to applying a gate. Future systems with more ions, however, will face greater nonthermal excitation due to increased amounts of ion transport and exacerbated by longer operational times and variations over the trap array. In addition, pregate sympathetic cooling may be limited due to time costs and laser access constraints. In this paper, we analyze the impact of such coherent motional excitation on entangling-gate error by performing simulations of Mølmer-Sørenson (MS) gates on a pair of trapped-ion qubits with both thermal and coherent excitation present in a shared motional mode at the start of the gate. We quantify how a small amount of coherent displacement erodes gate performance in the presence of experimental noise, and we demonstrate that adjusting the relative phase between the initial coherent displacement and the displacement induced by the gate or using Walsh modulation can suppress this error. We then use experimental data from transported ions to analyze the impact of coherent displacement on MS-gate error under realistic conditions.

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TYPE Journal Article YEAR 2022
DOIOSTIScopus

Xyce™ Parallel Electronic Simulator Reference Guide, Version 7.5

Keiter, Eric R.; Russo, Thomas V.; Schiek, Richard; Thornquist, Heidi K.; Mei, Ting; Verley, Jason C.; Aadithya, Karthik V.; Schickling, Joshua D.

This document is a reference guide to the Xyce Parallel Electronic Simulator, and is a companion document to the Xyce Users' Guide. The focus of this document is (to the extent possible) exhaustively list device parameters, solver options, parser options, and other usage details of Xyce. This document is not intended to be a tutorial. Users who are new to circuit simulation are better served by the Xyce Users' Guide.

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TYPE SAND Report YEAR 2022
DOIOSTI

Molecular Inclusion of Small Aging Products into the Hexanitrohexaazaisowurtzitane (CL-20) Lattice: Part I, Infrared Spectra

Propellants, Explosives, Pyrotechnics

Beste, Ariana; Alam, Mary K.

Accelerated aging studies of β CL-20 thin films deposited on glass surfaces in different environments (N2, air, air/water) were conducted. Samples were analyzed with attenuated total reflectance infrared (ATR-IR) spectroscopy. Spectral features of molecular lattice inclusions in CL-20 films aged in an air/water environment were observed. The features occurred after β CL-20 polymorph transformation to α CL-20 and were accompanied by the appearance of lattice water peaks. To assist ATR-IR peak assignment, density functional theory studies were performed, and IR spectra of α CL-20 lattice inclusions of small molecules that were identified as degradation products of CL-20 were computed. Simulated spectra of NO2, HNCO, N2O, and CO2 incorporated into partially hydrated α CL-20 matched the experimental spectrum of β CL-20 thin films aged in air/water.

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TYPE Journal Article YEAR 2022
DOIOSTIScopus

Measurements of Low-Mode Asymmetries in the Areal Density of Laser-Direct- Drive DT Cryogenic Implosions on OMEGA Using Neutron Spectroscopy

Forrest, Chad; Betti, Riccardo; Knauer, James; Glebov, Vladimir; Gopalaswamy, Varchas; Mohamed, Zaarah; Bahukutumbi, Radha; Regan, Sean; Schwemmlein, Arnold; Stoeckl, Christian; Theobald, Wolfgang; Frenje, Johan; Gatu Johnson, Maria; Appelbe, Brian; Crilly, Aidan; Mannion, Owen

Abstract not provided.

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TYPE Conference Presentation YEAR 2022
DOIOSTI

Phase transitions in high-purity zirconium under dynamic compression

Physical Review B

Greeff, C.W.; Brown, Justin L.; Velisavljevic, N.; Rigg, P.A.

We present results from ramp compression experiments on high-purity Zr that show the α→ω, ω→β, as well as reverse β→ω phase transitions. Simulations with a multiphase equation of state and phenomenological kinetic model match the experimental wave profiles well. While the dynamic α→ω transition occurs ∼9GPa above the equilibrium phase boundary, the ω→β transition occurs within 0.9 GPa of equilibrium. We estimate that the dynamic compression path intersects the equilibrium ω-β line at P=29.2GPa, and T=490K. The thermodynamic path in the interior of the sample lies ∼100K above the isentrope at the point of the ω→β transition. Approximately half of this dissipative temperature rise is due to plastic work, and half is due to the nonequilibrium α→ω transition. The inferred rate of the α→ω transition is several orders of magnitude higher than that measured in dynamic diamond anvil cell (DDAC) experiments in an overlapping pressure range. We discuss a model for the influence of shear stress on the nucleation rate. We find that the shear stress sji has the same effect on the nucleation rate as a pressure increase δP=cϵijsji/(ΔV/V), where c is a geometric constant ∼1 and ϵij are the transformation shear strains. The small fractional volume change ΔV/V≈0.1 at the α→ω transition amplifies the effect of shear stress, and we estimate that for this case δP is in the range of several GPa. Correcting our transition rate to a hydrostatic rate brings it approximately into line with the DDAC results, suggesting that shear stress plays a significant role in the transformation rate.

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TYPE Journal Article YEAR 2022
DOIOSTIScopus
Results 8701–8750 of 101,000
Results 8701–8750 of 101,000
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