Current technology is beginning to allow us to manipulate rather than just observe individual quantum phenomena. This opens up the possibility of exploiting quantum effects to perform computations beyond the scope of any classical computer. Recently Peter Shor discovered an efficient algorithm for factoring whole numbers, which uses characteristically quantum effects. The algorithm illustrates the potential power of quantum computation, as there is no known efficient classical method for solving this problem. The authors give an exposition of Shor's algorithm together with an introduction to quantum computation and complexity theory. They discuss experiments that may contribute to its practical implementation. [S0034-6861(96)00303-0]

http://www.phys.uni-sofia.bg/~svetivanov/FourierPapers/1996%20-%20(Th)%20Shor%20-%20Ekert%20-%20RevModPhys.pdf

Quantum Computation and Shor's Factoring Algorithm

Advances in atomic physics, such as cooling and trapping of atoms and molecules and developments in frequency metrology, have added orders of magnitude to the precision of atom-based clocks and sensors. Applications extend beyond atomic physics and this article reviews using these new techniques to address important challenges in physics and to look for variations in the fundamental constants, search for interactions beyond the standard model of particle physics, and test the principles of general relativity.

Search for New Physics with Atoms and Molecules

This White Paper presents the science case of an Electron-Ion Collider (EIC), focused on the structure and interactions of gluon-dominated matter, with the intent to articulate it to the broader nuclear science community. It was commissioned by the managements of Brookhaven National Laboratory (BNL) and Thomas Jefferson National Accelerator Facility (JLab) with the objective of presenting a summary of scientific opportunities and goals of the EIC as a follow-up to the 2007 NSAC Long Range plan. This document is a culmination of a community-wide effort in nuclear science following a series of workshops on EIC physics over the past decades and, in particular, the focused ten-week program on “Gluons and quark sea at high energies” at the Institute for Nuclear Theory in Fall 2010. It contains a brief description of a few golden physics measurements along with accelerator and detector concepts required to achieve them. It has been benefited profoundly from inputs by the users’ communities of BNL and JLab. This White Paper offers the promise to propel the QCD science program in the US, established with the CEBAF accelerator at JLab and the RHIC collider at BNL, to the next QCD frontier.

/pdf/electron-ion-collider-the-next-qcd-frontier-understanding-jgxuurgr4t.pdf

Electron-Ion Collider: The next QCD frontier: Understanding the glue that binds us all

Unraveling hadron structure with generalized parton distributions

With the advent of high-energy-density (HED) experimental facilities, such as high-energy lasers and fast Z-pinch, pulsed-power facilities, millimeter-scale quantities of matter can be placed in extreme states of density, temperature, and/or velocity. This has enabled the emergence of a new class of experimental science, HED laboratory astrophysics, wherein the properties of matter and the processes that occur under extreme astrophysical conditions can be examined in the laboratory. Areas particularly suitable to this class of experimental astrophysics include the study of opacities relevant to stellar interiors, equations of state relevant to planetary interiors, strong shock-driven nonlinear hydrodynamics and radiative dynamics relevant to supernova explosions and subsequent evolution, protostellar jets and high Mach number flows, radiatively driven molecular clouds and nonlinear photoevaporation front dynamics, and photoionized plasmas relevant to accretion disks around compact objects such as black holes and neutron stars.

/pdf/experimental-astrophysics-with-high-power-lasers-and-z-2ws0p4rgie.pdf

Experimental astrophysics with high power lasers and Z pinches

Relative erosion-rates and impingement ion production mechanisms have been identified for the discharge cathode of a 30 cm ion engine using laser-induced fluorescence (LIF). Mo and W erosion products as well as neutral and singly ionized xenon were interrogated. The erosion increases with both discharge current and voltage and spatially resolved measurements agree with observed erosion patterns. Ion velocity mapping identified back-flowing ions near the regions of erosion with energies sufficient to generate the level of observed erosion. A potential-hill downstream of the cathode was indicated and is suggested to be responsible for the erosion.

/pdf/fmt-2-discharge-cathode-erosion-rate-measurements-via-laser-42mknjsxts.pdf

FMT-2 discharge cathode erosion rate measurements via laser-induced fluorescence

Comparison of a deconvolved ion energy distribution taken in a 500 V ion beam with retarding potential analyzer data showed bulk ion energy agreement within 1%, but only qualified similarity between the distributions Grid misalignment during the LIF experiment may be responsible for the usually broad Doppler broadening As a result, we are presently unable to reliably validate our deconvolution method at 8347 nm

/pdf/diode-laser-induced-fluorescence-of-xenon-ion-velocity-32r2xt0x4n.pdf

Diode Laser-Induced Fluorescence of Xenon Ion Velocity Distributions

Chamber tests of simulated electrodynamic tethers (EDTs) of different geometries operating in a dense high-speed plasma are described. The geometries tested and described here are cylindrical and flat-ribbon tape. By moving the probe samples relative to the plasma source it was possible to vary the density and therefore the effective width over a range of approximately 1 to 2 Debye lengths (/spl lambda//sub D/) for the cylinder sample and 6 to 19 /spl lambda//sub D/ for the tape samples. Several important conclusions can be drawn from the tests. 1) The current-voltage characteristics of the cylinder behave as predicted by orbital-motion-limited (OML) current collection theory in the saturation region. 2) The tape tether had comparable current levels to a theoretical equal area OML cylinder up to an effective width of at least /spl sim/11/spl lambda//sub D/ and possibly wider. 3) Orienting the tape samples parallel or perpendicular to the plasma flow yielded different current responses (perpendicular is larger) above a bias potential that is near the estimated energy of the incoming beam ions. The observed difference was generally more pronounced at larger effective widths (higher densities). 4) It was also necessary to be above this bias potential to have a V/sup 0.5/ current-voltage character appropriate for an ideal cylinder in the OML regime. It is concluded that wide ribbon-like tape tethers can be effective current collectors but that velocity effects will be a factor to consider, especially as relative width of the tape tether (with respect to /spl lambda//sub D/) grows.

/pdf/analysis-of-chamber-simulations-of-long-collecting-probes-in-1aheyebots.pdf

Analysis of chamber simulations of long collecting probes in high-speed dense plasmas

We present and validate a method for extracting velocity distribution functions from laser-induced fluorescence measurements obtained using a xenon ion line with unknown hyperfine constants. The method involves a direct deconvolution of intermodulated experimental results from the laser-induced fluorescence measurements. The intermodulated experiments were done on the 5d[4]7/2 → 6p[3]5/2 transition for singlycharged xenon at 834.7 nm. The hyperfine constants for this line are large enough to distort the results but small enough to have eluded accurate measurement. This approach is validated using both simulated results and a set of measurements taken in a Hall thruster environment. The validity of the method is scrutinized through the uncertainty analysis that follows. The method was determined to contribute at most ±0.1% to the absolute uncertainty of the velocities and at most a 4% decrease to the full-width-at-half-maximum of the velocity distribution functions measured in the accelerating plasma of the Hall thruster.

/pdf/obtaining-velocity-distribution-using-a-xenon-ion-line-with-4230y7830a.pdf

Obtaining Velocity Distribution using a Xenon Ion Line with Unknown Hyperfine Constants

Laser-induced fluorescence and emission spectroscopy were used to interrogate the plasma downstream of the discharge cathode in the FMT-2 ion engine. Ion velocities consistent with a potential hill approximately 0.75 cm downstream of the unkeepered orifice were observed at higher powers. The high energy tail, discharge voltage oscillations, and the concentration of Xe III may collectively contribute to the erosion observed in NSTAR wear tests.

/pdf/characterization-of-the-fmt-2-discharge-cathode-plume-nxirbr7oxw.pdf

Timothy B. Smith

Papers

FMT-2 discharge cathode erosion rate measurements via laser-induced fluorescence

Diode Laser-Induced Fluorescence of Xenon Ion Velocity Distributions

Analysis of chamber simulations of long collecting probes in high-speed dense plasmas

Obtaining Velocity Distribution using a Xenon Ion Line with Unknown Hyperfine Constants

Characterization of the fmt-2 discharge cathode plume