Saint Mary's Faculty Articles and Other Works
http://library2.smu.ca:80/handle/01/21880
2017-11-03T20:02:03ZThe structure of superqubit states
http://library2.smu.ca:80/handle/01/27169
The structure of superqubit states
Superqubits provide a supersymmetric generalisation of the conventional qubit in quantum information theory. After a review of their current status, we address the problem of generating entangled states. We introduce the global unitary supergroup UOSp((3[superscript n] + 1)/2|(3[superscript n] - 1)/2) for an n-superqubit system, which contains as a subgroup the local unitary supergroup [UOSp](2|1)][superscript n]. While for 4 > n > 1 the bosonic subgroup in UOSp((3[superscript n] + 1)/2|(3[superscript n] - 1)/2) does not contain the standard global unitary group SU(2[superscript n]), it does have an USp(2[superscript n]) [subset] SU (2[superscript n]) subgroup which acts transitively on the n-qubit subspace, as required for consistency with the conventional multi-qubit framework. For two superqubits the UOSp(5|4) action is used to generate entangled states from the "bosonic" separable state |00>.
Preprint
2015-08-01T00:00:00ZEvidence of Soft Dipole Resonance in 11Li with Isoscalar Character
http://library2.smu.ca:80/handle/01/27163
Evidence of Soft Dipole Resonance in 11Li with Isoscalar Character
The first conclusive evidence of a dipole resonance in 11Li having isoscalar character observed from inelastic scattering with a novel solid deuteron target is reported. The experiment was performed at the newly commissioned IRIS facility at TRIUMF. The results show a resonance peak at an excitation energy of 1.03 [plus or minus] 0.03 MeV with a width of 0.51 [plus or minus] 0.11 MeV (FWHM). The angular distribution is consistent with a dipole excitation in the distorted-wave Born approximation framework. The observed resonance energy together with shell model calculations show the first signature that the monopole tensor interaction is important in 11Li. The first ab initio calculations in the coupled cluster framework are also presented.
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2015-05-12T00:00:00ZSpectroscopy of [superscript 9][subscript lambda]Li by electroproduction
http://library2.smu.ca:80/handle/01/27141
Spectroscopy of [superscript 9][subscript lambda]Li by electroproduction
Background: In the absence of accurate data on the free two-body hyperon-nucleon interaction, the spectra of hypernuclei provides information on the details of the effective hyperon-nucleon interaction.
Purpose: To obtain a high-resolution binding-energy spectrum for the [superscript 9]Be(e,e'K[superscript plus])[superscript 9][lambda] Li reaction.
Method: Electroproduction of the hypernucleus [superscript 9][lambda] Li has been studied for the first time with sub-MeV energy resolution in Hall A at Jefferson Lab on a [superscript 9]Be target. In order to increase the counting rate and to provide unambiguous kaon identification, two superconducting septum magnets and a ring imaging Cherenkov detector were added to the Hall A standard equipment.
Results: The cross section to low-lying states of [superscript 9][lambda] Li is concentrated within 3 MeV of the ground state and can be fit with four peaks. The positions of the doublets agree with theory while a disagreement could exist with respect to the relative strengths of the peaks in the doublets. The [lambda] separation energy, B[subscript lambda], of 8.36 [plus or minus] 0.08 (stat.) [plus or minus]0.08 (syst.) MeV was measured, in agreement with an earlier experiment.
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2015-03-04T00:00:00ZPhotoproduction of the [omega] meson on the proton near threshold
http://library2.smu.ca:80/handle/01/27075
Photoproduction of the [omega] meson on the proton near threshold
An experimental study of [omega] photoproduction on the proton was conducted by using the Crystal Ball and TAPS multiphoton spectrometers together with the photon tagging facility at the Mainz Microtron MAMI. The [gamma] p [right arrow] [omega] p differential cross sections are measured from threshold to the incident-photon energy E[subscript gamma] = 1.40 GeV (W = 1.87 GeV for the center-of-mass energy) with 15-MeV binning in E[subscript gamma] and full production-angle coverage. The quality of the present data near threshold gives access to a variety of interesting physics aspects. As an example, an estimation of the [omega]N scattering length [alpha subscript omega]p is provided.
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2015-04-30T00:00:00ZSeparated response functions in exclusive, forward [pi superscript plus or minus] electroproduction on deuterium
http://library2.smu.ca:80/handle/01/27074
Separated response functions in exclusive, forward [pi superscript plus or minus] electroproduction on deuterium
Measurements of forward exclusive meson production at different squared four-momenta of the exchanged virtual photon, Q[superscript 2], and at different four-momentum transfer, t, can be used to probe QCD’s transition from meson-nucleon degrees of freedom at long distances to quark-gluon degrees of freedom at short scales. Ratios of separated response functions in [pi superscript]− and[pi superscript]+ electroproduction are particularly informative. The ratio for transverse photons may allow this transition to be more easily observed, while the ratio for longitudinal photons provides a crucial verification of the assumed pole dominance, needed for reliable extraction of the pion form
factor from electroproduction data.
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2015-01-07T00:00:00ZSimultaneous analysis of the elastic scattering and breakup channel for the reaction [superscript 11]Li + [superscript 208]Pb at energies near the Coulomb barrier
http://library2.smu.ca:80/handle/01/27070
Simultaneous analysis of the elastic scattering and breakup channel for the reaction [superscript 11]Li + [superscript 208]Pb at energies near the Coulomb barrier
We present a detailed analysis of the elastic scattering and breakup channel for the reaction of [superscript 11]Li on [superscript 208]Pb at incident laboratory energies of 24.3 and 29.8 MeV, measured at the radioactive ion beam facility of TRIUMF, in Vancouver, Canada. A large yield of [superscript 9]Li fragments was detected by four charged particle telescopes in a wide angular range. The experimental angular and energy distributions of these [superscript 9]Li fragments have been compared to coupled-reaction-channel and continuum-discretized coupled-channel calculations. The large production of [superscript 9]Li fragments at small angles can be explained by considering a direct breakup mechanism, while at medium-large angles a competition between direct breakup and neutron transfer to the continuum of the [superscript 208]Pb target was observed.
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2015-10-15T00:00:00ZFirst measurement of target and beam-target asymmetries in the [gamma] p [right arrow] [pi superscript 0][eta] p reaction
http://library2.smu.ca:80/handle/01/27069
First measurement of target and beam-target asymmetries in the [gamma] p [right arrow] [pi superscript 0][eta] p reaction
The first data on target and beam-target asymmetries for the [gamma] p [right arrow] [pi superscript 0][eta] p reaction at photon energies from 1050 up to 1450 MeV are presented. The measurements were performed using the Crystal Ball and TAPS detector setup at the Glasgow tagged photon facility of the Mainz Microtron MAMI. The general assumption that the reaction is dominated by the [delta] 3/2 [superscript −] amplitude is confirmed. The data are in particular sensitive to small contributions from other partial waves.
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2015-05-26T00:00:00ZMeasurement of [pi superscript 0] photoproduction on the proton at MAMI C
http://library2.smu.ca:80/handle/01/27068
Measurement of [pi superscript 0] photoproduction on the proton at MAMI C
Differential cross sections for the [gamma]p[right arrow][pi superscript 0]p reaction have been measured with the A2 tagged-photon facilities at the Mainz Microtron, MAMI C, up to the center-of mass energy W = 1.9 GeV. The new results, obtained with a fine energy and angular binning, increase the existing quantity of [pi superscript 0] photoproduction data by ∼47%. Owing to the unprecedented statistical accuracy and the full angular coverage, the results are sensitive to high partial-wave amplitudes. This is demonstrated by the decomposition of the differential cross sections in terms of Legendre polynomials and by further comparison to model predictions. A new solution of the SAID partial-wave analysis obtained after adding the new data into the fit is presented.
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2015-08-24T00:00:00ZThe pitfalls of deciding whether a quantum channel is (conjugate) degradable and how to avoid them
http://library2.smu.ca:80/handle/01/27067
The pitfalls of deciding whether a quantum channel is (conjugate) degradable and how to avoid them
To decide whether a quantum channel is degradable is relatively easy: one has to find at least one example of a degrading quantum channel. But in general, no conclusive criterion exists to show the opposite. Using elementary methods we derive a necessary and sufficient condition to decide under what circumstances the conclusion is unambiguous. The findings lead to an extension of the antidegradability region for qubit and qutrit transpose depolarizing channels. In the qubit case we reproduce the known results for the class of qubit depolarizing channels (due to their equivalence). One of the consequences is that the optimal qubit and qutrit asymmetric cloners possess a single-letter quantum capacity formula. We also investigate the ramifications of the criterion for the search of exclusively conjugate degradable channels.
Post-print
2015-01-01T00:00:00ZIs HE 0436–4717 anemic? A deep look at a bare Seyfert 1 galaxy
http://library2.smu.ca:80/handle/01/27066
Is HE 0436–4717 anemic? A deep look at a bare Seyfert 1 galaxy
A multi-epoch, multi-instrument analysis of the Seyfert 1 galaxy HE 0436–4717 is conducted using optical to X-ray data from XMM–Newton and Swift (including the Burst Alert Telescope). Fitting of the UV-to-X-ray spectral energy distribution shows little evidence of extinction and the X-ray spectral analysis does not confirm previous reports of deep absorption edges from O VIII.HE 0436–4717 is a ‘bare’ Seyfert with negligible line-of-sight absorption making it ideal to study the central X-ray emitting region. Three scenarios were considered to describe the X-ray data: partial covering absorption, blurred reflection, and soft Comptonization. All three interpretations describe the 0.5–10.0 keV spectra well. Extrapolating the models to 100 keV results in poorer fits for the partial covering model.When also considering the rapid variability during one of the XMM–Newton observations, the blurred reflection model appears to describe all the observations in the most self-consistent manner. If adopted, the blurred reflection model requires a very low iron abundance in HE 0436–4717. We consider the possibilities that this is an artefact of the fitting process, but it appears possible that it is intrinsic to the object.
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2015-06-11T00:00:00Z