5,730 research outputs found
Exploiting boundary states of imperfect spin chains for high-fidelity state transfer
We study transfer of a quantum state through XX spin chains with static
imperfections. We combine the two standard approaches for state transfer based
on (i) modulated couplings between neighboring spins throughout the spin chain
and (ii) weak coupling of the outermost spins to an unmodulated spin chain. The
combined approach allows us to design spin chains with modulated couplings and
localized boundary states, permitting high-fidelity state transfer in the
presence of random static imperfections of the couplings. The modulated
couplings are explicitly obtained from an exact algorithm using the close
relation between tridiagonal matrices and orthogonal polynomials [Linear
Algebr. Appl. 21, 245 (1978)]. The implemented algorithm and a graphical user
interface for constructing spin chains with boundary states (spinGUIn) are
provided as Supplemental Material.Comment: 7 pages, 3 figures + spinGUIn description and Matlab files
iepsolve.m, spinGUIn.fig, spinGUIn.
Resolution of Single Spin-Flips of a Single Proton
The spin magnetic moment of a single proton in a cryogenic Penning trap was
coupled to the particle's axial motion with a superimposed magnetic bottle.
Jumps in the oscillation frequency indicate spin-flips and were identified
using a Bayesian analysis.Comment: accepted for publication by Phys. Rev. Lett., submitted 6.June.201
Towards a high-precision measurement of the antiproton magnetic moment
The recent observation of single spins flips with a single proton in a
Penning trap opens the way to measure the proton magnetic moment with high
precision. Based on this success, which has been achieved with our apparatus at
the University of Mainz, we demonstrated recently the first application of the
so called double Penning-trap method with a single proton. This is a major step
towards a measurement of the proton magnetic moment with ppb precision. To
apply this method to a single trapped antiproton our collaboration is currently
setting up a companion experiment at the antiproton decelerator of CERN. This
effort is recognized as the Baryon Antibaryon Symmetry Experiment (BASE). A
comparison of both magnetic moment values will provide a stringent test of CPT
invariance with baryons.Comment: Submitted to LEAP 2013 conference proceeding
Demonstration of the Double Penning Trap Technique with a Single Proton
Spin flips of a single proton were driven in a Penning trap with a
homogeneous magnetic field. For the spin-state analysis the proton was
transported into a second Penning trap with a superimposed magnetic bottle, and
the continuous Stern-Gerlach effect was applied. This first demonstration of
the double Penning trap technique with a single proton suggests that the
antiproton magnetic moment measurement can potentially be improved by three
orders of magnitude or more
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Asymmetry of high-velocity lower crust on the South Atlantic rifted margins and implications for the interplay of magmatism and tectonics in continental breakup
High-velocity lower crust (HVLC) and seaward-dipping reflector (SDR) sequences are typical features of volcanic rifted margins. However, the nature and origin of HVLC is under discussion. Here we provide a comprehensive analysis of deep crustal structures in the southern segment of the South Atlantic and an assessment of HVLC along the margins. Two new seismic refraction lines off South America fill a gap in the data coverage and together with five existing velocity models allow for a detailed investigation of the lower crustal properties on both margins. An important finding is the major asymmetry in volumes of HVLC on the conjugate margins. The seismic refraction lines across the South African margin reveal cross-sectional areas of HVLC 4 times larger than at the South American margin, a finding that is opposite to the asymmetric distribution of the flood basalts in the Paraná–Etendeka Large Igneous Province. Also, the position of the HVLC with respect to the SDR sequences varies consistently along both margins. Close to the Falkland–Agulhas Fracture Zone in the south, a small body of HVLC is not accompanied by SDRs. In the central portion of both margins, the HVLC is below the inner SDR wedges while in the northern area, closer to the Rio Grande Rise-Walvis Ridge, large volumes of HVLC extend far seaward of the inner SDRs.
This challenges the concept of a simple extrusive/intrusive relationship between SDR sequences and HVLC, and it provides evidence for formation of the HVLC at different times during the rifting and breakup process. We suggest that the drastically different HVLC volumes are caused by asymmetric rifting in a simple-shear-dominated extension
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