Siberian snakes and spin-flipping in storage rings

A Siberian snake, which is a 180° spin rotator, can be used to preserve electrons’, protons’ or light ions’ beam polarization during acceleration by forcing the spin tune to be constant and equal to 1/2, independent of the beam energy. A compact helical dipole snake, which creates only a small orbit excursion inside the snake, could be used in EPIC. Frequent polarization reversals, or spin-flips, of a stored polarized high-energy beam could greatly reduce the systematic errors of spin asymmetry measurements in a scattering asymmetry experiment. Such polarization reversals can be done by ramping an rf-dipole or an rf-solenoid magnet’s frequency through an rf-induced depolarizing resonance. The strength of an rf-solenoid decreases with the beam’s energy due to the Lorenz contraction of the solenoid’s longitudinal ∫ B⋅dl,∫B⋅dl, while the strength of an rf-dipole remains almost unchanged. Thus, it is more practical to use an rf-dipole spin-flipper in EPIC’s electron and ion rings. © 2001 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87419/2/355_1.pd

Experimental Bell Inequality Violation with an Atom and a Photon

We report the measurement of a Bell inequality violation with a single atom and a single photon prepared in a probabilistic entangled state. This is the first demonstration of such a violation with particles of different species. The entanglement characterization of this hybrid system may also be useful in quantum information applications.Comment: 4 pages, 2 figure

Extreme Starlight Polarization in a Region with Highly Polarized Dust Emission

Galactic dust emission is polarized at unexpectedly high levels, as revealed by Planck. The origin of the observed $\simeq 20\%$ polarization fractions can be identified by characterizing the properties of optical starlight polarization in a region with maximally polarized dust emission. We measure the R-band linear polarization of 22 stars in a region with a submillimeter polarization fraction of $\simeq 20$. A subset of 6 stars is also measured in the B, V and I bands to investigate the wavelength dependence of polarization. We find that starlight is polarized at correspondingly high levels. Through multiband polarimetry we find that the high polarization fractions are unlikely to arise from unusual dust properties, such as enhanced grain alignment. Instead, a favorable magnetic field geometry is the most likely explanation, and is supported by observational probes of the magnetic field morphology. The observed starlight polarization exceeds the classical upper limit of $\left[p_V/E\left(B-V\right)\right]_{\rm max} = 9$%mag$^{-1}$ and is at least as high as 13%mag$^{-1}$ that was inferred from a joint analysis of Planck data, starlight polarization and reddening measurements. Thus, we confirm that the intrinsic polarizing ability of dust grains at optical wavelengths has long been underestimated.Comment: Accepted by A&AL, data to appear on CDS after publication. 6 page

Efficient fluorescence collection from trapped ions with an integrated spherical mirror

Efficient collection of fluorescence from trapped ions is crucial for quantum optics and quantum computing applications, specifically, for qubit state detection and in generating single photons for ion-photon and remote ion entanglement. In a typical setup, only a few per cent of ion fluorescence is intercepted by the aperture of the imaging optics. We employ a simple metallic spherical mirror integrated with a linear Paul ion trap to achieve photon collection efficiency of at least 10% from a single Ba$^+$ ion. An aspheric corrector is used to reduce the aberrations caused by the mirror and achieve high image quality.Comment: 5 pages and 4 figure

Nuclear magnetic octupole moment and the hyperfine structure of the 5D3/2,5/25D_{3/2,5/2} states of the Ba+^+ ion

The hyperfine structure of the long-lived $5D_{3/2}$ and $5D_{5/2}$ levels of Ba$^+$ ion is analyzed. A procedure for extracting relatively unexplored nuclear magnetic moments $\Omega$ is presented. The relevant electronic matrix elements are computed in the framework of the ab initio relativistic many-body perturbation theory. Both the first- and the second-order (in the hyperfine interaction) corrections to the energy levels are analyzed. It is shown that a simultaneous measurement of the hyperfine structure of the entire $5D_J$ fine-structure manifold allows one to extract $\Omega$ without contamination from the second-order corrections. Measurements to the required accuracy should be possible with a single trapped barium ion using sensitive techniques already demonstrated in Ba$^+$ experiments.Comment: Phys Rev A in pres