Direct evidence for the magnetic ordering of Nd ions in NdFeAsO by high resolution inelastic neutron scattering

We investigated the low energy excitations in the parent compound NdFeAsO of the Fe-pnictide superconductor in the $\mu$eV range by a back scattering neutron spectrometer. The energy scans on a powder NdFeAsO sample revealed inelastic peaks at E = 1.600 $\pm 0.003 \mu$eV at T = 0.055 K on both energy gain and energy loss sides. The inelastic peaks move gradually towards lower energy with increasing temperature and finally merge with the elastic peak at about 6 K. We interpret the inelastic peaks to be due to the transition between hyperfine-split nuclear level of the $^{143}$Nd and $^{145}$Nd isotopes with spin $I = 7/2$. The hyperfine field is produced by the ordering of the electronic magnetic moment of Nd at low temperature and thus the present investigation gives direct evidence of the ordering of the Nd magnetic sublattice of NdFeAsO at low temperature

Quantum key distribution using non-classical photon number correlations in macroscopic light pulses

We propose a new scheme for quantum key distribution using macroscopic non-classical pulses of light having of the order 10^6 photons per pulse. Sub-shot-noise quantum correlation between the two polarization modes in a pulse gives the necessary sensitivity to eavesdropping that ensures the security of the protocol. We consider pulses of two-mode squeezed light generated by a type-II seeded parametric amplification process. We analyze the security of the system in terms of the effect of an eavesdropper on the bit error rates for the legitimate parties in the key distribution system. We also consider the effects of imperfect detectors and lossy channels on the security of the scheme.Comment: Modifications:added new eavesdropping attack, added more references Submitted to Physical Review A [email protected]

Production of a Fermi gas of atoms in an optical lattice

We prepare a degenerate Fermi gas of potassium atoms by sympathetic cooling with rubidium atoms in a one-dimensional optical lattice. In a tight lattice we observe a change of the density of states of the system, which is a signature of quasi two dimensional confinement. We also find that the dipolar oscillations of the Fermi gas along the tight lattice are almost completely suppressed.Comment: 4 pages, 4 figures, revised versio

George Biersack Selected to Serve on the Nominators Committee of the Emerson College

News release announces that Chairman of Communication Arts at the University of Dayton, George Biersack, has been selected to serve on the Nominators Committee of the Emerson College

Retinitis pigmentosa. A mimic of neurologic disease

Six patients with various forms of retinitis pigmentosa who were misdiagnosed as having neurologic disease are presented. In five of the patients, visual field defects were misinter-preted as being secondary to a neurologic rather than a retinal problem. In two patients, optic nerve drusen, which accompanied the retinal degeneration, were mistaken for papilledema. Since the diagnosis of retinitis pigmentosa is not always obvious on ophthalmoscopy, the clinician must be aware of the various manifestations of this disorder and be able to distinguish visual field defects on a retinal from a neurologic basis.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26648/1/0000191.pd