Multiparticle state tomography: hidden differences

We address the problem of completely characterizing multiparticle states including loss of information to unobserved degrees of freedom. In systems where nonclassical interference plays a role, such as linear-optics quantum gates, such information can degrade interference in two ways, by decoherence and by distinguishing the particles. Distinguishing information, often the limiting factor for quantum optical devices, is not correctly described by previous state-reconstruction techniques, which account only for decoherence. We extend these techniques and find that a single modified density matrix can completely describe partially coherent, partially distinguishable states. We use this observation to experimentally characterize two-photon polarization states in single-mode optical fiber.     

CALET Results after Three Years on Orbit on the International Space Station

Physics of Atomic Nuclei - The CALorimetric Electron Telescope (CALET) is an astroparticle physics experiment installed on the International Space Station since August 2015. The CALET mission was...     

Disconnections in simple and complex structures

Disconnections are interfacial defects with dislocation and step character; for example, twinning dislocations in homo-phase and transformation dislocations in hetero-phase materials. They play important structural roles and are classified as either ‘perfect’, separating energetically degenerate regions of interface, or ‘partial’, bounding a faulted region. In kinetic mechanisms, disconnection motion can be glissile, by conservative climb or climb. In the present paper, disconnection mobility is analyzed in terms of shear and shuffle-type atomic displacements and diffusional flux. This is applied to a sequence of hetero-phase materials with increasing structural complexity, namely the β to α transformation in Ti, θ′ precipitation in Al(Cu) and the orthorhombic to monoclinic martensitic transformation in ZrO₂. A disconnection source mechanism in Ti, involving conservative climb, is also described.     

Pulsed EPR imaging of nitroxides in mice

Nitroxides, unlike trityl radicals, have shorter T₂s which until now were not detectable in vivo by a time-domain pulsed Electron Paramagnetic Resonance (EPR) spectrometer at 300 MHz since their phase memory times were shorter than the spectrometer recovery times. In the current version of the time-domain EPR spectrometer with improved spectrometer recovery times, the feasibility of detecting signals from nitroxide radicals was tested. Among the nitroxides evaluated, deuterated ¹⁵N-Tempone (¹⁵N-PDT) was found to have the longest T₂. The signal intensity profile as a function of concentration of these agents was evaluated and a biphasic behavior was observed; beyond a nitroxide concentration of 1.5 mM, signal intensity was found to decrease as a result of self-broadening. Imaging experiments were carried out with ¹⁵N-PDT in solutions equilibrated with 0%, 5%, 10%, and 21% oxygen using the single point imaging (SPI) modality in EPR. The image intensity in these tubes was found to depend on the oxygen concentration which in turn influences the T₂ of ¹⁵N-PDT. In vivo experiments were demonstrated with ¹⁵N-PDT in anesthetized mice where the distribution and metabolism of ¹⁵N-PDT could be monitored. This study, for the first time shows the capability to image a cell-permeable nitroxide in mice using pulsed EPR in the SPI modality.     

Longitudinally diode-pumped Nd:YAG double-clad planar waveguide laser

We report the demonstration of a near-diffraction-limited, compact, diode-end-pumped double-clad planar waveguide Nd:YAG laser. Efficient laser operation was achieved for the three dominant Nd(3+) transitions, at 1.064, 0.946, and 1.32microm , with TE polarized output powers of 1.33, 0.57, and 0.33 W for the available output couplers. The output beam from the monolithic plane-plane laser cavity had measured M(2) values of 1.0 and 1.8 perpendicular and parallel, respectively, to the plane of the waveguide.     

Investigation of stress and structural damage in H and He implanted Ge using micro‐Raman mapping technique on bevelled samples

The results on structural damage in germanium wafers caused by hydrogen and helium implants of typical doses used in Smart Cut™ Technology (1–6 × 10¹⁶ atoms/cm²) are investigated using Raman mapping and spreading resistance profiling techniques. Raman line‐mapping measurements were performed up to the depth of ~400 nm into a Ge substrate (well beyond the limit of visible light penetration depth) using a bevelling technique. From analysis of the Ge–Ge Raman peak it was found that implantation of H and He introduced a different type of stress, tensile and compressive, respectively and significant structural damage with maximum at the projected range. The obtained data shows that hydrogen incorporation in Ge can act as an acceptor. This is undesirable when the hydrogen ion‐cut technology is applied to high resistivity Ge. The crystalline structure after implantation is completely recovered when annealed at 600 °C for both types of implants. Spreading resistance profiling results reveal that 4−8x10¹⁵ acceptors/cm³ remain after 600 °C, and these are thought to be because of vacancy related defect clusters. Copyright © 2011 John Wiley & Sons, Ltd.     

Structure and control of Coulomb crystals in a Penning trap

We apply rotating electric fields to ion plasmas in a Penning trap to obtain phase-locked rotation about the magnetic field axis. These plasmas, containing up to 10^{6 9}Be⁺ ions, are laser-cooled to millikelvin temperatures so that they freeze into solids. Single body-centered cubic (bcc) crystals have been observed by Bragg scattering in nearly spherical plasmas with ≳ 2 × 10⁵ ions. The detection of the Bragg patterns is synchronized with the plasma rotation, so individual peaks are observed. With phase-locked rotation, the crystal lattice and its orientation can be stable for longer than 30 min or ∼10⁸ rotations. This revised version was published online in July 2006 with corrections to the Cover Date.     

Probing the high momentum component of the deuteron at high Q2

The (2)H(e,e'p)n cross section at a momentum transfer of 3.5 (GeV/c)(2) was measured over a kinematical range that made it possible to study this reaction for a set of fixed missing momenta as a function of the neutron recoil angle θ(nq) and to extract missing momentum distributions for fixed values of θ(nq) up to 0.55 GeV/c. In the region of 35°≤θ(nq)≤45° recent calculations, which predict that final-state interactions are small, agree reasonably well with the experimental data. Therefore, these experimental reduced cross sections provide direct access to the high momentum component of the deuteron momentum distribution in exclusive deuteron electrodisintegration.     

Correlated strength in the nuclear spectral function

We have carried out an (e,e'p) experiment at high momentum transfer and in parallel kinematics to measure the strength of the nuclear spectral function S(k,E) at high nucleon momenta k and large removal energies E. This strength is related to the presence of short-range and tensor correlations, and was known hitherto only indirectly and with considerable uncertainty from the lack of strength in the independent-particle region. This experiment locates by direct measurement the correlated strength predicted by theory.