Tm3+^{3+}:Y3_3Ga5_5O12_{12} materials for spectrally multiplexed quantum memories

We investigate the relevant spectroscopic properties of the 795 nm $^3$H$_6$$\leftrightarrow$$^3$H$_4$ transition in 1% Tm$^{3+}$:Y$_3$Ga$_5$O$_{12}$ at temperatures as low as 1.2 K for optical quantum memories based on persistent spectral tailoring of narrow absorption features. Our measurements reveal that this transition has uniform coherence properties over a 56 GHz bandwidth, and a simple hyperfine structure split by $\pm$44 MHz/T with lifetimes of up to hours. Furthermore, we find a $^3$F$_4$ population lifetime of 64 ms -- one of the longest lifetimes observed for an electronic level in a solid --, and an exceptionally long coherence lifetime of 490 $\mu$s -- the longest ever observed for optical transitions of Tm$^{3+}$ ions in a crystal. Our results suggest that this material allows realizing broadband quantum memories that enable spectrally multiplexed quantum repeaters.Comment: 5 pages, 3 figure

Parity violating pion electroproduction off the nucleon

Parity violating (PV) contributions due to interference between $\gamma$ and $Z^0$ exchange are calculated for pion electroproduction off the nucleon. A phenomenological model with effective Lagrangians is used to determine the resulting asymmetry for the energy region between threshold and $\Delta(1232)$ resonance. The $\Delta$ resonance is treated as a Rarita-Schwinger field with phenomenological $N \Delta$ transition currents. The background contributions are given by the usual Born terms using the pseudovector $\pi N$ Lagrangian. Numerical results for the asymmetry are presented.Comment: 17 pages, RevTeX, 6 figures (in separate file figs.uu), uses epsf, accepted for publication in Z. Phys.

Human Immunodeficiency Virus Type 1 p24 Concentration Measured by Boosted ELISA of Heat-Denatured Plasma Correlates with Decline in CD4 Cells, Progression to AIDS, and Survival: Comparison with Viral RNA Measurement

Human immunodeficiency virus type 1 (HIV-1) RNA and p24 antigen concentrations were determined in plasma samples from 169 chronically infected patients (median CD4 cell count, 140 cells/μL; range, 0-1500 cells/μL). p24 quantification involved heat-mediated immune complex dissociation and tyramide signal amplification—boosted ELISA, which has a diagnostic sensitivity similar to that of RNA quantification by a commercial polymerase chain reaction kit. In Cox's proportional hazard models adjusted for CD4 cell count, both RNA (P < .005) and p24 (P = .043) levels were significant predictors of progression to AIDS. Measurement of p24 was superior to measurement of RNA in the model for survival (P = .032 vs. P = .19). p24 level was a significant predictor of CD4 cell decline in models adjusted for CD4 cell counts and was superior or equivalent to RNA level, depending on the group analyzed. Stratification by CD4 cell counts at baseline showed that the superiority of p24 measurement was more pronounced at lower levels of CD4 cells (<200/μL). p24 level may be of interest as a simple and inexpensive predictive marker of disease progressio

Narrow inhomogeneous and homogeneous optical linewidths in a rare earth doped transparent ceramic

Inhomogeneous and homogeneous linewidth are reported in a Eu3+ doped transparent Y2O3 ceramic for the 7F 0-5D0 transition, using high-resolution coherent spectroscopy. The 8.7-GHz inhomogeneous linewidth is close to that of single crystals, as is the 59-kHz homogeneous linewidth at 3 K (T2 = 5.4 μs). The homogeneous linewidth exhibits a temperature dependence that is typical of a crystalline environment, and additional dephasing observed in the ceramic is attributed to magnetic impurities or defects introduced during the synthesis process. The absence of Eu3+segregation at the grain boundaries, evidenced through confocal microfluorescence, further indicates that the majority of Eu3+ions in the ceramic experience an environment comparable to a single crystal. The obtained results suggest that ceramic materials can be competitive with single crystals for applications in quantum information and spectral hole burning devices, beyond their current applications in lasers and scintillatorsThis work was supported by National Science Foundation under award No. PHY-1212462, the European Union FP7 project QuRep (247743), the Spanish Ministry of Economy and Competitiveness (MAT2010-17443) and Comunidad de Madrid (S-2009/MAT-1756