Single-photon-level optical storage in a solid-state spin-wave memory

A long-lived quantum memory is a firm requirement for implementing a quantum repeater scheme. Recent progress in solid-state rare-earth-ion-doped systems justifies their status as very strong candidates for such systems. Nonetheless an optical memory based on spin-wave storage at the single-photon-level has not been shown in such a system to date, which is crucial for achieving the long storage times required for quantum repeaters. In this letter we show that it is possible to execute a complete atomic frequency comb (AFC) scheme, including spin-wave storage, with weak coherent pulses of $\bar{n} = 2.5 \pm 0.6$ photons per pulse. We discuss in detail the experimental steps required to obtain this result and demonstrate the coherence of a stored time-bin pulse. We show a noise level of $(7.1 \pm 2.3)10^{-3}$ photons per mode during storage, this relatively low-noise level paves the way for future quantum optics experiments using spin-waves in rare-earth-doped crystals

Atomic frequency comb memory with spin wave storage in 153Eu3+:Y2SiO5

153Eu3+:Y2SiO5 is a very attractive candidate for a long lived, multimode quantum memory due to the long spin coherence time (~15 ms), the relatively large hyperfine splitting (100 MHz) and the narrow optical homogeneous linewidth (~100 Hz). Here we show an atomic frequency comb memory with spin wave storage in a promising material 153Eu3+:Y2SiO5, reaching storage times slightly beyond 10 {\mu}s. We analyze the efficiency of the storage process and discuss ways of improving it. We also measure the inhomogeneous spin linewidth of 153Eu3+:Y2SiO5, which we find to be 69 \pm 3 kHz. These results represent a further step towards realising a long lived multi mode solid state quantum memory.Comment: 7 pages and 7 figure

Theoretical studies on structural and decay properties of Z=119Z=119 superheavy nuclei

In this manuscript, we analyze the structural properties of $Z=119$ superheavy nuclei in the mass range of 284 $\le$ A $\le$ 375 within the framework of deformed relativistic mean field theory (RMF) and calculate the binding energy, radii, quadrupole deformation parameter, separation energies and density profile. Further, a competition between possible decay modes such as $\alpha-$decay, $\beta-$decay and spontaneous fission (SF) of the isotopic chain of $Z=119$ superheavy nuclei under study is systematically analyzed within self-consistent relativistic mean field model. Moreover, our analysis confirmed that $\alpha-$decay is restricted within the mass range 284 $\leq$ A $\leq$ 296 and thus being the dominant decay channel in this mass range. However, for the mass range 297 $\leq$ A $\leq$ 375 the nuclei are unable to survive fission and hence SF is the principal mode of decay for these isotopes. There is no possibility of $\beta-$decay for the considered isotopic chain. In addition, we forecasted the mode of decay $^{284-296}$119 as one $\alpha$ chain from $^{284}$119 and $^{296}$119, two consistent $\alpha$ chains from $^{285}$119 and $^{295}$119, three consistent $\alpha$ chains from $^{286}$119 and $^{294}$119, four consistent alpha chains from $^{287}$119, six consistent alpha chains from $^{288-293}$119. Also from our analysis we inferred that for the isotopes $^{264-266,269}$Bh both $\alpha$ decay and SF are equally competent and can decay via either of these two modes. Thus, such studies can be of great significance to the experimentalists in very near future for synthesizing $Z=119$ superheavy nuclei.Comment: 14 pages, 6 figures. arXiv admin note: text overlap with arXiv:1611.00232, arXiv:1704.0315

Structural and decay properties of Z=132,138Z=132,138 superheavy nuclei

In this paper, we analyze the structural properties of $Z=132$ and $Z=138$ superheavy nuclei within the ambit of axially deformed relativistic mean-field framework with NL$3^{*}$ parametrization and calculate the total binding energies, radii, quadrupole deformation parameter, separation energies, density distributions. We also investigate the phenomenon of shape coexistence by performing the calculations for prolate, oblate and spherical configurations. For clear presentation of nucleon distributions, the two-dimensional contour representation of individual nucleon density and total matter density has been made. Further, a competition between possible decay modes such as $\alpha$-decay, $\beta$-decay and spontaneous fission of the isotopic chain of superheavy nuclei with $Z=132$ within the range 312 $\le$ A $\le$ 392 and 318 $\le$ A $\le$ 398 for $Z=138$ is systematically analyzed within self-consistent relativistic mean field model. From our analysis, we inferred that the $\alpha$-decay and spontaneous fission are the principal modes of decay in majority of the isotopes of superheavy nuclei under investigation apart from $\beta$ decay as dominant mode of decay in $^{318-322}138$ isotopes.Comment: 16 pages, 10 figures , 8 table

Phenomenological Lambda-Nuclear Interactions

Variational Monte Carlo calculations for ${_{\Lambda}^4}H$ (ground and excited states) and ${_{\Lambda}^5}He$ are performed to decipher information on ${\Lambda}$-nuclear interactions. Appropriate operatorial nuclear and ${\Lambda}$-nuclear correlations have been incorporated to minimize the expectation values of the energies. We use the Argonne $\upsilon_{18}$ two-body NN along with the Urbana IX three-body NNN interactions. The study demonstrates that a large part of the splitting energy in ${_{\Lambda}^4}H$ ($0^+-1^+$) is due to the three-body ${\Lambda}$ NN forces. $_{\Lambda}^{17}O$ hypernucleus is analyzed using the {\it s}-shell results. $\Lambda$ binding to nuclear matter is calculated within the variational framework using the Fermi-Hypernetted-Chain technique. There is a need to correctly incorporate the three-body ${\Lambda}$ NN correlations for $\Lambda$ binding to nuclear matter.Comment: 18 pages (TeX), 2 figure

A new species of the genus \u3ci\u3eGomphomastax\u3c/i\u3e Brunner von Wattenwyl (Orthoptera: Eumastacidae: Gomphomastacinae) from Indian Kashmir

A new species, Gomphomastax nigrovittata Usmani, from Kashmir is described and illustrated. In addition to conventional morphological characters, genitalic structures are also studied. A key to known species of Gomphomastax from Indian Kashmir is given