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Optical quantum communication utilizing satellite platforms has the potential to extend the reach of quantum key distribution (QKD) from terrestrial limits of ~200 km to global scales. We have developed a thorough ~ numerical simulation using realistic simulated orbits and incorporating the effects of pointing error, diffraction, atmosphere and telescope design, to obtain estimates of the loss and background noise which a satellite-based system would experience. Combining with quantum optics simulations of sources and detection, we determine the length of secure key for QKD, as well as entanglement visibility and achievable distances for fundamental experiments. We analyse the performance of a low Earth orbit satellite for downlink and uplink scenarios of the quantum optical signals. We argue that the advantages of locating the quantum source on the ground justify a greater scientific interest in an uplink as compared to a downlink. An uplink with a ground transmitter of at least 25 cm diameter and a 30 cm receiver telescope on the satellite could be used to successfully perform QKD multiple times per week with either an entangled photon source or with a weak coherent pulse source, as well as perform long-distance Bell tests and quantum teleportation. Our model helps to resolve important design considerations such as operating wavelength, type and specifications of sources and detectors, telescope designs, specific orbits and ground station locations, in view of anticipated overall system performance. [ABSTRACT FROM AUTHOR]

Some MIT researchers [Phys. Rev. A 75, 042327 (2007)] have recently claimed that their implementation of the Slutsky-Brandt attack [Phys. Rev. A 57, 2383 (1998); Phys. Rev. A 71, 042312 (2005)] to the BB84 quantum-key-distribution (QKD) protocol puts the security of this protocol “to the test” by simulating “the most powerful individual-photon attack” [Phys. Rev. A 73, 012315 (2006)]. A related unfortunate news feature by a scientific journal [G. Brumfiel, Quantum cryptography is hacked, News @ Nature (april 2007); Nature 447, 372 (2007)] has spurred some concern in the QKD community and among the general public by misinterpreting the implications of this work. The present article proves the existence of a stronger individual attack on QKD protocols with encrypted error correction, for which tight bounds are shown, and clarifies why the claims of the news feature incorrectly suggest a contradiction with the established “old-style” theory of BB84 individual attacks. The full implementation of a quantum cryptographic protocol includes a reconciliation and a privacy-amplification stage, whose choice alters in general both the maximum extractable secret and the optimal eavesdropping attack. The authors of [Phys. Rev. A 75, 042327 (2007)] are concerned only with the error-free part of the so-called sifted string, and do not consider faulty bits, which, in the version of their protocol, are discarded. When using the provably superior reconciliation approach of encrypted error correction (instead of error discard), the Slutsky-Brandt attack is no more optimal and does not “threaten” the security bound derived by Lütkenhaus [Phys. Rev. A 59, 3301 (1999)]. It is shown that the method of Slutsky and collaborators [Phys. Rev. A 57, 2383 (1998)] can be adapted to reconciliation with error correction, and that the optimal entangling probe can be explicitly found. Moreover, this attack fills Lütkenhaus bound, proving that it is tight (a fact which was not previously known). [ABSTRACT FROM AUTHOR]

Excited states in 124Xe were populated in the reaction 82Se(48Ca, 6 n)124Xe and γ -ray coincidence relationships were measured with the Gammasphere spectrometer. Two new bands are observed and several of the previously known bands are extended in the high- as well as in the low-spin region. Two irregular high-spin structures are also added. The irregularities are a fingerprint of a transition from collective to non-collective behaviour. Configuration assignments to the new structures are proposed on the basis of systematics and by comparing experimental properties with calculations within the framework of the cranking model. [ABSTRACT FROM AUTHOR]

An activation technique was used to investigate relative yields of fission products from the reaction 232Th(n, f ) for neutron energies between 1.3 and 1.8MeV covering the region around the first hyperdeformed resonances. Intensities of characteristic γ-ray transitions were analyzed to search for changes in the mass distribution for neutron energies corresponding to the resonances and below the resonances. Relative increases in yield between 7 and 23% are observed for A ≈ 100 and 132 in the resonance region around 1.6MeV. It is proposed that the yield enhancement of daughter nuclei of the preformed fragments 132Sn and 101Zr arises from cold fission of a di-cluster configuration. The experimental results support theoretical predictions for the existence of hyperdeformed octupole shapes based on the di-nuclear configuration 132Sn + 101Zr. [ABSTRACT FROM AUTHOR]

High-spin states in 124,125,126Xe have been populated in the reaction 82Se (48Ca, xn)130-xXe and γ-ray coincidences were measured with the GAMMASPHERE spectrometer. Twelve new bands extending into the spin 50-60 ħ region are identified in 125Xe and 126Xe and previously known rotational bands at low spins are confirmed and extended. Earlier known structures in 124Xe are confirmed and a new band is observed. Irregular structures are identified at the top of the yrast and a side band in this nucleus. Configuration assignments for the different structures are suggested. [ABSTRACT FROM AUTHOR]

The Euroball-IV γ-detector array, equipped with the ancillary charged particle detector array DIAMANT was used to study the residues of the fusion reaction 64Ni + 64Ni ⇒ 128Ba at Ebeam = 255 and 261 MeV, in an attempt to reach the highest angular momentum and verify the existence of predicted hyperdeformed rotational bands. No discrete hyperdeformed bands were identified, but nevertheless a breakthrough was obtained through a systematic search for rotational ridge structures with very large moments of inertia J(2) ≥ 100 ħ²MeV(-1), in agreement with theoretical predictions for hyperdeformed shapes. Evidence for hyperdeformation was obtained by charged particle + γ-ray gating, selecting triple correlated ridge structures in the continuum of each of the nuclei, 118Te, 124Xe and 124,125Cs. In 7 additional nuclei, rotational ridges were also identified with J(2) = 71-77ħ²MeV(-1),which most probably correspond to superdeformed shape. The angular distributions of the emitted charged particles show an excess in forward direction over expectations from pure compound evaporation, which may indicate that in-complete fusion plays an important role in the population of very elongated shapes. [ABSTRACT FROM AUTHOR]

The quadrupole interaction of the 11- and 12+ isomers in 192,194Pb nuclei has been investigated in the electric field gradient of metallic Bi polycrystalline lattice by the method of time-differential observation of the γ-rays perturbed angular distribution. The electric field gradient strength of the host Bi lattice has been calibrated by using as probe the 12+ isomer in 194Pb. The intrinsic quadrupole moments derived for the 11- isomers described by the π(1h9/21i13/2) intruder configuration are compared with the predictions of mean-field and interacting boson models. [ABSTRACT FROM AUTHOR]

Nuclear structure studies at GSI attracted recently increased interest for the results of present activities as well as for the future project FAIR. A broad range of physics phenomena can be addressed by high-resolution in-beam γ-ray spectroscopy experiments with radioactive beams offered within the Rare Isotopes Spectroscopic INvestigation at GSI (RISING) project. It combined the EUROBALL Ge-Cluster detectors, the MINIBALL Ge detectors, the HECTOR-BaF detectors, and the fragment separator FRS. The secondary beams produced at relativistic energies were used for Coulomb excitation or secondary fragmentation experiments to study projectile like nuclei by measuring de-excitation photons. The first results of the "fast beam campaign" is discussed in comparison to various shell model calculations. The discussion focuses on the N = 32, 34 sub-shell closure based on neutron rich Cr isotopes. Alternatively, the relativistic radioactive beams, both in their ground and isomeric states, were implanted and their decay could be investigated. The "stopped beam campaign" has started in October 2005 with a series of g-factor measurements. It continued from February 2006 with the next configuration and the main goal of identification of new isomers and angular momentum population in fragmentation reactions. [ABSTRACT FROM AUTHOR]

The first excited 2+ states in neutron-rich 54,56,58Cr were populated by relativistic Coulomb excitation and B (E2, 2 → 0+) values were determined for 56Cr and 58Cr. The B(E2) values show a minimum for 56Cr providing evidence for a subshell closure at N=32. [ABSTRACT FROM AUTHOR]

High-spin states in161Lu were investigated using the EUROBALL spectrometer. A previously known triaxial superdeformed band has been extended to higher spins and a new band with similar characteristics has been discovered. Comparison to systematically occurring wobbling bands in Lu isotopes strongly suggests that these two bands represent thenw = 0 and 1 wobbling excitations in161Lu. [ABSTRACT FROM AUTHOR]

High-spin states of the nucleus 163Lu have been populated through the fusion-evaporation reaction 139La(29Si, 5n) with a beam energy of 157 MeV. In addition to the two lowest excited triaxial strongly deformed (TSD) bands, recently interpreted as one- and two-phonon wobbling excitations, a third excited TSD band has been firmly established decaying to the yrast TSD band. The assignment of this band as a three-quasiparticle band shows together with the normal deformed (ND) level scheme the presence not only of shape coexistence between ND and TSD structures, but also an interplay of wobbling and quasiparticle excitations in the triaxial strongly deformed potential well of 163Lu. [ABSTRACT FROM AUTHOR]

Progress in the experimental techniques used to investigate superdeformed fission isomers in the actinides allowed for detailed spectroscopic results of collective properties as well as for the identification of the rotational structure of multiphonon vibrational excitations. A novel approach could be established to determine the depth of the second potential well. [ABSTRACT FROM AUTHOR]

High-spin states in161Lu and162Lu have been investigated using the GASP γ-ray spectrometer array. Excited states in these nuclei have been populated through the100Mo(65Cu, xn) reaction at a beam energy of 260 MeV. Four presumably triaxial superdeformed bands, three in162Lu and one in161Lu, have been observed. This is the first evidence for triaxial superdeformation in the two isotopes. [ABSTRACT FROM AUTHOR]

The even-even nucleus 136Nd was studied via in-beam γ-ray spectroscopy using the 16O + 125Te reaction at 100 MeV and the EUROBALL array. One new dipole band was observed. Together with a previously identified dipole band, whose position in the level scheme is revised, the new band forms a doublet structure similar to the recently observed chiral bands in the odd-odd neighboring nuclei. This would be the first case of a chiral doublet in an even-even nucleus. [ABSTRACT FROM AUTHOR]

Lifetimes of states in the yrast superdeformed bands of 163Lu and 164Lu were determined in a Doppler-shift attenuation-method experiment. From fractional Doppler shifts and line shapes, average transition quadrupole moments, Qt = 8.2-0.6 +1.0 b and 7.1-0.6 +0.5 b, were deduced for one of the bands in 163Lu and 164Lu, respectively. These values are much larger than the quadrupole moment of the normal-deformed yrast band in 163Yb, Qt = 4.9-0.4 +1.3 b, that was also determined in this experiment. Comparison to cranking calculations indicates that both superdeformed bands correspond to a local potential energy minimum with a pronounced triaxiality, γ∼ 20°. [ABSTRACT FROM AUTHOR]

High-spin properties of the nucleus 169Hf have been studied through the fusion evaporation reaction 96Zr(76Ge,3n)169Hf at a beam energy of 310 MeV. The known rotational bands have been extended considerably and 6 new bands have been established, four of which form coupled bands with pronounced M1 connections. Quasiparticle assignments are suggested for the new band structures, and it appears that coupling to vibrational degrees of freedom plays a role. Both coupled bands involve the excitation of quasiprotons. In the region of highest spin, a large alignment gain is interpreted in terms of a mixed crossing where an h9/2 and an h11/2 quasiproton provide the two signatures of the aligning configuration. [ABSTRACT FROM AUTHOR]

Lifetimes for low-lying members of the irregular Δ I = 1 band in 196Pb have been measured by means of the EUROBALL spectrometer using the coincidence recoil distance technique. The 164Dy(36S,4n)196Pb reaction at a beam energy of 168 MeV was used. The data were analyzed with the differential decay-curve method (DDCM). A characteristic drop in the reduced transition probabilities with increasing angular momentum was observed in agreement with predictions by the semiclassical model for the shears mechanism. [ABSTRACT FROM AUTHOR]

Transitions between nuclear states with a large deformation difference may have large transition probabilities for E0 decay. Such an E0 decay has been found in the decay of the superdeformed 238U fission isomer back into the normal-deformed states [1]. However, a search for the E0 back-decay in 236U showed no result [2]. A setup has been developed to search for conversion electrons in this decay. [ABSTRACT FROM AUTHOR]

We report the identification of six new superdeformed (SD) bands in 197,198Pb observed with the EUROBALL IV spectrometer. The results are interpreted in the framework of cranked Hartree-Fock calculations with approximate projection on the particle number by means of the Lipkin-Nogami method. A mixing between quasi-particle excitations and an octupole vibration is suggested in the two SD isotopes. We have estimated the ordering of the neutron valence orbitals and confirm indirectly a N = 118 SD gap. [ABSTRACT FROM AUTHOR]

Using conversion electron and γ-ray spectroscopy combined with a recoil gating method, excited states in 188Pb have been investigated. Further evidence for two excited low-lying 0+ states has been found leading to an interpretation as a multiple shape coexistence in 188Pb. [ABSTRACT FROM AUTHOR]

High-spin states in 202Pb and 203Pb have been investigated by in-beam γ-ray spectroscopy following the reaction 198Pt(9Be,xn). A search for magnetic rotational bands in these isotopes confirmed one of the two bands previously assigned to 202Pb and revealed a new band in this isotope. No evidence for magnetic rotation has been found in 203Pb. [ABSTRACT FROM AUTHOR]

This work has established eight cross-talk transitions between the two signature partner superdeformed (SD) bands in 197Pb with the EUROBALL IV spectrometer. Directional correlations from oriented states measurements confirm the Δ I = 1 character of these transitions. The flat behaviour of the dynamical moment of inertia and the agreement between the experimental and microscopic HF+BCS values of ( gK - gR) K/ Q0 suggest that the configuration of the SD bands is based upon the υ[752]5/2- neutron intruder orbital. The derived effective spin gyromagnetic factor gs eff is found to be not quenched, and is close to the theoretical gs free value. [ABSTRACT FROM AUTHOR]

The nucleus 166Hf has been populated by the reaction 96Zr(74Ge,4n) using a beam energy of 310MeV. γ-rays were detected with the EUROBALL III detector array. Fourteen new normal-deformed rotational bands, of which six form coupled pairs, have been observed in 166Hf. Four previously known bands have been extended to considerably higher spin, and configurations of the new bands are proposed. Two different bands have been assigned configurations involving the same orbitals at high spin. The two coupling schemes, deformation and rotation alignment, are discussed in connection with this new observation, which calls for a formulation of co-existing coupling schemes in six-quasiparticle structures involving the same orbitals at high spin. [ABSTRACT FROM AUTHOR]

High–spin states in 200Hg have been investigated by in–beam γ–ray spectroscopy following the reaction 198Pt(9Be,α3n). The α–emission channel leading to 200Hg is strongly enhanced which may be explained by an incomplete fusion reaction with pre–equilibrium emission of the α particle. The level scheme is extended to higher spins and new band crossings are observed. The band structures are compared to the lighter Hg isotopes with even mass number. [ABSTRACT FROM AUTHOR]

Magnetic–rotational bands in the nearly spherical nuclei 197Pb and 199Pb and their decay to the normal states have been investigated by in–beam conversion electron spectroscopy following (heavy ion,xn) reactions. The expected M1 multipolarity of the in–band transitions has been confirmed for the strongest bands and the multipolarity of several transitions in the decay of the bands has been determined. [ABSTRACT FROM AUTHOR]

The regular sequences of strongly enhanced M1 γ-ray transitions, that have been discovered in near-spherical neutron-deficient Pb isotopes, are caused by quantal rotation of anisotropic arrangements of nucleonic currents. This represents a new mode of nuclear excitation which has been called Magnetic Rotation. The properties of the magnetic-rotational bands are discussed. The experimental proof for their configuration, the angular momentum coupling scheme and its development along the bands is presented. [ABSTRACT FROM AUTHOR]

A new region of superdeformed shapes with a pronounced triaxiality coexisting with normal deformation exists for nuclei with N ~ 94 and Z ~ 71. Calculations with the Ultimate Cranker have revealed that triaxial SD minima with γ ~ ±20° are expected for all symmetry groups (π, α). In an odd-odd nucleus, the possibility exists to exploit the various combinations of proton and neutron orbitals which are expected to sample the triaxial minima differently. A search for such structures was performed as one of the first Euroball experiments using the reactionLa(Si,4n) with thin self-supporting targets at a beam energy of 145 MeV, provided by the Legnaro XTU tandem accelerator. The preliminary analysis has provided a major extension of the known (normal deformed) level scheme inLu, in addition to ~7 new, presumably triaxial, SD bands inLu. These bands have dynamical moments of inertia similar to those found inLu. The new data are compared to expectations from calculations with the code 'Ultimate Cranker'. [ABSTRACT FROM AUTHOR]

Lifetimes of ten states with spins between 23 and 32 have been measured in a cascade of dipole transitions inHg using the Doppler-shift recoil-distance method. Average reduced transition probabilities, deduced from the lifetimes, are B(M1)≈0.01 and 1.1 µ in the lower and higher spin region of the cascade, respectively, and B(E2)≈0.13 (eb). The jump in the B(M1) values can be explained by different multi-quasiparticle configurations in the lower and higher spin regions of the band. [ABSTRACT FROM AUTHOR]

We report on a measurement of the lifetime of the 1414 keV state inTh by the Doppler-shift recoil-distance method. This 4 state shows all characteristics of a nearly-harmonic two-phonon γ-vibrational excitation. The result for the B( E2) value obtained from the lifetime, τ=3.2 ± 0.7 ps, is in agreement with an earlier estimate of the collectivity from Coulomb-excitation yields and supports the interpretation of the 1414 keV state as a two-phonon γ-vibrational excitation. [ABSTRACT FROM AUTHOR]

High-spin states inHf, populated in theTe(Ca, 5 n) reaction, were investigated using the Berkeley HERA γ-ray spectrometer array. The previously known level scheme ofHf is appreciably extended. Intrinsic configurations, band crossing frequencies and aligned angular momenta are interpreted within the frame-work of the cranked shell model. It is suggested that the alignments of the second neutron pair and of the first proton pair inHf occur at ħω≈0.44 MeV and ≈0.48 MeV, respectively. The systematic trend of these alignment frequencies for the Hf isotopes and for the N=93 isotones is discussed. [ABSTRACT FROM AUTHOR]

High-spin states in the oblate-deformed nucleiHg andHg were populated in thePt( α, xn) reaction and investigated by in-beam γ-ray spectroscopy using six Compton-suppressed Ge detectors. The level schemes of both nuclei are extended considerably. The level structure is interpreted within the framework of the cranked shell model. Good agreement is obtained between model predictions and experimental results. [ABSTRACT FROM AUTHOR]

The level structure ofPo has been studied using aDy(Ar, 4n) reaction and a recoil-catcher technique to reduce fission. The results showed a sharp drop off in the first (2) and (4) energies relative to systematics implying an abrupt increase in the quadrupole collectivity at N=112. In addition, second (2) and(4) states were identified at 859 and 1388 keV, respectively, suggesting the discovery of a 4p2h deformed band in Po isotopes which is related to known 2p2h proton bands in several Pb isotopes. A promptW(Ne, 5n @#@) experiment located similar second 2 and 4 states at 1039 and 1483 keV inPo providing corroboration and extended information on the properties of the new Po deformed bands. A measured halflife of 850 (90) ns for the 2491 keV (11) state inPo implied collective E3 contributions to the extracted B (@#@ E3; 11→8)=27(5) W.u. [ABSTRACT FROM AUTHOR]

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