Crustal structure between the Knipovich Ridge and the Van Mijenfjorden (Svalbard)

The Alfred Wegener Institute of Polar and Marine Research, the University of Bergenand the Hokkaido University acquired new seismic refraction data along a transect fromthe Knipovich Ridge to the inner Van Mijenfjorden in southern Svalbard. A close spacing ofon- and offshore receivers and a dense marine shot pattern provide the data for a high resolutionp-wave velocity model for geological interpretation. Additional new seismic reflection data(University of Bergen) yield structural information for a more reliable analysis.Crustal thickness along the Van Mijenfjorden is 33 to 34 km. Seismic velocities of 5.0 km/sare observed within the upper crustal section of the Tertiary Central Spitsbergen Basin.A Paleozoic sedimentary basin with a depth of 8 to 10 km is associated with the Nordfjorden Block.The seismic velocities are up to 6.0 km/s. Paleozoic sedimentary rocks are expected furtherto the west of the Hornsund Lineament since seismic velocities reveal a similar range here.West of the Bellsund the continental crust thins gradually over a 90 km wide rifted zone.The velocity structure within this section is very complex and comprises zones of decreasedvelocities below the West Spitsbergen Fold Belt (down to 20 km depth) and slightly elevatedvelocities (7.2 km/s) at the crust-mantle transition. The first structure is interpreted as intensivelyfractured rocks linked to post-Late Paleocene transpressive orogenic activity and subsequentlyaffected by transtension during break-up from Greenland. The faster deep-crustal velocities aresupposed to express magmatic intrusions of an unidentified origin. Melts could either be channelled by theSpitsbergen Shear Zone from more distant sources, or originate in magmatic interaction between the northern Knipovich Ridgeand the neighbouring young rifted crust.Oceanic crust each side of the Knipovich Ridge is thin (~3.5 km) and is characterised by theabsence of oceanic layer 3 (3.5/4.1 to 4.7 km/s). The oceanic section exhibits zones of verythin crust (~1 km) that are interpreted as fracture zones. Beneath these we observed decreasedmantle velocities (~7.3 km/s) indicating probable serpentinization of peridotites along thesefracture zones. Thickness variations further provide information about the segmentationand magma supply along the northern Knipovich Ridge

Entangled states that cannot reproduce original classical games in their quantum version

A model of a quantum version of classical games should reproduce the original classical games in order to be able to make a comparative analysis of quantum and classical effects. We analyze a class of symmetric multipartite entangled states and their effect on the reproducibility of the classical games. We present the necessary and sufficient condition for the reproducibility of the original classical games. Satisfying this condition means that complete orthogonal bases can be constructed from a given multipartite entangled state provided that each party is restricted to two local unitary operators. We prove that most of the states belonging to the class of symmetric states with respect to permutations, including the N-qubit W state, do not satisfy this condition.Comment: 4 page

Probabilistic cloning with supplementary information

We consider probabilistic cloning of a state chosen from a mutually nonorthogonal set of pure states, with the help of a party holding supplementary information in the form of pure states. When the number of states is 2, we show that the best efficiency of producing m copies is always achieved by a two-step protocol in which the helping party first attempts to produce m-1 copies from the supplementary state, and if it fails, then the original state is used to produce m copies. On the other hand, when the number of states exceeds two, the best efficiency is not always achieved by such a protocol. We give examples in which the best efficiency is not achieved even if we allow any amount of one-way classical communication from the helping party.Comment: 6 pages, no figure

Faithful qubit distribution assisted by one additional qubit against collective noise

We propose a distribution scheme of polarization states of a single photon over collective-noise channel. By adding one extra photon with a fixed polarization, we can protect the state against collective noise via a parity-check measurement and post-selection. While the scheme succeeds only probabilistically, it is simpler and more flexible than the schemes utilizing decoherence-free subspace. An application to BB84 protocol through collective noise channel, which is robust to the Trojan horse attack, is also given.Comment: 4 pages, 3 figures; published version in Phys. Rev. Let