Reversibility in the Extended Measurement-based Quantum Computation

When applied on some particular quantum entangled states, measurements are universal for quantum computing. In particular, despite the fondamental probabilistic evolution of quantum measurements, any unitary evolution can be simulated by a measurement-based quantum computer (MBQC). We consider the extended version of the MBQC where each measurement can occur not only in the (X,Y)-plane of the Bloch sphere but also in the (X,Z)- and (Y,Z)-planes. The existence of a gflow in the underlying graph of the computation is a necessary and sufficient condition for a certain kind of determinism. We extend the focused gflow (a gflow in a particular normal form) defined for the (X,Y)-plane to the extended case, and we provide necessary and sufficient conditions for the existence of such normal forms

Experimental realization of Dicke states of up to six qubits for multiparty quantum networking

We report the first experimental generation and characterization of a six-photon Dicke state. The produced state shows a fidelity of F=0.56+/-0.02 with respect to an ideal Dicke state and violates a witness detecting genuine six-qubit entanglement by four standard deviations. We confirm characteristic Dicke properties of our resource and demonstrate its versatility by projecting out four- and five-photon Dicke states, as well as four-photon GHZ and W states. We also show that Dicke states have interesting applications in multiparty quantum networking protocols such as open-destination teleportation, telecloning and quantum secret sharing.Comment: 4 pages, 4 figures, RevTeX

Fatal lymphoproliferation and acute monocytic leukemia-like disease following infectious mononucleosis in the elderly

Three elderly patients are reported, in whom serologically confirmed recent infectious mononucleosis is followed by fatal lymphoproliferation (case 1), by acute monocytic leukemia (case 2), and by acute probably monocytic leukemia (case 3)

Target Zones in History and Theory: Lessons from an Austro-Hungarian Experiment (1896-1914)

The first known experiment with an exchange rate band took place in Austria- Hungary between 1896 and 1914. The rationale for introducing this policy rested on precisely those intuitions that the modern literature has emphasized: the band was designed to secure both exchange rate stability and monetary policy autonomy. However, unlike more recent experiences, such as the ERM, this policy was not undermined by credibility problems. The episode provides an ideal testing ground for some important ideas in modern macroeconomics: specifically, can formal rules, when faithfully adhered to, provide policy makers with some advantages such as short term autonomy? First, we find that a credible band has a "microeconomic" influence on exchange rate stability. By reducing uncertainty, a credible fluctuation band improves the quality of expectations, a channel that has been neglected in the modern literature. Second, we show that the standard test of the basic target zone model is flawed and develop an alternative methodology. We believe that these findings shed a new light on the economics of exchange rate bands

An alternative Mesozoic geodynamic model for the evolution of the Central Coastal ranges of Peru: the Rio Cañete Basin

Integration of detailed stratigraphic, sedimentologic and tectonic studies of the Río Cañete Basin with opening and divergence rates of the South Atlantic Ocean, overriding plate velocity, trench migration, subducting age (Fig. 1) etc. and the protracted Mesozoic Farallon Plate oblique convergence parameters provide new lines of evidence to suggest an alternative model for the evolution of the Peruvian margin. These unorthodox model departures significantly from the classic and simplistic Andean Model used in the literature. The western margin of Gondwana experience severe lithosphere extension coeval with arc magmatism since at least Middle Triassic. Actually, only the uppermost Jurassic unit is displayed along the Río Cañete Basin, however, it is important to take into account that northward the Jurassic arc sequence terminates against the accreted Amotape/Olmos Terrain and it overlies the Late Triassic to Jurassic Pucara Group. Slab stagnation in the mantle transition zone near the upper and lower mantle boundary perhaps triggered shallow subduction, which in turn caused drowning and Jurassic arc volcanism termination. Slab flattening increased upper plate stress coupling transferring the stresses eastward and causing basement-core block uplift and changing provenance to quartz-rich. Slab breakoff occurred soon after the water-bearing serpentinized slab changed to denser eclogite facies as recorded by linear alkaline volcanism with strong mantle source (low La/Nb ratio) along the high Andes. Locally, transform fault subduction enhanced fracturing during slab bending permitting the tapping of undepleted mantle by these deep faults and causing trench parallel extension coeval with explosive subaqueous volcanism with strong OIB signature (low La/Nb ratio). Higher South Atlantic spreading rates than the trench normal convergence imparted the mechanism for trench rollback, thus enhancing the upper plate extensional deformation. Aptian increase in spreading rates coeval with protracted increase in the normal absolute plate motion terminated the active basement uplift; however, they persisted as submerged highs allowing the diachronous northsouth encroaching of the Cretaceous epeiric sea in along the Marañón and Ucayali basins. Prolonged Farallón Plate oblique convergence triggered strain partitioning and set-up important strike slip deformation such as the Tapacocha and Hormigas faults. Basin development involved pervasive transtensional deformation and tectonic segmentation and each one distinguished by its own stratigraphy, geochemistry, heat flow and subsidence history. Transtensional deformation involved deep crustal faults and complex lithosphere boudinage permitting important asthenospheric mantle de- compression melting magmatism that mixed with partially metasomatized subduction slab as documented by relative low La/Yb and La/Nb ratios and the occurrence of Nb-Ta negative anomalies. Two distinctive magmatic regimes are separated by an important and major plutonic regime linked to the emplacement of the Peruvian Costal Batholith (PCB) encompassing episodic multi-scale stopping, caldron subsidence and assimilation. The oldest volcanic regime (Casma Group), has higher mantle contribution and insignificant crustal contamination compare to the younger one (Quilmaná Formation). However, locally detrital zircons (DZ) and Hf isotopes support the presence of juvenile zircons supporting the absence of crustal contamination

The Río Cañete Basin: Implications for the Mesozoic geoynamic evolution of the Peruvian margin

The evolution of the Río Cañete Basin provides a robust geodynamic model that can be extrapolated throughout the Peruvian margin. Transtensional crustal attenuation during the Jurassic early stages of Andean oblique subduction accounts for major crustal thinning and regional arc volcanism. Arrival of the lost “Chivaterous Plateau”, explains the termination of the Jurassic arc and development of a Neocomian shallow subduction and slab breakoff. Regional marine transgression was accompanied by patchy arc volcanism as well as localized subduction of an oceanic fracture. Protracted and persistent transtension supports the Albian/Cenomanian high rates of extension and upwelling of primitive mantle. The Jurassic calc-alkaline intra-arc is unbroken and displays different degrees of crustal contamination as documented in the Puente Piedra Group. Subduction slab input is displayed by the negative Nb and Ti anomaly. However, the LREE enrichment and moderately slope similar to the OIB contrast with the MREE and HREE gentler slope. The overall flattening and discrete HREE spoon shape suggest pyroxene and subordinate amphibole fractioning. Still, the negative Eu anomaly, and more siliceous magmatism in the south supports the significant feldspar fractioning and higher crustal contamination. Subduction Flattening during approach of an oceanic plateau triggered the abrupt collapsing and drowning of the Jurassic arc edifice and the sharp provenance change from a volcanic to a quartz rich basement source. Still, the timing and uplift of the Marañon Block and the Arequipa Massif, the synchronous subsidence between these basement uplifts, the Neocomian volcanic lull, and the restricted deposition of this Neocomian quartz rich clastic wedge west of the Marañon Block bolsters a Neocomian flat slab. The presence of 145-110 Ma alkaline to subalkaline basalts and andesites lavas along a linear belt west of the Marañon Block supports the slab breakoff. The chondrite normalized REE patterns amid OIB and EMORB, with almost flat HREE and almost absence of crustal contamination suggest amphibole and pyroxene fractioning. The continuous marine transgression is recorded by the shales and limestones of the Lima Group that terminated during Aptian times. The localized and anomalous subaqueous Pucusana Formation volcanism was associated with subduction of an oceanic fracture coeval with mantle upwelling. Indeed, the gently LREE and MREE slope and almost flat HREE chondrite normalized spider diagrams suggest pyroxene fractioning. The almost continuous transtension set up since the early Mesozoic triggered the large pull-apart basin developed during the Albian/Cenomanian. The basins thus developed, were characterized by variable crustal attenuation and subsidence and thick volcaniclastic deposition. The strong Nb negative anomaly in the Casma Group implied subduction slab input. But, the gentle and higher enrichment in LREE similar to OIB, and the almost flat HREE akin to EMORB and NMORB with and overall subtle Eu anomaly showed a significant contribution from undepleted mantle and important pyroxene fractionation

Thermal Excitation of Multi-Photon Dressed States in Circuit Quantum Electrodynamics

The exceptionally strong coupling realizable between superconducting qubits and photons stored in an on-chip microwave resonator allows for the detailed study of matter-light interactions in the realm of circuit quantum electrodynamics (QED). Here we investigate the resonant interaction between a single transmon-type multilevel artificial atom and weak thermal and coherent fields. We explore up to three photon dressed states of the coupled system in a linear response heterodyne transmission measurement. The results are in good quantitative agreement with a generalized Jaynes-Cummings model. Our data indicates that the role of thermal fields in resonant cavity QED can be studied in detail using superconducting circuits.Comment: ArXiv version of manuscript to be published in the Physica Scripta topical issue on the Nobel Symposium 141: Qubits for Future Quantum Computers(2009), 13 pages, 6 figures, hi-res version at http://qudev.ethz.ch/content/science/PubsPapers.htm

Experimental realization of a quantum game on a one-way quantum computer

We report the first demonstration of a quantum game on an all-optical one-way quantum computer. Following a recent theoretical proposal we implement a quantum version of Prisoner's Dilemma, where the quantum circuit is realized by a 4-qubit box-cluster configuration and the player's local strategies by measurements performed on the physical qubits of the cluster. This demonstration underlines the strength and versatility of the one-way model and we expect that this will trigger further interest in designing quantum protocols and algorithms to be tested in state-of-the-art cluster resources.Comment: 13 pages, 4 figure