Input-output Gaussian channels: theory and application

Setting off from the classic input-output formalism, we develop a theoretical framework to characterise the Gaussian quantum channels relating the initial correlations of an open bosonic system to those of properly identified output modes. We then proceed to apply our formalism to the case of quantum harmonic oscillators, such as the motional degrees of freedom of trapped ions or nanomechanical oscillators, interacting with travelling electromagnetic modes through cavity fields and subject to external white noise. Thus, we determine the degree of squeezing that can be transferred from an intra-cavity oscillator to light, and also show that the intra-cavity squeezing can be transformed into distributed optical entanglement if one can access both output fields of a two-sided cavity.Comment: 13+7 pages, 3 figure

PMR polyimides-review and update

Fiber reinforced PMR polyimides are finding increased acceptance as engineering materials for high performance structural applications. Prepreg materials based on this novel class of highly processable, high temperature resistant polyimides are commercially available and the PMR concept is used by other investigators. The current status of first and second generation PMR polyimides were reviewed. Emphasis is given to the chemistry, processing and applications of the first generation material known as PMR-15

Canonical and micro-canonical typical entanglement of continuous variable systems

We present a framework, compliant with the general canonical principle of statistical mechanics, to define measures on the set of pure Gaussian states of continuous variable systems. Within such a framework, we define two specific measures, referred to as `micro-canonical' and `canonical', and apply them to study systematically the statistical properties of the bipartite entanglement of n-mode pure Gaussian states (as quantified by the entropy of a subsystem). We rigorously prove the "concentration of measure" around a finite average, occurring for the entanglement in the thermodynamical limit in both the canonical and the micro-canonical approach. For finite n, we determine analytically the average and standard deviation of the entanglement (as quantified by the reduced purity) between one mode and all the other modes. Furthermore, we numerically investigate more general situations, clearly showing that the onset of the concentration of measure already occurs at relatively small n.Comment: 24 pages, 5 figures, IOP style; conclusions extended, minor layout adjustmen

Entanglement creation and distribution on a graph of exchange-coupled qutrits

We propose a protocol that allows both the creation and distribution of entanglement, resulting in two distant parties (Alice and Bob) conclusively sharing a bipartite Bell State. The system considered is a graph of three-level objects ("qutrits") coupled by SU(3) exchange operators. The protocol begins with a third party (Charlie) encoding two lattice sites in unentangled states, and allowing unitary evolution under time. Alice and Bob perform a projective measurement on their respective qutrits at a given time, and obtain a maximally-entangled Bell state with a certain probablility. We also consider two further protocols, one based on simple repetition and the other based on successive measurements and conditional resetting, and show that the cumulative probability of creating a Bell state between Alice and Bob tends to unity.Comment: Added seven references, clarified argument for eqn (16

Risultati preliminari sul nuovo rostro di ittiosauro trovato a Gombola (MO)

Un frammento di rostro di ittiosauro (251372) è stato recentemente rinvenuto nei calanchi presso Gombola (MO) e consegnato al Museo Civico “Augusta Redorici Rof ” di Vignola (MO). Frammenti rostrali simili (IPUM 30139 e IPUM 30140) e un frammento di omero (IPUM 30141) provenienti dal medesimo luogo si trovano nelle Collezioni di Paleontologia dell’Università di Modena e Reggio Emilia. In questo articolo, viene descritto l’esemplare 251372 che, sottoposto a tomogra a assiale computerizzata (TAC) e ad un accurato restauro, è stato oggetto di uno studio tassonomico e con- frontato con IPUM 30139. La morfologia delle radici dentarie consente di ascrivere entrambi alla sottofamiglia Platypterygiinae. Alcune caratteristiche tafonomiche suggeriscono che i due reperti potessero appartenere al medesimo esemplare. Sulla matrice del reperto 251372 è stata tentata la da- tazione sia per mezzo dei microfossili, sia per mezzo dei nannofossili calcarei. Purtroppo entrambi i metodi non hanno prodotto alcun risultato signi cativo. L’esemplare 251372 può essere quindi datato genericamente al Cretaceo Inferiore-Cenomaniano (145-94 milioni di anni fa).Preliminary results on the new ichthyosaur rostrum found in Gombola (Italy). An ichthyosaur rostrum (251372) was recently found in the badlands near Gombola (Modena Apennines, Italy) and is exhibited at the Civic Museum “Augusta Redorici Rof ” in Vignola (Modena province). Similar rostral fragments (IPUM 30139 and IPUM 30140) and a humerus fragment (IPUM 30141) from the same place are stored in the Palaeontological Collections of Modena and Reggio Emilia University. Specimen 251372, examined by CT scan and subsequently restored, is described and compared with IPUM 30139. The morphology of the dental root showed that both specimens could be ascribed to the Platypterygiinae subfamily. Some taphonomical features suggest that the two fragments could belong to the same specimen. The matrix of 251372 was examined to search for microfossils and calcareous nannofossils useful for precise dating. Unfortunately, no signi cant results came out of this survey. Therefore, specimen 251372 can be loosely dated to the Lower Cretaceous-Cenomanian (145-94 My)

A compact high-flux source of cold sodium atoms

We present a compact source of cold sodium atoms suitable for the production of quantum degenerate gases and versatile for a multi-species experiment. The magnetic field produced by permanent magnets allows to simultaneously realize a Zeeman slower and a two-dimensional MOT within an order of magnitude smaller length than standard sodium sources. We achieve an atomic flux exceeding 4x10^9 atoms/s loaded in a MOT, with a most probable longitudinal velocity of 20 m/s, and a brightness larger than 2.5x10^(12) atoms/s/sr. This atomic source allowed us to produce a pure BEC with more than 10^7 atoms and a background pressure limited lifetime of 5 minutes.Comment: 8 pages, 6 figures, submitted to Phys. Rev.

Long-lived driven solid-state quantum memory

We investigate the performance of inhomogeneously broadened spin ensembles as quantum memories under continuous dynamical decoupling. The role of the continuous driving field is two-fold: first, it decouples individual spins from magnetic noise; second and more important, it suppresses and reshapes the spectral inhomogeneity of spin ensembles. We show that a continuous driving field, which itself may also be inhomogeneous over the ensemble, can enhance the decay of the tails of the inhomogeneous broadening distribution considerably. This fact enables a spin ensemble based quantum memory to exploit the effect of cavity protection and achieve a much longer storage time. In particular, for a spin ensemble with a Lorentzian spectral distribution, our calculations demonstrate that continuous dynamical decoupling has the potential to improve its storage time by orders of magnitude for the state-of-art experimental parameters

Distributed coherent manipulation of qutrits by virtual excitation processes

We propose a scheme for the deterministic coherent manipulation of two atomic qutrits, trapped in separate cavities coupled through a short optical fibre or optical resonator. We study such a system in the regime of dispersive atom-field interactions, where the dynamics of atoms, cavities and fibre operates through virtual population of both the atomic excited states and photonic states in the cavities and fibre. We show that the resulting effective dynamics allows for the creation of robust qutrit entanglement, and thoroughly investigate the influence of imperfections and dissipation, due to atomic spontaneous emission and photon leakage, on the entanglement of the two qutrits state.Comment: 15 pages, 4 figure