An Investigation of the N-Arylsulfonylation of 2-Azetidinones

N-Arylsulfonylation of 2-azetidinones can lead to the diastereoselective formation of oligomerization products. However, a simple increase of arylsulfonyl chloride concentration minimized oligomerization and allowed preparation of 1-arylsulfonyl-2-azetidinones in good yield.     

Selective functionalization of 3-D polymer microstructures

We demonstrate the selective functionalization of 3-D polymer microstructures that were created using multiphoton absorption polymerization. By fabricating different portions of the structures with acrylic and methacrylic polymers, we are able to take advantage of the differential reactivities of these materials to perform functionalization chemistry on a single polymeric component. We demonstrate the selective deposition of metal to create structures, such as a functional microinductor. Our strategy is quite general and can be extended readily to the deposition of materials, such as metal oxides and biomolecules.     

Polarization-sensitive quantum optical coherence tomography: Experiment

Polarization-sensitive quantum optical coherence tomography (PS-QOCT) makes use of a Type-II twin-photon light source for carrying out optical sectioning with polarization sensitivity. A BBO nonlinear optical crystal pumped by a Ti:sapphire psec-pulsed laser is used to confirm the theoretical underpinnings of this imaging paradigm. PS-QOCT offers even-order dispersion cancellation with simultaneous access to the group-velocity dispersion characteristics of the interstitial medium between the reflecting surfaces of the sample.     

Decoherence-free subspaces in quantum key distribution

We demonstrate that two recent innovations in the field of practical quantum key distribution (one-way autocompensation and passive detection) are closely related to the methods developed to protect quantum computations from decoherence. We present a new scheme that combines these advantages, and propose a practical implementation of this scheme that is feasible using existing technology.     

Spatial energy estimates in dynamical problems for a semi-infinite piezoelectric beam

The behaviour of the total energy for a semi-infinite piezoelectricbeam, with uniform or variable cross-section, in dynamical conditionsis investigated. Precisely, we obtain some estimates in termsof the data for the energy of the portion of the body at distancegreater than z from the base and for its norm in L¹(0,t) (wheret is an arbitrary positive time). We obtain some estimates whichdepend on the initial data if t z/V (where V is a computablepositive material constant); if t > z/V, by using also theKorn inequality, we show that the bounds depend on all the data.Under mild hypotheses on the initial data we derive the asymptoticbehaviour of the energy as z +. All possible combinations ofboundary conditions are examined and the kind of the estimateis formally the same for all the problems whether the beam isa cylinder or not.     

Synthesis and analysis of entangled photonic qubits in spatial-parity space

We present the novel embodiment of a photonic qubit that makes use of one continuous spatial degree of freedom of a single photon and relies on the parity of the photon's transverse spatial distribution. Using optical spontaneous parametric down-conversion to produce photon pairs, we demonstrate the controlled generation of entangled-photon states in this new space. Specifically, two Bell states, and a continuum of their superpositions, are generated by simple manipulation of a classical parameter, the optical-pump spatial parity, and not by manipulation of the entangled photons themselves. An interferometric device, isomorphic in action to a polarizing beam splitter, projects the spatial-parity states onto an even-odd basis. This new physical realization of photonic qubits could be used as a foundation for future experiments in quantum information processing.     

Coincidence Doppler shift lifetime measurements in 73,74Se and 74Br using the EUROBALL Cluster cube array

Subpicosecond lifetimes of high spin states in the rotational nuclei ⁷³Se, ⁷⁴Se and ⁷⁴Br have been measured using the ⁵⁸Ni +¹⁹F compound reaction and the Doppler Shift Attenuation method. Six EUROBALL Cluster detectors arranged in cube geometry allowed us to select the relevant transitions in γγ coincidence mode. The high counting statistics achieved in this setup also facilitated the determination of average sidefeeding times, which were found to agree rather well with the results of Monte-Carlo calculations of the particle and γ-ray evaporation process. The deduced quadrupole strengths and deformations are compared with the results of previous measurements and the predictions of Cranked Shell Model calculations. In ⁷⁴Br, a large and constant prolate deformation of β₂= 0.37(1) was found for the presumed 4⁺ and 3⁻ two-quasiparticle bands. Received: 2 July 1999     

Magnetic moment measurements in the semi-magic nuclei 94Ru and 95Rh after recoil implantation into iron and nickel

The magnetic moments of the 12⁺ and 11⁻ yrast states in ⁹⁴Ru and of the 25/2⁻, 29/2⁺, and 35/2⁺ levels in ⁹⁵Rh have been measured via the IMPAD technique. The nuclei were produced in the reaction ⁵⁸Ni +⁴⁰Ca and recoil-implanted into polarized Ni and Fe hosts. The g-factors were deduced from the measured time-integral Larmor precessions. The comparison between the experimental results and large-scale shell model calculations suggests that the 12⁺ and 11⁻ states in ⁹⁴Ru and the 25/2⁻ level in ⁹⁵Rh are pure proton states whereas the 29/2⁺ and 35/2⁺ states in ⁹⁵Rh contain a neutron excitation across the N=50 shell gap. This interpretation supports the conclusion drawn from recent lifetime measurements. Received: 2 June 1999