Demonstration of a simple entangling optical gate and its use in bell-state analysis

We demonstrate a new architecture for an optical entangling gate that is significantly simpler than previous realizations, using partially polarizing beam splitters so that only a single optical mode-matching condition is required. We demonstrate operation of a controlled-z gate in both continuous-wave and pulsed regimes of operation, fully characterizing it in each case using quantum process tomography. We also demonstrate a fully resolving, nondeterministic optical Bell-state analyzer based on this controlled-z gate. This new architecture is ideally suited to guided optics implementations of optical gates.     

Remark on lower bounds to eigenvalues

It is shown that the familiar Temple, Stevenson-Crawford, and Weinstein lower bound formulas for eigenvalues are consequences of a much stronger general lower bound formula and the weak “Eckart criterion” for the overlap of the approximate and true wave functions.     

Imaging of trapped ions with a microfabricated optic for quantum information processing

Trapped ions are a leading system for realizing quantum information processing (QIP). Most of the technologies required for implementing large-scale trapped-ion QIP have been demonstrated, with one key exception: a massively parallel ion-photon interconnect. Arrays of microfabricated phase Fresnel lenses (PFL) are a promising interconnect solution that is readily integrated with ion trap arrays for large-scale QIP. Here we show the first imaging of trapped ions with a microfabricated in-vacuum PFL, demonstrating performance suitable for scalable QIP. A single ion fluorescence collection efficiency of 4.2±1.5% was observed. The depth of focus for the imaging system was 19.4±2.4 μm and the field of view was 140±20 μm. Our approach also provides an integrated solution for high-efficiency optical coupling in neutral atom and solid-state QIP architectures.     

Ueber eine vergleichbare Spectralscala

Ohne Zusammenfassung     

Piezoelectricity of porous polytetrafluoroethylene single- and multiple-film electrets containing high charge densities of both polarities

Single-film bipolar electrets of porous polytetrafluoroethylene are generated by means of a two-step corona-charging process at elevated temperatures. Quasi-static direct piezoelectric coefficients of up to 0.15 nC/N have been observed on these films. In addition, multiple-layer stacks of porous and non-porous polytetrafluoroethylene films with monopolar charge were also investigated. While the piezoelectric responses of the stacks were not as high as those of the single films, the multiple-film arrangements may have other advantages such as better electrical shielding or tunable mechanical properties and adjustable acoustical impedance. Our new results are discussed in the context of the emerging field of porous polymer electrets with many potential device applications.     

The crystal structure of the alternating copolymer of hexafluoroisobutylene and vinylidene fluoride

The crystal structure of the alternating copolymer of hexafluoroisobutylene and vinylidene fluoride, P(HFIB/VF₂), was determined using x-ray diffraction techniques. Oriented specimens of the copolymer were produced by drawing melt-pressed film at 300°C. The unit cell of P(HFIB/VF₂) is orthorhombic with dimensions at a = 1.064, b = 1.837, and c = 0.783 nm. The chain conformation is a 2₁ helix with an approximate trans-trans-gauche-gauche backbone dihedral-angle sequence. Severe intrachain steric crowding exists; as a consequence, the chain is quite rigid and some of the backbone bond angles are highly extended. The unit cell contains four such chains packed according to the symmetry of space group Iba2. Neighboring chains in a crystal are mechanically interlocked; in combination with the rigidity of the chains, this is the basis for the superior mechanical properties of the copolymer compared to PTFE. A structure containing up to 20-30% of head-to-head residues was found to be statistically indistinguishable from a completely head-to-tail structure.     

Criteria of accuracy of resonance eigenvalues

Various criteria that have been suggested for assessing the accuracy of complex-coordinate eigenvalues are critically tested in an application to the lowest helium ¹S resonance, and found to be relatively ineffective. An alternative criterion is described, based on a generalized stabilization procedure, which seems better able to select the “best” resonance eigenvalue and to guide the construction of variational trial functions.     

Entanglement generation by Fock-state filtration

We demonstrate a Fock-state filter which is capable of preferentially blocking single photons over photon pairs. The large conditional nonlinearities are based on higher-order quantum interference, using linear optics, an ancilla photon, and measurement. We demonstrate that the filter acts coherently by using it to convert unentangled photon pairs to a path-entangled state. We quantify the degree of entanglement by transforming the path information to polarization information; applying quantum state tomography we measure a tangle of T=(20+/-9)%.