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Author (down) Edlmayr, V.; Harzer, T. P.; Hoffmann, R.; Kiener, D.; Scheu, C.; Mitterer, C.
Title Effects of thermal annealing on the microstructure of sputtered Al2O3 coatings Type Journal Article
Year 2011 Publication J. Vac. Sci. Technol. A Abbreviated Journal
Volume 29 Issue 4 Pages 8
Keywords Annealing
Abstract The morphology and microstructure of Al2O3 thin films deposited by pulsed direct current magnetron sputtering were studied in the as-grown state and after vacuum annealing at 1000 °C for 12 h using transmission electron microscopy. For the coating deposited under low ion bombardment conditions, the film consists of small γ- and/or δ-Al2O3 grains embedded in an amorphous matrix. The grain size at the region close to the interface to the substrate was much larger than that of the remaining layer. Growth of the γ-Al2O3 phase is promoted during annealing but no transformation to α-Al2O3 was detected. For high-energetic growth conditions, clear evidence for γ-Al2O3 formation was found in the upper part of the coating with grain size much larger than for low-energetic growth, but the film was predominately amorphous at the interface region. Annealing resulted in the transformation of γ-Al2O3 to α-Al2O3, while the mainly amorphous part crystallized to γ-Al2O3.
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Notes Annealing Approved no
Call Number RPLAB @ gujma @ Serial 693
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Author (down) Dorenbos, S. N.; Heeres, R.W.; Driessen, E.F.C; Zwiller, V.
Title Efficient and robust fiber coupling of superconducting single photon detectors Type Journal Article
Year 2011 Publication arXiv Abbreviated Journal arXiv
Volume Issue Pages 6
Keywords SSPD
Abstract We applied a recently developed fiber coupling technique to superconducting single photon detectors (SSPDs). As the detector area of SSPDs has to be kept as small as possible, coupling to an optical fiber has been either inefficient or unreliable. Etching through the silicon substrate allows fabrication of a circularly shaped chip which self aligns to the core of a ferrule terminated fiber in a fiber sleeve. In situ alignment at cryogenic temperatures is unnecessary and no thermal stress during cooldown, causing misalignment, is induced. We measured the quantum efficiency of these devices with an attenuated tunable broadband source. The combination of a lithographically defined chip and high precision standard telecommunication components yields near unity coupling efficiency and a system detection efficiency of 34% at a wavelength of 1200 nm. This quantum efficiency measurement is confirmed by an absolute efficiency measurement using correlated photon pairs (with $\lambda$ = 1064 nm) produced by spontaneous parametric down-conversion. The efficiency obtained via this method agrees well with the efficiency measured with the attenuated tunable broadband source.
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Publisher Place of Publication arXiv:1109.5809 Editor
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Notes Approved no
Call Number RPLAB @ gujma @ Serial 689
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Author (down) Dada, Adetunmise C.; Leach, Jonathan; Buller, Gerald S.; Padgett, Miles J.; Andersson, Erika
Title Experimental high-dimensional two-photon entanglement and violations of generalized Bell inequalities Type Journal Article
Year 2011 Publication Nature Physics Abbreviated Journal Nat. Phys.
Volume 7 Issue 9 Pages 677-680
Keywords fromIPMRAS
Abstract Quantum entanglement plays a vital role in many quantum-information and communication tasks. Entangled states of higher-dimensional systems are of great interest owing to the extended possibilities they provide. For example, they enable the realization of new types of quantum information scheme that can offer higher-information-density coding and greater resilience to errors than can be achieved with entangled two-dimensional systems (see ref. and references therein). Closing the detection loophole in Bell test experiments is also more experimentally feasible when higher-dimensional entangled systems are used. We have measured previously untested correlations between two photons to experimentally demonstrate high-dimensional entangled states. We obtain violations of Bell-type inequalities generalized to d-dimensional systems up to d=12. Furthermore, the violations are strong enough to indicate genuine 11-dimensional entanglement. Our experiments use photons entangled in orbital angular momentum, generated through spontaneous parametric down-conversion, and manipulated using computer-controlled holograms.
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Call Number RPLAB @ gujma @ Serial 828
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Author (down) Crespi, Andrea; Ramponi, Roberta; Osellame, Roberto; Sansoni, Linda; Bongioanni, Irene; Sciarrino, Fabio; Vallone, Giuseppe; Mataloni, Paolo
Title Integrated photonic quantum gates for polarization qubits Type Journal Article
Year 2011 Publication Nature Communications Abbreviated Journal Nat. Comm.
Volume 2 Issue 566 Pages 6
Keywords fromIPMRAS
Abstract The ability to manipulate quantum states of light by integrated devices may open new perspectives both for fundamental tests of quantum mechanics and for novel technological applications. However, the technology for handling polarization-encoded qubits, the most commonly adopted approach, is still missing in quantum optical circuits. Here we demonstrate the first integrated photonic controlled-NOT (CNOT) gate for polarization-encoded qubits. This result has been enabled by the integration, based on femtosecond laser waveguide writing, of partially polarizing beam splitters on a glass chip. We characterize the logical truth table of the quantum gate demonstrating its high fidelity to the expected one. In addition, we show the ability of this gate to transform separable states into entangled ones and vice versa. Finally, the full accessibility of our device is exploited to carry out a complete characterization of the CNOT gate through a quantum process tomography.
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Call Number RPLAB @ gujma @ Serial 765
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Author (down) Capmany, José; Gasulla, Ivana; Sales, Salvador
Title Microwave photonics: Harnessing slow light Type Journal Article
Year 2011 Publication Nature Photonics Abbreviated Journal Nat. Photon.
Volume 5 Issue 12 Pages 731-733
Keywords fromIPMRAS
Abstract Slow-light techniques originally conceived for buffering high-speed digital optical signals now look set to play an important role in providing broadband phase and true time delays for microwave signals.
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Call Number RPLAB @ gujma @ Serial 778
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