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Author 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 (up) 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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Call Number RPLAB @ gujma @ Serial 693
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Author Mariantoni, Matteo; Wang, H.; Bialczak, Radoslaw C.; Lenander, M.; Lucero, Erik; Neeley, M.; O'Connell, A. D.; Sank, D.; Weides, M.; Wenner, J.; Yamamoto, T.; Yin, Y.; Zhao, J.; Martinis, John M.; Cleland, A. N.
Title Photon shell game in three-resonator circuit quantum electrodynamics Type Journal Article
Year 2011 Publication Nature Physics Abbreviated Journal Nat. Phys.
Volume 7 Issue (up) 4 Pages 287-293
Keywords fromIPMRAS
Abstract The generation and control of quantum states of light constitute fundamental tasks in cavity quantum electrodynamics (QED). The superconducting realization of cavity QED, circuit QED (refs 11, 12, 13, 14), enables on-chip microwave photonics, where superconducting qubits control and measure individual photon states. A long-standing issue in cavity QED is the coherent transfer of photons between two or more resonators. Here, we use circuit QED to implement a three-resonator architecture on a single chip, where the resonators are interconnected by two superconducting phase qubits. We use this circuit to shuffle one- and two-photon Fock states between the three resonators, and demonstrate qubit-mediated vacuum Rabi swaps between two resonators. By shuffling superposition states we are also able to demonstrate the high-fidelity phase coherence of the transfer. Our results illustrate the potential for using multi-resonator circuits as photon quantum registers and for creating multipartite entanglement between delocalized bosonic modes.
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Call Number RPLAB @ gujma @ Serial 838
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Author Lee, B. G.; Assefa, S.; Green, W. M. J.; Min Yang; Schow, C. L.; Jahnes, C. V.; Sheng Zhang; Singer, J.; Kopp, V. I.; Kash, J. A.; Vlasov, Y. A.
Title Multichannel high-bandwidth coupling of ultradense silicon photonic waveguide array to standard-pitch fiber array Type Journal Article
Year 2011 Publication J. Lightwave Technol. Abbreviated Journal
Volume 29 Issue (up) 4 Pages 475-482
Keywords optical waveguides, from chiralphotonics
Abstract A multichannel tapered coupler interfacing standard 250-μm-pitch low-numerical-aperture (NA) polarization-maintaining fiber arrays with ultradense 20- μm-pitch high-NA silicon waveguides is designed and fabricated. The coupler is based on an array of 12 dual-core glass waveguides on 250-μ m pitch that are tapered to a 20- μm pitch, simultaneously providing both pitch and spot-size conversion. At the wide end, the inner core matches the NA and mode profile of standard single-mode fiber. When drawn and tapered, the inner core “vanishes” and the outer core, surrounded by the clad, matches the NA and mode profile of the on-chip photonic waveguide. Ultradense high-efficiency coupling to an array of Si photonic waveguides is demonstrated using a 12-channel polarization-maintaining-fiber pigtailed tapered coupler. Coupling to Si waveguides is facilitated using SiON spot-size converters integrated into the Si photonic IC to provide 2-3-μm mode field diameters compatible with the tapered coupler. The tapered coupler achieves <; 1 dB coupling losses to photonic waveguides. Furthermore, eight-channel coupling is shown with less than -35 dB crosstalk between channels. Finally, a 640-Gb/s wavelength-division-multiplexing signal is coupled into four waveguides occupying 80 μm of chip edge, providing 160-Gb/s per-channel bandwidths.
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Call Number Serial 849
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Author Marsili, Francesco; Najafi, Faraz; Dauler, Eric; Bellei, Francesco; Hu, Xiaolong; Csete, Maria; Molnar, Richard J.; Berggren, Karl K.
Title Single-photon detectors based on ultranarrow superconducting nanowires Type Journal Article
Year 2011 Publication Nano Letters Abbreviated Journal Nano Lett.
Volume 11 Issue (up) 5 Pages 2048–2053
Keywords SNSPD
Abstract We report efficient single-photon detection (η = 20% at 1550 nm wavelength) with ultranarrow (20 and 30 nm wide) superconducting nanowires, which were shown to be more robust to constrictions and more responsive to 1550 nm wavelength photons than standard superconducting nanowire single-photon detectors, based on 90 nm wide nanowires. We also improved our understanding of the physics of superconducting nanowire avalanche photodetectors, which we used to increase the signal-to-noise ratio of ultranarrow-nanowire detectors by a factor of 4, thus relaxing the requirements on the read-out circuitry and making the devices suitable for a broader range of applications.
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Call Number RPLAB @ gujma @ Serial 659
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Author Manova, N. N.; Korneeva, Yu. P.; Korneev, A. A.; Slysz, W.; Voronov, B. M.; Gol'tsman, G. N.
Title Superconducting NbN single-photon detector integrated with quarter-wave resonator Type Journal Article
Year 2011 Publication Tech. Phys. Lett. Abbreviated Journal Tech. Phys. Lett.
Volume 37 Issue (up) 5 Pages 469-471
Keywords SSPD, SNSPD
Abstract The spectral dependence of the quantum efficiency of superconducting NbN single-photon detectors integrated with quarter-wave resonators based on Si3N4, SiO2, and SiO layers has been studied.
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Call Number RPLAB @ gujma @ Serial 664
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Author Васильева, И. А.; Компанеец, В. В.; Красная, Ж. А.; Чижикова, З. А.
Title Проявление внутримолекулярных вибронных взаимодействий в тонкоструктурных спектрах флуоресценции и возбуждения флуоресценции полиеновых δ-диметиламинокетонов Type Journal Article
Year 2011 Publication Оптический журнал Abbreviated Journal Опт. ж.
Volume 78 Issue (up) 5 Pages 3-8
Keywords спектры флуоресценции; вибрационный анализ; адиабатическое гармоническое приближение; бесфононная линия; фононное крыло
Abstract Проведен вибрационный анализ спектров флуоресценции и возбуждения флуоресценции, полученных методом Шпольского при 4,2 K. Рассчитаны параметры внутримолекулярных взаимодействий двух δ-диметиламинокетонов. Для определения интегральных интенсивностей вибронных полос в спектрах с тонкой структурой на интенсивном сплошном фоне выполнено моделирование спектров путем представления полосы каждого из вибронных переходов бесфононной линией и фононным крылом с определенными параметрами (полуширинами, фактором Дебая–Валлера). Показано, что нарушение зеркальной симметрии в сопряженных спектрах флуоресценции и возбуждения флуоресценции этих двух соединений может быть обÑŠяснено интерференцией франк-кондоновского и герцберг-теллеровского взаимодействий.
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Call Number RPLAB @ gujma @ Serial 721
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Author Baumert, Thomas
Title Quantum technology: Wave packets get a kick Type Journal Article
Year 2011 Publication Nature Physics Abbreviated Journal Nat. Phys.
Volume 7 Issue (up) 5 Pages 373-374
Keywords fromIPMRAS
Abstract Intense femtosecond pulses of infrared light can manipulate molecules. It is now shown that such control even extends to making different molecular eigenstates interfere with each other in a way never considered before -- a potential tool for optically engineered chemical reactions and for ultrafast information encoding and manipulation.
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Call Number RPLAB @ gujma @ Serial 830
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Author Ma, Xiao-Song; Dakic, Borivoje; Naylor, William; Zeilinger, Anton; Walther, Philip
Title Quantum simulation of the wavefunction to probe frustrated Heisenberg spin systems Type Journal Article
Year 2011 Publication Nature Physics Abbreviated Journal Nat. Phys.
Volume 7 Issue (up) 5 Pages 399-405
Keywords fromIPMRAS
Abstract Quantum simulators are controllable quantum systems that can reproduce the dynamics of the system of interest in situations that are not amenable to classical computers. Recent developments in quantum technology enable the precise control of individual quantum particles as required for studying complex quantum systems. In particular, quantum simulators capable of simulating frustrated Heisenberg spin systems provide platforms for understanding exotic matter such as high-temperature superconductors. Here we report the analogue quantum simulation of the ground-state wavefunction to probe arbitrary Heisenberg-type interactions among four spin-1/2 particles. Depending on the interaction strength, frustration within the system emerges such that the ground state evolves from a localized to a resonating-valence-bond state. This spin-1/2 tetramer is created using the polarization states of four photons. The single-particle addressability and tunable measurement-induced interactions provide us with insights into entanglement dynamics among individual particles. We directly extract ground-state energies and pairwise quantum correlations to observe the monogamy of entanglement.
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Call Number RPLAB @ gujma @ Serial 842
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Author Berlín, Guido; Brassard, Gilles; Bussières, Félix; Godbout, Nicolas; Slater, Joshua A.; Tittel, Wolfgang
Title Experimental loss-tolerant quantum coin flipping Type Journal Article
Year 2011 Publication Nature Communications Abbreviated Journal Nat. Comm.
Volume 2 Issue (up) 561 Pages 7
Keywords fromIPMRAS
Abstract Coin flipping is a cryptographic primitive in which two distrustful parties wish to generate a random bit to choose between two alternatives. This task is impossible to realize when it relies solely on the asynchronous exchange of classical bits: one dishonest player has complete control over the final outcome. It is only when coin flipping is supplemented with quantum communication that this problem can be alleviated, although partial bias remains. Unfortunately, practical systems are subject to loss of quantum data, which allows a cheater to force a bias that is complete or arbitrarily close to complete in all previous protocols and implementations. Here we report on the first experimental demonstration of a quantum coin-flipping protocol for which loss cannot be exploited to cheat better. By eliminating the problem of loss, which is unavoidable in any realistic setting, quantum coin flipping takes a significant step towards real-world applications of quantum communication.
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Call Number RPLAB @ gujma @ Serial 766
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Author 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 (up) 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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