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Author Scheel, Stefan
Title Single-photon sources–an introduction Type Journal Article
Year 2009 Publication J. Modern Opt. Abbreviated Journal (up)
Volume 56 Issue 2-3 Pages 141-160
Keywords LOQC; quantum cryptography; QKD
Abstract This review surveys the physical principles and recent developments in manufacturing single-photon sources. Special emphasis is placed on important potential applications such as linear optical quantum computing (LOQC), quantum key distribution (QKD) and quantum metrology that drive the development of these sources of single photons. We discuss the quantum-mechanical properties of light prepared in a quantum state of definite photon number and compare it with coherent light that shows a Poissonian distribution of photon numbers. We examine how the single-photon fidelity directly influences the ability to transmit secure quantum bits over a predefined distance. The theoretical description of modified spontaneous decay, the main principle behind single-photon generation, provides the background for many experimental implementations such as those using microresonators or pillar microcavities. The main alternative way to generate single photons using postselection of entangled photon pairs from parametric down-conversion, will be discussed. We concentrate on describing the underlying physical principles and we will point out limitations and open problems associated with single-photon production.
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Call Number RPLAB @ gujma @ Serial 669
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Author Karpowicz, Nicholas; Lu, Xiaofei; Zhang, X.-C.
Title Terahertz gas photonics Type Journal Article
Year 2009 Publication J. Modern Opt. Abbreviated Journal (up)
Volume 56 Issue 10 Pages 1137-1150
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Abstract The underlying physics of the generation and detection of terahertz (THz) waves in gases are described. The THz wave generation process takes place in two steps: asymmetric gas ionization by two-frequency laser fields, followed by interaction of the ionized electron wave packets with the surrounding medium, producing an intense ‘echo' with tunable spectral content. In order to clarify the physical picture at the moment of ionization, the laser–atom interaction is treated through solution of the time-dependent Schrödinger equation, yielding an ab initio understanding of the release of the electron wave packets. The second step, where the electrons interact with the surrounding plasma is treated analytically. The resulting pressure dependence of the THz radiation is explored in detail. The THz wave detection process is shown to be the result of four-wave mixing, leading to analytical expressions of the signal obtained which allow for improved optimization of systems that exploit these effects.
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Call Number RPLAB @ gujma @ Serial 670
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Author Polyakov, Sergey V.; Migdalla, Alan L.
Title Quantum radiometry Type Journal Article
Year 2009 Publication J. Modern Opt. Abbreviated Journal (up)
Volume 56 Issue 9 Pages 1045-1052
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Abstract We review radiometric techniques that take advantage of photon counting and stem from the quantum laws of nature. We present a brief history of metrological experiments and review the current state of experimental quantum radiometry.
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Call Number RPLAB @ gujma @ Serial 671
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Author Wang, Zhen; Miki, S.; Fujiwara, M.
Title Superconducting nanowire single-photon detectors for quantum information and communications Type Journal Article
Year 2009 Publication IEEE J. Sel. Topics Quantum Electron. Abbreviated Journal (up)
Volume 15 Issue 6 Pages 1741-1747
Keywords SSPD
Abstract Superconducting nanowire single-photon detectors (SNSPDs or SSPD) are highly promising devices in the growing field of quantum information and communications technology. We have developed a practical SSPD system with our superconducting thin films and devices fabrication, optical coupling packaging, and cryogenic technology. The SSPD system consists of six-channel SSPD devices and a compact Gifford-McMahon (GM) cryocooler, and can operate continuously on 100 V ac power without the need for any cryogens. The SSPD devices were fabricated from high-quality niobium nitride (NbN) ultrathin films that were epitaxially grown on single-crystal MgO substrates. The packaged SSPD devices were temperature stabilized to 2.96 K ± 10 mK. The system detection efficiency for an SSPD device with an area of 20 × 20 ¿m2 was found to be 2.6% and 4.5% at wavelengths of 1550 and 1310 nm, respectively, at a dark count rate of 100 Hz, and a jitter of 100 ps full-width at half maximum. We also performed ultrafast BB84 quantum key distribution (QKD) field testing and entanglement-based QKD experiments using these SSPD devices.
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Call Number RPLAB @ gujma @ Serial 676
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Author Yang, J.K.W.; Kerman, A.J.; Dauler, E.A.; Cord, B.; Anant, V.; Molnar, R.J.; Berggren, K.K.
Title Suppressed critical current in superconducting nanowire single-photon detectors with high fill-factors Type Journal Article
Year 2009 Publication IEEE Trans. Appl. Supercond. Abbreviated Journal (up)
Volume 19 Issue 3 Pages 318-322
Keywords SNSPD
Abstract In this work we present a new fabrication process that enabled the fabrication of superconducting nanowire single photon detectors SNSPD with fill-factors as high as 88% with gaps between nanowires as small as 12 nm. This fabrication process combined high-resolution electron-beam lithography with photolithography. Although this work was motivated by the potential of increased detection efficiency with higher fill-factor devices, test results showed an unexpected systematic suppression in device critical currents with increasing fill-factor.
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Call Number RPLAB @ gujma @ Serial 677
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