Shor, P. W. (2009). Quantum information theory: The bits don't add up. Nat. Phys., 5, 247–248.
Abstract: A counterexample to the 'additivity question', the most celebrated open problem in the mathematical theory of quantum information, casts doubt on the possibility of finding a simple expression for the information capacity of a quantum channel.
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Smith, D. H., Gillett, G., de Almeida, M. P., Branciard, C., Fedrizzi, A., Weinhold, T. J., et al. (2012). Conclusive quantum steering with superconducting transition-edge sensors. Nat. Comm., 3(625), 6.
Abstract: Quantum steering allows two parties to verify shared entanglement even if one measurement device is untrusted. A conclusive demonstration of steering through the violation of a steering inequality is of considerable fundamental interest and opens up applications in quantum communication. To date, all experimental tests with single-photon states have relied on post selection, allowing untrusted devices to cheat by hiding unfavourable events in losses. Here we close this 'detection loophole' by combining a highly efficient source of entangled photon pairs with superconducting transition-edge sensors. We achieve an unprecedented ~62% conditional detection efficiency of entangled photons and violate a steering inequality with the minimal number of measurement settings by 48 s.d.s. Our results provide a clear path to practical applications of steering and to a photonic loophole-free Bell test.
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Takesue, H., Nam, S. W., Zhang, Q., Hadfield, R. H., Honjo, T., Tamaki, K., et al. (2007). Quantum key distribution over a 40-dB channel loss using superconducting single-photon detectors. Nat. Photon., 1, 343–348.
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Tang, L., Kocabas, S. E., Latif, S., Okyay, A. K., Ly-Gagnon, D. - S., Saraswat, K. C., et al. (2008). Nanometre-scale germanium photodetector enhanced by a near-infrared dipole antenna. Nature Photonics, 2, 226–229.
Abstract: A critical challenge for the convergence of optics and electronics is that the micrometre scale of optics is significantly larger than the nanometre scale of modern electronic devices. In the conversion from photons to electrons by photodetectors, this size incompatibility often leads to substantial penalties in power dissipation, area, latency and noise. A photodetector can be made smaller by using a subwavelength active region; however, this can result in very low responsivity because of the diffraction limit of the light. Here we exploit the idea of a half-wave Hertz dipole antenna (length approx 380 nm) from radio waves, but at near-infrared wavelengths (length approx 1.3 microm), to concentrate radiation into a nanometre-scale germanium photodetector. This gives a polarization contrast of a factor of 20 in the resulting photocurrent in the subwavelength germanium element, which has an active volume of 0.00072 microm3, a size that is two orders of magnitude smaller than previously demonstrated detectors at such wavelengths.
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Tassin, P., Koschny, T., Kafesaki, M., & Soukoulis, C. M. (2012). A comparison of graphene, superconductors and metals as conductors for metamaterials and plasmonics. Nat. Photon., 6(4), 259–264.
Abstract: Recent advancements in metamaterials and plasmonics have promised a number of exciting applications, in particular at terahertz and optical frequencies. Unfortunately, the noble metals used in these photonic structures are not particularly good conductors at high frequencies, resulting in significant dissipative loss. Here, we address the question of what is a good conductor for metamaterials and plasmonics. For resonant metamaterials, we develop a figure-of-merit for conductors that allows for a straightforward classification of conducting materials according to the resulting dissipative loss in the metamaterial. Application of our method predicts that graphene and high-Tc superconductors are not viable alternatives for metals in metamaterials. We also provide an overview of a number of transition metals, alkali metals and transparent conducting oxides. For plasmonic systems, we predict that graphene and high-Tc superconductors cannot outperform gold as a platform for surface plasmon polaritons, because graphene has a smaller propagation length-to-wavelength ratio.
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