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Author (down) Kumar, Sushil; Chan, Chun Wang I.; Hu, Qing; Reno, John L. openurl 
  Title A 1.8-THz quantum cascade laser operating significantly above the temperature of hw/k Type Journal Article
  Year 2011 Publication Nature Physics Abbreviated Journal  
  Volume 7 Issue Pages 166-171  
  Keywords QCL, 2 mW at 155 K and 1.8 THz  
  Abstract Several competing technologies continue to advance the field of terahertz science; of particular importance has been the development of a terahertz semiconductor quantum cascade laser (QCL), which is arguably the only solid-state terahertz source with average optical power levels of much greater than a milliwatt. Terahertz QCLs are required to be cryogenically cooled and improvement of their temperature performance is the single most important research goal in the field. Thus far, their maximum operating temperature has been empirically limited to ~planckω/kB, a largely inexplicable trend that has bred speculation that a room-temperature terahertz QCL may not be possible in materials used at present. Here, we argue that this behaviour is an indirect consequence of the resonant-tunnelling injection mechanism employed in all previously reported terahertz QCLs. We demonstrate a new scattering-assisted injection scheme to surpass this limit for a 1.8-THz QCL that operates up to ~1.9planckω/kB (163 K). Peak optical power in excess of 2 mW was detected from the laser at 155 K. This development should make QCL technology attractive for applications below 2 THz, and initiate new design strategies for realizing a room-temperature terahertz semiconductor laser.  
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  Call Number Serial 631  
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Author (down) Kosako, Terukazu; Kadoya, Yutaka; Hofmann, Holger F. openurl 
  Title Directional control of light by a nano-optical Yagi–Uda antenna Type Journal Article
  Year 2010 Publication Nature Photonics Abbreviated Journal Nat. Photon.  
  Volume 4 Issue Pages 312 - 315  
  Keywords optical antennas  
  Abstract The plasmon resonance of metal nanoparticles can direct light from optical emitters in much the same way that radiofrequency antennas direct the emission from electrical circuits. Recently, rapid progress has been made in the realization of single-element antennas for optical waves. Because most of these devices are designed to optimize the local near-field coupling between the antenna and an emitter, the possibility of modifying the spatial radiation pattern has not yet received as much attention. In the radiofrequency regime, a typical antenna design for high directivity is the Yagi–Uda antenna, which essentially consists of a one-dimensional array of antenna elements driven by a single feed element. By fabricating a corresponding array of nanoparticles, similar radiation patterns can be obtained in the optical regime. Here, we present the experimental demonstration of directional control of radiation from a nano-optical Yagi–Uda antenna composed of appropriately tuned gold nanorods.  
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  Call Number RPLAB @ gujma @ Serial 747  
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Author (down) Korotkov, Alexander N. openurl 
  Title Entanglement preservation: The Sleeping Beauty approach Type Journal Article
  Year 2012 Publication Nature Physics Abbreviated Journal Nat. Phys.  
  Volume 8 Issue 2 Pages 107-108  
  Keywords fromIPMRAS  
  Abstract Two-qubit entanglement can be preserved by partially measuring the qubits to leave them in a 'lethargic' state. The original state is restored using quantum measurement reversal after the qubits have travelled through a decoherence channel.  
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  Notes Approved no  
  Call Number RPLAB @ gujma @ Serial 814  
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Author (down) Konstantatos, Gerasimos; Sargent, Edward H. openurl 
  Title Nanostructured materials for photon detection Type Journal Article
  Year 2010 Publication Nature Nanotechnology Abbreviated Journal Nat. Nanotech.  
  Volume 5 Issue 6 Pages 391–400  
  Keywords  
  Abstract The detection of photons underpins imaging, spectroscopy, fibre-optic communications and time-gated distance measurements. Nanostructured materials are attractive for detection applications because they can be integrated with conventional silicon electronics and flexible, large-area substrates, and can be processed from the solution phase using established techniques such as spin casting, spray coating and layer-by-layer deposition. In addition, their performance has improved rapidly in recent years. Here we review progress in light sensing using nanostructured materials, focusing on solution-processed materials such as colloidal quantum dots and metal nanoparticles. These devices exhibit phenomena such as absorption of ultraviolet light, plasmonic enhancement of absorption, size-based spectral tuning, multiexciton generation, and charge carrier storage in surface and interface traps.  
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  Notes SSPD Approved no  
  Call Number RPLAB @ gujma @ Serial 684  
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Author (down) Kono, Junichiro openurl 
  Title Coherent terahertz control Type Journal Article
  Year 2011 Publication Nature Photonics Abbreviated Journal Nat. Photon.  
  Volume 5 Issue Pages 5-6  
  Keywords fromIPMRAS  
  Abstract Spin and charge terahertz excitations in solids are promising for implementing future technologies such as spintronics and quantum computation, but coherently controlling them has been a significant challenge. Researchers have now manipulated coherent spin waves in an antiferromagnet using the intense magnetic field of ultrashort terahertz pulses.  
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  Call Number RPLAB @ gujma @ Serial 773  
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Author (down) Kok, Pieter openurl 
  Title Quantum optics: Entangled photons report for duty Type Journal Article
  Year 2010 Publication Nature Photonics Abbreviated Journal Nat. Photon.  
  Volume 4 Issue 8 Pages 504-505  
  Keywords fromIPMRAS  
  Abstract Entangled photons are a key ingredient in optical quantum technologies, but researchers have so far been unable to produce a single pair of entangled photons. Now, two groups from China and Austria independently report just that, with a technique that avoids the need to infer entanglement from detection signatures.  
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  Call Number RPLAB @ gujma @ Serial 772  
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Author (down) Knee, George C.; Simmons, Stephanie; Gauger, Erik M.; Morton, John J. L.; Riemann, Helge; Abrosimov, Nikolai V.; Becker, Peter; Pohl, Hans-Joachim; Itoh, Kohei M.; Thewalt, Mike L. W.; Briggs, G. Andrew D.; Benjamin, Simon C. openurl 
  Title Violation of a Leggett–Garg inequality with ideal non-invasive measurements Type Journal Article
  Year 2012 Publication Nature Communications Abbreviated Journal Nat. Comm.  
  Volume 3 Issue 606 Pages 6  
  Keywords fromIPMRAS  
  Abstract The quantum superposition principle states that an entity can exist in two different states simultaneously, counter to our 'classical' intuition. Is it possible to understand a given system's behaviour without such a concept? A test designed by Leggett and Garg can rule out this possibility. The test, originally intended for macroscopic objects, has been implemented in various systems. However to date no experiment has employed the 'ideal negative result' measurements that are required for the most robust test. Here we introduce a general protocol for these special measurements using an ancillary system, which acts as a local measuring device but which need not be perfectly prepared. We report an experimental realization using spin-bearing phosphorus impurities in silicon. The results demonstrate the necessity of a non-classical picture for this class of microscopic system. Our procedure can be applied to systems of any size, whether individually controlled or in a spatial ensemble.  
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  Notes Approved no  
  Call Number RPLAB @ gujma @ Serial 767  
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Author (down) Kim, Yong-Su; Lee, Jong-Chan; Kwon, Osung; Kim, Yoon-Ho openurl 
  Title Protecting entanglement from decoherence using weak measurement and quantum measurement reversal Type Journal Article
  Year 2012 Publication Nature Physics Abbreviated Journal Nat. Phys.  
  Volume 8 Issue 2 Pages 117-120  
  Keywords fromIPMRAS  
  Abstract Decoherence, often caused by unavoidable coupling with the environment, leads to degradation of quantum coherence. For a multipartite quantum system, decoherence leads to degradation of entanglement and, in certain cases, entanglement sudden death. Tackling decoherence, thus, is a critical issue faced in quantum information, as entanglement is a vital resource for many quantum information applications including quantum computing, quantum cryptography, quantum teleportation and quantum metrology. Here, we propose and demonstrate a scheme to protect entanglement from decoherence. Our entanglement protection scheme makes use of the quantum measurement itself for actively battling against decoherence and it can effectively circumvent even entanglement sudden death.  
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  Notes Approved no  
  Call Number RPLAB @ gujma @ Serial 815  
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Author (down) Kawano, Yukio; Ishibashi, Koji url  doi
openurl 
  Title An on-chip near-field terahertz probe and detector Type Journal Article
  Year 2008 Publication Nature Photonics Abbreviated Journal Nature Photon  
  Volume 2 Issue 10 Pages 618-621  
  Keywords single molecule, terahertz, THz, near-field, microscopy, imaging, 2DEG, GaAs/AlGaAs, detector, applications  
  Abstract The advantageous properties of terahertz waves, such as their transmission through objects opaque to visible light, are attracting attention for imaging applications. A promising approach for achieving high spatial resolution is the use of near-field imaging. Although this method has been well established in the visible and microwave regions, it is challenging to perform in the terahertz region. In the terahertz techniques investigated to date, detectors have been located remotely from the probe, which degrades sensitivity, and the influence of far-field waves is unavoidable. Here we present a new integrated detection device for terahertz near-field imaging in which all the necessary detection components — an aperture, a probe and a terahertz detector — are integrated on one semiconductor chip, which is cryogenically cooled. This scheme allows highly sensitive, high-resolution detection of the evanescent field alone and promises new capabilities for high-resolution terahertz imaging.  
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  ISSN 1749-4885 ISBN Medium  
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  Notes Approved no  
  Call Number Serial 570  
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Author (down) Johnson, B. R.; Reed, M. D.; Houck, A. A.; Schuster, D. I.; Bishop, Lev S.; Ginossar, E.; Gambetta, J. M.; Dicarlo, L.; Frunzio, L.; Girvin, S. M.; Schoelkopf, R. J. openurl 
  Title Quantum non-demolition detection of single microwave photons in a circuit Type Journal Article
  Year 2010 Publication Nature Physics Abbreviated Journal Nat. Phys.  
  Volume 6 Issue 9 Pages 663-667  
  Keywords fromIPMRAS  
  Abstract Thorough control of quantum measurement is key to the development of quantum information technologies. Many measurements are destructive, removing more information from the system than they obtain. Quantum non-demolition (QND) measurements allow repeated measurements that give the same eigenvalue. They could be used for several quantum information processing tasks such as error correction, preparation by measurement and one-way quantum computing. Achieving QND measurements of photons is especially challenging because the detector must be completely transparent to the photons while still acquiring information about them. Recent progress in manipulating microwave photons in superconducting circuits has increased demand for a QND detector that operates in the gigahertz frequency range. Here we demonstrate a QND detection scheme that measures the number of photons inside a high-quality-factor microwave cavity on a chip. This scheme maps a photon number, n, onto a qubit state in a single-shot by means of qubit-photon logic gates. We verify the operation of the device for n=0 and 1 by analysing the average correlations of repeated measurements, and show that it is 90% QND. It differs from previously reported detectors because its sensitivity is strongly selective to chosen photon number states. This scheme could be used to monitor the state of a photon-based memory in a quantum computer.  
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  Call Number RPLAB @ gujma @ Serial 806  
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Author (down) Ikuta, Rikizo; Kusaka, Yoshiaki; Kitano, suyoshi; Kato, Hiroshi; Yamamoto, Takashi; Koashi, Masato; Imoto, Nobuyuki openurl 
  Title Wide-band quantum interface for visible-totelecommunication wavelength conversion Type Journal Article
  Year 2011 Publication Nature Communications Abbreviated Journal Nat. Comm.  
  Volume 2 Issue Pages 5  
  Keywords fromIPMRAS  
  Abstract Although near-infrared photons in telecommunication bands are required for long-distance quantum communication, various quantum information tasks have been performed by using visible photons for the past two decades. Recently, such visible photons from diverse media including atomic quantum memories have also been studied. Optical frequency down-conversion from visible to telecommunication bands while keeping the quantum states is thus required for bridging such wavelength gaps. Here we report demonstration of a quantum interface of frequency down-conversion from visible to telecommunication bands by using a nonlinear crystal, which has a potential to work over wide bandwidths, leading to a high-speed interface of frequency conversion. We achieved the conversion of a picosecond visible photon at 780 nm to a 1,522-nm photon, and observed that the conversion process retained entanglement between the down-converted photon and another photon.  
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  Call Number RPLAB @ gujma @ Serial 764  
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Author (down) Hosseini, M.; Campbell, G.; Sparkes, B. M.; Lam, P. K.; Buchler, B. C. openurl 
  Title Unconditional room-temperature quantum memory Type Journal Article
  Year 2011 Publication Nature Physics Abbreviated Journal Nat. Phys.  
  Volume 7 Issue 10 Pages 794-798  
  Keywords fromIPMRAS  
  Abstract Just as classical information systems require buffers and memory, the same is true for quantum information systems. The potential that optical quantum information processing holds for revolutionizing computation and communication is therefore driving significant research into developing optical quantum memory. A practical optical quantum memory must be able to store and recall quantum states on demand with high efficiency and low noise. Ideally, the platform for the memory would also be simple and inexpensive. Here, we present a complete tomographic reconstruction of quantum states that have been stored in the ground states of rubidium in a vapour cell operating at around 80 °C. Without conditional measurements, we show recall fidelity up to 98% for coherent pulses containing around one photon. To unambiguously verify that our memory beats the quantum no-cloning limit we employ state-independent verification using conditional variance and signal-transfer coefficients.  
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  Call Number RPLAB @ gujma @ Serial 824  
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Author (down) Home, Jonathan openurl 
  Title Quantum entanglement: Watching correlations disappear Type Journal Article
  Year 2010 Publication Nature Physics Abbreviated Journal Nat. Phys.  
  Volume 6 Issue 12 Pages 938-939  
  Keywords fromIPMRAS  
  Abstract Engineered decoherence enables tracking of multipartite entanglement as a quantum state decays.  
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  Call Number RPLAB @ gujma @ Serial 832  
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Author (down) Hollenberg, Lloyd C. L. openurl 
  Title Quantum control: Through the quantum chicane Type Journal Article
  Year 2012 Publication Nature Physics Abbreviated Journal Nat. Phys.  
  Volume 8 Issue 2 Pages 113-114  
  Keywords fromIPMRAS  
  Abstract In quantum control there is an inherent tension between high fidelity requirements and the need for speed to avoid decoherence. A direct comparison of quantum control protocols at these two extremes indicates where the sweet spot may lie.  
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  Call Number RPLAB @ gujma @ Serial 812  
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Author (down) He, Rongrui; Sazio, Pier J. A.; Peacock, Anna C.; Healy, Noel; Sparks, Justin R.; Krishnamurthi, Mahesh; Gopalan, Venkatraman; Badding, John V. openurl 
  Title Integration of gigahertz-bandwidth semiconductor devices inside microstructured optical fibres Type Journal Article
  Year 2012 Publication Nature Photonics Abbreviated Journal Nat. Photon.  
  Volume 6 Issue 3 Pages 174-179  
  Keywords fromIPMRAS  
  Abstract The prospect of an all-fibre optical communications network in which light can be generated, modulated and detected within the fibre itself without the need for discrete optoelectronic devices is an appealing one. However, to become a reality, this approach requires the incorporation of optoelectronic materials and functionalities into silica fibres to create a new breed of semiconductor-fibre hybrid devices for performing various tasks. Here, we report the integration of precisely doped semiconductor materials and high-quality rectifying semiconductor junctions into microstructured optical fibres, enabling high-speed, in-fibre functionalities such as photodetection at telecommunications wavelengths. These semiconductor-fibre hybrid devices exhibit a bandwidth of up to 3 GHz and seamless coupling to standard single-mode optical fibres.  
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  Notes Approved no  
  Call Number RPLAB @ gujma @ Serial 783  
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