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Author Kumar, Sushil; Chan, Chun Wang I.; Hu, Qing; Reno, John L. openurl 
  Title (up) 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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  Notes Approved no  
  Call Number Serial 631  
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Author Kumar, Sushil; Wang I. Chan, Chun; Hu, Qing; Reno, John L. openurl 
  Title (up) A 1.8-THz quantum cascade laser operating significantly above the temperature of ω/kB Type Journal Article
  Year 2011 Publication Nature Physics Abbreviated Journal Nat. Phys.  
  Volume 7 Issue Pages  
  Keywords fromIPMRAS  
  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 ~ω/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 ~1.9ω/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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  Notes Approved no  
  Call Number RPLAB @ gujma @ Serial 836  
Permanent link to this record
 
 
Author Zhu, J.; Christensen, J.; Jung, J.; Martin-Moreno, L.; Yin, X.; Fok, L.; Zhang, X.; Garcia-Vidal, F. J. openurl 
  Title (up) A holey-structured metamaterial for acoustic deep-subwavelength imaging Type Journal Article
  Year 2011 Publication Nature Physics Abbreviated Journal Nat. Phys.  
  Volume 7 Issue 1 Pages 52-55  
  Keywords fromIPMRAS  
  Abstract For classical waves such as light or sound, diffraction sets a natural limit on how finely the details of an object can be recorded on its image. Recently, various optical superlenses based on the metamaterials concept have shown the possibility of overcoming the diffraction limit. Similar two-dimensional (2D) acoustic hyperlens designs have also been explored. Here we demonstrate a 3D holey-structured metamaterial that achieves acoustic imaging down to a feature size of λ/50. The evanescent field components of a subwavelength object are efficiently transmitted through the structure as a result of their strong coupling with Fabry-Pérot resonances inside the holey plate. This capability of acoustic imaging at a very deep-subwavelength scale may open the door for a broad range of applications, including medical ultrasonography, underwater sonar and ultrasonic non-destructive evaluation.  
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  Notes Approved no  
  Call Number RPLAB @ gujma @ Serial 809  
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Author Hannay, Timo openurl 
  Title (up) A new kind of science? Type Journal Article
  Year 2011 Publication Nature Physics Abbreviated Journal Nat. Phys.  
  Volume 7 Issue Pages 742  
  Keywords fromIPMRAS  
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  Notes Approved no  
  Call Number RPLAB @ gujma @ Serial 818  
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Author Fuchs, G. D.; Burkard, G.; Klimov, P. V.; Awschalom, D. D. openurl 
  Title (up) A quantum memory intrinsic to single nitrogen–vacancy centres in diamond Type Journal Article
  Year 2011 Publication Nature Physics Abbreviated Journal Nat. Phys.  
  Volume 7 Issue 10 Pages 789-793  
  Keywords fromIPMRAS  
  Abstract A quantum memory, composed of a long-lived qubit coupled to each processing qubit, is important to building a scalable platform for quantum information science. These two qubits should be connected by a fast and high-fidelity operation to store and retrieve coherent quantum states. Here, we demonstrate a room-temperature quantum memory based on the spin of the nitrogen nucleus intrinsic to each nitrogen–vacancy (NV) centre in diamond. We perform coherent storage of a single NV centre electronic spin in a single nitrogen nuclear spin using Landau–Zener transitions across a hyperfine-mediated avoided level crossing. By working outside the asymptotic regime, we demonstrate coherent state transfer in as little as 120 ns with total storage fidelity of 88±6%. This work demonstrates the use of a quantum memory that is compatible with scaling as the nitrogen nucleus is deterministically present in each NV centre defect.  
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  Call Number RPLAB @ gujma @ Serial 823  
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Author Biercuk, Michael J. openurl 
  Title (up) A quantum spectrum analyser Type Journal Article
  Year 2011 Publication Nature Physics Abbreviated Journal Nat. Phys.  
  Volume 7 Issue Pages 525–526  
  Keywords fromIPMRAS  
  Abstract Noise filters based on so-called dynamical decoupling pulse sequences can suppress decoherence in quantum systems. Turning this idea on its head now provides a new technique for studying the noise itself.  
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  Notes Approved no  
  Call Number RPLAB @ gujma @ Serial 826  
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Author Arcizet, O.; Jacques, V.; Siria, A.; Poncharal, P.; Vincent, P.; Seidelin, S. openurl 
  Title (up) A single nitrogen-vacancy defect coupled to a nanomechanical oscillator Type Journal Article
  Year 2011 Publication Nature Physics Abbreviated Journal Nat. Phys.  
  Volume 7 Issue 11 Pages 879-883  
  Keywords fromIPMRAS  
  Abstract We position a single nitrogen-vacancy (NV) centre hosted in a diamond nanocrystal at the extremity of a SiC nanowire. This novel hybrid system couples the degrees of freedom of two radically different systems: a nanomechanical oscillator and a single quantum object. We probe the dynamics of the nano-resonator through time-resolved nanocrystal fluorescence and photon-correlation measurements, conveying the influence of a mechanical degree of freedom on a non-classical photon emitter. Moreover, by immersing the system in a strong magnetic field gradient, we induce a magnetic coupling between the nanomechanical oscillator and the NV electronic spin, providing nanomotion readout through a single electronic spin. Spin-dependent forces inherent to this coupling scheme are essential in a variety of active cooling and entanglement protocols used in atomic physics, and should now be within the reach of nanomechanical hybrid systems.  
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  Call Number RPLAB @ gujma @ Serial 819  
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Author Bozyigit, D.; Lang, C.; Steffen, L.; Fink, J. M.; Eichler, C.; Baur, M.; Bianchetti, R.; Leek, P. J.; Filipp, S.; da Silva, M. P.; Blais, A.; Wallraff, A. openurl 
  Title (up) Antibunching of microwave-frequency photons observed in correlation measurements using linear detectors Type Journal Article
  Year 2011 Publication Nature Physics Abbreviated Journal Nat. Phys.  
  Volume 7 Issue 2 Pages 154-158  
  Keywords fromIPMRAS  
  Abstract At optical frequencies the radiation produced by a source, such as a laser, a black body or a single-photon emitter, is frequently characterized by analysing the temporal correlations of emitted photons using single-photon counters. At microwave frequencies, however, there are no efficient single-photon counters yet. Instead, well-developed linear amplifiers allow for efficient measurement of the amplitude of an electromagnetic field. Here, we demonstrate first- and second-order correlation function measurements of a pulsed microwave-frequency single-photon source integrated on the same chip with a 50/50 beam splitter followed by linear amplifiers and quadrature amplitude detectors. We clearly observe single-photon coherence in first-order and photon antibunching in second-order correlation function measurements of the propagating fields.  
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  Notes Approved no  
  Call Number RPLAB @ gujma @ Serial 835  
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Author Buchanan, Mark openurl 
  Title (up) Body of evidence Type Manuscript
  Year 2010 Publication Nature Physics Abbreviated Journal Nat. Phys.  
  Volume 6 Issue Pages  
  Keywords fromIPMRAS  
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  Notes Approved no  
  Call Number RPLAB @ gujma @ Serial 837  
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Author Pirandola, Stefano; Mancini, Stefano; Lloyd, Seth; Braunstein, Samuel L. openurl 
  Title (up) Continuous-variable quantum cryptography using two-way quantum communication Type Journal Article
  Year 2008 Publication Nature Physics Abbreviated Journal Nat. Phys.  
  Volume 4 Issue 9 Pages 726-730  
  Keywords fromIPMRAS  
  Abstract Quantum cryptography has recently been extended to continuous-variable systems, such as the bosonic modes of the electromagnetic field possessing continuous degrees of freedom. In particular, several cryptographic protocols have been proposed and experimentally implemented using bosonic modes with Gaussian statistics. These protocols have shown the possibility of reaching very high secret key rates, even in the presence of strong losses in the quantum communication channel. Despite this robustness to loss, their security can be affected by more general attacks where extra Gaussian noise is introduced by the eavesdropper. Here, we show a `hardware solution' for enhancing the security thresholds of these protocols. This is possible by extending them to two-way quantum communication where subsequent uses of the quantum channel are suitably combined. In the resulting two-way schemes, one of the honest parties assists the secret encoding of the other, with the chance of a non-trivial superadditive enhancement of the security thresholds. These results should enable the extension of quantum cryptography to more complex quantum communications.  
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  Notes Approved no  
  Call Number RPLAB @ gujma @ Serial 798  
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