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Author 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 (up) 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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  Area Expedition Conference  
  Notes Approved no  
  Call Number Serial 631  
Permanent link to this record
 
 
Author Shor, Peter W. openurl 
  Title Quantum information theory: The bits don't add up Type Journal Article
  Year 2009 Publication Nature Physics Abbreviated Journal Nat. Phys.  
  Volume 5 Issue (up) Pages 247 - 248  
  Keywords fromIPMRAS  
  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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  Area Expedition Conference  
  Notes Approved no  
  Call Number RPLAB @ gujma @ Serial 800  
Permanent link to this record
 
 
Author Haviland, David openurl 
  Title Superconducting circuits: Quantum phase slips Type Journal Article
  Year 2010 Publication Nature Physics Abbreviated Journal Nat. Phys.  
  Volume 6 Issue (up) Pages 565–566  
  Keywords fromIPMRAS  
  Abstract Coulomb interactions can cause a rapid change in the phase of the wavefunction along a very narrow superconducting system. Such a phase slip at the quantum level is now measured in a chain of Josephson junctions.  
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  Notes Approved no  
  Call Number RPLAB @ gujma @ Serial 807  
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Author Mineev, Vladimir P. openurl 
  Title Superfluid helium: Order in disorder Type Journal Article
  Year 2012 Publication Nature Physics Abbreviated Journal Nat. Phys.  
  Volume 8 Issue (up) Pages 253–254  
  Keywords fromIPMRAS  
  Abstract Confining liquid 3He in porous silica aerogel prepared with strong anisotropy stabilizes a state of axial superfluidity.  
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  Notes Approved no  
  Call Number RPLAB @ gujma @ Serial 810  
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Author Barreiro, Julio T. openurl 
  Title Quantum physics: Environmental effects controlled Type Journal Article
  Year 2011 Publication Nature Physics Abbreviated Journal Nat. Phys.  
  Volume 7 Issue (up) Pages 927–928  
  Keywords fromIPMRAS  
  Abstract An open quantum system loses its 'quantumness' when information about the state leaks into its surroundings. Researchers now show how this decoherence can be controlled between two incompatible regimes in the case of a single photon.  
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  Notes Approved no  
  Call Number RPLAB @ gujma @ Serial 817  
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Author Hannay, Timo openurl 
  Title A new kind of science? Type Journal Article
  Year 2011 Publication Nature Physics Abbreviated Journal Nat. Phys.  
  Volume 7 Issue (up) Pages 742  
  Keywords fromIPMRAS  
  Abstract  
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  Notes Approved no  
  Call Number RPLAB @ gujma @ Serial 818  
Permanent link to this record
 
 
Author Vishveshwara, Smitha openurl 
  Title Topological qubits: A bit of both Type Journal Article
  Year 2011 Publication Nature Physics Abbreviated Journal Nat. Phys.  
  Volume 7 Issue (up) Pages 450–451  
  Keywords fromIPMRAS  
  Abstract 'Standard' qubits have been implemented in diverse physical systems. Now, so-called topological qubits are coming into the limelight, and could potentially be used for decoherence-free quantum computing. Coupling these two types of qubit might enable devices that exploit the virtues of both.  
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  Notes Approved no  
  Call Number RPLAB @ gujma @ Serial 825  
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Author Biercuk, Michael J. openurl 
  Title A quantum spectrum analyser Type Journal Article
  Year 2011 Publication Nature Physics Abbreviated Journal Nat. Phys.  
  Volume 7 Issue (up) 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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  Area Expedition Conference  
  Notes Approved no  
  Call Number RPLAB @ gujma @ Serial 826  
Permanent link to this record
 
 
Author Kumar, Sushil; Wang I. Chan, Chun; Hu, Qing; Reno, John L. openurl 
  Title 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 (up) 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.  
  Address  
  Corporate Author Thesis  
  Publisher Place of Publication Editor  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN ISBN Medium  
  Area Expedition Conference  
  Notes Approved no  
  Call Number RPLAB @ gujma @ Serial 836  
Permanent link to this record
 
 
Author Buchanan, Mark openurl 
  Title Body of evidence Type Manuscript
  Year 2010 Publication Nature Physics Abbreviated Journal Nat. Phys.  
  Volume 6 Issue (up) Pages  
  Keywords fromIPMRAS  
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  Notes Approved no  
  Call Number RPLAB @ gujma @ Serial 837  
Permanent link to this record
 
 
Author Buchanan, Mark openurl 
  Title Nothing's impossible Type Manuscript
  Year 2011 Publication Nature Physics Abbreviated Journal Nat. Phys.  
  Volume 7 Issue (up) Pages 5  
  Keywords fromIPMRAS  
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  Notes Approved no  
  Call Number RPLAB @ gujma @ Serial 839  
Permanent link to this record
 
 
Author Nevou, L.; Liverini, V.; Friedli, P.; Castellano, F.; Bismuto, A.; Sigg, H.; Gramm, F.; Müller, E.; Faist, J. openurl 
  Title Current quantization in an optically driven electron pump based on self-assembled quantum dots Type Journal Article
  Year 2011 Publication Nature Physics Abbreviated Journal Nat. Phys.  
  Volume 7 Issue (up) Pages 423–427  
  Keywords fromIPMRAS  
  Abstract The electronic structure of self-assembled semiconductor quantum dots consists of discrete atom-like states that can be populated with a well-defined number of electrons. This property can be used to fabricate a d.c. current standard that enables the unit of ampere to be independently defined. Here we report an optically pumped current source based on self-assembled InAs/GaAs quantum dots. The accuracy obtained so far is 10–1 and is limited by the uncertainty in the number of dots. At 10 K the device generates a current difference of 2.39 nA at a frequency of 1 kHz. The accuracy could be improved by site-selective growth techniques where the number of dots is fixed by pre-patterning. The results are promising for applications in electrical metrology, where a current standard is needed to close the so-called quantum metrological triangle.  
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  Notes Approved no  
  Call Number RPLAB @ gujma @ Serial 841  
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Author Hanneke, D.; Home, J. P.; Jost, J. D.; Amini, J. M.; Leibfried, D.; Wineland, D. J. openurl 
  Title Realization of a programmable two-qubit quantum processor Type Journal Article
  Year 2010 Publication Nature Physics Abbreviated Journal Nat. Phys.  
  Volume 6 Issue (up) 1 Pages 13-16  
  Keywords fromIPMRAS  
  Abstract The universal quantum computer is a device capable of simulating any physical system and represents a major goal for the field of quantum information science. In the context of quantum information, `universal' refers to the ability to carry out arbitrary unitary transformations in the system's computational space. Combining arbitrary single-quantum-bit (qubit) gates with an entangling two-qubit gate provides a set of gates capable of achieving universal control of any number of qubits, provided that these gates can be carried out repeatedly and between arbitrary pairs of qubits. Although gate sets have been demonstrated in several technologies, they have so far been tailored towards specific tasks, forming a small subset of all unitary operators. Here we demonstrate a quantum processor that can be programmed with 15 classical inputs to realize arbitrary unitary transformations on two qubits, which are stored in trapped atomic ions. Using quantum state and process tomography, we characterize the fidelity of our implementation for 160 randomly chosen operations. This universal control is equivalent to simulating any pairwise interaction between spin-1/2 systems. A programmable multiqubit register could form a core component of a large-scale quantum processor, and the methods used here are suitable for such a device.  
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  Notes Approved no  
  Call Number RPLAB @ gujma @ Serial 801  
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Author Zhu, J.; Christensen, J.; Jung, J.; Martin-Moreno, L.; Yin, X.; Fok, L.; Zhang, X.; Garcia-Vidal, F. J. openurl 
  Title A holey-structured metamaterial for acoustic deep-subwavelength imaging Type Journal Article
  Year 2011 Publication Nature Physics Abbreviated Journal Nat. Phys.  
  Volume 7 Issue (up) 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  
Permanent link to this record
 
 
Author Zhang, Qiang; Goebel, Alexander; Wagenknecht, Claudia; Chen, Yu-Ao; Zhao, Bo; Yang, Tao; Mair, Alois; Schmiedmayer, Jörg; Pan, Jian-Wei openurl 
  Title Experimental quantum teleportation of a two-qubit composite system Type Journal Article
  Year 2006 Publication Nature Physics Abbreviated Journal Nat. Phys.  
  Volume 2 Issue (up) 10 Pages 678-682  
  Keywords fromIPMRAS; quantum teleportation  
  Abstract Quantum teleportation, a way to transfer the state of a quantum system from one location to another, is central to quantum communication and plays an important role in a number of quantum computation protocols. Previous experimental demonstrations have been implemented with single photonic or ionic qubits. However, teleportation of single qubits is insufficient for a large-scale realization of quantum communication and computation. Here, we present the experimental realization of quantum teleportation of a two-qubit composite system. In the experiment, we develop and exploit a six-photon interferometer to teleport an arbitrary polarization state of two photons. The observed teleportation fidelities for different initial states are all well beyond the state estimation limit of 0.40 for a two-qubit system. Not only does our six-photon interferometer provide an important step towards teleportation of a complex system, it will also enable future experimental investigations on a number of fundamental quantum communication and computation protocols  
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  Notes Approved no  
  Call Number RPLAB @ gujma @ Serial 795  
Permanent link to this record
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