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Author Hase, Muneaki; Katsuragawa, Masayuki; Constantinescu, Anca Monia; Petek, Hrvoje openurl 
  Title Frequency comb generation at terahertz frequencies by coherent phonon excitation in silicon Type Journal Article
  Year 2012 Publication Nature Photonics Abbreviated Journal Nat. Photon.  
  Volume 6 Issue Pages 243–247  
  Keywords fromIPMRAS  
  Abstract (up) High-order nonlinear light–matter interactions in gases enable the generation of X-ray and attosecond light pulses, metrology and spectroscopy1. Optical nonlinearities in solid-state materials are particularly interesting for combining optical and electronic functions for high-bandwidth information processing2. Third-order nonlinear optical processes in silicon have been used to process optical signals with bandwidths greater than 1 GHz (ref. 2). However, fundamental physical processes for a silicon-based optical modulator in the terahertz bandwidth range have not yet been explored. Here, we demonstrate ultrafast phononic modulation of the optical index of silicon by irradiation with intense few-cycle femtosecond pulses. The anisotropic reflectivity modulation by the resonant Raman susceptibility at the fundamental frequency of the longitudinal optical phonon of silicon (15.6 THz) generates a frequency comb up to seventh order. All-optical >100 THz frequency comb generation is realized by harnessing the coherent atomic motion of the silicon crystalline lattice at its highest mechanical frequency.  
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  Call Number RPLAB @ gujma @ Serial 794  
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Author Toyabe, Shoichi; Sagawa, Takahiro; Ueda, Masahito; Muneyuki, Eiro; Sano, Masaki openurl 
  Title Experimental demonstration of information-to-energy conversion and validation of the generalized Jarzynski equality Type Journal Article
  Year 2010 Publication Nature Physics Abbreviated Journal Nat. Phys.  
  Volume 6 Issue 12 Pages 988-992  
  Keywords fromIPMRAS  
  Abstract (up) In 1929, Leo Szilard invented a feedback protocol in which a hypothetical intelligence called Maxwell's demon pumps heat from an isothermal environment and transduces it to work. After an intense controversy that lasted over eighty years; it was finally clarified that the demon's role does not contradict the second law of thermodynamics, implying that we can convert information to free energy in principle. Nevertheless, experimental demonstration of this information-to-energy conversion has been elusive. Here, we demonstrate that a nonequilibrium feedback manipulation of a Brownian particle based on information about its location achieves a Szilard-type information-energy conversion. Under real-time feedback control, the particle climbs up a spiral-stairs-like potential exerted by an electric field and obtains free energy larger than the amount of work performed on it. This enables us to verify the generalized Jarzynski equality, or a new fundamental principle of “information-heat engine” which converts information to energy by feedback control.  
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  Call Number RPLAB @ gujma @ Serial 831  
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Author 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 (up) 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 Gustafsson, Martin V.; Santos, Paulo V.; Johansson, Göran; Delsing, Per openurl 
  Title Local probing of propagating acoustic waves in a gigahertz echo chamber Type Journal Article
  Year 2012 Publication Nature Physics Abbreviated Journal Nat. Phys.  
  Volume 8 Issue 4 Pages 338-343  
  Keywords fromIPMRAS  
  Abstract (up) In the same way that micro-mechanical resonators resemble guitar strings and drums, surface acoustic waves resemble the sound these instruments produce, but moving over a solid surface rather than through air. In contrast with oscillations in suspended resonators, such propagating mechanical waves have not before been studied near the quantum mechanical limits. Here, we demonstrate local probing of surface acoustic waves with a displacement sensitivity of 30amRMSHz-1/2 and detection sensitivity on the single-phonon level after averaging, at a frequency of 932MHz. Our probe is a piezoelectrically coupled single-electron transistor, which is sufficiently fast, non-destructive and localized to enable us to track pulses echoing back and forth in a long acoustic cavity, self-interfering and ringing the cavity up and down. We project that strong coupling to quantum circuits will enable new experiments, and hybrids using the unique features of surface acoustic waves. Prospects include quantum investigations of phonon-phonon interactions, and acoustic coupling to superconducting qubits for which we present favourable estimates.  
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  Call Number RPLAB @ gujma @ Serial 813  
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Author Baumert, Thomas openurl 
  Title Quantum technology: Wave packets get a kick Type Journal Article
  Year 2011 Publication Nature Physics Abbreviated Journal Nat. Phys.  
  Volume 7 Issue 5 Pages 373-374  
  Keywords fromIPMRAS  
  Abstract (up) Intense femtosecond pulses of infrared light can manipulate molecules. It is now shown that such control even extends to making different molecular eigenstates interfere with each other in a way never considered before -- a potential tool for optically engineered chemical reactions and for ultrafast information encoding and manipulation.  
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  Call Number RPLAB @ gujma @ Serial 830  
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Author 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 (up) 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 Raussendorf, Robert openurl 
  Title Quantum computing: Shaking up ground states Type Journal Article
  Year 2010 Publication Nature Physics Abbreviated Journal Nat. Phys.  
  Volume 6 Issue 11 Pages 840-841  
  Keywords fromIPMRAS  
  Abstract (up) Measurement-based quantum computation with an Affleck-Kennedy-Lieb-Tasaki state is experimentally realized for the first time.  
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  Call Number RPLAB @ gujma @ Serial 834  
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Author Clerk, Aashish openurl 
  Title Quantum phononics: To see a SAW Type Journal Article
  Year 2012 Publication Nature Physics Abbreviated Journal Nat. Phys.  
  Volume 8 Issue 4 Pages 256-257  
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  Abstract (up) Mechanical oscillations of microscopic resonators have recently been observed in the quantum regime. This idea could soon be extended from localized vibrations to travelling waves thanks to a sensitive probe of so-called surface acoustic waves.  
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  Call Number RPLAB @ gujma @ Serial 811  
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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 Pages 525–526  
  Keywords fromIPMRAS  
  Abstract (up) 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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  Call Number RPLAB @ gujma @ Serial 826  
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Author Nozaki, Kengo; Shinya, Akihiko; Matsuo, Shinji; Suzaki, Yasumasa; Segawa, Toru; Sato, Tomonari; Kawaguchi, Yoshihiro; Takahashi, Ryo; Notomi, Masaya openurl 
  Title Ultralow-power all-optical RAM based on nanocavities Type Journal Article
  Year 2012 Publication Nature Photonics Abbreviated Journal Nat. Photon.  
  Volume 6 Issue 4 Pages 248-252  
  Keywords fromIPMRAS  
  Abstract (up) Optical random-access memory (o-RAM) has been regarded as one of the most difficult challenges in terms of replacing its various functionalities in electronic circuitry with their photonic counterparts. Nevertheless, it constitutes a key device in optical routing and processing. Here, we demonstrate that photonic crystal nanocavities with an ultrasmall buried heterostructure design can solve most of the problems encountered in previous o-RAMs. By taking advantage of the strong confinement of photons and carriers and allowing heat to escape efficiently, we have realized all-optical RAMs with a power consumption of only 30 nW, which is more than 300 times lower than the previous record, and have achieved continuous operation. We have also demonstrated their feasibility in multibit integration. This paves the way for constructing a low-power large-scale o-RAM system that can handle high-bit-rate optical signals.  
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  Call Number RPLAB @ gujma @ Serial 786  
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Author Fazal, Furqan M.; Block, Steven M. openurl 
  Title Optical tweezers study life under tension Type Journal Article
  Year 2011 Publication Nature Photonics Abbreviated Journal Nat. Photon.  
  Volume 5 Issue 6 Pages 318-321  
  Keywords fromIPMRAS  
  Abstract (up) Optical tweezers have become one of the primary weapons in the arsenal of biophysicists, and have revolutionized the new field of single-molecule biophysics. Today's techniques allow high-resolution experiments on biological macromolecules that were mere pipe dreams only a decade ago.  
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  Call Number RPLAB @ gujma @ Serial 776  
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Author Peruzzo, Alberto; Laing, Anthony; Politi, Alberto; Rudolph, Terry; O'Brien, Jeremy L. openurl 
  Title Multimode quantum interference of photons in multiport integrated devices Type Journal Article
  Year 2011 Publication Nature Communications Abbreviated Journal Nat. Comm.  
  Volume 2 Issue 224 Pages 6  
  Keywords fromIPMRAS  
  Abstract (up) Photonics is a leading approach in realizing future quantum technologies and recently, optical waveguide circuits on silicon chips have demonstrated high levels of miniaturization and performance. Multimode interference (MMI) devices promise a straightforward implementation of compact and robust multiport circuits. Here, we show quantum interference in a 2×2 MMI coupler with visibility of V=95.6+/-0.9%. We further demonstrate the operation of a 4×4 port MMI device with photon pairs, which exhibits complex quantum interference behaviour. We have developed a new technique to fully characterize such multiport devices, which removes the need for phase-sensitive measurements and may find applications for a wide range of photonic devices. Our results show that MMI devices can operate in the quantum regime with high fidelity and promise substantial simplification and concatenation of photonic quantum circuits.  
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  Call Number RPLAB @ gujma @ Serial 763  
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Author Bylander, Jonas; Gustavsson, Simon; Yan, Fei; Yoshihara, Fumiki; Harrabi, Khalil; Fitch, George; Cory, David G.; Nakamura, Yasunobu; Tsai, Jaw-Shen; Oliver, William D. openurl 
  Title Noise spectroscopy through dynamical decoupling with a superconducting flux qubit Type Journal Article
  Year 2011 Publication Nature Physics Abbreviated Journal Nat. Phys.  
  Volume 7 Issue 7 Pages 565-570  
  Keywords fromIPMRAS  
  Abstract (up) Quantum coherence in natural and artificial spin systems is fundamental to applications ranging from quantum information science to magnetic-resonance imaging and identification. Several multipulse control sequences targeting generalized noise models have been developed to extend coherence by dynamically decoupling a spin system from its noisy environment. In any particular implementation, however, the efficacy of these methods is sensitive to the specific frequency distribution of the noise, suggesting that these same pulse sequences could also be used to probe the noise spectrum directly. Here we demonstrate noise spectroscopy by means of dynamical decoupling using a superconducting qubit with energy-relaxation time T1=12μs. We first demonstrate that dynamical decoupling improves the coherence time T2 in this system up to the T2=2T1 limit (pure dephasing times exceeding 100μs), and then leverage its filtering properties to probe the environmental noise over a frequency (f) range 0.2-20MHz, observing a 1/fα distribution with α<1. The characterization of environmental noise has broad utility for spin-resonance applications, enabling the design of optimized coherent-control methods, promoting device and materials engineering, and generally improving coherence.  
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  Call Number RPLAB @ gujma @ Serial 829  
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Author Grinolds, M. S.; Maletinsky, P.; Hong, S.; Lukin, M. D.; Walsworth, R. L.; Yacoby, A. openurl 
  Title Quantum control of proximal spins using nanoscale magnetic resonance imaging Type Journal Article
  Year 2011 Publication Nature Physics Abbreviated Journal Nat. Phys.  
  Volume 7 Issue 9 Pages 687-692  
  Keywords fromIPMRAS  
  Abstract (up) Quantum control of individual spins in condensed-matter systems is an emerging field with wide-ranging applications in spintronics, quantum computation and sensitive magnetometry. Recent experiments have demonstrated the ability to address and manipulate single electron spins through either optical or electrical techniques. However, it is a challenge to extend individual-spin control to nanometre-scale multi-electron systems, as individual spins are often irresolvable with existing methods. Here we demonstrate that coherent individual-spin control can be achieved with few- nanometre resolution for proximal electron spins by carrying out single-spin magnetic resonance imaging (MRI), which is realized using a scanning-magnetic-field gradient that is both strong enough to achieve nanometre spatial resolution and sufficiently stable for coherent spin manipulations. We apply this scanning-field-gradient MRI technique to electronic spins in nitrogen-vacancy (NV) centres in diamond and achieve nanometre resolution in imaging, characterization and manipulation of individual spins. For NV centres, our results in individual-spin control demonstrate an improvement of nearly two orders of magnitude in spatial resolution when compared with conventional optical diffraction-limited techniques. This scanning-field-gradient microscope enables a wide range of applications including materials characterization, spin entanglement and nanoscale magnetometry.  
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  Call Number RPLAB @ gujma @ Serial 827  
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Author Pirandola, Stefano; Mancini, Stefano; Lloyd, Seth; Braunstein, Samuel L. openurl 
  Title 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 (up) 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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  Call Number RPLAB @ gujma @ Serial 798  
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