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Author Lupascu, Adrian
Title Nonlinear dynamics: Quantum pendula locked in Type Journal Article
Year 2011 Publication Nature Physics Abbreviated Journal Nat. Phys.
Volume 7 Issue 2 Pages 100-101
Keywords fromIPMRAS
Abstract A study of the autoresonant behaviour of a superconducting pendulum reveals that quantum fluctuations determine only the initial oscillator motion and not its subsequent dynamics. This could be important in the development of more efficient methods for reading solid-state qubits.
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Call Number RPLAB @ gujma @ Serial 840
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Author Ma, Xiao-Song; Dakic, Borivoje; Naylor, William; Zeilinger, Anton; Walther, Philip
Title Quantum simulation of the wavefunction to probe frustrated Heisenberg spin systems Type Journal Article
Year 2011 Publication Nature Physics Abbreviated Journal Nat. Phys.
Volume 7 Issue 5 Pages 399-405
Keywords fromIPMRAS
Abstract Quantum simulators are controllable quantum systems that can reproduce the dynamics of the system of interest in situations that are not amenable to classical computers. Recent developments in quantum technology enable the precise control of individual quantum particles as required for studying complex quantum systems. In particular, quantum simulators capable of simulating frustrated Heisenberg spin systems provide platforms for understanding exotic matter such as high-temperature superconductors. Here we report the analogue quantum simulation of the ground-state wavefunction to probe arbitrary Heisenberg-type interactions among four spin-1/2 particles. Depending on the interaction strength, frustration within the system emerges such that the ground state evolves from a localized to a resonating-valence-bond state. This spin-1/2 tetramer is created using the polarization states of four photons. The single-particle addressability and tunable measurement-induced interactions provide us with insights into entanglement dynamics among individual particles. We directly extract ground-state energies and pairwise quantum correlations to observe the monogamy of entanglement.
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Call Number RPLAB @ gujma @ Serial 842
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Author Mariantoni, Matteo; Wang, H.; Bialczak, Radoslaw C.; Lenander, M.; Lucero, Erik; Neeley, M.; O'Connell, A. D.; Sank, D.; Weides, M.; Wenner, J.; Yamamoto, T.; Yin, Y.; Zhao, J.; Martinis, John M.; Cleland, A. N.
Title Photon shell game in three-resonator circuit quantum electrodynamics Type Journal Article
Year 2011 Publication Nature Physics Abbreviated Journal Nat. Phys.
Volume 7 Issue 4 Pages 287-293
Keywords fromIPMRAS
Abstract The generation and control of quantum states of light constitute fundamental tasks in cavity quantum electrodynamics (QED). The superconducting realization of cavity QED, circuit QED (refs 11, 12, 13, 14), enables on-chip microwave photonics, where superconducting qubits control and measure individual photon states. A long-standing issue in cavity QED is the coherent transfer of photons between two or more resonators. Here, we use circuit QED to implement a three-resonator architecture on a single chip, where the resonators are interconnected by two superconducting phase qubits. We use this circuit to shuffle one- and two-photon Fock states between the three resonators, and demonstrate qubit-mediated vacuum Rabi swaps between two resonators. By shuffling superposition states we are also able to demonstrate the high-fidelity phase coherence of the transfer. Our results illustrate the potential for using multi-resonator circuits as photon quantum registers and for creating multipartite entanglement between delocalized bosonic modes.
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Call Number RPLAB @ gujma @ Serial 838
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Author Mineev, Vladimir P.
Title Superfluid helium: Order in disorder Type Journal Article
Year 2012 Publication Nature Physics Abbreviated Journal Nat. Phys.
Volume 8 Issue 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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Call Number RPLAB @ gujma @ Serial 810
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Author Nevou, L.; Liverini, V.; Friedli, P.; Castellano, F.; Bismuto, A.; Sigg, H.; Gramm, F.; Müller, E.; Faist, J.
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 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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Call Number RPLAB @ gujma @ Serial 841
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Author Nozaki, Kengo; Shinya, Akihiko; Matsuo, Shinji; Suzaki, Yasumasa; Segawa, Toru; Sato, Tomonari; Kawaguchi, Yoshihiro; Takahashi, Ryo; Notomi, Masaya
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 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 Paiella, Roberto
Title Terahertz quantum cascade lasers: Going ultrafast Type Journal Article
Year 2011 Publication Nature Photonics Abbreviated Journal Nat. Photon.
Volume 5 Issue Pages 253–255
Keywords fromIPMRAS
Abstract A new asynchronous coherent optical sampling method allows for the direct visualization of actively mode-locked quantum cascade laser pulses at terahertz wavelengths.
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Call Number RPLAB @ gujma @ Serial 774
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Author Perseguers, S.; Lewenstein, M.; Acín, A.; Cirac, J. I.
Title Quantum random networks Type Journal Article
Year 2010 Publication Nature Physics Abbreviated Journal Nat. Phys.
Volume 6 Issue 7 Pages 539-543
Keywords fromIPMRAS
Abstract Quantum mechanics offers new possibilities to process and transmit information. In recent years, algorithms and cryptographic protocols exploiting the superposition principle and the existence of entangled states have been designed. They should allow us to realize communication and computational tasks that outperform any classical strategy. Here we show that quantum mechanics also provides fresh perspectives in the field of random networks. Already the simplest model of a classical random graph changes markedly when extended to the quantum case, where we obtain a distinct behaviour of the critical probabilities at which different subgraphs appear. In particular, in a network of N nodes, any quantum subgraph can be generated by local operations and classical communication if the entanglement between pairs of nodes scales as N-2. This result also opens up new vistas in the domain of quantum networks and their applications.
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Call Number RPLAB @ gujma @ Serial 804
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Author Peruzzo, Alberto; Laing, Anthony; Politi, Alberto; Rudolph, Terry; O'Brien, Jeremy L.
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 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 Pile, David
Title How many bits can a photon carry Type Journal Article
Year 2012 Publication Nature Photonics Abbreviated Journal Nat. Photon.
Volume 6 Issue 1 Pages 14-15
Keywords fromIPMRAS
Abstract Quantum physics offers a way to enhance the amount of information a photon can carry, with potential applications in optical communication, lithography, metrology and imaging.
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Notes View from... OSA Frontiers in Optics 2011: How many bits can a photon carry? Approved no
Call Number RPLAB @ gujma @ Serial 780
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Author Pirandola, Stefano; Mancini, Stefano; Lloyd, Seth; Braunstein, Samuel L.
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 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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Author Prevedel, Robert; Hamel, Deny R.; Colbeck, Roger; Fisher, Kent; Resch, Kevin J.
Title Experimental investigation of the uncertainty principle in the presence of quantum memory and its application to witnessing entanglement Type Journal Article
Year 2011 Publication Nature Physics Abbreviated Journal Nat. Phys.
Volume 7 Issue 10 Pages 757-761
Keywords fromIPMRAS
Abstract Heisenberg's uncertainty principle provides a fundamental limitation on the ability of an observer holding classical information to predict the outcome when one of two measurements is performed on a quantum system. However, an observer with access to a particle (stored in a quantum memory) which is entangled with the system generally has a reduced uncertainty: indeed, if the particle and system are maximally entangled, the observer can perfectly predict the outcome of whichever measurement is chosen. This effect has recently been quantified in a new entropic uncertainty relation. Here we experimentally investigate this relation, showing its effectiveness as an efficient entanglement witness. We use entangled photon pairs, an optical delay line serving as a simple quantum memory and fast, active feed-forward. Our results quantitatively agree with the new uncertainty relation. Our technique acts as a witness for almost all entangled states in our experiment as we obtain lower uncertainties than would be possible without the entangled particle.
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Call Number RPLAB @ gujma @ Serial 821
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Author Pris, Andrew D.; Utturkar, Yogen; Surman, Cheryl; Morris, William G.; Vert, Alexey; Zalyubovskiy, Sergiy; Deng, Tao; Ghiradella, Helen T.; Potyrailo, Radislav A.
Title Towards high-speed imaging of infrared photons with bio-inspired nanoarchitectures Type Journal Article
Year 2012 Publication Nature Photonics Abbreviated Journal Nat. Photon.
Volume 6 Issue 3 Pages 195-200
Keywords fromIPMRAS
Abstract Existing infrared detectors rely on complex microfabrication and thermal management methods. Here, we report an attractive platform of low-thermal-mass resonators inspired by the architectures of iridescent Morpho butterfly scales. In these resonators, the optical cavity is modulated by its thermal expansion and refractive index change, resulting in `wavelength conversion' of mid-wave infrared (3-8 µm) radiation into visible iridescence changes. By doping Morpho butterfly scales with single-walled carbon nanotubes, we achieved mid-wave infrared detection with 18-62 mK noise-equivalent temperature difference and 35-40 Hz heat-sink-free response speed. The nanoscale pitch and the extremely small thermal mass of individual `pixels' promise significant improvements over existing detectors. Computational analysis explains the origin of this thermal response and guides future conceptually new bio-inspired thermal imaging sensor designs.
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Call Number RPLAB @ gujma @ Serial 785
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Author Raussendorf, Robert
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 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 Saffman, Mark
Title Quantum computing: A quantum telecom link Type Journal Article
Year 2010 Publication Nature Physics Abbreviated Journal Nat. Phys.
Volume 6 Issue 11 Pages 838-839
Keywords fromIPMRAS
Abstract Converting data-carrying photons to telecommunication wavelengths enables distribution of quantum information over long distances.
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Call Number RPLAB @ gujma @ Serial 833
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