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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 (up) 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 Zurek, Wojciech Hubert
Title Quantum Darwinism Type Journal Article
Year 2009 Publication Nature Physics Abbreviated Journal Nat. Phys.
Volume 5 Issue (up) 3 Pages 181-188
Keywords fromIPMRAS
Abstract Quantum Darwinism describes the proliferation, in the environment, of multiple records of selected states of a quantum system. It explains how the quantum fragility of a state of a single quantum system can lead to the classical robustness of states in their correlated multitude; shows how effective `wave-packet collapse' arises as a result of the proliferation throughout the environment of imprints of the state of the system; and provides a framework for the derivation of Born's rule, which relates the probabilities of detecting states to their amplitudes. Taken together, these three advances mark considerable progress towards settling the quantum measurement problem.
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Call Number RPLAB @ gujma @ Serial 799
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Author Clerk, Aashish
Title Quantum phononics: To see a SAW Type Journal Article
Year 2012 Publication Nature Physics Abbreviated Journal Nat. Phys.
Volume 8 Issue (up) 4 Pages 256-257
Keywords fromIPMRAS
Abstract 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 Gustafsson, Martin V.; Santos, Paulo V.; Johansson, Göran; Delsing, Per
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 (up) 4 Pages 338-343
Keywords fromIPMRAS
Abstract 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 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 (up) 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 Baumert, Thomas
Title Quantum technology: Wave packets get a kick Type Journal Article
Year 2011 Publication Nature Physics Abbreviated Journal Nat. Phys.
Volume 7 Issue (up) 5 Pages 373-374
Keywords fromIPMRAS
Abstract 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 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 (up) 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 Bialczak, R. C.; Ansmann, M.; Hofheinz, M.; Lucero, E.; Neeley, M.; O'Connell, A. D.; Sank, D.; Wang, H.; Wenner, J.; Steffen, M.; Cleland, A. N.; Martinis, J. M.
Title Quantum process tomography of a universal entangling gate implemented with Josephson phase qubits Type Journal Article
Year 2010 Publication Nature Physics Abbreviated Journal Nat. Phys.
Volume 6 Issue (up) 6 Pages 409-413
Keywords fromIPMRAS
Abstract Quantum gates must perform reliably when operating on standard input basis states and on complex superpositions thereof. Experiments using superconducting qubits have validated truth tables for particular implementations of, for example, the controlled-NOT gate, but have not fully characterized gate operation for arbitrary superpositions of input states. Here we demonstrate the use of quantum process tomography (QPT) to fully characterize the performance of a universal entangling gate between two superconducting qubits. Process tomography permits complete gate analysis, but requires precise preparation of arbitrary input states, control over the subsequent qubit interaction and ideally simultaneous single-shot measurement of output states. In recent work, it has been proposed to use QPT to probe noise properties and time dynamics of qubit systems and to apply techniques from control theory to create scalable qubit benchmarking protocols. We use QPT to measure the fidelity and noise properties of an entangling gate. In addition to demonstrating a promising fidelity, our entangling gate has an on-to-off ratio of 300, a level of adjustable coupling that will become a requirement for future high-fidelity devices. This is the first solid-state demonstration of QPT in a two-qubit system, as QPT has previously been demonstrated only with single solid-state qubits.
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Call Number RPLAB @ gujma @ Serial 803
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Author Ursin, R.; Tiefenbacher, F.; Schmitt-Manderbach, T.; Weier, H.; Scheidl, T.; Lindenthal, M.; Blauensteiner, B.; Jennewein, T.; Perdigues, J.; Trojek, P.; Ömer, B.; Fürst, M.; Meyenburg, M.; Rarity, J.; Sodnik, Z.; Barbieri, C.; Weinfurter, H.; Zeilinger, A.
Title Entanglement-based quantum communication over 144km Type Journal Article
Year 2007 Publication Nature Physics Abbreviated Journal Nat. Phys.
Volume 3 Issue (up) 7 Pages 481-486
Keywords fromIPMRAS
Abstract Quantum entanglement is the main resource to endow the field of quantum information processing with powers that exceed those of classical communication and computation. In view of applications such as quantum cryptography or quantum teleportation, extension of quantum-entanglement-based protocols to global distances is of considerable practical interest. Here we experimentally demonstrate entanglement-based quantum key distribution over 144km. One photon is measured locally at the Canary Island of La Palma, whereas the other is sent over an optical free-space link to Tenerife, where the Optical Ground Station of the European Space Agency acts as the receiver. This exceeds previous free-space experiments by more than an order of magnitude in distance, and is an essential step towards future satellite-based quantum communication and experimental tests on quantum physics in space.
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Call Number RPLAB @ gujma @ Serial 797
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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 (up) 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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