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  • 1
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    Fast Tunable Coupler for Superconducting Qubits (2011)
    American Physical Society (APS)
    Details
    Publication Date: 2011-02-10
    Description: Author(s): R. C. Bialczak, M. Ansmann, M. Hofheinz, M. Lenander, E. Lucero, M. Neeley, A. D. O’Connell, D. Sank, H. Wang, M. Weides, J. Wenner, T. Yamamoto, A. N. Cleland, and J. M. Martinis A major challenge in the field of quantum computing is the construction of scalable qubit coupling architectures. Here, we demonstrate a novel tunable coupling circuit that allows superconducting qubits to be coupled over long distances. We show that the interqubit coupling strength can be arbitrari... [Phys. Rev. Lett. 106, 060501] Published Wed Feb 09, 2011
    Keywords: General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.
    Print ISSN: 0031-9007
    Electronic ISSN: 1079-7114
    Topics: Physics
    Published by American Physical Society (APS)
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  • 2
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    Quantum ground state and single-phonon control of a mechanical resonator (2010)
    Nature Publishing Group (NPG)
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    Publication Date: 2010-03-20
    Description: Quantum mechanics provides a highly accurate description of a wide variety of physical systems. However, a demonstration that quantum mechanics applies equally to macroscopic mechanical systems has been a long-standing challenge, hindered by the difficulty of cooling a mechanical mode to its quantum ground state. The temperatures required are typically far below those attainable with standard cryogenic methods, so significant effort has been devoted to developing alternative cooling techniques. Once in the ground state, quantum-limited measurements must then be demonstrated. Here, using conventional cryogenic refrigeration, we show that we can cool a mechanical mode to its quantum ground state by using a microwave-frequency mechanical oscillator-a 'quantum drum'-coupled to a quantum bit, which is used to measure the quantum state of the resonator. We further show that we can controllably create single quantum excitations (phonons) in the resonator, thus taking the first steps to complete quantum control of a mechanical system.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉O'Connell, A D -- Hofheinz, M -- Ansmann, M -- Bialczak, Radoslaw C -- Lenander, M -- Lucero, Erik -- Neeley, M -- Sank, D -- Wang, H -- Weides, M -- Wenner, J -- Martinis, John M -- Cleland, A N -- England -- Nature. 2010 Apr 1;464(7289):697-703. doi: 10.1038/nature08967. Epub 2010 Mar 17.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Physics, University of California, Santa Barbara, California 93106, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20237473" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 3
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    Generation of Fock states in a superconducting quantum circuit (2008)
    Nature Publishing Group (NPG)
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    Publication Date: 2008-07-18
    Description: Spin systems and harmonic oscillators comprise two archetypes in quantum mechanics. The spin-1/2 system, with two quantum energy levels, is essentially the most nonlinear system found in nature, whereas the harmonic oscillator represents the most linear, with an infinite number of evenly spaced quantum levels. A significant difference between these systems is that a two-level spin can be prepared in an arbitrary quantum state using classical excitations, whereas classical excitations applied to an oscillator generate a coherent state, nearly indistinguishable from a classical state. Quantum behaviour in an oscillator is most obvious in Fock states, which are states with specific numbers of energy quanta, but such states are hard to create. Here we demonstrate the controlled generation of multi-photon Fock states in a solid-state system. We use a superconducting phase qubit, which is a close approximation to a two-level spin system, coupled to a microwave resonator, which acts as a harmonic oscillator, to prepare and analyse pure Fock states with up to six photons. We contrast the Fock states with coherent states generated using classical pulses applied directly to the resonator.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hofheinz, Max -- Weig, E M -- Ansmann, M -- Bialczak, Radoslaw C -- Lucero, Erik -- Neeley, M -- O'Connell, A D -- Wang, H -- Martinis, John M -- Cleland, A N -- England -- Nature. 2008 Jul 17;454(7202):310-4. doi: 10.1038/nature07136.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Physics, University of California, Santa Barbara, California 93106, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18633412" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 4
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    Violation of Bell's inequality in Josephson phase qubits (2009)
    Nature Publishing Group (NPG)
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    Publication Date: 2009-09-26
    Description: The measurement process plays an awkward role in quantum mechanics, because measurement forces a system to 'choose' between possible outcomes in a fundamentally unpredictable manner. Therefore, hidden classical processes have been considered as possibly predetermining measurement outcomes while preserving their statistical distributions. However, a quantitative measure that can distinguish classically determined correlations from stronger quantum correlations exists in the form of the Bell inequalities, measurements of which provide strong experimental evidence that quantum mechanics provides a complete description. Here we demonstrate the violation of a Bell inequality in a solid-state system. We use a pair of Josephson phase qubits acting as spin-1/2 particles, and show that the qubits can be entangled and measured so as to violate the Clauser-Horne-Shimony-Holt (CHSH) version of the Bell inequality. We measure a Bell signal of 2.0732 +/- 0.0003, exceeding the maximum amplitude of 2 for a classical system by 244 standard deviations. In the experiment, we deterministically generate the entangled state, and measure both qubits in a single-shot manner, closing the detection loophole. Because the Bell inequality was designed to test for non-classical behaviour without assuming the applicability of quantum mechanics to the system in question, this experiment provides further strong evidence that a macroscopic electrical circuit is really a quantum system.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Ansmann, Markus -- Wang, H -- Bialczak, Radoslaw C -- Hofheinz, Max -- Lucero, Erik -- Neeley, M -- O'Connell, A D -- Sank, D -- Weides, M -- Wenner, J -- Cleland, A N -- Martinis, John M -- England -- Nature. 2009 Sep 24;461(7263):504-6. doi: 10.1038/nature08363.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Physics, University of California, Santa Barbara, California 93106, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19779447" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 5
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    Synthesizing arbitrary quantum states in a superconducting resonator (2009)
    Nature Publishing Group (NPG)
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    Publication Date: 2009-05-30
    Description: The superposition principle is a fundamental tenet of quantum mechanics. It allows a quantum system to be 'in two places at the same time', because the quantum state of a physical system can simultaneously include measurably different physical states. The preparation and use of such superposed states forms the basis of quantum computation and simulation. The creation of complex superpositions in harmonic systems (such as the motional state of trapped ions, microwave resonators or optical cavities) has presented a significant challenge because it cannot be achieved with classical control signals. Here we demonstrate the preparation and measurement of arbitrary quantum states in an electromagnetic resonator, superposing states with different numbers of photons in a completely controlled and deterministic manner. We synthesize the states using a superconducting phase qubit to phase-coherently pump photons into the resonator, making use of an algorithm that generalizes a previously demonstrated method of generating photon number (Fock) states in a resonator. We completely characterize the resonator quantum state using Wigner tomography, which is equivalent to measuring the resonator's full density matrix.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hofheinz, Max -- Wang, H -- Ansmann, M -- Bialczak, Radoslaw C -- Lucero, Erik -- Neeley, M -- O'Connell, A D -- Sank, D -- Wenner, J -- Martinis, John M -- Cleland, A N -- England -- Nature. 2009 May 28;459(7246):546-9. doi: 10.1038/nature08005.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Physics, University of California, Santa Barbara, California 93106, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19478780" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 6
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    Coherent state evolution in a superconducting qubit from partial-collapse measurement (2006)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2006-06-10
    Description: Measurement is one of the fundamental building blocks of quantum-information processing systems. Partial measurement, where full wavefunction collapse is not the only outcome, provides a detailed test of the measurement process. We introduce quantum-state tomography in a superconducting qubit that exhibits high-fidelity single-shot measurement. For the two probabilistic outcomes of partial measurement, we find either a full collapse or a coherent yet nonunitary evolution of the state. This latter behavior explicitly confirms modern quantum-measurement theory and may prove important for error-correction algorithms in quantum computation.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Katz, N -- Ansmann, M -- Bialczak, Radoslaw C -- Lucero, Erik -- McDermott, R -- Neeley, Matthew -- Steffen, Matthias -- Weig, E M -- Cleland, A N -- Martinis, John M -- Korotkov, A N -- New York, N.Y. -- Science. 2006 Jun 9;312(5779):1498-500.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Physics and California NanoSystems Institute, University of California, Santa Barbara, CA 93106, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/16763142" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 7
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    Emulation of a quantum spin with a superconducting phase qudit (2009)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2009-08-08
    Description: In quantum information processing, qudits (d-level systems) are an extension of qubits that could speed up certain computing tasks. We demonstrate the operation of a superconducting phase qudit with a number of levels d up to d = 5 and show how to manipulate and measure the qudit state, including simultaneous control of multiple transitions. We used the qudit to emulate the dynamics of single spins with principal quantum number s = 1/2, 1, and 3/2, allowing a measurement of Berry's phase and the even parity of integer spins (and odd parity of half-integer spins) under 2pi-rotation. This extension of the two-level qubit to a multilevel qudit holds promise for more-complex quantum computational architectures and for richer simulations of quantum mechanical systems.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Neeley, Matthew -- Ansmann, Markus -- Bialczak, Radoslaw C -- Hofheinz, Max -- Lucero, Erik -- O'Connell, Aaron D -- Sank, Daniel -- Wang, Haohua -- Wenner, James -- Cleland, Andrew N -- Geller, Michael R -- Martinis, John M -- New York, N.Y. -- Science. 2009 Aug 7;325(5941):722-5. doi: 10.1126/science.1173440.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Physics, University of California at Santa Barbara (UCSB), Santa Barbara, CA 93106, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19661423" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 8
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    Measurement of the entanglement of two superconducting qubits via state tomography (2006)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2006-09-09
    Description: Demonstration of quantum entanglement, a key resource in quantum computation arising from a nonclassical correlation of states, requires complete measurement of all states in varying bases. By using simultaneous measurement and state tomography, we demonstrated entanglement between two solid-state qubits. Single qubit operations and capacitive coupling between two super-conducting phase qubits were used to generate a Bell-type state. Full two-qubit tomography yielded a density matrix showing an entangled state with fidelity up to 87%. Our results demonstrate a high degree of unitary control of the system, indicating that larger implementations are within reach.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Steffen, Matthias -- Ansmann, M -- Bialczak, Radoslaw C -- Katz, N -- Lucero, Erik -- McDermott, R -- Neeley, Matthew -- Weig, E M -- Cleland, A N -- Martinis, John M -- New York, N.Y. -- Science. 2006 Sep 8;313(5792):1423-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Physics and California Nano Systems Institute, University of California, Santa Barbara, CA 93106, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/16960003" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 9
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    State Tomography of Capacitively Shunted Phase Qubits with High Fidelity (2006)
    American Physical Society
    Details
    Publication Date: 2006-08-02
    Print ISSN: 0031-9007
    Electronic ISSN: 1079-7114
    Topics: Physics
    Published by American Physical Society
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  • 10
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    Decoherence Dynamics of Complex Photon States in a Superconducting Circuit (2009)
    American Physical Society
    Details
    Publication Date: 2009-11-13
    Print ISSN: 0031-9007
    Electronic ISSN: 1079-7114
    Topics: Physics
    Published by American Physical Society
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