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51. Multiplexed dispersive readout of superconducting phase qubits

Author

Chen, Yu, Sank, D., O'Malley, P., White, T., Barends, R., Chiaro, B., Kelly, J., Lucero, E., Mariantoni, M., Megrant, A., Neill, C., Vainsencher, A., Wenner, J., Yin, Yi, Cleland, A. N., and Martinis, John M.

Subjects
Condensed Matter - Superconductivity, Condensed Matter - Mesoscale and Nanoscale Physics, Quantum Physics
Abstract

We introduce a frequency-multiplexed readout scheme for superconducting phase qubits. Using a quantum circuit with four phase qubits, we couple each qubit to a separate lumped-element superconducting readout resonator, with the readout resonators connected in parallel to a single measurement line. The readout resonators and control electronics are designed so that all four qubits can be read out simultaneously using frequency multiplexing on the one measurement line. This technology provides a highly efficient and compact means for reading out multiple qubits, a significant advantage for scaling up to larger numbers of qubits., Comment: 4 pages, 4 figures

Published
2012
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52. Excitation of superconducting qubits from hot non-equilibrium quasiparticles

Author

Wenner, J., Yin, Yi, Lucero, Erik, Barends, R., Chen, Yu, Chiaro, B., Kelly, J., Lenander, M., Mariantoni, Matteo, Megrant, A., Neill, C., O'Malley, P. J. J., Sank, D., Vainsencher, A., Wang, H., White, T. C., Cleland, A. N., and Martinis, John M.

Subjects
Condensed Matter - Superconductivity, Condensed Matter - Mesoscale and Nanoscale Physics, Quantum Physics
Abstract

Superconducting qubits probe environmental defects such as non-equilibrium quasiparticles, an important source of decoherence. We show that "hot" non-equilibrium quasiparticles, with energies above the superconducting gap, affect qubits differently from quasiparticles at the gap, implying qubits can probe the dynamic quasiparticle energy distribution. For hot quasiparticles, we predict a non-neligable increase in the qubit excited state probability P_e. By injecting hot quasiparticles into a qubit, we experimentally measure an increase of P_e in semi-quantitative agreement with the model and rule out the typically assumed thermal distribution., Comment: Main paper: 5 pages, 5 figures. Supplement: 1 page, 1 figure, 1 table. Updated to user-prepared accepted version. Key changes: Supplement added, Introduction rewritten, Figs.2,3,5 revised, Fig.4 added

Published
2012
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53. Controlled catch and release of microwave photon states

Author

Yin, Yi, Chen, Yu, Sank, Daniel, O'Malley, P. J. J., White, T. C., Barends, R., Kelly, J., Lucero, Erik, Mariantoni, Matteo, Megrant, A., Neill, C., Vainsencher, A., Wenner, J., Korotkov, Alexander N., Cleland, A. N., and Martinis, John M.

Subjects
Condensed Matter - Superconductivity, Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

The quantum behavior of superconducting qubits coupled to resonators is very similar to that of atoms in optical cavities [1, 2], in which the resonant cavity confines photons and promotes strong light-matter interactions. The cavity end-mirrors determine the performance of the coupled system, with higher mirror reflectivity yielding better quantum coherence, but higher mirror transparency giving improved measurement and control, forcing a compromise. An alternative is to control the mirror transparency, enabling switching between long photon lifetime during quantum interactions and large signal strength when performing measurements. Here we demonstrate the superconducting analogue, using a quantum system comprising a resonator and a qubit, with variable coupling to a measurement transmission line. The coupling can be adjusted through zero to a photon emission rate 1,000 times the intrinsic photon decay rate. We use this system to control photons in coherent states as well as in non-classical Fock states, and dynamically shape the waveform of released photons. This has direct applications to circuit quantum electrodynamics [3], and may enable high-fidelity quantum state transfer between distant qubits, for which precisely-controlled waveform shaping is a critical and non-trivial requirement [4, 5].

Published
2012
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54. Power Handling and Responsivity of Submicron Wide Superconducting Coplanar Waveguide Resonators

Author

Janssen, R. M. J., Endo, A., Baselmans, J. J. A., de Visser, P. J., Barends, R., and Klapwijk, T. M.

Subjects
Condensed Matter - Superconductivity, Physics - Instrumentation and Detectors
Abstract

The sensitivity of microwave kinetic inductance detectors (MKIDs) based on coplanar waveguides (CPWs) needs to be improved by at least an order of magnitude to satisfy the requirements for space-based terahertz astronomy. Our aim is to investigate if this can be achieved by reducing the width of the CPW to much below what has typically been made using optical lithography (> 1 {\mu}m). CPW resonators with a central line width as narrow as 300 nm were made in NbTiN using electron beam lithography and reactive ion etching. In a systematic study of quarter-wave CPW resonators with varying widths it is shown that the behavior of responsivity, noise and power handling as a function of width continues down to 300 nm. This encourages the development of narrow KIDs using Al in order to improve their sensitivity., Comment: 6 pages, 3 figures

Published
2012
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55. Planar Superconducting Resonators with Internal Quality Factors above One Million

Author

Megrant, A., Neill, C., Barends, R., Chiaro, B., Chen, Yu, Feigl, L., Kelly, J., Lucero, Erik, Mariantoni, Matteo, O'Malley, P. J. J., Sank, D., Vainsencher, A., Wenner, J., White, T. C., Yin, Y., Zhao, J., Palmstrøm, C. J., Martinis, John M., and Cleland, A. N.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science, Condensed Matter - Superconductivity, Quantum Physics
Abstract

We describe the fabrication and measurement of microwave coplanar waveguide resonators with internal quality factors above 10 million at high microwave powers and over 1 million at low powers, with the best low power results approaching 2 million, corresponding to ~1 photon in the resonator. These quality factors are achieved by controllably producing very smooth and clean interfaces between the resonators' aluminum metallization and the underlying single crystal sapphire substrate. Additionally, we describe a method for analyzing the resonator microwave response, with which we can directly determine the internal quality factor and frequency of a resonator embedded in an imperfect measurement circuit., Comment: 4 pages, 3 figures, 1 table

Published
2012
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56. Surface spin fluctuations probed with flux noise and coherence in Josephson phase qubits

Author

Sank, Daniel, Barends, R., Bialczak, Radoslaw C., Chen, Yu, Kelly, J., Lenander, M., Lucero, E., Mariantoni, Matteo, Neeley, M., O'Malley, P. J. J., Vaisencher, A., Wang, H., Wenner, J., White, T. C., Yamamoto, T., Yin, Yi, Cleland, A. N., and Martinis, John M.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

We measure the dependence of qubit phase coherence and surface spin induced flux noise on inductor loop geometry. While wider inductor traces change neither the flux noise power spectrum nor the qubit dephasing time, increased inductance leads to a simultaneous increase in both. Using our protocol for measuring low frequency flux noise, we make a direct comparison between the flux noise spectrum and qubit phase decay, finding agreement within 10% of theory. The dependence of the measured flux noise on inductor geometry is consistent with a noise source correlation length between 6 and 400 um.

Published
2011

57. Surface loss simulations of superconducting coplanar waveguide resonators

Author

Wenner, J., Barends, R., Bialczak, R. C., Chen, Yu, Kelly, J., Lucero, Erik, Mariantoni, Matteo, Megrant, A., O'Malley, P. J. J., Sank, D., Vainsencher, A., Wang, H., White, T. C., Yin, Y., Zhao, J., Cleland, A. N., and Martinis, John M.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

Losses in superconducting planar resonators are presently assumed to predominantly arise from surface-oxide dissipation, due to experimental losses varying with choice of materials. We model and simulate the magnitude of the loss from interface surfaces in the resonator, and investigate the dependence on power, resonator geometry, and dimensions. Surprisingly, the dominant surface loss is found to arise from the metal-substrate and substrate-air interfaces. This result will be useful in guiding device optimization, even with conventional materials., Comment: Main paper: 4 pages, 4 figures, 1 table. Supplementary material: 4 pages, 2 figures, 1 table

Published
2011
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58. Loss and decoherence due to stray infrared light in superconducting quantum circuits

Author

Barends, R., Wenner, J., Lenander, M., Chen, Y., Bialczak, R. C., Kelly, J., Lucero, E., O'Malley, P., Mariantoni, M., Sank, D., Wang, H., White, T. C., Yin, Y., Zhao, J., Cleland, A. N., Martinis, John M., and Baselmans, J. J. A.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Superconductivity, Quantum Physics
Abstract

We find that stray infrared light from the 4 K stage in a cryostat can cause significant loss in superconducting resonators and qubits. For devices shielded in only a metal box, we measured resonators with quality factors Q = 10^5 and qubits with energy relaxation times T_1=120 ns, consistent with a stray light-induced quasiparticle density of 170-230 \mu m^{-3}. By adding a second black shield at the sample temperature, we found about an order of magnitude improvement in performance and no sensitivity to the 4 K radiation. We also tested various shielding methods, implying a lower limit of Q = 10^8 due to stray light in the light-tight configuration., Comment: 4 pages, 4 figures

Published
2011
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59. Reduced frequency noise in superconducting resonators

Author

Barends, R., Vercruyssen, N., Endo, A., de Visser, P. J., Zijlstra, T., Klapwijk, T. M., and Baselmans, J. J. A.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Superconductivity
Abstract

We report a reduction of the frequency noise in coplanar waveguide superconducting resonators. The reduction of 7 dB is achieved by removing the exposed dielectric substrate surface from the region with high electric fields and by using NbTiN. In a model-analysis the surface of NbTiN is found to be a negligible source of noise, experimentally supported by a comparison with NbTiN on SiOx resonators. The reduction is additive to decreasing the noise by widening the resonators., Comment: 4 pages, 4 figures

Published
2010
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60. Minimal resonator loss for circuit quantum electrodynamics

Author

Barends, R., Vercruyssen, N., Endo, A., de Visser, P. J., Zijlstra, T., Klapwijk, T. M., Diener, P., Yates, S. J. C., and Baselmans, J. J. A.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Superconductivity
Abstract

Single photon level quality factors of 500x10^3 are shown in NbTiN superconducting resonators at millikelvin temperatures. This result originates from the intrinsic low dielectric loss of NbTiN, as demonstrated by comparison with Ta, and by removing unnecessary parts of the dielectric substrate., Comment: 4 pages, 3 figures

Published
2010
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61. Compressed sensing quantum process tomography for superconducting quantum gates

Author

Rodionov, AV, Veitia, A, Barends, R, Kelly, J, Sank, D, Wenner, J, Martinis, JM, Kosut, RL, and Korotkov, AN

Subjects
quant-ph, Fluids & Plasmas, Physical Sciences, Chemical Sciences, Engineering
Abstract

We apply the method of compressed sensing (CS) quantum process tomography (QPT) to characterize quantum gates based on superconducting Xmon and phase qubits. Using experimental data for a two-qubit controlled-Z gate, we obtain an estimate for the process matrix χ with reasonably high fidelity compared to full QPT, but using a significantly reduced set of initial states and measurement configurations. We show that the CS method still works when the amount of used data is so small that the standard QPT would have an underdetermined system of equations. We also apply the CS method to the analysis of the three-qubit Toffoli gate with numerically added noise, and similarly show that the method works well for a substantially reduced set of data. For the CS calculations, we use two different bases in which the process matrix χ is approximately sparse, and show that the resulting estimates of the process matrices match each other with reasonably high fidelity. For both two-qubit and three-qubit gates, we characterize the quantum process by not only its process matrix and fidelity, but also by the corresponding standard deviation, defined via variation of the state fidelity for different initial states.

Published
2014

62. Rolling quantum dice with a superconducting qubit

Author

Barends, R, Kelly, J, Veitia, A, Megrant, A, Fowler, AG, Campbell, B, Chen, Y, Chen, Z, Chiaro, B, Dunsworth, A, Hoi, IC, Jeffrey, E, Neill, C, O'Malley, PJJ, Mutus, J, Quintana, C, Roushan, P, Sank, D, Wenner, J, White, TC, Korotkov, AN, Cleland, AN, and Martinis, JM

Subjects
quant-ph, cond-mat.mes-hall, cond-mat.supr-con, General Physics, Physical Sciences, Mathematical Sciences, Chemical Sciences
Abstract

One of the key challenges in quantum information is coherently manipulating the quantum state. However, it is an outstanding question whether control can be realized with low error. Only gates from the Clifford group - containing π, π/2, and Hadamard gates - have been characterized with high accuracy. Here, we show how the Platonic solids enable implementing and characterizing larger gate sets. We find that all gates can be implemented with low error. The results fundamentally imply arbitrary manipulation of the quantum state can be realized with high precision, providing practical possibilities for designing efficient quantum algorithms.

Published
2014

63. Catching Time-Reversed Microwave Coherent State Photons with 99.4% Absorption Efficiency

Author

Wenner, J, Yin, Yi, Chen, Yu, Barends, R, Chiaro, B, Jeffrey, E, Kelly, J, Megrant, A, Mutus, JY, Neill, C, O’Malley, PJJ, Roushan, P, Sank, D, Vainsencher, A, White, TC, Korotkov, Alexander N, Cleland, AN, and Martinis, John M

Subjects
quant-ph, cond-mat.supr-con, Mathematical Sciences, Physical Sciences, Engineering, General Physics
Abstract

We demonstrate a high-efficiency deterministic quantum receiver to convert flying qubits to stationary qubits. We employ a superconducting resonator, which is driven with a shaped pulse through an adjustable coupler. For the ideal "time-reversed" shape, we measure absorption and receiver fidelities at the single microwave photon level of, respectively, 99.41% and 97.4%. These fidelities are comparable with gates and measurement and exceed the deterministic quantum communication and computation fault-tolerant thresholds, enabling new designs of deterministic qubit interconnects and hybrid quantum computers. © 2014 American Physical Society.

Published
2014

64. Superconducting quantum circuits at the surface code threshold for fault tolerance

Author

Barends, R, Kelly, J, Megrant, A, Veitia, A, Sank, D, Jeffrey, E, White, TC, Mutus, J, Fowler, AG, Campbell, B, Chen, Y, Chen, Z, Chiaro, B, Dunsworth, A, Neill, C, O’Malley, P, Roushan, P, Vainsencher, A, Wenner, J, Korotkov, AN, Cleland, AN, and Martinis, John M

Subjects
quant-ph, cond-mat.mes-hall, cond-mat.supr-con, General Science & Technology
Abstract

A quantum computer can solve hard problems, such as prime factoring, database searching and quantum simulation, at the cost of needing to protect fragile quantum states from error. Quantum error correction provides this protection by distributing a logical state among many physical quantum bits (qubits) by means of quantum entanglement. Superconductivity is a useful phenomenon in this regard, because it allows the construction of large quantum circuits and is compatible with microfabrication. For superconducting qubits, the surface code approach to quantum computing is a natural choice for error correction, because it uses only nearest-neighbour coupling and rapidly cycled entangling gates. The gate fidelity requirements are modest: the per-step fidelity threshold is only about 99 per cent. Here we demonstrate a universal set of logic gates in a superconducting multi-qubit processor, achieving an average single-qubit gate fidelity of 99.92 per cent and a two-qubit gate fidelity of up to 99.4 per cent. This places Josephson quantum computing at the fault-tolerance threshold for surface code error correction. Our quantum processor is a first step towards the surface code, using five qubits arranged in a linear array with nearest-neighbour coupling. As a further demonstration, we construct a five-qubit Greenberger-Horne-Zeilinger state using the complete circuit and full set of gates. The results demonstrate that Josephson quantum computing is a high-fidelity technology, with a clear path to scaling up to large-scale, fault-tolerant quantum circuits.

Published
2014

65. Enhancement of quasiparticle recombination in Ta and Al superconductors by implantation of magnetic and nonmagnetic atoms

Author

Barends, R., van Vliet, S., Baselmans, J. J. A., Yates, S. J. C., Gao, J. R., and Klapwijk, T. M.

Subjects
Condensed Matter - Superconductivity, Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

The quasiparticle recombination time in superconducting films, consisting of the standard electron-phonon interaction and a yet to be identified low temperature process, is studied for different densities of magnetic and nonmagnetic atoms. For both Ta and Al, implanted with Mn, Ta and Al, we observe an increase of the recombination rate. We conclude that the enhancement of recombination is not due to the magnetic moment, but arises from an enhancement of disorder., Comment: 4 pages, 4 figures

Published
2008
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66. Contribution of dielectrics to frequency and noise of NbTiN superconducting resonators

Author

Barends, R., Hortensius, H. L., Zijlstra, T., Baselmans, J. J. A., Yates, S. J. C., Gao, J. R., and Klapwijk, T. M.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Superconductivity
Abstract

We study NbTiN resonators by measurements of the temperature dependent resonance frequency and frequency noise. Additionally, resonators are studied covered with SiOx dielectric layers of various thicknesses. The resonance frequency develops a non-monotonic temperature dependence with increasing SiOx layer thickness. The increase in the noise is independent of the SiOx thickness, demonstrating that the noise is not dominantly related to the low temperature resonance frequency deviations., Comment: 4 pages, 3 figures

Published
2008
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67. Quasiparticle relaxation in optically excited high-Q superconducting resonators

Author

Barends, R., Baselmans, J. J. A., Yates, S. J. C., Gao, J. R., Hovenier, J. N., and Klapwijk, T. M.

Subjects
Condensed Matter - Superconductivity, Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

The quasiparticle relaxation time in superconducting films has been measured as a function of temperature using the response of the complex conductivity to photon flux. For tantalum and aluminium, chosen for their difference in electron-phonon coupling strength, we find that at high temperatures the relaxation time increases with decreasing temperature, as expected for electron-phonon interaction. At low temperatures we find in both superconducting materials a saturation of the relaxation time, suggesting the presence of a second relaxation channel not due to electron-phonon interaction., Comment: 4 pages, 3 figures

Published
2008
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68. A blueprint for demonstrating quantum supremacy with superconducting qubits

Author

Neill, C., Roushan, P., Kechedzhi, K., Boixo, S., Isakov, S. V., Smelyanskiy, V., Megrant, A., Chiaro, B., Dunsworth, A., Arya, K., Barends, R., Burkett, B., Chen, Y., Chen, Z., Fowler, A., Foxen, B., Giustina, M., Graff, R., Jeffrey, E., Huang, T., Kelly, J., Klimov, P., Lucero, E., Mutus, J., Neeley, M., Quintana, C., Sank, D., Vainsencher, A., Wenner, J., White, T. C., Neven, H., and Martinis, J. M.

Published
2018

69. Spectroscopic signatures of localization with interacting photons in superconducting qubits

Author

Roushan, P., Neill, C., Tangpanitanon, J., Bastidas, V. M., Megrant, A., Barends, R., Chen, Y., Chen, Z., Chiaro, B., Dunsworth, A., Fowler, A., Foxen, B., Giustina, M., Jeffrey, E., Kelly, J., Lucero, E., Mutus, J., Neeley, M., Quintana, C., Sank, D., Vainsencher, A., Wenner, J., White, T., Neven, H., Angelakis, D. G., and Martinis, J.

Published
2017

70. Digitized adiabatic quantum computing with a superconducting circuit

Author

Barends, R., Shabani, A., Lamata, L., Kelly, J., Mezzacapo, A., Heras, U. Las, Babbush, R., Fowler, A.G., Campbell, B., Chen, Yu, Chen, Z., Chiaro, B., Dunsworth, A., Jeffrey, E., Lucero, E., Megrant, A., Mutus, J.Y., Neeley, M., Neill, C., O'Malley, P.J.J., Quintana, C., Roushan, P., Sank, D., Vainsencher, A., Wenner, J., White, T.C., Solano, E., Neven, H., and Martinis, John M.

Subjects
Research, Superconductors -- Research, Quantum computing -- Research, Physics research, Adiabatic processes (Thermodynamics) -- Research
Abstract

A key challenge in adiabatic quantum computing is to construct a device that is capable of encoding problem Hamiltonians that are classically intractable, that is, non-stoquastic (13). Such Hamiltonians would [...], Quantum mechanics can help to solve complex problems in physics (1) and chemistry (2), provided they can be programmed in a physical device. In adiabatic quantum computing (3-5), a system is slowly evolved from the ground state of a simple initial Hamiltonian to a final Hamiltonian that encodes a computational problem. The appeal of this approach lies in the combination of simplicity and generality; in principle, any problem can be encoded. In practice, applications are restricted by limited connectivity, available interactions and noise. A complementary approach is digital quantum computing (6), which enables the construction of arbitrary interactions and is compatible with error correction (7,8), but uses quantum circuit algorithms that are problem-specific. Here we combine the advantages of both approaches by implementing digitized adiabatic quantum computing in a superconducting system. We tomographically probe the system during the digitized evolution and explore the scaling of errors with system size. We then let the full system find the solution to random instances of the one-dimensional Ising problem as well as problem Hamiltonians that involve more complex interactions. This digital quantum simulation (9-12) of the adiabatic algorithm consists of up to nine qubits and up to 1,000 quantum logic gates. The demonstration of digitized adiabatic quantum computing in the solid state opens a path to synthesizing long-range correlations and solving complex computational problems. When combined with fault-tolerance, our approach becomes a general-purpose algorithm that is scalable.

Published
2016

71. Direct measurement of nonlocal interactions in the many-body localized phase

Author

Chiaro, B., Neill, C., Bohrdt, A., Filippone, M., Arute, F., Arya, K., Babbush, R., Bacon, D., Bardin, J., Barends, R., Boixo, S., Buell, D., Burkett, B., Chen, Y., Chen, Z., Collins, R., Dunsworth, A., Farhi, E., Fowler, A., Foxen, B., Gidney, C., Giustina, M., Harrigan, M., Huang, T., Isakov, S., Jeffrey, E., Jiang, Z., Kafri, D., Kechedzhi, K., Kelly, J., Klimov, P., Korotkov, A., Kostritsa, F., Landhuis, D., Lucero, E., McClean, J., Mi, X., Megrant, A., Mohseni, M., Mutus, J., McEwen, M., Naaman, O., Neeley, M., Niu, M., Petukhov, A., Quintana, C., Rubin, N., Sank, D., Satzinger, K., White, T., Yao, Z., Yeh, P., Zalcman, A., Smelyanskiy, V., Neven, H., Gopalakrishnan, S., Abanin, D., Knap, M., Martinis, J., and Roushan, P.

Subjects
General Medicine
Published
2022
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72. State preservation by repetitive error detection in a superconducting quantum circuit

Author

Kelly, J., Barends, R., Fowler, A.G., Megrant, A., Jeffrey, E., White, T.C., Sank, D., Mutus, J.Y., Campbell, B., Chen, Yu, Chen, Z., Chiaro, B., Dunsworth, A., Hoi, I.-C., Neill, C., O'Malley, P.J.J., Quintana, C., Roushan, P., Vainsencher, A., Wenner, J., Cleland, A.N., and Martinis, John M.

Subjects
Analysis, Research, Standard IC, Error-correcting codes -- Analysis, Integrated circuits -- Research, Semiconductor chips -- Research
Abstract

Quantum computing becomes viable when a quantum state can be protected from environment-induced error. If quantum bits (qubits) are sufficiently reliable, errors are sparse and quantum error correction (QEC) (1-6) [...]

Published
2015

73. Realizing topologically ordered states on a quantum processor

Author

Satzinger, K. J., primary, Liu, Y.-J, additional, Smith, A., additional, Knapp, C., additional, Newman, M., additional, Jones, C., additional, Chen, Z., additional, Quintana, C., additional, Mi, X., additional, Dunsworth, A., additional, Gidney, C., additional, Aleiner, I., additional, Arute, F., additional, Arya, K., additional, Atalaya, J., additional, Babbush, R., additional, Bardin, J. C., additional, Barends, R., additional, Basso, J., additional, Bengtsson, A., additional, Bilmes, A., additional, Broughton, M., additional, Buckley, B. B., additional, Buell, D. A., additional, Burkett, B., additional, Bushnell, N., additional, Chiaro, B., additional, Collins, R., additional, Courtney, W., additional, Demura, S., additional, Derk, A. R., additional, Eppens, D., additional, Erickson, C., additional, Faoro, L., additional, Farhi, E., additional, Fowler, A. G., additional, Foxen, B., additional, Giustina, M., additional, Greene, A., additional, Gross, J. A., additional, Harrigan, M. P., additional, Harrington, S. D., additional, Hilton, J., additional, Hong, S., additional, Huang, T., additional, Huggins, W. J., additional, Ioffe, L. B., additional, Isakov, S. V., additional, Jeffrey, E., additional, Jiang, Z., additional, Kafri, D., additional, Kechedzhi, K., additional, Khattar, T., additional, Kim, S., additional, Klimov, P. V., additional, Korotkov, A. N., additional, Kostritsa, F., additional, Landhuis, D., additional, Laptev, P., additional, Locharla, A., additional, Lucero, E., additional, Martin, O., additional, McClean, J. R., additional, McEwen, M., additional, Miao, K. C., additional, Mohseni, M., additional, Montazeri, S., additional, Mruczkiewicz, W., additional, Mutus, J., additional, Naaman, O., additional, Neeley, M., additional, Neill, C., additional, Niu, M. Y., additional, O’Brien, T. E., additional, Opremcak, A., additional, Pató, B., additional, Petukhov, A., additional, Rubin, N. C., additional, Sank, D., additional, Shvarts, V., additional, Strain, D., additional, Szalay, M., additional, Villalonga, B., additional, White, T. C., additional, Yao, Z., additional, Yeh, P., additional, Yoo, J., additional, Zalcman, A., additional, Neven, H., additional, Boixo, S., additional, Megrant, A., additional, Chen, Y., additional, Kelly, J., additional, Smelyanskiy, V., additional, Kitaev, A., additional, Knap, M., additional, Pollmann, F., additional, and Roushan, P., additional

Published
2021
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74. Noise in NbTiN, Al, and Ta superconducting resonators on silicon and sapphire substrates

Author

Barends, R., Hortensius, H.L., Zijlstra, T., Baselmans, J.J.A., Yates, S.J.C., Gao, J.R., and Klapwijk, T.M.

Subjects
Niobium -- Electric properties, Resonators -- Design and construction, Sapphires -- Electric properties, Silica -- Electric properties, Titanium compounds -- Electric properties, Business, Electronics, Electronics and electrical industries
Published
2009

77. Resistivity of ultrathin superconducting NbN films for bolometer mixers

Author

Loudkov, D., Barends, R., Hajenius, M., Gao, J.R., and Klapwijk, T.M.

Subjects
Dielectric films -- Electric properties, Thin films -- Electric properties, Bolometers -- Usage, Superconductors -- Electric properties, Superconductors -- Usage, Business, Electronics, Electronics and electrical industries
Abstract

The study results of the NbN bolometric mixers that could be applied in far infrared heterodyne detection reveal that the resistive properties of superconducting films is due to free vortices described in Berezinskii-Kosterlitz-Thouless theory.

Published
2007

78. Niobium and tantalum high Q resonators for photon detectors

Author

Barends, R., Baselmans, J.J.A., Hovenier, J.N., Gao, J.R., Yates, S.J.C., Klapwijk, T.M., and Hoevers, H.F.C.

Subjects
Niobium -- Acoustic properties, Silicon -- Acoustic properties, Quality factor meters -- Usage, Business, Electronics, Electronics and electrical industries
Abstract

The measurements of the quality factors and phase noise of niobium and tantalum coplanar waveguide microwave resonators on silicon showed an anomalous increase at low temperature while resonance frequency remained constant for increasing power levels.

Published
2007

79. Terahertz superconducting hot electron bolometer heterodyne receivers

Author

Gao, J.R., Hajenius, M., Z.Q. Yang, Baselmans, J.J.A., Khosropanah, P., Barends, R., and Klapwijk, T.M.

Subjects
Bolometers -- Usage, Dielectric films -- Electric properties, Thin films -- Electric properties, Business, Electronics, Electronics and electrical industries
Abstract

A significant improvement of the performance of NbN hot electron bolometer (HEB) mixers achieved by combining a spiral antenna NbN HEB mixer with a QCL as local oscillator which exhibit low receiver noise temperature at 2.8 THz is reported.

Published
2007

81. Accurately computing the electronic properties of a quantum ring

Author

Neill, C., primary, McCourt, T., additional, Mi, X., additional, Jiang, Z., additional, Niu, M. Y., additional, Mruczkiewicz, W., additional, Aleiner, I., additional, Arute, F., additional, Arya, K., additional, Atalaya, J., additional, Babbush, R., additional, Bardin, J. C., additional, Barends, R., additional, Bengtsson, A., additional, Bourassa, A., additional, Broughton, M., additional, Buckley, B. B., additional, Buell, D. A., additional, Burkett, B., additional, Bushnell, N., additional, Campero, J., additional, Chen, Z., additional, Chiaro, B., additional, Collins, R., additional, Courtney, W., additional, Demura, S., additional, Derk, A. R., additional, Dunsworth, A., additional, Eppens, D., additional, Erickson, C., additional, Farhi, E., additional, Fowler, A. G., additional, Foxen, B., additional, Gidney, C., additional, Giustina, M., additional, Gross, J. A., additional, Harrigan, M. P., additional, Harrington, S. D., additional, Hilton, J., additional, Ho, A., additional, Hong, S., additional, Huang, T., additional, Huggins, W. J., additional, Isakov, S. V., additional, Jacob-Mitos, M., additional, Jeffrey, E., additional, Jones, C., additional, Kafri, D., additional, Kechedzhi, K., additional, Kelly, J., additional, Kim, S., additional, Klimov, P. V., additional, Korotkov, A. N., additional, Kostritsa, F., additional, Landhuis, D., additional, Laptev, P., additional, Lucero, E., additional, Martin, O., additional, McClean, J. R., additional, McEwen, M., additional, Megrant, A., additional, Miao, K. C., additional, Mohseni, M., additional, Mutus, J., additional, Naaman, O., additional, Neeley, M., additional, Newman, M., additional, O’Brien, T. E., additional, Opremcak, A., additional, Ostby, E., additional, Pató, B., additional, Petukhov, A., additional, Quintana, C., additional, Redd, N., additional, Rubin, N. C., additional, Sank, D., additional, Satzinger, K. J., additional, Shvarts, V., additional, Strain, D., additional, Szalay, M., additional, Trevithick, M. D., additional, Villalonga, B., additional, White, T. C., additional, Yao, Z., additional, Yeh, P., additional, Zalcman, A., additional, Neven, H., additional, Boixo, S., additional, Ioffe, L. B., additional, Roushan, P., additional, Chen, Y., additional, and Smelyanskiy, V., additional

Published
2021
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82. Local resistivity and the current-voltage characteristics of hot electron bolometer mixers

Author

Hajenius, M., Barends, R., Gao, J.R., Klapwijk, T.M., Baselmans, J.J.A., Voronov, B., and Gol'tsman, G.

Subjects
Terahertz radiation -- Analysis, Bolometers -- Design and construction, Mixers (Electronics) -- Design and construction, Business, Electronics, Electronics and electrical industries
Abstract

An analysis of hot-electron bolometer devices used in low noise heterodyne mixing at frequencies up to 2.5 THz is presented. It is concluded that in the current generation of hot electron bolometer devices the resistive transition and the current-voltage characteristics contain contributions, which should be carefully distinguished from one, which is relevant for understanding the mixing properties.

Published
2005

84. Diabatic Gates for Frequency-Tunable Superconducting Qubits

Author

Barends, R., primary, Quintana, C. M., additional, Petukhov, A. G., additional, Chen, Yu, additional, Kafri, D., additional, Kechedzhi, K., additional, Collins, R., additional, Naaman, O., additional, Boixo, S., additional, Arute, F., additional, Arya, K., additional, Buell, D., additional, Burkett, B., additional, Chen, Z., additional, Chiaro, B., additional, Dunsworth, A., additional, Foxen, B., additional, Fowler, A., additional, Gidney, C., additional, Giustina, M., additional, Graff, R., additional, Huang, T., additional, Jeffrey, E., additional, Kelly, J., additional, Klimov, P. V., additional, Kostritsa, F., additional, Landhuis, D., additional, Lucero, E., additional, McEwen, M., additional, Megrant, A., additional, Mi, X., additional, Mutus, J., additional, Neeley, M., additional, Neill, C., additional, Ostby, E., additional, Roushan, P., additional, Sank, D., additional, Satzinger, K. J., additional, Vainsencher, A., additional, White, T., additional, Yao, J., additional, Yeh, P., additional, Zalcman, A., additional, Neven, H., additional, Smelyanskiy, V. N., additional, and Martinis, John M., additional

Published
2019
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86. High speed flux sampling for tunable superconducting qubits with an embedded cryogenic transducer

Author

Foxen, B, primary, Mutus, J Y, additional, Lucero, E, additional, Jeffrey, E, additional, Sank, D, additional, Barends, R, additional, Arya, K, additional, Burkett, B, additional, Chen, Yu, additional, Chen, Zijun, additional, Chiaro, B, additional, Dunsworth, A, additional, Fowler, A, additional, Gidney, C, additional, Giustina, M, additional, Graff, R, additional, Huang, T, additional, Kelly, J, additional, Klimov, P, additional, Megrant, A, additional, Naaman, O, additional, Neeley, M, additional, Neill, C, additional, Quintana, C, additional, Roushan, P, additional, Vainsencher, A, additional, Wenner, J, additional, White, T C, additional, and Martinis, John M, additional

Published
2018
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87. Fluctuations of Energy-Relaxation Times in Superconducting Qubits

Author

Klimov, P. V., primary, Kelly, J., additional, Chen, Z., additional, Neeley, M., additional, Megrant, A., additional, Burkett, B., additional, Barends, R., additional, Arya, K., additional, Chiaro, B., additional, Chen, Yu, additional, Dunsworth, A., additional, Fowler, A., additional, Foxen, B., additional, Gidney, C., additional, Giustina, M., additional, Graff, R., additional, Huang, T., additional, Jeffrey, E., additional, Lucero, Erik, additional, Mutus, J. Y., additional, Naaman, O., additional, Neill, C., additional, Quintana, C., additional, Roushan, P., additional, Sank, Daniel, additional, Vainsencher, A., additional, Wenner, J., additional, White, T. C., additional, Boixo, S., additional, Babbush, R., additional, Smelyanskiy, V. N., additional, Neven, H., additional, and Martinis, John M., additional

Published
2018
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88. A method for building low loss multi-layer wiring for superconducting microwave devices

Author

Dunsworth, A., primary, Barends, R., additional, Chen, Yu, additional, Chen, Zijun, additional, Chiaro, B., additional, Fowler, A., additional, Foxen, B., additional, Jeffrey, E., additional, Kelly, J., additional, Klimov, P. V., additional, Lucero, E., additional, Mutus, J. Y., additional, Neeley, M., additional, Neill, C., additional, Quintana, C., additional, Roushan, P., additional, Sank, D., additional, Vainsencher, A., additional, Wenner, J., additional, White, T. C., additional, Neven, H., additional, Martinis, John M., additional, and Megrant, A., additional

Published
2018
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89. Qubit compatible superconducting interconnects

Author

Foxen, B, primary, Mutus, J Y, additional, Lucero, E, additional, Graff, R, additional, Megrant, A, additional, Chen, Yu, additional, Quintana, C, additional, Burkett, B, additional, Kelly, J, additional, Jeffrey, E, additional, Yang, Yan, additional, Yu, Anthony, additional, Arya, K, additional, Barends, R, additional, Chen, Zijun, additional, Chiaro, B, additional, Dunsworth, A, additional, Fowler, A, additional, Gidney, C, additional, Giustina, M, additional, Huang, T, additional, Klimov, P, additional, Neeley, M, additional, Neill, C, additional, Roushan, P, additional, Sank, D, additional, Vainsencher, A, additional, Wenner, J, additional, White, T C, additional, and Martinis, John M, additional

Published
2017
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91. Characterization and reduction of capacitive loss induced by sub-micron Josephson junction fabrication in superconducting qubits

Author

Dunsworth, A., primary, Megrant, A., additional, Quintana, C., additional, Chen, Zijun, additional, Barends, R., additional, Burkett, B., additional, Foxen, B., additional, Chen, Yu, additional, Chiaro, B., additional, Fowler, A., additional, Graff, R., additional, Jeffrey, E., additional, Kelly, J., additional, Lucero, E., additional, Mutus, J. Y., additional, Neeley, M., additional, Neill, C., additional, Roushan, P., additional, Sank, D., additional, Vainsencher, A., additional, Wenner, J., additional, White, T. C., additional, and Martinis, John M., additional

Published
2017
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92. Preserving entanglement during weak measurement demonstrated with a violation of the Bell-Leggett-Garg inequality

Author

White, TC, Mutus, JY, Dressel, J, Kelly, J, Barends, R, Jeffrey, E, Sank, D, Megrant, A, Campbell, B, Chen, Y, Chen, Z, Chiaro, B, Dunsworth, A, Hoi, I-C, Neill, C, O'Malley, PJJ, Roushan, P, Vainsencher, A, Wenner, J, Korotkov, AN, and Martinis, JM

Subjects
Superconductivity (cond-mat.supr-con), Quantum Physics, cond-mat.supr-con, Condensed Matter - Mesoscale and Nanoscale Physics, quant-ph, Condensed Matter - Superconductivity, cond-mat.mes-hall, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), FOS: Physical sciences, Quantum Physics (quant-ph)
Abstract

Weak measurement has provided new insight into the nature of quantum measurement, by demonstrating the ability to extract average state information without fully projecting the system. For single qubit measurements, this partial projection has been demonstrated with violations of the Leggett-Garg inequality. Here we investigate the effects of weak measurement on a maximally entangled Bell state through application of the Hybrid Bell-Leggett-Garg inequality (BLGI) on a linear chain of four transmon qubits. By correlating the results of weak ancilla measurements with subsequent projective readout, we achieve a violation of the BLGI with 27 standard deviations of certainty.

Published
2015
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93. Observation of Classical-Quantum Crossover of 1/f Flux Noise and Its Paramagnetic Temperature Dependence

Author

Quintana, C. M., primary, Chen, Yu, additional, Sank, D., additional, Petukhov, A. G., additional, White, T. C., additional, Kafri, Dvir, additional, Chiaro, B., additional, Megrant, A., additional, Barends, R., additional, Campbell, B., additional, Chen, Z., additional, Dunsworth, A., additional, Fowler, A. G., additional, Graff, R., additional, Jeffrey, E., additional, Kelly, J., additional, Lucero, E., additional, Mutus, J. Y., additional, Neeley, M., additional, Neill, C., additional, O’Malley, P. J. J., additional, Roushan, P., additional, Shabani, A., additional, Smelyanskiy, V. N., additional, Vainsencher, A., additional, Wenner, J., additional, Neven, H., additional, and Martinis, John M., additional

Published
2017
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94. Measurement-Induced State Transitions in a Superconducting Qubit: Beyond the Rotating Wave Approximation

Author

Sank, Daniel, primary, Chen, Zijun, additional, Khezri, Mostafa, additional, Kelly, J., additional, Barends, R., additional, Campbell, B., additional, Chen, Y., additional, Chiaro, B., additional, Dunsworth, A., additional, Fowler, A., additional, Jeffrey, E., additional, Lucero, E., additional, Megrant, A., additional, Mutus, J., additional, Neeley, M., additional, Neill, C., additional, O’Malley, P. J. J., additional, Quintana, C., additional, Roushan, P., additional, Vainsencher, A., additional, White, T., additional, Wenner, J., additional, Korotkov, Alexander N., additional, and Martinis, John M., additional

Published
2016
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95. Chiral ground-state currents of interacting photons in a synthetic magnetic field

Author

Roushan, P., primary, Neill, C., additional, Megrant, A., additional, Chen, Y., additional, Babbush, R., additional, Barends, R., additional, Campbell, B., additional, Chen, Z., additional, Chiaro, B., additional, Dunsworth, A., additional, Fowler, A., additional, Jeffrey, E., additional, Kelly, J., additional, Lucero, E., additional, Mutus, J., additional, O’Malley, P. J. J., additional, Neeley, M., additional, Quintana, C., additional, Sank, D., additional, Vainsencher, A., additional, Wenner, J., additional, White, T., additional, Kapit, E., additional, Neven, H., additional, and Martinis, J., additional

Published
2016
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96. Scalablein situqubit calibration during repetitive error detection

Author

Kelly, J., primary, Barends, R., additional, Fowler, A. G., additional, Megrant, A., additional, Jeffrey, E., additional, White, T. C., additional, Sank, D., additional, Mutus, J. Y., additional, Campbell, B., additional, Chen, Yu, additional, Chen, Z., additional, Chiaro, B., additional, Dunsworth, A., additional, Lucero, E., additional, Neeley, M., additional, Neill, C., additional, O'Malley, P. J. J., additional, Quintana, C., additional, Roushan, P., additional, Vainsencher, A., additional, Wenner, J., additional, and Martinis, John M., additional

Published
2016
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97. Dielectric surface loss in superconducting resonators with flux-trapping holes

Author

Chiaro, B, primary, Megrant, A, additional, Dunsworth, A, additional, Chen, Z, additional, Barends, R, additional, Campbell, B, additional, Chen, Y, additional, Fowler, A, additional, Hoi, I C, additional, Jeffrey, E, additional, Kelly, J, additional, Mutus, J, additional, Neill, C, additional, O’Malley, P J J, additional, Quintana, C, additional, Roushan, P, additional, Sank, D, additional, Vainsencher, A, additional, Wenner, J, additional, White, T C, additional, and Martinis, John M, additional

Published
2016
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98. Scalable Quantum Simulation of Molecular Energies

Author

O’Malley, P. J. J., primary, Babbush, R., additional, Kivlichan, I. D., additional, Romero, J., additional, McClean, J. R., additional, Barends, R., additional, Kelly, J., additional, Roushan, P., additional, Tranter, A., additional, Ding, N., additional, Campbell, B., additional, Chen, Y., additional, Chen, Z., additional, Chiaro, B., additional, Dunsworth, A., additional, Fowler, A. G., additional, Jeffrey, E., additional, Lucero, E., additional, Megrant, A., additional, Mutus, J. Y., additional, Neeley, M., additional, Neill, C., additional, Quintana, C., additional, Sank, D., additional, Vainsencher, A., additional, Wenner, J., additional, White, T. C., additional, Coveney, P. V., additional, Love, P. J., additional, Neven, H., additional, Aspuru-Guzik, A., additional, and Martinis, J. M., additional

Published
2016
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99. Controlled catch and release of microwave photon states

Author

Yin, Y, Chen, Y, Sank, D, O'Malley, PJJ, White, TC, Barends, R, Kelly, J, Lucero, E, Mariantoni, M, Megrant, A, Neill, C, Vainsencher, A, Wenner, J, Korotkov, AN, Cleland, AN, and Martinis, JM

Subjects
Superconductivity (cond-mat.supr-con), cond-mat.supr-con, Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Superconductivity, cond-mat.mes-hall, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), FOS: Physical sciences
Abstract

The quantum behavior of superconducting qubits coupled to resonators is very similar to that of atoms in optical cavities [1, 2], in which the resonant cavity confines photons and promotes strong light-matter interactions. The cavity end-mirrors determine the performance of the coupled system, with higher mirror reflectivity yielding better quantum coherence, but higher mirror transparency giving improved measurement and control, forcing a compromise. An alternative is to control the mirror transparency, enabling switching between long photon lifetime during quantum interactions and large signal strength when performing measurements. Here we demonstrate the superconducting analogue, using a quantum system comprising a resonator and a qubit, with variable coupling to a measurement transmission line. The coupling can be adjusted through zero to a photon emission rate 1,000 times the intrinsic photon decay rate. We use this system to control photons in coherent states as well as in non-classical Fock states, and dynamically shape the waveform of released photons. This has direct applications to circuit quantum electrodynamics [3], and may enable high-fidelity quantum state transfer between distant qubits, for which precisely-controlled waveform shaping is a critical and non-trivial requirement [4, 5].

Published
2012

100. Digital quantum simulation of fermionic models with a superconducting circuit

Author

Barends, R., primary, Lamata, L., additional, Kelly, J., additional, García-Álvarez, L., additional, Fowler, A. G., additional, Megrant, A, additional, Jeffrey, E, additional, White, T. C., additional, Sank, D., additional, Mutus, J. Y., additional, Campbell, B., additional, Chen, Yu, additional, Chen, Z., additional, Chiaro, B., additional, Dunsworth, A., additional, Hoi, I.-C., additional, Neill, C., additional, O’Malley, P. J. J., additional, Quintana, C., additional, Roushan, P., additional, Vainsencher, A., additional, Wenner, J., additional, Solano, E., additional, and Martinis, John M., additional

Published
2015
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