Saturation of Two Level Systems and Charge Noise in Josephson Junction Qubits (2008)
Constantin, Magdalena, Yu, Clare C., Martinis, John M.
We study the charge noise $S_Q$ in Josephson qubits produced by fluctuating two level systems (TLS) with electric dipole moments in the substrate. The TLS are driven by an alternating electric field...
Measurement of the decay of Fock states in a superconducting quantum circuit (2008)
Wang, H., Hofheinz, M., Ansmann, M., Bialczak, R. C., Lucero, E., Neeley, M., ...
We demonstrate the controlled generation of Fock states with up to 15 photons in a microwave coplanar waveguide resonator coupled to a superconducting phase qubit. The subsequent decay of the Fock...
Uncollapsing of a quantum state in a superconducting phase qubit (2008)
Katz, Nadav, Neeley, Matthew, Ansmann, M., Bialczak, Radoslaw C., Hofheinz, M., Lucero, Erik, ...
We demonstrate in a superconducting qubit the conditional recovery ("uncollapsing") of a quantum state after a partial-collapse measurement. A weak measurement extracts information and results in a...
A semiempirical model for two-level system noise in superconducting microresonators (2008)
Gao, Jiansong, Daal, Miguel, Martinis, John M., Vayonakis, Anastasios, Zmuidzinas, Jonas, Sadoulet, Bernard, ...
We present measurements of the low-temperature excess frequency noise of four niobium superconducting coplanar waveguide microresonators, with center strip widths sr ranging from 3 to 20 µm. For a...
Maximally entangling tripartite protocols for Josephson phase qubits (2008)
Galiautdinov, Andrei, Martinis, John M.
We introduce a suit of simple entangling protocols for generating tripartite GHZ and W states in systems with anisotropic exchange interaction g(XX+YY)+g'ZZ. An interesting example is provided by...
A semi-empirical model for two-level system noise in superconducting microresonators (2008)
Gao, Jiansong, Daal, Miguel, Martinis, John M., Mazin, Benjamin A., Day, Peter K., Leduc, Henry G., ...
We present measurements of the low--temperature excess frequency noise of four niobium superconducting coplanar waveguide microresonators, with center strip widths $s_r$ ranging from 3 $\mu$m to 20...
Calculations for Magnetism in SQUIDs at Millikelvin Temperatures (2008)
Sendelbach, S., Hover, D., Kittel, A., Mück, M., Martinis, John M., McDermott, R.
Here we present details of a calculation that allows us to extract a surface density of unpaired spins from flux vs. temperature experiments performed on field-cooled dc Superconducting QUantum...
Magnetism in SQUIDs at Millikelvin Temperatures (2008)
Sendelbach, S., Hover, D., Kittel, A., Mück, M., Martinis, John M., McDermott, R.
We have characterized the temperature dependence of the flux threading dc SQUIDs cooled to millikelvin temperatures. The flux increases as 1/T as temperature is lowered; moreover, the flux change is...
High-fidelity gates in a Josephson qubit (2008)
Lucero, Erik, Hofheinz, M., Ansmann, M., Bialczak, Radoslaw C., Katz, N., Neeley, Matthew, ...
We demonstrate new experimental procedures for measuring small errors in a superconducting quantum bit (qubit). By carefully separating out gate and measurement errors, we construct a complete error...
Transformed Dissipation in Superconducting Quantum Circuits (2008)
Neeley, Matthew, Ansmann, M., Bialczak, Radoslaw C., Hofheinz, M., Katz, N., Lucero, Erik, ...
Superconducting quantum circuits must be designed carefully to avoid dissipation from coupling to external control circuitry. Here we introduce the concept of current transformation to quantify...
1/f Flux Noise in Josephson Phase Qubits (2007)
Bialczak, Radoslaw C., McDermott, R., Ansmann, M., Hofheinz, M., Katz, N., Lucero, Erik, ...
We present a new method to measure 1/f noise in Josephson quantum bits (qubits) that yields low-frequency spectra below 1Hz. Comparison of noise taken at positive and negative bias of a phase qubit...
Effect of Two Level System Saturation on Charge Noise in Josephson Junction Qubits (2007)
Yu, Clare C., Constantin, Magdalena, Martinis, John M.
We show that charge noise $S_Q$ in Josephson qubits can be produced by fluctuating two level systems (TLS) with electric dipole moments in the substrate using a flat density of states. At high...
Analysis of measurement errors for a superconducting phase qubit (2006)
Zhang, Qin, Kofman, Abraham G., Martinis, John M., Korotkov, Alexander N.
We analyze several mechanisms leading to errors in a course of measurement of a superconducting flux-biased phase qubit. Insufficiently long measurement pulse may lead to nonadiabatic transitions...
State tomography of capacitively shunted phase qubits with high fidelity (2006)
Steffen, Matthias, Ansmann, M., McDermott, R., Katz, N., Bialczak, Radoslaw C., Lucero, Erik, ...
We introduce a new design concept for superconducting quantum bits (qubits) in which we explicitly separate the capacitive element from the Josephson tunnel junction for improved qubit performance....
Decoherence in Josephson Qubits from Dielectric Loss (2005)
Martinis, John M., Cooper, K. B., McDermott, R., Steffen, Matthias, Ansmann, Markus, Osborn, K., ...
Dielectric loss from two-level states is shown to be a dominant decoherence source in superconducting quantum bits. Depending on the qubit design, dielectric loss from insulating materials or the...
Cooper, K. B., Steffen, Matthias, McDermott, R., Simmonds, R. W., Oh, Seongshik, Hite, D. A., ...
We have detected coherent quantum oscillations between Josephson phase qubits and microscopic critical-current fluctuators by implementing a new state readout technique that is an order of magnitude...
Decoherence in Josephson Qubits from Junction Resonances (2004)
Simmonds, R. W., Lang, K. M., Hite, D. A., Pappas, D. P., Martinis, John M.
Although Josephson junction qubits show great promise for quantum computing, the origin of dominant decoherence mechanisms remains unknown. We report Rabi oscillations for an improved phase qubit,...
Superconducting Qubits and the Physics of Josephson Junctions (2004)
Martinis, John M., Osborne, Kevin
We describe in this paper how the nonlinear Josephson inductance is the crucial circuit element for all Josephson qubits. We discuss the three types of qubit circuits, and show how these circuits use...
Nonequilibrium quasiparticles and $2e$ periodicity in single-Cooper-pair transistors (2003)
Aumentado, J., Keller, Mark W., Martinis, John M., Devoret, M. H.
We have fabricated single-Cooper-pair transistors in which the spatial profile of the superconducting gap energy was controlled by oxygen doping. The profile dramatically affects the switching...
Phase-resolved Crab Studies with a Cryogenic TES Spectrophotometer (2001)
Romani, Roger W., Miller, A. J., Cabrera, B., Nam, S. W., Martinis, John M.
We are developing time- and energy-resolved near-IR/optical/UV photon detectors based on sharp superconducting-normal transition edges in thin films. We report observations of the Crab pulsar made...
Radiofrequency Amplifier Based on a DC Superconducting Quantum Interference Device. (1998)
Hilbert,Claude, Martinis,John M., Clarke,John
A low noise radiofrequency amplifier, using a dc SQUID (superconducting quantum interference device) as the input amplifying element. The dc SQUID and an input coil are maintained at...