885 research outputs found
Density-matrix simulation of small surface codes under current and projected experimental noise
We present a full density-matrix simulation of the quantum memory and
computing performance of the distance-3 logical qubit Surface-17, following a
recently proposed quantum circuit and using experimental error parameters for
transmon qubits in a planar circuit QED architecture. We use this simulation to
optimize components of the QEC scheme (e.g., trading off stabilizer measurement
infidelity for reduced cycle time) and to investigate the benefits of feedback
harnessing the fundamental asymmetry of relaxation-dominated error in the
constituent transmons. A lower-order approximate calculation extends these
predictions to the distance- Surface-49. These results clearly indicate
error rates below the fault-tolerance threshold of surface code, and the
potential for Surface-17 to perform beyond the break-even point of quantum
memory. At state-of-the-art qubit relaxation times and readout speeds,
Surface-49 could surpass the break-even point of computation.Comment: 10 pages + 8 pages appendix, 12 figure
Polymer, metal and ceramic matrix composites for advanced aircraft engine applications
Advanced aircraft engine research within NASA Lewis is being focused on propulsion systems for subsonic, supersonic, and hypersonic aircraft. Each of these flight regimes requires different types of engines, but all require advanced materials to meet their goals of performance, thrust-to-weight ratio, and fuel efficiency. The high strength/weight and stiffness/weight properties of resin, metal, and ceramic matrix composites will play an increasingly key role in meeting these performance requirements. At NASA Lewis, research is ongoing to apply graphite/polyimide composites to engine components and to develop polymer matrices with higher operating temperature capabilities. Metal matrix composites, using magnesium, aluminum, titanium, and superalloy matrices, are being developed for application to static and rotating engine components, as well as for space applications, over a broad temperature range. Ceramic matrix composites are also being examined to increase the toughness and reliability of ceramics for application to high-temperature engine structures and components
Lower-temperature fabrication of airbridges by grayscale lithography to increase yield of nanowire transmons in circuit QED quantum processors
Quantum hardware based on circuit quantum electrodynamics makes extensive use
of airbridges to suppress unwanted modes of wave propagation in
coplanar-waveguide transmission lines. Airbridges also provide an interconnect
enabling transmission lines to cross. Traditional airbridge fabrication
produces a curved profile by reflowing resist at elevated temperature prior to
metallization. The elevated temperature can affect the coupling energy and even
yield of pre-fabricated Josephson elements of superconducting qubits, tuneable
couplers and resonators. We employ grayscale lithography in place of reflow to
reduce the peak airbridge processing temperature from to
, showing a substantial yield increase of transmon qubits
with Josephson elements realized using Al-contacted InAs nanowires.Comment: 10 pages, 7 figures, 1 tabl
Digital Quantum Rabi and Dicke Models in Superconducting Circuits
We propose the analog-digital quantum simulation of the quantum Rabi and
Dicke models using circuit quantum electrodynamics (QED). We find that all
physical regimes, in particular those which are impossible to realize in
typical cavity QED setups, can be simulated via unitary decomposition into
digital steps. Furthermore, we show the emergence of the Dirac equation
dynamics from the quantum Rabi model when the mode frequency vanishes. Finally,
we analyze the feasibility of this proposal under realistic superconducting
circuit scenarios.Comment: 5 pages, 3 figures. Published in Scientific Report
High Kinetic Inductance Superconducting Nanowire Resonators for Circuit QED in a Magnetic Field
We present superconducting microwave-frequency resonators based on NbTiN
nanowires. The small cross section of the nanowires minimizes vortex
generation, making the resonators resilient to magnetic fields. Measured
intrinsic quality factors exceed in a T in-plane magnetic
field, and in a mT perpendicular magnetic field. Due to
their high characteristic impedance, these resonators are expected to develop
zero-point voltage fluctuations one order of magnitude larger than in standard
coplanar waveguide resonators. These properties make the nanowire resonators
well suited for circuit QED experiments needing strong coupling to quantum
systems with small electric dipole moments and requiring a magnetic field, such
as electrons in single and double quantum dots
Implementing optimal control pulse shaping for improved single-qubit gates
We employ pulse shaping to abate single-qubit gate errors arising from the
weak anharmonicity of transmon superconducting qubits. By applying shaped
pulses to both quadratures of rotation, a phase error induced by the presence
of higher levels is corrected. Using a derivative of the control on the
quadrature channel, we are able to remove the effect of the anharmonic levels
for multiple qubits coupled to a microwave resonator. Randomized benchmarking
is used to quantify the average error per gate, achieving a minimum of
0.007+/-0.005 using 4 ns-wide pulse.Comment: 4 pages, 4 figure
Entanglement genesis by ancilla-based parity measurement in 2D circuit QED
We present an indirect two-qubit parity meter in planar circuit quantum
electrodynamics, realized by discrete interaction with an ancilla and a
subsequent projective ancilla measurement with a dedicated, dispersively
coupled resonator. Quantum process tomography and successful entanglement by
measurement demonstrate that the meter is intrinsically quantum non-demolition.
Separate interaction and measurement steps allow commencing subsequent data
qubit operations in parallel with ancilla measurement, offering time savings
over continuous schemes.Comment: 5 pages, 4 figures; supplemental material with 5 figure
High-Fidelity Readout in Circuit Quantum Electrodynamics Using the Jaynes-Cummings Nonlinearity
We demonstrate a qubit readout scheme that exploits the Jaynes-Cummings
nonlinearity of a superconducting cavity coupled to transmon qubits. We find
that in the strongly-driven dispersive regime of this system, there is the
unexpected onset of a high-transmission "bright" state at a critical power
which depends sensitively on the initial qubit state. A simple and robust
measurement protocol exploiting this effect achieves a single-shot fidelity of
87% using a conventional sample design and experimental setup, and at least 61%
fidelity to joint correlations of three qubits.Comment: 5 pages, 4 figure
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