313 research outputs found
Launch vehicle trajectory optimization computer program, phase 4 Final technical report
Computer program for retrieving stored data and determining variations in launch vehicle performance as function of mission and vehicle parameter
Launch vehicle trajectory optimization computer program, phase 4 Summary report
Computer program for launch vehicle trajectory optimizatio
Microwave response of vortices in superconducting thin films of Re and Al
Vortices in superconductors driven at microwave frequencies exhibit a
response related to the interplay between the vortex viscosity, pinning
strength, and flux creep effects. At the same time, the trapping of vortices in
superconducting microwave resonant circuits contributes excess loss and can
result in substantial reductions in the quality factor. Thus, understanding the
microwave vortex response in superconducting thin films is important for the
design of such circuits, including superconducting qubits and photon detectors,
which are typically operated in small, but non-zero, magnetic fields. By
cooling in fields of the order of 100 T and below, we have characterized
the magnetic field and frequency dependence of the microwave response of a
small density of vortices in resonators fabricated from thin films of Re and
Al, which are common materials used in superconducting microwave circuits.
Above a certain threshold cooling field, which is different for the Re and Al
films, vortices become trapped in the resonators. Vortices in the Al resonators
contribute greater loss and are influenced more strongly by flux creep effects
than in the Re resonators. This different behavior can be described in the
framework of a general vortex dynamics model.Comment: Published in Physical Review B 79,174512(2009); preprint version with
higher resolution figures available at
http://physics.syr.edu/~bplourde/bltp-publications.ht
Generation of Three-Qubit Entangled States using Superconducting Phase Qubits
Entanglement is one of the key resources required for quantum computation, so
experimentally creating and measuring entangled states is of crucial importance
in the various physical implementations of a quantum computer. In
superconducting qubits, two-qubit entangled states have been demonstrated and
used to show violations of Bell's Inequality and to implement simple quantum
algorithms. Unlike the two-qubit case, however, where all maximally-entangled
two-qubit states are equivalent up to local changes of basis, three qubits can
be entangled in two fundamentally different ways, typified by the states
and . Here we demonstrate the operation of three coupled
superconducting phase qubits and use them to create and measure
and states. The states are fully characterized
using quantum state tomography and are shown to satisfy entanglement witnesses,
confirming that they are indeed examples of three-qubit entanglement and are
not separable into mixtures of two-qubit entanglement.Comment: 9 pages, 5 figures. Version 2: added supplementary information and
fixed image distortion in Figure 2
Deterministic entanglement of photons in two superconducting microwave resonators
Quantum entanglement, one of the defining features of quantum mechanics, has
been demonstrated in a variety of nonlinear spin-like systems. Quantum
entanglement in linear systems has proven significantly more challenging, as
the intrinsic energy level degeneracy associated with linearity makes quantum
control more difficult. Here we demonstrate the quantum entanglement of photon
states in two independent linear microwave resonators, creating N-photon NOON
states as a benchmark demonstration. We use a superconducting quantum circuit
that includes Josephson qubits to control and measure the two resonators, and
we completely characterize the entangled states with bipartite Wigner
tomography. These results demonstrate a significant advance in the quantum
control of linear resonators in superconducting circuits.Comment: 11 pages, 11 figures, and 3 tables including supplementary materia
Implementation of a Toffoli Gate with Superconducting Circuits
The quantum Toffoli gate allows universal reversible classical computation.
It is also an important primitive in many quantum circuits and quantum error
correction schemes. Here we demonstrate the realization of a Toffoli gate with
three superconducting transmon qubits coupled to a microwave resonator. By
exploiting the third energy level of the transmon qubit, the number of
elementary gates needed for the implementation of the Toffoli gate, as well as
the total gate time can be reduced significantly in comparison to theoretical
proposals using two-level systems only. We characterize the performance of the
gate by full process tomography and Monte Carlo process certification. The gate
fidelity is found to be %.Comment: 4 pages, 5figure
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