52,035 research outputs found
Bound States for Magic State Distillation in Fault-Tolerant Quantum Computation
Magic state distillation is an important primitive in fault-tolerant quantum
computation. The magic states are pure non-stabilizer states which can be
distilled from certain mixed non-stabilizer states via Clifford group
operations alone. Because of the Gottesman-Knill theorem, mixtures of Pauli
eigenstates are not expected to be magic state distillable, but it has been an
open question whether all mixed states outside this set may be distilled. In
this Letter we show that, when resources are finitely limited, non-distillable
states exist outside the stabilizer octahedron. In analogy with the bound
entangled states, which arise in entanglement theory, we call such states bound
states for magic state distillation.Comment: Published version. This paper builds on a theorem proven in "On the
Structure of Protocols for Magic State Distillation", arXiv:0908.0838. These
two papers jointly form the content of a talk entitled "Neither Magical nor
Classical?", which was presented at TQC 2009, Waterlo
Qudit Colour Codes and Gauge Colour Codes in All Spatial Dimensions
Two-level quantum systems, qubits, are not the only basis for quantum
computation. Advantages exist in using qudits, d-level quantum systems, as the
basic carrier of quantum information. We show that color codes, a class of
topological quantum codes with remarkable transversality properties, can be
generalized to the qudit paradigm. In recent developments it was found that in
three spatial dimensions a qubit color code can support a transversal
non-Clifford gate, and that in higher spatial dimensions additional
non-Clifford gates can be found, saturating Bravyi and K\"onig's bound [Phys.
Rev. Lett. 110, 170503 (2013)]. Furthermore, by using gauge fixing techniques,
an effective set of Clifford gates can be achieved, removing the need for state
distillation. We show that the qudit color code can support the qudit analogues
of these gates, and show that in higher spatial dimensions a color code can
support a phase gate from higher levels of the Clifford hierarchy which can be
proven to saturate Bravyi and K\"onig's bound in all but a finite number of
special cases. The methodology used is a generalisation of Bravyi and Haah's
method of triorthogonal matrices [Phys. Rev. A 86 052329 (2012)], which may be
of independent interest. For completeness, we show explicitly that the qudit
color codes generalize to gauge color codes, and share the many of the
favorable properties of their qubit counterparts.Comment: Authors' final cop
A technology development program for large space antennas
The design and application of the offset wrap rib and the maypole (hoop/column) antenna configurations are described. The NASA mission model that generically categorizes the classes of user requirements, as well as the methods used to determine critical technologies and requirements are discussed. Performance estimates for the mesh deployable antenna selected for development are presented
Kink-antikink interactions in the double sine-Gordon equation and the problem of resonance frequencies
We studied the kink-antikink collision process for the "double sine-Gordon"
(DSG) equation in 1+1 dimensions at different values of the potential parameter
. For small values of we discuss the problem of resonance frequencies.
We give qualitative explanation of the frequency shift in comparison with the
frequency of the discrete level in the potential well of isolated kink. We show
that in this region of the parameter the effective long-range interaction
between kink and antikink takes place.Comment: 9 pages, LaTeX, 4 figures (eps
Reinventing spacetime on a dynamical hypersurface
In braneworld models, Space-Time-Matter and other Kaluza-Klein theories, our
spacetime is devised as a four-dimensional hypersurface {\it orthogonal} to the
extra dimension in a five-dimensional bulk. We show that the FRW line element
can be "reinvented" on a dynamical four-dimensional hypersurface, which is {\it
not} orthogonal to the extra dimension, without any internal contradiction.
This hypersurface is selected by the requirement of continuity of the metric
and depends explicitly on the evolution of the extra dimension. The main
difference between the "conventional" FRW, on an orthogonal hypersurface, and
the new one is that the later contains higher-dimensional modifications to the
regular matter density and pressure in 4D. We compare the evolution of the
spacetime in these two interpretations. We find that a wealth of "new" physics
can be derived from a five-dimensional metric if it is interpreted on a
dynamical (non-orthogonal) 4D hypersurface. In particular, in the context of a
well-known cosmological metric in , we construct a FRW model which is
consistent with the late accelerated expansion of the universe, while fitting
simultaneously the observational data for the deceleration parameter. The model
predicts an effective equation of state for the universe, which is consistent
with observations.Comment: References added to the Introduction, and Abstract modified. Accepted
for publication in Mod. Phys. Lett.
The design, development, and flight test results of the Boeing 737 aircraft antennas for the ICAO demonstration of the TRSB microwave landing system
The Research Support Flight System, a modified Boeing 737, was used to evaluate the performance of several aircraft antennas and locations for the Time Reference Scanning Beam (TRSB) Microwave Landing System (MLS). These tests were conducted at the National Aviation Facilities Experimental Center (NAFEC), Atlantic City, New Jersey on December 18, 1975. The flight tests measured the signal strength and all pertinent MLS data during a straight-in approach, a racetrack approach, and ICAO approach profiles using the independent antenna-receiver combinations simultaneously on the aircraft. Signal drop-outs were experienced during the various approaches but only a small percentage could be attributed to antenna pattern effects
Contour measurement system
A measurement system for measuring the departures from a straight line of discrete track sections of a track along a coal face in a mine employing a vehicle having a pair of spaced wheel assemblies which align with the track is presented. A reference arm pivotally connects between the wheel assemblies, and there is indicating means for measuring the angle of pivot between the arm and each of the wheel assemblies. The length of the device is less than the length of a track section, and thus when one of the wheel assemblies is on one track section and one is on an adjoining track section, the sum of the indicated angles will be indicative of the angle between track sections. Thus, from the length of a track section and angle, the departure of each track section from the line may be calculated
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