2,069 research outputs found
Numerically Exact Long Time Behavior of Nonequilibrium Quantum Impurity Models
A Monte Carlo sampling of diagrammatic corrections to the non-crossing
approximation is shown to provide numerically exact estimates of the long-time
dynamics and steady state properties of nonequilibrium quantum impurity models.
This `bold' expansion converges uniformly in time and significantly ameliorates
the sign problem that has heretofore limited the power of real-time Monte Carlo
approaches to strongly interacting real-time quantum problems. The new approach
enables the study of previously intractable problems ranging from generic long
time nonequilibrium transport characteristics in systems with large onsite
repulsion to the direct description of spectral functions on the real frequency
axis in Dynamical Mean Field Theory
Resilient Quantum Computation: Error Models and Thresholds
Recent research has demonstrated that quantum computers can solve certain
types of problems substantially faster than the known classical algorithms.
These problems include factoring integers and certain physics simulations.
Practical quantum computation requires overcoming the problems of environmental
noise and operational errors, problems which appear to be much more severe than
in classical computation due to the inherent fragility of quantum
superpositions involving many degrees of freedom. Here we show that arbitrarily
accurate quantum computations are possible provided that the error per
operation is below a threshold value. The result is obtained by combining
quantum error-correction, fault tolerant state recovery, fault tolerant
encoding of operations and concatenation. It holds under physically realistic
assumptions on the errors.Comment: 19 pages in RevTex, many figures, the paper is also avalaible at
http://qso.lanl.gov/qc
Improved magic states distillation for quantum universality
Given stabilizer operations and the ability to repeatedly prepare a
single-qubit mixed state rho, can we do universal quantum computation? As
motivation for this question, "magic state" distillation procedures can reduce
the general fault-tolerance problem to that of performing fault-tolerant
stabilizer circuits.
We improve the procedures of Bravyi and Kitaev in the Hadamard "magic"
direction of the Bloch sphere to achieve a sharp threshold between those rho
allowing universal quantum computation, and those for which any calculation can
be efficiently classically simulated. As a corollary, the ability to repeatedly
prepare any pure state which is not a stabilizer state (e.g., any single-qubit
pure state which is not a Pauli eigenstate), together with stabilizer
operations, gives quantum universality. It remains open whether there is also a
tight separation in the so-called T direction.Comment: 6 pages, 5 figure
Design of a Mobile Application for Providing Information to Advanced Level Students in Uganda
Education is the key to success in the existing world. Providing necessary information to students at the right stage of education that determines their future is useful to students, simplifies work, and reduces responsibilities for educators. Unfortunately, the existing ways of providing information to A'Level students in Uganda are unmodernized, and thus, important information is inadequately accessible to the students. Because of this, most students make uninformed decisions and study without focus. A prototype mobile application was designed to enable A'Level students to access necessary information about qualifications requirements, study materials, subjects, schools, etc. A rule-based method was also used to help students choose subjects that match their desired career options. The user interface design process followed a User-Centered Design approach to meet the students' requirements. SPSS software was used for analyzing the data, and results were obtained. The evaluation of the design showed that 95.76% of Advanced Level students who were participants agreed with the designed application prototype. This result indicated that A'Level students are interested in using mobile application technology to access information. This prototype design will ease students' getting information and ease educators' work, thereby saving the time wasted in attending to students physically to deliver all the necessary information.https://dorl.net/dor/20.1001.1.20088302.2022.20.2.2.7 Â Â
Assessment of Indoor and Outdoor Background Radiation Levels in Plateau State University Bokkos Jos, Nigeria
Survey taken by the world health organization (WHO) and the international commission on radiation protection (ICRP) shows that residents of temperate climate spends only about 20% of their time outdoor and about 80% indoors and certain materials use for the construction of such buildings (rocks soils) are known to be radioactive. This work set out to assess the background ionizing radiations at Biochemistry, Chemistry, Microbiology and physics laboratories all of Plateau State University Bokkos to determine the radiation levels both within the laboratories and their immediate surroundings. The gamma-scout used for the purpose of the study was adjusted to detect the alpha, beta and gamma types of radiation in ?Sv/hr. The mean equivalent dose rate per hour for indoor background radiation for the laboratories was found to be 0.256?Sv/hr while the outdoor was 0.249?Sv/hr. The mean annual equivalent dose rate of the laboratories were compute for indoor and outdoor background radiation level to be 1.54mSv/yr and 0.44mSv/yr respectively, and are in a good proportion below the world wide average dose of 2.4mSv/yr. Keywords: Cancer,equivalent, dose rate, gamma-scout, background ionizing radiation.
Restrictions on Transversal Encoded Quantum Gate Sets
Transversal gates play an important role in the theory of fault-tolerant
quantum computation due to their simplicity and robustness to noise. By
definition, transversal operators do not couple physical subsystems within the
same code block. Consequently, such operators do not spread errors within code
blocks and are, therefore, fault tolerant. Nonetheless, other methods of
ensuring fault tolerance are required, as it is invariably the case that some
encoded gates cannot be implemented transversally. This observation has led to
a long-standing conjecture that transversal encoded gate sets cannot be
universal. Here we show that the ability of a quantum code to detect an
arbitrary error on any single physical subsystem is incompatible with the
existence of a universal, transversal encoded gate set for the code.Comment: 4 pages, v2: minor change
Dynamical Decoupling of Open Quantum Systems
We propose a novel dynamical method for beating decoherence and dissipation
in open quantum systems. We demonstrate the possibility of filtering out the
effects of unwanted (not necessarily known) system-environment interactions and
show that the noise-suppression procedure can be combined with the capability
of retaining control over the effective dynamical evolution of the open quantum
system. Implications for quantum information processing are discussed.Comment: 4 pages, no figures; Plain ReVTeX. Final version to appear in
Physical Review Letter
Bis(6-diphenylphosphino-acenaphth-5-yl)sulfoxide. A New Ligand for Late Transition Metal Complexes
The synthesis of the new ligand bis(6-diphenylphosphinoacenaphth-5-yl)sulfoxide, [6-(Ph2P)-5-Ace-6](2)-SO (1), is presented along with six transition metal complexes thereof, namely,1 center dot MCl (M = Rh, Cu, Ag, Au) and1 center dot MCl2(M = Ni, Pd). Within these novel complexes, close metal-sulfur distances are observed and the nature of the M-S coordination, as well as the response of the(+)S-O(-)bond, are investigated in detail with a set of spectroscopic, crystallographic and real-space bonding indicators
Decoherence Bounds on Quantum Computation with Trapped Ions
Using simple physical arguments we investigate the capabilities of a quantum
computer based on cold trapped ions. From the limitations imposed on such a
device by spontaneous decay, laser phase coherence, ion heating and other
sources of error, we derive a bound between the number of laser interactions
and the number of ions that may be used. The largest number which may be
factored using a variety of species of ion is determined.Comment: 5 pages in RevTex, 2 figures, the paper is also avalaible at
http://qso.lanl.gov/qc
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