1,949 research outputs found
Quantum Interactive Proofs with Competing Provers
This paper studies quantum refereed games, which are quantum interactive
proof systems with two competing provers: one that tries to convince the
verifier to accept and the other that tries to convince the verifier to reject.
We prove that every language having an ordinary quantum interactive proof
system also has a quantum refereed game in which the verifier exchanges just
one round of messages with each prover. A key part of our proof is the fact
that there exists a single quantum measurement that reliably distinguishes
between mixed states chosen arbitrarily from disjoint convex sets having large
minimal trace distance from one another. We also show how to reduce the
probability of error for some classes of quantum refereed games.Comment: 13 pages, to appear in STACS 200
The transformation of irreducible tensor operators under spherical functions
The irreducible tensor operators and their tensor products employing Racah
algebra are studied. Transformation procedure of the coordinate system
operators act on are introduced. The rotation matrices and their
parametrization by the spherical coordinates of vector in the fixed and rotated
coordinate systems are determined. A new way of calculation of the irreducible
coupled tensor product matrix elements is suggested. As an example, the
proposed technique is applied for the matrix element construction for two
electrons in a field of a fixed nucleus.Comment: To appear in Int. J. Theor. Phy
Dissolution and permeation characteristics of artemether tablets formulated with two gums of different surface activity
Purpose: To evaluate the dissolution and permeation characteristics of artemether tablets formulated with cashew and prosopis gums, and compare with tablets prepared with acacia gum.Methods: Artemether tablets containing varying concentrations (1.0 to 4.0 %w/w) of cashew and prosopis gums or 3 %w/w of acacia (control) gum as binders were formulated by wet granulation method. The tablets were evaluated for crushing strength, friability and disintegration time. Dissolution and permeation characteristics of the formulations were studied using USP methods.Results: Tablets formulated with prosopis gum had higher crushing strength, higher friability and higher disintegration time compared to those of cashew gum at corresponding binder concentrations. Tablets formulated with 3 %w/w cashew gum exhibited complete drug release within 1 h, 95 % drug permeation in 188 min (in simulated gastric fluid [SGF]) and 95 % permeation in 224 min (under simulated intestinal fluid [SIF] condition) while those made with 3 %w/w prosopis gum exhibited 70.7 % drug release in 1 h, 95 % permeation in 135 min (in SGF) and 95 % permeation in 170 min (under SIF condition).Conclusion: Cashew gum is effective as a binder over a relatively wide range of concentrations to achieve fast drug release though with minimal permeation enhancement while prosopis gum is characterized by delayed drug release but enhanced permeation of the released drug.Keywords: Cashew gum, Acacia, Prosopis, Artemether, Drug release, Dissolution, Permeatio
A Quantum-Proof Non-Malleable Extractor, With Application to Privacy Amplification against Active Quantum Adversaries
In privacy amplification, two mutually trusted parties aim to amplify the
secrecy of an initial shared secret in order to establish a shared private
key by exchanging messages over an insecure communication channel. If the
channel is authenticated the task can be solved in a single round of
communication using a strong randomness extractor; choosing a quantum-proof
extractor allows one to establish security against quantum adversaries.
In the case that the channel is not authenticated, Dodis and Wichs (STOC'09)
showed that the problem can be solved in two rounds of communication using a
non-malleable extractor, a stronger pseudo-random construction than a strong
extractor.
We give the first construction of a non-malleable extractor that is secure
against quantum adversaries. The extractor is based on a construction by Li
(FOCS'12), and is able to extract from source of min-entropy rates larger than
. Combining this construction with a quantum-proof variant of the
reduction of Dodis and Wichs, shown by Cohen and Vidick (unpublished), we
obtain the first privacy amplification protocol secure against active quantum
adversaries
Dynamical Quantum Error Correction of Unitary Operations with Bounded Controls
Dynamically corrected gates were recently introduced [Khodjasteh and Viola,
Phys. Rev. Lett. 102, 080501 (2009)] as a tool to achieve decoherence-protected
quantum gates based on open-loop Hamiltonian engineering. Here, we further
expand the framework of dynamical quantum error correction, with emphasis on
elucidating under what conditions decoherence suppression can be ensured while
performing a generic target quantum gate, using only available bounded-strength
control resources. Explicit constructions for physically relevant error models
are detailed, including arbitrary linear decoherence and pure dephasing on
qubits. The effectiveness of dynamically corrected gates in an illustrative
non-Markovian spin-bath setting is investigated numerically, confirming the
expected fidelity performance in a wide parameter range. Robutness against a
class of systematic control errors is automatically incorporated in the
perturbative error regime.Comment: 21 pages, 7 figures (errors fixed, figures added, text updated
On the nature of the X-ray source in GK Per
We report XMM-Newton observations of the intermediate polar (IP) GK Per on
the rise to the 2002 outburst and compare them to Chandra observations during
quiescence. We find an asymmetric spin light curve implying an asymmetric shape
of a semi-transparent accretion curtain. A low Fe xvii (15.01/15.26 A) line
flux ratio confirms the need for an asymmetric geometry and significant effects
of resonant line scattering. Medium resolution spectra in outburst and
quiescence are both fitted with a leaky absorber model for the post shock hard
X-ray emission, a black body (outburst) for the thermalized X-ray emission from
the white dwarf and an optically thin spectrum. The difference between high and
low spin as well as QPO/flares states can be explained by a variation in the
absorbing column density. The Fe fluorescence at 6.4 keV (equivalent width of
447 eV) is not significantly variable during spin cycle or on QPO periods.
High-resolution RGS spectra reveal a number of emission lines from H-like and
He-like elements. The lines are broader than the instrumental response with a
roughly constant velocity dispersion for different lines, indicating identical
origin. He-like emission lines are used to give values for the electron
densities of log n_e ~ 12. We do not detect any variation in the emission lines
during the spin cycle, implying that the lines are not noticeably obscured or
absorbed. We conclude that they originate in the accretion curtains and propose
a model for their shape.Comment: 14 pages, 22 figures, accepted by A&A; text re quiescent data changed
slightly, references adde
Statistical-mechanical theory of ultrasonic absorption in molecular liquids
We present results of theoretical description of ultrasonic phenomena in
molecular liquids. In particular, we are interested in the development of
microscopical, i.e., statistical-mechanical framework capable to explain the
long living puzzle of the excess ultrasonic absorption in liquids. Typically,
ultrasonic wave in a liquid can be generated by applying the periodically
alternating external pressure with the angular frequency that corresponds to
the ultrasound. If the perturbation introduced by such process is weak - its
statistical-mechanical treatment can be done with the use of the linear
response theory. We treat the liquid as a system of interacting sites, so that
all the response/aftereffect functions as well as the energy dissipation and
generalized (wave-vector and frequency dependent) ultrasonic absorption
coefficient are obtained in terms of familiar site-site static and time
correlation functions such as static structure factors or intermediate
scattering functions. To express the site-site intermediate scattering
functions we refer to the site-site memory equations in the mode-coupling
approximation for the first-order memory kernels, while equilibrium properties
such as site-site static structure factors, direct and total correlation
functions are deduced from the integral equation theory of molecular liquids
known as RISM or one of its generalizations. All the formalism is phrased in a
general manner, hence the obtained results are expected to work for arbitrary
type of molecular liquid including simple, ionic, polar, and non-polar liquids.Comment: 14 pages, 1 eps-figure, RevTeX4-forma
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