3,128 research outputs found
Grover's search with faults on some marked elements
Grover's algorithm is a quantum query algorithm solving the unstructured
search problem of size using queries. It provides a
significant speed-up over any classical algorithm \cite{Gro96}.
The running time of the algorithm, however, is very sensitive to errors in
queries. It is known that if query may fail (report all marked elements as
unmarked) the algorithm needs queries to find a marked element
\cite{RS08}. \cite{AB+13} have proved the same result for the model where each
marked element has its own probability to be reported as unmarked.
We study the behavior of Grover's algorithm in the model where the search
space contains both faulty and non-faulty marked elements. We show that in this
setting it is indeed possible to find one of non-faulty marked items in
queries.
We also analyze the limiting behavior of the algorithm for a large number of
steps and show the existence and the structure of limiting state .Comment: 17 pages, 6 figure
Light scattering and phase behavior of Lysozyme-PEG mixtures
Measurements of liquid-liquid phase transition temperatures (cloud points) of
mixtures of a protein (lysozyme) and a polymer, poly(ethylene glycol) (PEG)
show that the addition of low molecular weight PEG stabilizes the mixture
whereas high molecular weight PEG was destabilizing. We demonstrate that this
behavior is inconsistent with an entropic depletion interaction between
lysozyme and PEG and suggest that an energetic attraction between lysozyme and
PEG is responsible. In order to independently characterize the lysozyme/PEG
interactions, light scattering experiments on the same mixtures were performed
to measure second and third virial coefficients. These measurements indicate
that PEG induces repulsion between lysozyme molecules, contrary to the
depletion prediction. Furthermore, it is shown that third virial terms must be
included in the mixture's free energy in order to qualitatively capture our
cloud point and light scattering data. The light scattering results were
consistent with the cloud point measurements and indicate that attractions do
exist between lysozyme and PEG.Comment: 5 pages, 2 figures, 1 tabl
SMEI observations of previously unseen pulsation frequencies in γ Doradus
Aims. As g-mode pulsators, gamma-Doradus-class stars may naïvely be expected to show a large number of modes. Taking advantage of the long photometric time-series generated by the solar mass ejection imager (SMEI) instrument, we have studied the star gamma Doradus to determine whether any other modes than the three already known are present at observable amplitude.
Methods. High-precision photometric data from SMEI taken between April 2003 and March 2006 were subjected to periodogram analysis with the PERIOD04 package.
Results. We confidently determine three additional frequencies at 1.39, 1.87, and 2.743 d−1. These are above and beyond the known frequencies of 1.320, 1.364, and 1.47 d−1.
Conclusions. Two of the new frequencies, at 1.39 and 1.87 d−1, are speculated to be additional modes of oscillation, with the third frequency at 2.743−1 a possible combination frequency
State-space distribution and dynamical flow for closed and open quantum systems
We present a general formalism for studying the effects of dynamical
heterogeneity in open quantum systems. We develop this formalism in the state
space of density operators, on which ensembles of quantum states can be
conveniently represented by probability distributions. We describe how this
representation reduces ambiguity in the definition of quantum ensembles by
providing the ability to explicitly separate classical and quantum sources of
probabilistic uncertainty. We then derive explicit equations of motion for
state space distributions of both open and closed quantum systems and
demonstrate that resulting dynamics take a fluid mechanical form analogous to a
classical probability fluid on Hamiltonian phase space, thus enabling a
straightforward quantum generalization of Liouville's theorem. We illustrate
the utility of our formalism by analyzing the dynamics of an open two-level
system using the state-space formalism that are shown to be consistent with the
derived analytical results
Approximating Fractional Time Quantum Evolution
An algorithm is presented for approximating arbitrary powers of a black box
unitary operation, , where is a real number, and
is a black box implementing an unknown unitary. The complexity of
this algorithm is calculated in terms of the number of calls to the black box,
the errors in the approximation, and a certain `gap' parameter. For general
and large , one should apply a total of times followed by our procedure for approximating the fractional
power . An example is also given where for
large integers this method is more efficient than direct application of
copies of . Further applications and related algorithms are also
discussed.Comment: 13 pages, 2 figure
Impact of COVID-19 pandemic on chronic pain management: Looking for the best way to deliver care
Although pain treatment has been described as a fundamental human right, the Coronavirus disease 2019 (COVID-19) pandemic forced healthcare systems worldwide to redistribute healthcare resources toward intensive care units and other COVID-19 dedicated sites. As most chronic pain services were subsequently deemed non-urgent, all outpatient and elective interventional procedures have been reduced or interrupted during the COVID-19 pandemic in order to reduce the risk of viral spread. The shutdown of pain services jointly to the home lockdown imposed by governments has affected chronic pain management worldwide with additional impact on patients' psychological health. Therefore, the aim of this review is to analyze the impact of COVID-19 pandemic on chronic pain treatment and to address what types of strategies can be implemented or supported in order to overcome imposed limitations in delivery of chronic pain patient care
The use of positive end expiratory pressure in patients affected by COVID-19: Time to reconsider the relation between morphology and physiology
Coronavirus disease 2019 (COVID-19) is a new disease with different phases that can be catastrophic for subpopulations of patients with cardiovascular and pulmonary disease states at baseline. Appreciation for these different phases and treatment modalities, including manipulation of ventilatory settings and therapeutics, has made it a less lethal disease than when it emerged earlier this year. Different aspects of the disease are still largely unknown. However, laboratory investigation and clinical course of the COVID-19 show that this new disease is not a typical acute respiratory distress syndrome process, especially during the first phase. For this reason, the best strategy to be applied is to treat differently the single phases and to support the single functions of the failing organs as they appear
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