9,114 research outputs found
Graphical Nonbinary Quantum Error-Correcting Codes
In this paper, based on the nonbinary graph state, we present a systematic
way of constructing good non-binary quantum codes, both additive and
nonadditive, for systems with integer dimensions. With the help of computer
search, which results in many interesting codes including some nonadditive
codes meeting the Singleton bounds, we are able to construct explicitly four
families of optimal codes, namely, , ,
and for any odd dimension and a family of nonadditive code
for arbitrary . In the case of composite numbers as
dimensions, we also construct a family of stabilizer codes for odd , whose coding subspace is {\em not} of a dimension
that is a power of the dimension of the physical subsystem.Comment: 12 pages, 5 figures (pdf
Greenberger-Horne-Zeilinger paradoxes from qudit graph states
One fascinating way of revealing the quantum nonlocality is the
all-versus-nothing test due to Greenberger, Horne, and Zeilinger (GHZ) known as
GHZ paradox. So far genuine multipartite and multilevel GHZ paradoxes are known
to exist only in systems containing an odd number of particles. Here we shall
construct GHZ paradoxes for an arbitrary number (greater than 3) of particles
with the help of qudit graph states on a special kind of graphs, called as GHZ
graphs. Based on the GHZ paradox arising from a GHZ graph, we derive a Bell
inequality with two -outcome observables for each observer, whose maximal
violation attained by the corresponding graph state, and a Kochen-Specker
inequality testing the quantum contextuality in a state-independent fashion
Performance formula-based optimal deployments of multilevel indices for service retrieval.
There are many different index structures for service repositories, such as sequential index, inverted index, and multilevel indices that include three deployments. Different service sets maybe have different characteristics that may affect performance from different aspects. For a given service set, which index structure is the most optimal one? To address these issues, this paper analyses five indexing models and proposes expectation of traversed service count to estimate performance of service retrieval. Based on these expectation formulas, an optimal deployment method can be identified to maximize efficiency of service retrieval. Our experiments first validate correctness of the proposed formulas and then validate the effective of the optimal method.UK-China Knowledge Economy Education Partnershi
Efficiency, Fairness, and Stability in Non-Commercial Peer-to-Peer Ridesharing
Unlike commercial ridesharing, non-commercial peer-to-peer (P2P) ridesharing
has been subject to limited research -- although it can promote viable
solutions in non-urban communities. This paper focuses on the core problem in
P2P ridesharing: the matching of riders and drivers. We elevate users'
preferences as a first-order concern and introduce novel notions of fairness
and stability in P2P ridesharing. We propose algorithms for efficient matching
while considering user-centric factors, including users' preferred departure
time, fairness, and stability. Results suggest that fair and stable solutions
can be obtained in reasonable computational times and can improve baseline
outcomes based on system-wide efficiency exclusively
Observing in space and time the ephemeral nucleation of liquid-to-crystal phase transitions
The phase transition of crystalline ordering is a general phenomenon, but its evolution in space and time requires microscopic probes for visualization. Here we report direct imaging of the transformation of amorphous titanium dioxide nanofilm, from the liquid state, passing through the nucleation step and finally to the ordered crystal phase. Single-pulse transient diffraction profiles at different times provide the structural transformation and the specific degree of crystallinity (??) in the evolution process. It is found that the temporal behaviour of ?? exhibits unique 'two-step' dynamics, with a robust 'plateau' that extends over a microsecond; the rate constants vary by two orders of magnitude. Such behaviour reflects the presence of intermediate structure(s) that are the precursor of the ordered crystal state. Theoretically, we extend the well-known Johnson-Mehl-Avrami-Kolmogorov equation, which describes the isothermal process with a stretched-exponential function, but here over the range of times covering the melt-to-crystal transformation. © 2015 Macmillan Publishers Limited.open
Reinforced degradation of ibuprofen with MnCo2O4/FCNTs nanocatalyst as peroxymonosulfate activator : Performance and mechanism
In order to efficiently degrade ibuprofen (IBU) by peroxymonosulfate (PMS) activation, manganese cobalt oxide nanoparticles-decorated functionalized multi-walled carbon nanotubes (MnCo2O4/FCNTs) were prepared using a facile hydrothermal method. Comprehensive characterization of this PMS activator in multi-scale suggested that MnCo2O4 nanoparticles were uniformly decorated on FCNTs. The catalytic performance was systematical evaluated under various environmental conditions, including temperature, pH, and the presence of different common water matrix species (e.g., Cl-, HCO3-, and natural organic matter). The as-synthesized MnCo2O4/FCNTs demonstrated excellent catalytic activity with kapp ranging 0.285-0.327 min-1 under a wide pH range of 3-9 within 10 min, which achieved a complete removal of IBU and a mineralization rate higher than 90%. During oxidation process for stability and reusability test, recycled MnCo2O4/FCNTs was found durable with negligible leaching of metal ions from spent catalyst, exhibiting its high stability for PMS activation with merely slight decrease of kapp from 0.285 to 0.201 min-1 in the fourth cycle. Electron paramagnetic resonance analysis further confirmed that •OH, SO4•- and 1O2 were generated in the robust MnCo2O4/FCNTs-PMS system. Both radical and nonradical reactions were found to be responsible for the enhanced IBU degradation. Overall, this study sheds light on practical knowledge of IBU removal using MnCo2O4/FCNTs for PMS activation.publishedVersionPeer reviewe
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