1,946 research outputs found
Entangling characterization of (SWAP)1/m and Controlled unitary gates
We study the entangling power and perfect entangler nature of (SWAP)1/m, for
m>=1, and controlled unitary (CU) gates. It is shown that (SWAP)1/2 is the only
perfect entangler in the family. On the other hand, a subset of CU which is
locally equivalent to CNOT is identified. It is shown that the subset, which is
a perfect entangler, must necessarily possess the maximum entangling power.Comment: 12 pages, 1 figure, One more paragraph added in Introductio
Detection of Asynchronous Message Passing Errors Using Static Analysis
Concurrent programming is hard and prone to subtle errors. In this paper we present a static analysis that is able to detect some commonly occurring kinds of message passing errors in languages with dynamic process creation and communication based on asynchronous message passing. Our analysis is completely automatic, fast, and strikes a proper balance between soundness and completeness: it is effective in detecting errors and avoids false alarms by computing a close approximation of the interprocess communication topology of programs. We have integrated our analysis in dialyzer, a widely used tool for detecting software defects in Erlang programs, and demonstrate its effectiveness on libraries and applications of considerable size. Despite the fact that these applications have been developed over a long period of time and are reasonably well-tested, our analysis has managed to detect a significant number of previously unknown message passing errors in their code
A true concurrent model of smart contracts executions
The development of blockchain technologies has enabled the trustless
execution of so-called smart contracts, i.e. programs that regulate the
exchange of assets (e.g., cryptocurrency) between users. In a decentralized
blockchain, the state of smart contracts is collaboratively maintained by a
peer-to-peer network of mutually untrusted nodes, which collect from users a
set of transactions (representing the required actions on contracts), and
execute them in some order. Once this sequence of transactions is appended to
the blockchain, the other nodes validate it, re-executing the transactions in
the same order. The serial execution of transactions does not take advantage of
the multi-core architecture of modern processors, so contributing to limit the
throughput. In this paper we propose a true concurrent model of smart contract
execution. Based on this, we show how static analysis of smart contracts can be
exploited to parallelize the execution of transactions.Comment: Full version of the paper presented at COORDINATION 202
Generalized Limits for Parameter Sensitivity via Quantum Ziv-Zakai Bound
We study the generalized limit for parameter sensitivity in quantum
estimation theory considering the effects of repeated and adaptive
measurements. Based on the quantum Ziv-Zakai bound, we derive some lower bounds
for parameter sensitivity when the Hamiltonian of system is unbounded and when
the adaptive measurements are implemented on the system. We also prove that the
parameter sensitivity is bounded by the limit of the minimum detectable
parameter. In particular, we examine several known states in quantum phase
estimation with non-interacting photons, and show that they can not perform
better than Heisenberg limit in a much simpler way with our result.Comment: 8pages, 5 figure
Liveness-Driven Random Program Generation
Randomly generated programs are popular for testing compilers and program
analysis tools, with hundreds of bugs in real-world C compilers found by random
testing. However, existing random program generators may generate large amounts
of dead code (computations whose result is never used). This leaves relatively
little code to exercise a target compiler's more complex optimizations.
To address this shortcoming, we introduce liveness-driven random program
generation. In this approach the random program is constructed bottom-up,
guided by a simultaneous structural data-flow analysis to ensure that the
generator never generates dead code.
The algorithm is implemented as a plugin for the Frama-C framework. We
evaluate it in comparison to Csmith, the standard random C program generator.
Our tool generates programs that compile to more machine code with a more
complex instruction mix.Comment: Pre-proceedings paper presented at the 27th International Symposium
on Logic-Based Program Synthesis and Transformation (LOPSTR 2017), Namur,
Belgium, 10-12 October 2017 (arXiv:1708.07854
The Progression of β-amyloid Deposition in the Frontal Cortex of the Aged Canine
Brains from 41 aged canines (≥10 years of age) were examined immunohistochemically to characterize the laminar distribution and age-related progression of β-amyloid (Aβ) in frontal cortex. We classified the Aβ patterns into four distinct types. Type I was characterized by small, faint deposits of Aβ in deep cortical layers. Type II consisted of diffuse deposits of Aβ mainly in layers V and VI. Type III had both dense plaques in superficial layers, and diffuse deposits in deep layers. Finally, Type IV had solely dense plaques throughout all layers of cortex. We compared the Aβ distribution pattern between the Old canines (10–15 years, n=22) and the Very Old canines (\u3e15 years, n=19). The Old group primarily had negative staining, or Type I and Type II patterns of amyloid deposition (73%). Conversely, the Very Old group had predominantly Types II, III and IV deposits (89.5%), a difference that was significant (Pβ deposition in canine frontal cortex is a progressive age-related process beginning with diffuse deposits in the deep cortical layers followed by the development of deposits in outer layers. In support of this hypothesis, the deeper layer diffuse plaques in the Very Old group of dogs also contain the largest proportion of β-amyloid with an isomerized aspartic acid residue at position 7, indicating that these deposits had been present for some time. We also observed fiber-like Aβ immunoreactivity within regions of diffuse Aβ deposits. These fibers appeared to be degenerating neurites, which were negative for hyperphosphorylated tau. Therefore, these fibers may represent a very early form of neuritic change that precede tau hyperphosphorylation or develop by an alternative pathway
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