247,546 research outputs found
State- and event-based refinement
In this paper we give simple example abstract data types, with atomic operations, that are related by data refinement under a definition used widely in the literature, but these abstract data types are not related by singleton failure refinement. This contradicts results found in the literature. Further we show that a common way to change a model of atomic operations to one of value passing operations actually changes the underlying atomic operational semantics
Ultracold molecules: vehicles to scalable quantum information processing
We describe a novel scheme to implement scalable quantum information
processing using Li-Cs molecular state to entangle Li and Cs
ultracold atoms held in independent optical lattices. The Li atoms will
act as quantum bits to store information, and Cs atoms will serve as
messenger bits that aid in quantum gate operations and mediate entanglement
between distant qubit atoms. Each atomic species is held in a separate optical
lattice and the atoms can be overlapped by translating the lattices with
respect to each other. When the messenger and qubit atoms are overlapped,
targeted single spin operations and entangling operations can be performed by
coupling the atomic states to a molecular state with radio-frequency pulses. By
controlling the frequency and duration of the radio-frequency pulses,
entanglement can either be created or swapped between a qubit messenger pair.
We estimate operation fidelities for entangling two distant qubits and discuss
scalability of this scheme and constraints on the optical lattice lasers
Clones from Creatures
A clone on a set X is a set of finitary operations on X which contains all
the projections and is closed under composition.
The set of all clones forms a complete lattice Cl(X) with greatest element O,
the set of all finitary operations. For finite sets X the lattice is "dually
atomic": every clone other than O is below a coatom of Cl(X).
It was open whether Cl(X) is also dually atomic for infinite X. Assuming the
continuum hypothesis, we show that there is a clone C on a countable set such
that the interval of clones above C is linearly ordered, uncountable, and has
no coatoms.Comment: LaTeX2e, 20 pages. Revised version: some concepts simplified, proof
details adde
A Wait-free Multi-word Atomic (1,N) Register for Large-scale Data Sharing on Multi-core Machines
We present a multi-word atomic (1,N) register for multi-core machines
exploiting Read-Modify-Write (RMW) instructions to coordinate the writer and
the readers in a wait-free manner. Our proposal, called Anonymous Readers
Counting (ARC), enables large-scale data sharing by admitting up to
concurrent readers on off-the-shelf 64-bits machines, as opposed to the most
advanced RMW-based approach which is limited to 58 readers. Further, ARC avoids
multiple copies of the register content when accessing it---this affects
classical register's algorithms based on atomic read/write operations on single
words. Thus it allows for higher scalability with respect to the register size.
Moreover, ARC explicitly reduces improves performance via a proper limitation
of RMW instructions in case of read operations, and by supporting constant time
for read operations and amortized constant time for write operations. A proof
of correctness of our register algorithm is also provided, together with
experimental data for a comparison with literature proposals. Beyond assessing
ARC on physical platforms, we carry out as well an experimentation on
virtualized infrastructures, which shows the resilience of wait-free
synchronization as provided by ARC with respect to CPU-steal times, proper of
more modern paradigms such as cloud computing.Comment: non
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