282 research outputs found
Combined Integer and Floating Point Multiplication Architecture(CIFM) for FPGAs and Its Reversible Logic Implementation
In this paper, the authors propose the idea of a combined integer and
floating point multiplier(CIFM) for FPGAs. The authors propose the replacement
of existing 18x18 dedicated multipliers in FPGAs with dedicated 24x24
multipliers designed with small 4x4 bit multipliers. It is also proposed that
for every dedicated 24x24 bit multiplier block designed with 4x4 bit
multipliers, four redundant 4x4 multiplier should be provided to enforce the
feature of self repairability (to recover from the faults). In the proposed
CIFM reconfigurability at run time is also provided resulting in low power. The
major source of motivation for providing the dedicated 24x24 bit multiplier
stems from the fact that single precision floating point multiplier requires
24x24 bit integer multiplier for mantissa multiplication. A reconfigurable,
self-repairable 24x24 bit multiplier (implemented with 4x4 bit multiply
modules) will ideally suit this purpose, making FPGAs more suitable for integer
as well floating point operations. A dedicated 4x4 bit multiplier is also
proposed in this paper. Moreover, in the recent years, reversible logic has
emerged as a promising technology having its applications in low power CMOS,
quantum computing, nanotechnology, and optical computing. It is not possible to
realize quantum computing without reversible logic. Thus, this paper also paper
provides the reversible logic implementation of the proposed CIFM. The
reversible CIFM designed and proposed here will form the basis of the
completely reversible FPGAs.Comment: Published in the proceedings of the The 49th IEEE International
Midwest Symposium on Circuits and Systems (MWSCAS 2006), Puerto Rico, August
2006. Nominated for the Student Paper Award(12 papers are nominated for
Student paper Award among all submissions
Exact and Asymptotic Measures of Multipartite Pure State Entanglement
In an effort to simplify the classification of pure entangled states of multi
(m) -partite quantum systems, we study exactly and asymptotically (in n)
reversible transformations among n'th tensor powers of such states (ie n copies
of the state shared among the same m parties) under local quantum operations
and classical communication (LOCC). With regard to exact transformations, we
show that two states whose 1-party entropies agree are either locally-unitarily
(LU) equivalent or else LOCC-incomparable. In particular we show that two
tripartite Greenberger-Horne-Zeilinger (GHZ) states are LOCC-incomparable to
three bipartite Einstein-Podolsky-Rosen (EPR) states symmetrically shared among
the three parties. Asymptotic transformations result in a simpler
classification than exact transformations. We show that m-partite pure states
having an m-way Schmidt decomposition are simply parameterizable, with the
partial entropy across any nontrivial partition representing the number of
standard ``Cat'' states (|0^m>+|1^m>) asymptotically interconvertible to the
state in question. For general m-partite states, partial entropies across
different partitions need not be equal, and since partial entropies are
conserved by asymptotically reversible LOCC operations, a multicomponent
entanglement measure is needed, with each scalar component representing a
different kind of entanglement, not asymptotically interconvertible to the
other kinds. In particular the m=4 Cat state is not isentropic to, and
therefore not asymptotically interconvertible to, any combination of bipartite
and tripartite states shared among the four parties. Thus, although the m=4 cat
state can be prepared from bipartite EPR states, the preparation process is
necessarily irreversible, and remains so even asymptotically.Comment: 13 pages including 3 PostScript figures. v3 has updated references
and discussion, to appear Phys. Rev.
Perfect initialization of a quantum computer of neutral atoms in an optical lattice of large lattice constant
We propose a scheme for the initialization of a quantum computer based on
neutral atoms trapped in an optical lattice with large lattice constant. Our
focus is the development of a compacting scheme to prepare a perfect optical
lattice of simple orthorhombic structure with unit occupancy. Compacting is
accomplished by sequential application of two types of operations: a flip
operator that changes the internal state of the atoms, and a shift operator
that moves them along the lattice principal axis. We propose physical
mechanisms for realization of these operations and we study the effects of
motional heating of the atoms. We carry out an analysis of the complexity of
the compacting scheme and show that it scales linearly with the number of
lattice sites per row of the lattice, thus showing good scaling behavior with
the size of the quantum computer.Comment: 18 page
Entanglement molecules
We investigate the entanglement properties of multiparticle systems,
concentrating on the case where the entanglement is robust against disposal of
particles. Two qubits -belonging to a multipartite system- are entangled in
this sense iff their reduced density matrix is entangled. We introduce a family
of multiqubit states, for which one can choose for any pair of qubits
independently whether they should be entangled or not as well as the relative
strength of the entanglement, thus providing the possibility to construct all
kinds of ''Entanglement molecules''. For some particular configurations, we
also give the maximal amount of entanglement achievable.Comment: 4 pages, 1 figur
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