974 research outputs found
Optimal observables to determine entanglement of a two qubit state
Experimental determination of entanglement is important not only to
characterize the state and use it in quantum information, but also in
understanding complicated phenomena such as phase transitions. In this paper we
show that in many cases, it is possible to determine entanglement of a two
qubit state, as represented by concurrence, with a few observables, most of
which are local. In particular, rank 1 and rank 2 states need exclusively
measurement of local observables while rank 3 states need measurement of just
one correlation observable in addition to local observables. Only the rank 4
states are shown to require a more detailed tomography. The analysis also sheds
light on the other measure, non separability since it is a lower bound on
concurrence.Comment: 8 pages, 1 figur
A Fast Eigen Solution for Homogeneous Quadratic Minimization with at most Three Constraints
We propose an eigenvalue based technique to solve the Homogeneous Quadratic
Constrained Quadratic Programming problem (HQCQP) with at most 3 constraints
which arise in many signal processing problems. Semi-Definite Relaxation (SDR)
is the only known approach and is computationally intensive. We study the
performance of the proposed fast eigen approach through simulations in the
context of MIMO relays and show that the solution converges to the solution
obtained using the SDR approach with significant reduction in complexity.Comment: 15 pages, The same content without appendices is accepted and is to
be published in IEEE Signal Processing Letter
Knowledge Reuse for Customization: Metamodels in an Open Design Community for 3d Printing
Theories of knowledge reuse posit two distinct processes: reuse for
replication and reuse for innovation. We identify another distinct process,
reuse for customization. Reuse for customization is a process in which
designers manipulate the parameters of metamodels to produce models that
fulfill their personal needs. We test hypotheses about reuse for customization
in Thingiverse, a community of designers that shares files for
three-dimensional printing. 3D metamodels are reused more often than the 3D
models they generate. The reuse of metamodels is amplified when the metamodels
are created by designers with greater community experience. Metamodels make the
community's design knowledge available for reuse for customization-or further
extension of the metamodels, a kind of reuse for innovation
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