494 research outputs found
MaxEnt assisted MaxLik tomography
Maximum likelihood estimation is a valuable tool often applied to inverse
problems in quantum theory. Estimation from small data sets can, however, have
non unique solutions. We discuss this problem and propose to use Jaynes maximum
entropy principle to single out the most unbiased maximum-likelihood guess.Comment: 10 pages, 5 figures, presented at MaxEnt conference in Jackson, WY,
200
Quantum tomography as normalization of incompatible observations
Quantum states are successfully reconstructed using the maximum likelihood
estimation on the subspace where the measured projectors reproduce the identity
operator. Reconstruction corresponds to normalization of incompatible
observations. The proposed approach handles the noisy data corresponding to
realistic incomplete observation with finite resolution.Comment: RevTeX, 4 pages, 3 figure
Iterative algorithm for reconstruction of entangled states
An iterative algorithm for the reconstruction of an unknown quantum state
from the results of incompatible measurements is proposed. It consists of
Expectation-Maximization step followed by a unitary transformation of the
eigenbasis of the density matrix. The procedure has been applied to the
reconstruction of the entangled pair of photons.Comment: 4 pages, no figures, some formulations changed, a minor mistake
correcte
Quantum state estimation
New algorithm for quantum state estimation based on the maximum likelihood
estimation is proposed. Existing techniques for state reconstruction based on
the inversion of measured data are shown to be overestimated since they do not
guarantee the positive definiteness of the reconstructed density matrix.Comment: 4 pages, twocolumn Revte
Quantum theory of incompatible observations
Maximum likelihood principle is shown to be the best measure for relating the
experimental data with the predictions of quantum theory.Comment: 3 page
An assessment of service and resource needs of university students with disabilities
Two studies focusing on the need for supportive services and resources for persons with disabilities at universities are described. Both studies took place in the Kitchener-Waterloo community. In Study One, students and faculty at the University of Waterloo and community service workers were surveyed. In Study Two, students and staff at Wilfrid Laurier University and high school students and staff at the Waterloo County Board of Education were surveyed. In total, eighty-two participants were surveyed by interview or questionnaire methods. The results from the two studies provided information about needs and concerns specific to individual participants and settings as well as a number of shared concerns and ideas. From these results, recommendations regarding the future programming of support services and resources into the community, increasing awareness about disability within universities and more globally in the community, and implementing policies and guidelines for the use of special needs services and resources
On the local unitary equivalence of states of multi-partite systems
Two pure states of a multi-partite system are alway are related by a unitary
transformation acting on the Hilbert space of the whole system. This
transformation involves multi-partite transformations. On the other hand some
quantum information protocols such as the quantum teleportation and quantum
dense coding are based on equivalence of some classes of states of bi-partite
systems under the action of local (one-particle) unitary operations. In this
paper we address the question: ``Under what conditions are the two states
states, and , of a multi-partite system locally unitary
equivalent?'' We present a set of conditions which have to be satisfied in
order that the two states are locally unitary equivalent. In addition, we study
whether it is possible to prepare a state of a multi-qudit system. which is
divided into two parts A and B, by unitary operations acting only on the
systems A and B, separately.Comment: 6 revtex pages, 1 figur
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