555 research outputs found
Non locality, closing the detection loophole and communication complexity
It is shown that the detection loophole which arises when trying to rule out
local realistic theories as alternatives for quantum mechanics can be closed if
the detection efficiency is larger than
where is the dimension of the entangled system. Furthermore it is argued
that this exponential decrease of the detector efficiency required to close the
detection loophole is almost optimal. This argument is based on a close
connection that exists between closing the detection loophole and the amount of
classical communication required to simulate quantum correlation when the
detectors are perfect.Comment: 4 pages Latex, minor typos correcte
Construction of SO(5)>SO(3) spherical harmonics and Clebsch-Gordan coefficients
The SO(5)>SO(3) spherical harmonics form a natural basis for expansion of
nuclear collective model angular wave functions. They underlie the
recently-proposed algebraic method for diagonalization of the nuclear
collective model Hamiltonian in an SU(1,1)xSO(5) basis. We present a computer
code for explicit construction of the SO(5)>SO(3) spherical harmonics and use
them to compute the Clebsch-Gordan coefficients needed for collective model
calculations in an SO(3)-coupled basis. With these Clebsch-Gordan coefficients
it becomes possible to compute the matrix elements of collective model
observables by purely algebraic methods.Comment: LaTeX (RevTeX), 15 pages; to be published in Computer Phys. Comm
Validation of a CT-free navigation system for the measurement of native acetabular alignment
Computer assisted surgery is becoming more frequently used in medical world. OrthoPilot Hip Suite CT-free navigation system (BBraun Aesculap) is one such computer assisted navigation system used for total hip replacement surgery. The validity of OrthoPilot system remains to be determined independent of the manufacturer. The main aims of this study were to investigate the accuracy of OrthoPilot data, while using surgical instruments and to confirm the suitability of the cup navigation algorithm. OrthoPilot was compared with the gold standard of a VICON movement analysis system. An aluminium pelvic phantom was machined with high accuracy to perform the experiments. Data were captured simultaneously from both OrthoPilot and VICON systems and acetabular angles were compared. Both systems produce comparable results for the distance between anatomical landmarks and acetabular angles. It can be concluded that data from OrthoPilot system, if used correctly, are sufficiently accurate for orthopaedic applications
Excited state quantum phase transitions in many-body systems
Phenomena analogous to ground state quantum phase transitions have recently
been noted to occur among states throughout the excitation spectra of certain
many-body models. These excited state phase transitions are manifested as
simultaneous singularities in the eigenvalue spectrum (including the gap or
level density), order parameters, and wave function properties. In this
article, the characteristics of excited state quantum phase transitions are
investigated. The finite-size scaling behavior is determined at the mean field
level. It is found that excited state quantum phase transitions are universal
to two-level bosonic and fermionic models with pairing interactions.Comment: LaTeX (elsart), 37 pages; to be published in Ann. Phys. (N.Y.
A Proposed Master of Social Work Based in Indigenous Knowledges Program in Manitoba
This article focuses on an innovative proposed Master of Social Work based in Indigenous Knowledges program developed by an Indigenous Caucus within the Faculty of Social Work at the University of Manitoba in Canada. This culturally based program intends to ground students with a solid foundation in traditional Indigenous teachings and perspectives, and contemporary Indigenous philosophies, knowledges, concepts, critiques, and ways of being that stem from these traditions. The proposed Master of Social Work based in Indigenous Knowledges was developed as a lived program that builds community and social supports, and reclaims and re-energizes a sense of self, responsibility, self-sufficiency, self-determination, and self-government. The programâs aim is to deconstruct oppressive and colonialist structures and reconstruct, in a contemporary sense, what has been previously destroyed. An overview of the visions, objectives, program design, foundational themes and description of courses is provided, along with reflections on what teachings its development has provided
A Zoology of Bell inequalities resistant to detector inefficiency
We derive both numerically and analytically Bell inequalities and quantum
measurements that present enhanced resistance to detector inefficiency. In
particular we describe several Bell inequalities which appear to be optimal
with respect to inefficient detectors for small dimensionality d=2,3,4 and 2 or
more measurement settings at each side. We also generalize the family of Bell
inequalities described in Collins et all (Phys. Rev. Lett. 88, 040404) to take
into account the inefficiency of detectors. In addition we consider the
possibility for pairs of entangled particles to be produced with probability
less than one. We show that when the pair production probability is small, one
must in general use different Bell inequalities than when the pair production
probability is high.Comment: 12 pages, revtex. Appendix completed, minor revision
Against `Realism'
We examine the prevalent use of the phrase ``local realism'' in the context of Bell's Theorem and associated experiments, with a focus on the question: what exactly is the ``realism'' in ``local realism'' supposed to mean? Carefully surveying several possible meanings, we argue that all of them are flawed in one way or another as attempts to point out a second premise (in addition to locality) on which the Bell inequalities rest, and (hence) which might be rejected in the face of empirical data violating the inequalities. We thus suggest that this vague and abused phrase ``local realism'' should be banned from future discussions of these issues, and urge physicists to revisit the foundational questions behind Bell's Theorem
Dissipation-assisted quantum gates with cold trapped ions
It is shown that a two-qubit phase gate and SWAP operation between ground
states of cold trapped ions can be realised in one step by simultaneously
applying two laser fields. Cooling during gate operations is possible without
perturbing the computation and the scheme does not require a second ion species
for sympathetic cooling. On the contrary, the cooling lasers even stabilise the
desired time evolution of the system. This affords gate operation times of
nearly the same order of magnitude as the inverse coupling constant of the ions
to a common vibrational mode.Comment: 4 pages, 5 figures, substantially revised versio
Qubits from Number States and Bell Inequalities for Number Measurements
Bell inequalities for number measurements are derived via the observation
that the bits of the number indexing a number state are proper qubits.
Violations of these inequalities are obtained from the output state of the
nondegenerate optical parametric amplifier.Comment: revtex4, 7 pages, v2: results identical but extended presentation,
v3: published versio
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