288 research outputs found
Notes on coarse grainings and functions of observables
Using the Naimark dilation theory we investigate the question under what
conditions an observable which is a coarse graining of another observable is a
function of it. To this end, conditions for the separability and for the
Boolean structure of an observable are given
Two questions on quantum statistics
The determination of a quantum observable from the first and second moments
of its measurement outcome statistics is investigated. Operational conditions
for the moments of a probability measure are given which suffice to determine
the probability measure. Differential operators are shown to lead to physically
relevant cases where the expectation values of large classes of noncommuting
observables do not distinguish superpositions of states and, in particular,
where the full moment information does not determine the probability measure.Comment: 8 page
The norm-1-property of a quantum observable
A normalized positive operator measure has the
norm-1-property if \no{E(X)}=1 whenever . This property reflects
the fact that the measurement outcome probabilities for the values of such
observables can be made arbitrary close to one with suitable state
preparations. Some general implications of the norm-1-property are
investigated. As case studies, localization observables, phase observables, and
phase space observables are considered.Comment: 14 page
Complementary Observables in Quantum Mechanics
We review the notion of complementarity of observables in quantum mechanics,
as formulated and studied by Paul Busch and his colleagues over the years. In
addition, we provide further clarification on the operational meaning of the
concept, and present several characterisations of complementarity - some of
which new - in a unified manner, as a consequence of a basic factorisation
lemma for quantum effects. We work out several applications, including the
canonical cases of position-momentum, position-energy, number-phase, as well as
periodic observables relevant to spatial interferometry. We close the paper
with some considerations of complementarity in a noisy setting, focusing
especially on the case of convolutions of position and momentum, which was a
recurring topic in Paul's work on operational formulation of quantum
measurements and central to his philosophy of unsharp reality
Moment operators of the Cartesian margins of the phase space observables
The theory of operator integrals is used to determine the moment operators of
the Cartesian margins of the phase space observables generated by the mixtures
of the number states. The moments of the -margin are polynomials of the
position operator and those of the -margin are polynomials of the momentum
operator.Comment: 14 page
The uniqueness question in the multidimensional moment problem with applications to phase space observables
The theory of holomorphic functions of several complex variables is applied
in proving a multidimensional variant of a theorem involving an exponential
boundedness criterion for the classical moment problem. A theorem of Petersen
concerning the relation between the multidimensional and one-dimensional moment
problems is extended for half-lines and compact subsets of the real line. These
results are used to solve the moment problem for the quantum phase space
observables generated by the number states.Comment: 13 pages, submitted to Reports on Mathematical Physic
Positive sesquilinear form measures and generalized eigenvalue expansions
Positive operator measures (with values in the space of bounded operators on
a Hilbert space) and their generalizations, mainly positive sesquilinear form
measures, are considered with the aim of providing a framework for their
generalized eigenvalue type expansions. Though there are formal similarities
with earlier approaches to special cases of the problem, the paper differs e.g.
from standard rigged Hilbert space constructions and avoids the introduction of
nuclear spaces. The techniques are predominantly measure theoretic and hence
the Hilbert spaces involved are separable. The results range from a Naimark
type dilation result to direct integral representations and a fairly concrete
generalized eigenvalue expansion for unbounded normal operators.Comment: 23 pages, to appear in J. Math. Anal. App
The Finnish Biodiversity Information Facility as a best-practice model for biodiversity data infrastructures
Biodiversity informatics has advanced rapidly with the maturation of major biodiversity data infrastructures (BDDIs), such as the Global Biodiversity Information Facility sharing unprecedented data volumes. Nevertheless, taxonomic, temporal and spatial data coverage remains unsatisfactory. With an increasing data need, the global BDDIs require continuous inflow from local data mobilisation, and national BDDIs are being developed around the world. The global BDDIs are specialised in certain data types or data life cycle stages which, despite possible merits, renders the BDDI landscape fragmented and complex. That this often is repeated at the national level creates counterproductive redundancy, complicates user services, and frustrates funders. Here, we present the Finnish Biodiversity Information Facility (FinBIF) as a model of an all-inclusive BDDI. It integrates relevant data types and phases of the data life cycle, manages them under one IT architecture, and distributes the data through one service portal under one brand. FinBIF has experienced diverse funder engagement and rapid user uptake. Therefore, we suggest the integrated and inclusive approach be adopted in national BDDI development.peerReviewe
Review of LTCC technology for millimeter waves and photonics
VTT Technical Research Centre of Finland Ltd. has developed and utilized Low Temperature Co-fired Ceramic (LTCC) technology for about 25 years. This paper presents our activities related to photonics and millimetre-waves, including also a relevant literature survey. First a short summary of the technology is given. Especially, the unique features of LTCC technology are described in more details. In addition, several examples have been given to show the validity of LTCC technology in these high-performance fields
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