773 research outputs found
Aspects of mutually unbiased bases in odd prime power dimensions
We rephrase the Wootters-Fields construction [Ann. Phys., {\bf 191}, 363
(1989)] of a full set of mutually unbiased bases in a complex vector space of
dimensions , where is an odd prime, in terms of the character
vectors of the cyclic group of order . This form may be useful in
explicitly writing down mutually unbiased bases for .Comment: 3 pages, latex, no figure
Probabilistic quantum multimeters
We propose quantum devices that can realize probabilistically different
projective measurements on a qubit. The desired measurement basis is selected
by the quantum state of a program register. First we analyze the
phase-covariant multimeters for a large class of program states, then the
universal multimeters for a special choice of program. In both cases we start
with deterministic but erroneous devices and then proceed to devices that never
make a mistake but from time to time they give an inconclusive result. These
multimeters are optimized (for a given type of a program) with respect to the
minimum probability of inconclusive result. This concept is further generalized
to the multimeters that minimize the error rate for a given probability of an
inconclusive result (or vice versa). Finally, we propose a generalization for
qudits.Comment: 12 pages, 3 figure
How well can you know the edge of a quantum pyramid?
We consider a symmetric quantum communication scenario in which the signal
states are edges of a quantum pyramid of arbitrary dimension and arbitrary
shape, and all edge states are transmitted with the same probability. The
receiver could employ different decoding strategies: he could minimize the
error probability, or discriminate without ambiguity, or extract the accessible
information. We state the optimal measurement scheme for each strategy. For
large parameter ranges, the standard square-root measurement does not extract
the information optimally.Comment: 13 pages, 5 figures, 1 tabl
Optimal Conclusive Discrimination of Two Non-orthogonal Pure Product Multipartite States Locally
We consider one copy of a quantum system prepared in one of two
non-orthogonal pure product states of multipartite distributed among separated
parties. We show that there exist protocols which obtain optimal probability in
the sense of conclusive discrimination by means of local operations and
classical communications(LOCC) as good as by global operations. Also, we show a
protocol which minimezes the average number of local operations. Our result
implies that two product pure multipartite states might not have the non-local
property though more than two can have.Comment: revtex, 3 pages, no figur
Standardized Monitoring of Post-Operative Morbidity and Mortality for the Evaluation of Thoracic Surgical Quality
The contact drag of towed demersal fishing gear components
This study was funded in part by Fisheries Innovation Scotland, project FIS02, and by the FP7 project BENTHIS (312088). It does not necessarily reflect the views of the European Commission and does not anticipate the Commission's future policy in this area.Peer reviewedPostprin
Modelling global-scale climate impacts of the late Miocene Messinian Salinity Crisis
Late Miocene tectonic changes in Mediterranean–Atlantic connectivity and climatic changes caused Mediterranean salinity to fluctuate dramatically, including a ten-fold increase and near-freshening. Recent proxy- and model-based evidence suggests that at times during this Messinian Salinity Crisis (MSC, 5.96–5.33 Ma), highly saline and highly fresh Mediterranean water flowed into the North Atlantic Ocean, whilst at others, no Mediterranean Outflow Water (MOW) reached the Atlantic. By running extreme, sensitivity-type experiments with a fully coupled ocean–atmosphere general circulation model, we investigate the potential of these various MSC MOW scenarios to impact global-scale climate.
The simulations suggest that although the effect remains relatively small, MOW had a greater influence on North Atlantic Ocean circulation and climate than it does today. We also find that depending on the presence, strength and salinity of MOW, the MSC could have been capable of cooling mid–high northern latitudes by a few degrees, with the greatest cooling taking place in the Labrador, Greenland–Iceland–Norwegian and Barents seas. With hypersaline MOW, a component of North Atlantic Deep Water formation shifts to the Mediterranean, strengthening the Atlantic Meridional Overturning Circulation (AMOC) south of 35° N by 1.5–6 Sv. With hyposaline MOW, AMOC completely shuts down, inducing a bipolar climate anomaly with strong cooling in the north (mainly −1 to −3 °C, but up to −8 °C) and weaker warming in the south (up to +0.5 to +2.7 °C).
These simulations identify key target regions and climate variables for future proxy reconstructions to provide the best and most robust test cases for (a) assessing Messinian model performance, (b) evaluating Mediterranean–Atlantic connectivity during the MSC and (c) establishing whether or not the MSC could ever have affected global-scale climate
Reduction Theorems for Optimal Unambiguous State Discrimination of Density Matrices
We present reduction theorems for the problem of optimal unambiguous state
discrimination (USD) of two general density matrices. We show that this problem
can be reduced to that of two density matrices that have the same rank and
are described in a Hilbert space of dimensions . We also show how to use
the reduction theorems to discriminate unambiguously between N mixed states (N
\ge 2).Comment: 6 pages, 1 figur
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