683,379 research outputs found
Quantifying the resource of sharing a reference frame
We define a new quantity called refbit, which allows one to quantify the
resource of sharing a reference frame in quantum communication protocols. By
considering both asymptotic and nonasymptotic protocols we find relations
between refbits and other communication resources. We also consider the same
resources in encoded, reference-frame independent, form. This allows one to
rephrase and unify previous work on phase references, reference frames, and
superselection rules.Comment: Updated title as PRA did not accept the word "refbit" in the title:
PRA accepts neither neologisms (="a meaningless word coined by a psychotic",
according to Webster), nor novophasm
Milnor’s Conjecture on Monotonicity of Topological Entropy: results and questions
This note discusses Milnor’s conjecture on monotonicity of entropy and gives a short exposition of the ideas used in its proof which was obtained in joint work with Henk Bruin, see [BvS09]. At the end of this note we explore some related conjectures and questions
Calculation of percolation thresholds in high dimensions for fcc, bcc, and diamond lattices
In a recent article, Galam and Mauger proposed an invariant for site and bond
percolation thresholds, based on known values for twenty lattices (Eur. Phys.
J. B 1 (1998) 255-258). Here we give a larger list of values for more than
forty lattices in two to six dimensions. In this list are new results for fcc,
bcc, and diamond lattices in 4, 5, and 6 dimensions.
The list contains examples of lattices with equal site percolation
thresholds, but different bond percolation thresholds. These and other examples
show that there are deviations from the proposed invariant of up to 12% in two
dimensions, increasing to 69% in higher dimensions.Comment: 12 pages, 3 figures (EPS), LaTe
Quantum communication, reference frames and gauge theory
We consider quantum communication in the case that the communicating parties
not only do not share a reference frame but use imperfect quantum communication
channels, in that each channel applies some fixed but unknown unitary rotation
to each qubit. We discuss similarities and differences between reference frames
within that quantum communication model and gauge fields in gauge theory. We
generalize the concept of refbits and analyze various quantum communication
protocols within the communication model.Comment: pretty pointless, published nonetheles
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