42 research outputs found
Topological color codes on Union Jack lattices: A stable implementation of the whole Clifford group
We study the error threshold of topological color codes on Union Jack
lattices that allow for the full implementation of the whole Clifford group of
quantum gates. After mapping the error-correction process onto a statistical
mechanical random 3-body Ising model on a Union Jack lattice, we compute its
phase diagram in the temperature-disorder plane using Monte Carlo simulations.
Surprisingly, topological color codes on Union Jack lattices have similar error
stability than color codes on triangular lattices, as well as the Kitaev toric
code. The enhanced computational capabilities of the topological color codes on
Union Jack lattices with respect to triangular lattices and the toric code
demonstrate the inherent robustness of this implementation.Comment: 8 pages, 4 figures, 1 tabl
Tricolored Lattice Gauge Theory with Randomness: Fault-Tolerance in Topological Color Codes
We compute the error threshold of color codes, a class of topological quantum
codes that allow a direct implementation of quantum Clifford gates, when both
qubit and measurement errors are present. By mapping the problem onto a
statistical-mechanical three-dimensional disordered Ising lattice gauge theory,
we estimate via large-scale Monte Carlo simulations that color codes are stable
against 4.5(2)% errors. Furthermore, by evaluating the skewness of the Wilson
loop distributions, we introduce a very sensitive probe to locate first-order
phase transitions in lattice gauge theories.Comment: 12 pages, 5 figures, 1 tabl
Generalized Toric Codes Coupled to Thermal Baths
We have studied the dynamics of a generalized toric code based on qudits at
finite temperature by finding the master equation coupling the code's degrees
of freedom to a thermal bath. As a consequence, we find that for qutrits new
types of anyons and thermal processes appear that are forbidden for qubits.
These include creation, annihilation and diffusion throughout the system code.
It is possible to solve the master equation in a short-time regime and find
expressions for the decay rates as a function of the dimension of the
qudits. Although we provide an explicit proof that the system relax to the
Gibbs state for arbitrary qudits, we also prove that above a certain crossing
temperature, qutrits initial decay rate is smaller than the original case for
qubits. Surprisingly this behavior only happens with qutrits and not with other
qudits with .Comment: Revtex4 file, color figures. New Journal of Physics' versio
Epidemiologic survey in Swiss group-housed breeding rabbits: extent of lesions and potential risk factors
In Switzerland, group-housing for breeding rabbit does is not explicitly required by law, but label programmes, as well as the general public and animal welfare groups, are advocating it. Although group-housing is of great benefit to the gregariously living rabbits, the establishment of a social hierarchy within the group might lead to stress and lesions. In the present epidemiological study, lesions were scored twice on 30% of the breeding does on all 28 commercial Swiss farms with group-housed breeding does. Additionally, a detailed questionnaire was filled out with all producers to determine risk factors potentially associated with lesions. Data were analysed using hierarchical proportional odds models. About 33% of the does examined had lesions, including wounds that were almost healed and small scratches. Severe lesions were counted on 9% of the animals. Differences between seasons in lesions score were identified, with the extent of lesions being higher in summer than in spring. Fewer lesions occurred on farms on which mastitis was more common. More lesions were found on farms where the does were isolated between littering and artificial insemination than on farms without isolation. According to the producers, most of the aggression occurred directly after the isolation phase when the does were regrouped again. We conclude that lesions in group-housed breeding does might be reduced by appropriate reproductive management