14 research outputs found
The efficiencies of generating cluster states with weak non-linearities
We propose a scalable approach to building cluster states of matter qubits
using coherent states of light. Recent work on the subject relies on the use of
single photonic qubits in the measurement process. These schemes can be made
robust to detector loss, spontaneous emission and cavity mismatching but as a
consequence the overhead costs grow rapidly, in particular when considering
single photon loss. In contrast, our approach uses continuous variables and
highly efficient homodyne measurements. We present a two-qubit scheme, with a
simple bucket measurement system yielding an entangling operation with success
probability 1/2. Then we extend this to a three-qubit interaction, increasing
this probability to 3/4. We discuss the important issues of the overhead cost
and the time scaling. This leads to a "no-measurement" approach to building
cluster states, making use of geometric phases in phase space.Comment: 21 pages, to appear in special issue of New J. Phys. on
"Measurement-Based Quantum Information Processing
Cluster state preparation using gates operating at arbitrary success probabilities
Several physical architectures allow for measurement-based quantum computing
using sequential preparation of cluster states by means of probabilistic
quantum gates. In such an approach, the order in which partial resources are
combined to form the final cluster state turns out to be crucially important.
We determine the influence of this classical decision process on the expected
size of the final cluster. Extending earlier work, we consider different
quantum gates operating at various probabilites of success. For finite
resources, we employ a computer algebra system to obtain the provably optimal
classical control strategy and derive symbolic results for the expected final
size of the cluster. We identify two regimes: When the success probability of
the elementary gates is high, the influence of the classical control strategy
is found to be negligible. In that case, other figures of merit become more
relevant. In contrast, for small probabilities of success, the choice of an
appropriate strategy is crucial.Comment: 7 pages, 9 figures, contribution to special issue of New J. Phys. on
"Measurement-Based Quantum Information Processing". Replaced with published
versio
Vampires in the village Žrnovo on the island of Korčula: following an archival document from the 18th century
Središnja tema rada usmjerena je na raščlambu spisa pohranjenog u Državnom arhivu u Mlecima (fond: Capi del Consiglio de’ Dieci: Lettere di Rettori e di altre cariche) koji se odnosi na događaj iz 1748. godine u korčulanskom selu Žrnovo, kada su mještani – vjerujući da su se pojavili vampiri – oskvrnuli nekoliko mjesnih grobova. U radu se podrobno iznose osnovni podaci iz spisa te rečeni događaj analizira u širem društvenom kontekstu i prate se lokalna vjerovanja.The main interest of this essay is the analysis of the document from the State Archive in Venice (file: Capi del Consiglio de’ Dieci: Lettere di Rettori e di altre cariche) which is connected with the episode from 1748 when the inhabitants of the village Žrnove on the island of Korčula in Croatia opened tombs on the local cemetery in the fear of the vampires treating.
This essay try to show some social circumstances connected with this event as well as a local vernacular tradition concerning superstitions