3,374 research outputs found
Communicating via ignorance: Increasing communication capacity via superposition of order
Classically, no information can be transmitted through a depolarising, that
is a completely noisy, channel. We show that by combining a depolarising
channel with another channel in an indefinite causal order---that is, when
there is superposition of the order that these two channels were applied---it
becomes possible to transmit significant information. We consider two limiting
cases. When both channels are fully-depolarising, the ideal limit is
communication of 0.049 bits; experimentally we achieve
bits. When one channel is fully-depolarising,
and the other is a known unitary, the ideal limit is communication of 1 bit. We
experimentally achieve 0.640.02 bits. Our results offer intriguing
possibilities for future communication strategies beyond conventional quantum
Shannon theory
Optimally combining dynamical decoupling and quantum error correction
We show how dynamical decoupling (DD) and quantum error correction (QEC) can
be optimally combined in the setting of fault tolerant quantum computing. To
this end we identify the optimal generator set of DD sequences designed to
protect quantum information encoded into stabilizer subspace or subsystem
codes. This generator set, comprising the stabilizers and logical operators of
the code, minimizes a natural cost function associated with the length of DD
sequences. We prove that with the optimal generator set the restrictive
local-bath assumption used in earlier work on hybrid DD-QEC schemes, can be
significantly relaxed, thus bringing hybrid DD-QEC schemes, and their
potentially considerable advantages, closer to realization.Comment: 6 pages, 1 figur
Ocorrência de Diadiplosis multifila (Diptera: Cecidomyiidae) associada à Planococcus citri (Hemiptera: Pseudococcidae) em videira no Semiárido brasileiro.
O objetivo deste trabalho foi identificar a ocorrência de inimigos naturais associados a populações de P. citri na cultura da videira. Foram realizadas coletas em áreas de produção de uvas finas de mesa no município de Petrolina-PE.SICONBIOL 2013
Efficient quantum computing with weak measurements
Projective measurements with high quantum efficiency is often assumed to be
required for efficient circuit based quantum computing. We argue that this is
not the case and show that this fact has actually be known previously though
not deeply explored. We examine this issue by giving an example of how to
perform the quantum ordering finding algorithm efficiently using non-local weak
measurements given that the measurements used are of bounded weakness and some
fixed but arbitrary probability of success less than unity is required. We also
show that it is possible to perform the same computation with only local weak
measurements but this must necessarily introduce an exponential overhead
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