2,184 research outputs found
Unconditionally verifiable blind computation
Blind Quantum Computing (BQC) allows a client to have a server carry out a
quantum computation for them such that the client's input, output and
computation remain private. A desirable property for any BQC protocol is
verification, whereby the client can verify with high probability whether the
server has followed the instructions of the protocol, or if there has been some
deviation resulting in a corrupted output state. A verifiable BQC protocol can
be viewed as an interactive proof system leading to consequences for complexity
theory. The authors, together with Broadbent, previously proposed a universal
and unconditionally secure BQC scheme where the client only needs to be able to
prepare single qubits in separable states randomly chosen from a finite set and
send them to the server, who has the balance of the required quantum
computational resources. In this paper we extend that protocol with new
functionality allowing blind computational basis measurements, which we use to
construct a new verifiable BQC protocol based on a new class of resource
states. We rigorously prove that the probability of failing to detect an
incorrect output is exponentially small in a security parameter, while resource
overhead remains polynomial in this parameter. The new resource state allows
entangling gates to be performed between arbitrary pairs of logical qubits with
only constant overhead. This is a significant improvement on the original
scheme, which required that all computations to be performed must first be put
into a nearest neighbour form, incurring linear overhead in the number of
qubits. Such an improvement has important consequences for efficiency and
fault-tolerance thresholds.Comment: 46 pages, 10 figures. Additional protocol added which allows
arbitrary circuits to be verified with polynomial securit
Genuinely Multipartite Concurrence of N-qubit X-matrices
We find an algebraic formula for the N-partite concurrence of N qubits in an
X-matrix. X- matricies are density matrices whose only non-zero elements are
diagonal or anti-diagonal when written in an orthonormal basis. We use our
formula to study the dynamics of the N-partite entanglement of N remote qubits
in generalized N-party Greenberger-Horne-Zeilinger (GHZ) states. We study the
case when each qubit interacts with a partner harmonic oscillator. It is shown
that only one type of GHZ state is prone to entanglement sudden death; for the
rest, N-partite entanglement dies out momentarily. Algebraic formulas for the
entanglement dynamics are given in both cases
Equivalence of operator-splitting schemes for the integration of the Langevin equation
We investigate the equivalence of different operator-splitting schemes for
the integration of the Langevin equation. We consider a specific problem, so
called the directed percolation process, which can be extended to a wider class
of problems. We first give a compact mathematical description of the
operator-splitting method and introduce two typical splitting schemes that will
be useful in numerical studies. We show that the two schemes are essentially
equivalent through the map that turns out to be an automorphism. An associated
equivalent class of operator-splitting integrations is also defined by
generalizing the specified equivalence.Comment: 4 page
Psychosocial predictors of exclusive breastfeeding duration to six moths postpartum
The World Health Organization recommend that for optimal growth and development all infants worldwide should be exclusively breastfed for the first six months of life. Previous studies have identified that psychosocial factors are important for the maintenance of exclusive breastfeeding. This study aimed to examine the psychosocial factors associated with exclusive breastfeeding duration to six months postpartum. Method: 125 women completed questionnaires at three time points; 32 weeks gestation, two and six months postpartum. Self-efficacy, body attitude, psychological adjustment, attitude, intention, confidence, motivation and importance of exclusive breastfeeding and breastfeeding status were measured. Findings: At 32 weeks gestation a woman’s confidence to achieve exclusive breastfeeding was a predictor of exclusive breastfeeding to six months postpartum. At two months postpartum, psychological adjustment and self-efficacy were predictive of exclusive breastfeeding duration. At six months postpartum, psychological adjustment, self-efficacy, confidence to maintain and feeling fat were predictive of exclusive breastfeeding duration. Conclusion: Self-efficacy, psychological adjustment, body image, motivation and confidence are important for the maintenance of exclusive breastfeeding to six months. This has clinical application for health psychology as antenatal breastfeeding education and postpartum support may be strengthened by strategies that build a woman’s confidence to exclusively breastfeed
Psychosocial predictors of exclusive breastfeeding duration to six moths postpartum
The World Health Organization recommend that for optimal growth and development all infants worldwide should be exclusively breastfed for the first six months of life. Previous studies have identified that psychosocial factors are important for the maintenance of exclusive breastfeeding. This study aimed to examine the psychosocial factors associated with exclusive breastfeeding duration to six months postpartum. Method: 125 women completed questionnaires at three time points; 32 weeks gestation, two and six months postpartum. Self-efficacy, body attitude, psychological adjustment, attitude, intention, confidence, motivation and importance of exclusive breastfeeding and breastfeeding status were measured. Findings: At 32 weeks gestation a woman’s confidence to achieve exclusive breastfeeding was a predictor of exclusive breastfeeding to six months postpartum. At two months postpartum, psychological adjustment and self-efficacy were predictive of exclusive breastfeeding duration. At six months postpartum, psychological adjustment, self-efficacy, confidence to maintain and feeling fat were predictive of exclusive breastfeeding duration. Conclusion: Self-efficacy, psychological adjustment, body image, motivation and confidence are important for the maintenance of exclusive breastfeeding to six months. This has clinical application for health psychology as antenatal breastfeeding education and postpartum support may be strengthened by strategies that build a woman’s confidence to exclusively breastfeed
Improving the economic value of photographic screening for optical coherence tomography-detectable macular oedema : a prospective, multicentre, UK study
Peer reviewedPublisher PD
Collapsible Pushdown Parity Games
International audienceThis paper studies a large class of two-player perfect-information turn-based parity games on infinite graphs, namely those generated by collapsible pushdown automata. The main motivation for studying these games comes from the connections from collapsible pushdown automata and higher-order recursion schemes, both models being equi-expressive for generating infinite trees. Our main result is to establish the decidability of such games and to provide an effective representation of the winning region as well as of a winning strategy. Thus, the results obtained here provide all necessary tools for an in-depth study of logical properties of trees generated by collapsible pushdown automata/recursion schemes
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