1,133 research outputs found
On the correction of anomalous phase oscillation in entanglement witnesses using quantum neural networks
Entanglement of a quantum system depends upon relative phase in complicated
ways, which no single measurement can reflect. Because of this, entanglement
witnesses are necessarily limited in applicability and/or utility. We propose
here a solution to the problem using quantum neural networks. A quantum system
contains the information of its entanglement; thus, if we are clever, we can
extract that information efficiently. As proof of concept, we show how this can
be done for the case of pure states of a two-qubit system, using an
entanglement indicator corrected for the anomalous phase oscillation. Both the
entanglement indicator and the phase correction are calculated by the quantum
system itself acting as a neural network
Quantum state transfer with untuneable couplings
We present a general scheme for implementing bi-directional quantum state
transfer in a quantum swapping channel. Unlike many other schemes for quantum
computation and communication, our method does not require qubit couplings to
be switched on and off. The only control variable is the bias acting on
individual qubits. We show how to derive the parameters of the system (fixed
and variable) such that perfect state transfer can be achieved. Since these
parameters vary linearly with the pulse width, our scheme allows flexibility in
the time scales under which qubits evolve. Unlike quantum spin networks, our
scheme allows the transmission of several quantum states at a time, requiring
only a two qubit separation between quantum states. By pulsing the biases of
several qubits at the same time, we show that only eight bias control lines are
required to achieve state transfer along a channel of arbitrary length.
Furthermore, when the information to be transferred is purely classical in
nature, only three bias control lines are required, greatly simplifying the
circuit complexity
What a difference a term makes:the effect of educational attainment on marital outcomes in the UK
Abstract In the past, students in England and Wales born within the first 5 monthsof the academic year could leave school one term earlier than those born later inthe year. Focusing on women, those who were required to stay on an extra termmore frequently hold some academic qualification. Using having been required tostay on as an exogenous factor affecting academic attainment, we find that holding alow-level academic qualification has no effect on the probability of being currentlymarried for women aged 25 or above, but increases the probability of the husbandholding some academic qualification and being economically active.33 Halama
Comparative population genomics of latitudinal variation in \u3ci\u3eDrosophila simulans\u3c/i\u3e and \u3ci\u3eDrosophila melanogaster\u3c/i\u3e
Examples of clinal variation in phenotypes and genotypes across latitudinal transects have served as important models for understanding how spatially varying selection and demographic forces shape variation within species. Here, we examine the selective and demographic contributions to latitudinal variation through the largest comparative genomic study to date of Drosophila simulans and Drosophila melanogaster, with genomic sequence data from 382 individual fruit flies, collected across a spatial transect of 19 degrees latitude and at multiple time points over 2 years. Consistent with phenotypic studies, we find less clinal variation in D. simulans than D. melanogaster, particularly for the autosomes. Moreover, we find that clinally varying loci in D. simulans are less stable over multiple years than comparable clines in D. melanogaster. D. simulans shows a significantly weaker pattern of isolation by distance than D. melanogaster and we find evidence for a stronger contribution of migration to D. simulans population genetic structure. While population bottlenecks and migration can plausibly explain the differences in stability of clinal variation between the two species, we also observe a significant enrichment of shared clinal genes, suggesting that the selective forces associated with climate are acting on the same genes and phenotypes in D. simulans and D. melanogaster.
Includes supplementary materials
- …