3,023 research outputs found
Experimental Violation of Two-Party Leggett-Garg Inequalities with Semi-weak Measurements
We generalize the derivation of Leggett-Garg inequalities to systematically
treat a larger class of experimental situations by allowing multi-particle
correlations, invasive detection, and ambiguous detector results. Furthermore,
we show how many such inequalities may be tested simultaneously with a single
setup. As a proof of principle, we violate several such two-particle
inequalities with data obtained from a polarization-entangled biphoton state
and a semi-weak polarization measurement based on Fresnel reflection. We also
point out a non- trivial connection between specific two-party Leggett-Garg
inequality violations and convex sums of strange weak values.Comment: 4 pages, 6 figure
Improving Einstein-Podolsky-Rosen Steering Inequalities with State Information
We discuss the relationship between entropic Einstein-Podolsky-Rosen
(EPR)-steering inequalities and their underlying uncertainty relations, along
with the hypothesis that improved uncertainty relations lead to tighter
EPR-steering inequalities. In particular, we discuss how the intrinsic
uncertainty in a mixed quantum state is used to improve existing uncertainty
relations and how this information affects one's ability to witness
EPR-steering. As an example, we consider the recent improvement (using a
quantum memory) to the entropic uncertainty relation between pairs of discrete
observables (Nat. Phys. 6, 659 (2010)) and show that a trivial substitution of
the tighter bound in the steering inequality leads to contradictions, due in
part to the fact that the improved bound depends explicitly on the state being
measured. By considering the assumptions that enter into the development of a
steering inequality, we derive correct steering inequalities from these
improved uncertainty relations and find that they are identical to ones already
developed (Phys. Rev. A, 87, 062103 (2013)). In addition, we consider how one
can use the information about the quantum state to improve our ability to
witness EPR-steering, and develop a new symmetric EPR-steering inequality as a
result.Comment: 6 page
Uncertainty Relation for Mutual Information
We postulate the existence of a universal uncertainty relation between the
quantum and classical mutual informations between pairs of quantum systems.
Specifically, we propose that the sum of the classical mutual information,
determined by two mutually unbiased pairs of observables, never exceeds the
quantum mutual information. We call this the complementary-quantum correlation
(CQC) relation and prove its validity for pure states, for states with one
maximally mixed subsystem, and for all states when one measurement is minimally
disturbing. We provide results of a Monte Carlo simulation suggesting the CQC
relation is generally valid. Importantly, we also show that the CQC relation
represents an improvement to an entropic uncertainty principle in the presence
of a quantum memory, and that it can be used to verify an achievable secret key
rate in the quantum one-time pad cryptographic protocol.Comment: 6 pages, 2 figure
Bounding the entanglement of N qubits with only four measurements
We introduce a new measure for the genuinely N-partite (all-party)
entanglement of N-qubit states using the trace distance metric, and find an
algebraic formula for the GHZ-diagonal states. We then use this formula to show
how the all-party entanglement of experimentally produced GHZ states of an
arbitrary number of qubits may be bounded with only four measurements
Exact bond percolation thresholds in two dimensions
Recent work in percolation has led to exact solutions for the site and bond
critical thresholds of many new lattices. Here we show how these results can be
extended to other classes of graphs, significantly increasing the number and
variety of solved problems. Any graph that can be decomposed into a certain
arrangement of triangles, which we call self-dual, gives a class of lattices
whose percolation thresholds can be found exactly by a recently introduced
triangle-triangle transformation. We use this method to generalize Wierman's
solution of the bow-tie lattice to yield several new solutions. We also give
another example of a self-dual arrangement of triangles that leads to a further
class of solvable problems. There are certainly many more such classes.Comment: Accepted for publication in J. Phys
Hippocampal Infusion of Zeta Inhibitory Peptide Impairs Recent, but Not Remote, Recognition Memory in Rats.
Spatial memory in rodents can be erased following the infusion of zeta inhibitory peptide (ZIP) into the dorsal hippocampus via indwelling guide cannulas. It is believed that ZIP impairs spatial memory by reversing established late-phase long-term potentiation (LTP). However, it is unclear whether other forms of hippocampus-dependent memory, such as recognition memory, are also supported by hippocampal LTP. In the current study, we tested recognition memory in rats following hippocampal ZIP infusion. In order to combat the limited targeting of infusions via cannula, we implemented a stereotaxic approach for infusing ZIP throughout the dorsal, intermediate, and ventral hippocampus. Rats infused with ZIP 3-7 days after training on the novel object recognition task exhibited impaired object recognition memory compared to control rats (those infused with aCSF). In contrast, rats infused with ZIP 1 month after training performed similar to control rats. The ability to form new memories after ZIP infusions remained intact. We suggest that enhanced recognition memory for recent events is supported by hippocampal LTP, which can be reversed by hippocampal ZIP infusion
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