62 research outputs found
Entanglement Wedge Cross Sections Require Tripartite Entanglement
We argue that holographic CFT states require a large amount of tripartite
entanglement, in contrast to the conjecture that their entanglement is mostly
bipartite. Our evidence is that this mostly-bipartite conjecture is in sharp
conflict with two well-supported conjectures about the entanglement wedge cross
section surface . If is related to either the CFT's reflected
entropy or its entanglement of purification, then those quantities can differ
from the mutual information at . We prove that this
implies holographic CFT states must have amounts
of tripartite entanglement. This proof involves a new Fannes-type inequality
for the reflected entropy, which itself has many interesting applications.Comment: 20 pages, 5 figures, comments added in v
Holographic Renyi Entropy from Quantum Error Correction
We study Renyi entropies in quantum error correcting codes and compare
the answer to the cosmic brane prescription for computing . We find that general operator
algebra codes have a similar, more general prescription. Notably, for the
AdS/CFT code to match the specific cosmic brane prescription, the code must
have maximal entanglement within eigenspaces of the area operator. This gives
us an improved definition of the area operator, and establishes a stronger
connection between the Ryu-Takayanagi area term and the edge modes in lattice
gauge theory. We also propose a new interpretation of existing holographic
tensor networks as area eigenstates instead of smooth geometries. This
interpretation would explain why tensor networks have historically had trouble
modeling the Renyi entropy spectrum of holographic CFTs, and it suggests a
method to construct holographic networks with the correct spectrum.Comment: 24 pages, 1 figure, V2: Fixed typos and revised explanation
Leading order corrections to the quantum extremal surface prescription
We show that a na\"{i}ve application of the quantum extremal surface (QES)
prescription can lead to paradoxical results and must be corrected at leading
order. The corrections arise when there is a second QES (with strictly larger
generalized entropy at leading order than the minimal QES), together with a
large amount of highly incompressible bulk entropy between the two surfaces. We
trace the source of the corrections to a failure of the assumptions used in the
replica trick derivation of the QES prescription, and show that a more careful
derivation correctly computes the corrections. Using tools from one-shot
quantum Shannon theory (smooth min- and max-entropies), we generalize these
results to a set of refined conditions that determine whether the QES
prescription holds. We find similar refinements to the conditions needed for
entanglement wedge reconstruction (EWR), and show how EWR can be reinterpreted
as the task of one-shot quantum state merging (using zero-bits rather than
classical bits), a task gravity is able to achieve optimally efficiently.Comment: 87 pages, 9 figures, 4 appendices; v2 fixed typo
An examination of interprofessional education in a pre‑registration children’s nursing course
Aim: This study set out to gain insight into views held by children's nursing students, lecturers and clinically based nurse mentors about interprofessional education (IPE). Method: A qualitative research design was undertaken. Small focus groups were held with pre-registration children's nursing students, and semi-structured interviews with university lecturers and clinically based nurse mentors to find out information about their understanding of IPE. Findings: Participants not only valued IPE, but they agreed that it had the potential to positively affect the care of children, young people and their families. Conclusion: It is important that professionals collaborate to ensure students receive high quality IPE learning experiences.Peer reviewe
Simple holographic models of black hole evaporation
Several recent papers have shown a close relationship between entanglement
wedge reconstruction and the unitarity of black hole evaporation in AdS/CFT.
The analysis of these papers however has a rather puzzling feature: all
calculations are done using bulk dynamics which are essentially those Hawking
used to predict information loss, but applying ideas from entanglement wedge
reconstruction seems to suggest a Page curve which is consistent with
information conservation. Why should two different calculations in the same
model give different answers for the Page curve?
In this note we present a new pair of models which clarify this situation.
Our first model gives a holographic illustration of unitary black hole
evaporation, in which the analogue of the Hawking radiation purifies itself as
expected, and this purification is reproduced by the entanglement wedge
analysis. Moreover a smooth black hole interior persists until the last stages
the evaporation process. Our second model gives an alternative holographic
interpretation of the situation where the bulk evolution leads to information
loss: unlike in the models proposed so far, this bulk information loss is
correctly reproduced by the entanglement wedge analysis. This serves as an
illustration that quantum extremal surfaces are in some sense kinematic: the
time-dependence of the entropy they compute depends on the choice of bulk
dynamics. In both models no bulk quantum corrections need to be considered:
classical extremal surfaces are enough to do the job. We argue that our first
model is the one which gives the right analogy for what actually happens to
evaporating black holes, but we also emphasize that any complete resolution of
the information problem will require an understanding of non-perturbative bulk
dynamics.Comment: 15 pages, 5 figures. v2: Improved the octopus picture. Also an
expanded discussion of the motivation for and lessons from the model
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