16,840 research outputs found
Holographic Euclidean thermal correlator
In this paper, we compute holographic Euclidean thermal correlators of the
stress tensor and current from the AdS planar black hole. To this end,
we set up perturbative boundary value problems for Einstein's gravity and
Maxwell theory in the spirit of Gubser-Klebanov-Polyakov-Witten, with
appropriate gauge fixing and regularity boundary conditions at the horizon of
the black hole. The linearized Einstein equation and Maxwell equation in the
black hole background are related to the Heun equation of degenerate local
monodromy. Leveraging the connection relation of local solutions of the Heun
equation, we partly solve the boundary value problem and obtain exact two-point
thermal correlators for current and stress tensor in the scalar and
shear channels.Comment: 19 pages. References added. Some typos corrected. Some minor changes
in wordin
Numerical simulation of the optimal two-mode attacks for two-way continuous-variable quantum cryptography in reverse reconciliation
We analyze the security of the two-way continuous-variable quantum key
distribution protocol in reverse reconciliation against general two-mode
attacks, which represent all accessible attacks at fixed channel parameters.
Rather than against one specific attack model, the expression of secret key
rates of the two-way protocol are derived against all accessible attack models.
It is found that there is an optimal two-mode attack to minimize the
performance of the protocol in terms of both secret key rates and maximal
transmission distances. We identify the optimal two-mode attack, give the
specific attack model of the optimal two-mode attack and show the performance
of the two-way protocol against the optimal two-mode attack. Even under the
optimal two-mode attack, the performances of two-way protocol are still better
than the corresponding one-way protocol, which shows the advantage of making a
double use of the quantum channel and the potential of long-distance secure
communication using two-way protocol.Comment: 14 pages, 8 figure
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