1,171 research outputs found
Universally-composable finite-key analysis for efficient four-intensity decoy-state quantum key distribution
We propose an efficient four-intensity decoy-state BB84 protocol and derive
concise security bounds for this protocol with the universally composable
finite-key analysis method. Comparing with the efficient three-intensity
protocol, we find that our efficient four-intensity protocol can increase the
secret key rate by at least . Particularly, this increasing rate of
secret key rate will be raised as the transmission distance increases. At a
large transmission distance, our efficient four-intensity protocol can improve
the performance of quantum key distribution profoundly.Comment: accepted by Eur. Phys. J.
Valley-Layer Coupling: A New Design Principle for Valleytronics
We introduce the concept of valley-layer coupling (VLC) in two-dimensional
materials, where the low-energy electronic states in the emergent valleys have
valley-contrasted layer polarization such that each state is spatially
localized on the top or bottom super-layer. The VLC enables a direct coupling
between valley and gate electric field, opening a new route towards
electrically controlled valleytronics. We analyze the symmetry requirements for
the system to host VLC, demonstrate our idea via first-principles calculations
and model analysis of a concrete 2D material example, and show that an
electric, continuous, wide-range, and switchable control of valley polarization
can be achieved by VLC. Furthermore, we find that systems with VLC can exhibit
other interesting physics, such as valley-contrasting linear dichroism and
optical selection of the electric polarization of interlayer excitons.Comment: 6 pages, 4 figure
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