18,717 research outputs found
Finding and breaking the realistic rate-distance limit of continuous variable quantum key distribution
In this work, the rate-distance limit of continuous variable quantum key
distribution is studied. We find that the excess noise generated on Bob's side
and the method for calculating the excess noise restrict the rate-distance
limit. Then, a realistic rate-distance limit is found. To break the realistic
limit, a method for calculating the secret key rate using pure excess noise is
proposed. The improvement in the rate-distance limit due to a higher
reconciliation efficiency is analyzed. It is found that this improvement is
dependent on the excess noise. From a finite-size analysis, the monotonicity of
the Holevo bound versus the transmission efficiency is studied, and a tighter
rate-distance limit is presented.Comment: 5 pages,5 figure
Advantages of the coherent state compared with squeeze state in unidimensional continuous variable quantum key distribution
In this work, a comparison study between unidimensional (UD) coherent-state
and UD squeeze-state protocols is performed in the continuous variable quantum
key distribution domain. First, the UD squeeze-state protocol is proposed and
the equivalence between the prepare-and-measure and entanglement-based schemes
of UD squeeze-state protocol is proved. Then, the security of the UD
squeeze-state protocol under collective attack in realistic conditions is
analyzed. Lastly, the performances of the two UD protocols are analyzed. Based
on the uniform expressions established in our study, the squeeze-state and
coherent-state protocols can be analyzed simultaneously. Our results show that
the UD squeeze-state protocols are quite different from the two-dimensional
protocols in that the UD squeeze-state protocols have a poorer performance
compared with UD coherent-state protocols, which is opposite in the case of
two-dimensional protocols.Comment: 12 pages, 8 figures
On Reliability of Underwater Magnetic Induction Communications with Tri-Axis Coils
Underwater magnetic induction communications (UWMICs) provide a low-power and
high-throughput solution for autonomous underwater vehicles (AUVs), which are
envisioned to explore and monitor the underwater environment. UWMIC with
tri-axis coils increases the reliability of the wireless channel by exploring
the coil orientation diversity. However, the UWMIC channel is different from
typical fading channels and the mutual inductance information (MII) is not
always available. It is not clear the performance of the tri-axis coil MIMO
without MII. Also, its performances with multiple users have not been
investigated. In this paper, we analyze the reliability and multiplexing gain
of UWMICs with tri-axis coils by using coil selection. We optimally select the
transmit and receive coils to reduce the computation complexity and power
consumption and explore the diversity for multiple users. We find that without
using all the coils and MII, we can still achieve reliability. Also, the
multiplexing gain of UWMIC without MII is 5dB smaller than typical terrestrial
fading channels. The results of this paper provide a more power-efficient way
to use UWMICs with tri-axis coils
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