250 research outputs found
Source monitoring for continuous-variable quantum key distribution
The noise in optical source needs to be characterized for the security of
continuous-variable quantum key distribution (CVQKD). Two feasible schemes,
based on either active optical switch or passive beamsplitter are proposed to
monitor the variance of source noise, through which, Eve's knowledge can be
properly estimated. We derive the security bounds for both schemes against
collective attacks in the asymptotic case, and find that the passive scheme
performs better.Comment: The first version. 9 pages and 4 figure
Randomness Quantification for Quantum Random Number Generation Based on Detection of Amplified Spontaneous Emission Noise
The amplified spontaneous emission (ASE) noise has been extensively studied
and employed to build quantum random number generators (QRNGs). While the
previous relative works mainly focus on the realization and verification of the
QRNG system, the comprehensive physical model and randomness quantification for
the general detection of the ASE noise are still incomplete, which is essential
for the quantitative security analysis. In this paper, a systematical physical
model for the emission, detection and acquisition of the ASE noise with added
electronic noise is developed and verified, based on which the numerical
simulations are performed under various setups and the simulation results all
significantly fit well with the corresponding experimental data. Then, a
randomness quantification method and the corresponding experimentally
verifiable approach are proposed and validated, which quantifies the randomness
purely resulted from the quantum process and improves the security analysis for
the QRNG based on the detection of the ASE noise. The physical model and the
randomness quantification method proposed in this paper are of significant
feasibility and applicable for the QRNG system with randomness originating from
the detection of the photon number with arbitrary distributions
Forecasting the chaotic dynamics of external cavity semiconductor lasers
Chaotic time series prediction has been paid intense attention in recent years due to its important applications. Herein, we present a single-node photonic reservoir computing approach to forecasting the chaotic behavior of external cavity semiconductor lasers using only observed data. In the reservoir, we employ a semiconductor laser with delay as the sole nonlinear physical node. By investigating the effect of the reservoir meta-parameters on the prediction performance, we numerically demonstrate that there exists an optimal meta-parameter space for forecasting optical-feedback-induced chaos. Simulation results demonstrate that using our method, the upcoming chaotic time series can be continuously predicted for a time period in excess of 2 ns with a normalized mean squared error lower than 0.1. This proposed method only utilizes simple nonlinear semiconductor lasers and thus offers a hardware-friendly approach for complex chaos prediction. In addition, this work may provide a roadmap for the meta-parameter selection of a delay-based photonic reservoir to obtain optimal prediction performance
Sub-Mbps key-rate continuous-variable quantum key distribution with local-local-oscillator over 100 km fiber
We experimentally demonstrated a sub-Mbps key rate Gaussian-modulated
coherent-state continuous-variable quantum key distribution (CV-QKD) over 100
km transmission distance. To efficiently control the excess noise, the quantum
signal and the pilot tone are co-transmitted in fiber channel based on
wide-band frequency and polarization multiplexing methods. Furthermore, a
high-accuracy data-assisted time domain equalization algorithm is carefully
designed to compensate the phase noise and polarization variation in low
signal-to-noise ratio. The asymptotic secure key rate (SKR) of the demonstrated
CV-QKD is experimentally evaluated to be 10.36 Mbps, 2.59 Mbps, and 0.69 Mbps
over transmission distance of 50 km, 75 km, and 100 km, respectively. The
experimental demonstrated CV-QKD system significantly improves transmission
distance and SKR compared to the state-of-art GMCS CV-QKD experimental results,
and shows the potential for long-distance and high-speed secure quantum key
distribution.Comment: 4 pages, 7 figure
Analysis of factors affecting the effectiveness of oil spill clean-up: A bayesian entwork approach
Ship-related marine oil spills pose a significant threat to the environment, and while it may not be possible to prevent such incidents entirely, effective clean-up efforts can minimize their impact on the environment. The success of these clean-up efforts is influenced by various factors, including accident-related factors such as the type of accident, location, and environmental weather conditions, as well as emergency response-related factors such as available resources and response actions. To improve targeted and effective responses to oil spills resulting from ship accidents and enhance oil spill emergency response methods, it is essential to understand the factors that affect their effectiveness. In this study, a data-driven Bayesian network (TAN) analysis approach was used with data from the U.S. Coast Guard (USCG) to identify the key accident-related factors that impact oil spill clean-up performance. The analysis found that the amount of discharge, severity, and the location of the accident are the most critical factors affecting the clean-up ratio. These findings are significant for emergency management and planning oil spill clean-up efforts.Postprint (published version
High-speed Gaussian modulated continuous-variable quantum key distribution with a local local oscillator based on pilot-tone-assisted phase compensation
A high-speed Gaussian modulated continuous-variable quantum key distribution
(CVQKD) with a local local oscillator (LLO) is experimentally demonstrated
based on pilot-tone-assisted phase compensation. In the proposed scheme, the
frequency-multiplexing and polarization-multiplexing techniques are used for
the separate transmission and heterodyne detection between quantum signal and
pilot tone, guaranteeing no crosstalk from strong pilot tone to weak quantum
signal and different detection requirements of low-noise for quantum signal and
high-saturation limitation for pilot tone. Moreover, compared with the
conventional CVQKD based on homodyne detection, the proposed LLO-CVQKD scheme
can measure X and P quadrature simultaneously using heterodyne detection
without need of extra random basis selection. Besides, the phase noise, which
contains the fast-drift phase noise due to the relative phase of two
independent lasers and the slow-drift phase noise introduced by quantum channel
disturbance, has been compensated experimentally in real time, so that a low
level of excess noise with a 25km optical fiber channel is obtained for the
achievable secure key rate of 7.04 Mbps in the asymptotic regime and 1.85 Mbps
under the finite-size block of 10^7
Experimental Demonstration of High-Rate Discrete-Modulated Continuous-Variable Quantum Key Distribution System
A high-rate continuous-variable quantum key distribution (CV-QKD) system
based on high-order discrete modulation is experimentally investigated. With
the help of the novel system scheme, effective digital signal processing
algorithms and advanced analytical security proof method, the transmission
results of 5 km, 10 km, 25 km, and 50 km are achieved for the 1 GBaud optimized
quantum signals. Correspondingly, the asymptotic secret key rate (SKR) is
288.421 Mbps, 159.395 Mbps, 50.004 Mbps and 7.579 Mbps for discrete Gaussian
(DG) 64QAM, and 326.708 Mbps, 179.348 Mbps, 50.623 Mbps and 9.212 Mbps for DG
256QAM. Under the same parameters, the achieved SKRs of DG 256QAM is almost
same to ideal Gaussian modulation. In this case, the demonstrated high-rate
discrete modulated CV-QKD system has the application potential for high speed
security communication under tens of kilometers.Comment: 5 pages, 5 figure
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