scholarly journals Parameter Optimization Based BPNN of Atmosphere Continuous-Variable Quantum Key Distribution

Entropy ◽  
2019 ◽  
Vol 21 (9) ◽  
pp. 908
Author(s):  
Yu Su ◽  
Ying Guo ◽  
Duan Huang
Keyword(s):  
Quantum Key Distribution ◽  
Signal To Noise Ratio ◽  
Back Propagation ◽  
Key Distribution ◽  
Back Propagation Neural Network ◽  
Continuous Variable ◽  
Secret Key ◽  
Quantum Communications ◽  
Atmospheric Channel ◽  
Crucial Part

The goal of continuous variable quantum key distribution (CVQKD) is to be diffusely used and adopted in diverse scenarios, so the adhibition of atmospheric channel will play a crucial part in constituting global secure quantum communications. Atmospheric channel transmittance is affected by many factors and does not vary linearly, leading to great changes in signal-to-noise ratio. It is crucial to choose the appropriate modulation variance under different turbulence intensities to acquire the optimal secret key rate. In this paper, the four-state protocol, back-propagation neural network (BPNN) algorithm was discussed in the proposed scheme. We employ BPNN to CVQKD, which could adjust the modulation variance to an optimum value for ensuring the system security and making the system performance optimal. The numerical results show that the proposed scheme is equipped to improve the secret key rate efficiently.

scholarly journals High-Rate Continuous-Variable Quantum Key Distribution with Orbital Angular Momentum Multiplexing

Entropy ◽  
2021 ◽  
Vol 23 (9) ◽  
pp. 1187
Author(s):  
Xinchao Ruan ◽  
Wenhao Shi ◽  
Guojun Chen ◽  
Wei Zhao ◽  
Hang Zhang ◽  
...  
Keyword(s):  
Angular Momentum ◽  
Orbital Angular Momentum ◽  
Quantum Key Distribution ◽  
Key Distribution ◽  
Continuous Variable ◽  
High Rate ◽  
Secret Key ◽  
Quantum Communications ◽  
Transmission Distance ◽  
Atmospheric Channel

The secret key rate is one of the main obstacles to the practical application of continuous-variable quantum key distribution (CVQKD). In this paper, we propose a multiplexing scheme to increase the secret key rate of the CVQKD system with orbital angular momentum (OAM). The propagation characteristics of a typical vortex beam, involving the Laguerre–Gaussian (LG) beam, are analyzed in an atmospheric channel for the Kolmogorov turbulence model. Discrete modulation is utilized to extend the maximal transmission distance. We show the effect of the transmittance of the beam over the turbulent channel on the secret key rate and the transmission distance. Numerical simulations indicate that the OAM multiplexing scheme can improve the performance of the CVQKD system and hence has potential use for practical high-rate quantum communications.

scholarly journals Continuous-Variable Quantum Key Distribution Robust Against Polarization-Dependent Loss

2019 ◽  
Vol 9 (18) ◽  
pp. 3937
Author(s):  
Ying Guo ◽  
Minglu Cai ◽  
Duan Huang
Keyword(s):  
Quantum Key Distribution ◽  
Transmission Rate ◽  
Signal To Noise Ratio ◽  
Key Distribution ◽  
Continuous Variable ◽  
Optical Signal ◽  
Orthogonal Polarization ◽  
Secret Key ◽  
Polarization Dependent Loss ◽  
Transmission Distance

Polarization is one of the physical characteristics of optical waves, and the polarization-division-multiplexing (PDM) scheme has gained much attraction thanks to its capability of achieving high transmission rate. In the PDM-based quantum key distribution (QKD), the key information could be encoded independently by the optical fields E x and E y , where the 2-dimensional modulation and orthogonal polarization multiplexing usually result in two-fold channel capacity. Unfortunately, the non-negligible polarization-dependent loss (PDL) caused by the crystal dichroism in optical devices may result in the signal distortion, leading to an imbalanced optical signal-to-noise ratio. Here, we present a polarization-pairwise coding (PPC) scheme for the PDM-based continuous-variable (CV) QKD systems to overcome the PDL problem. Numerical simulation results indicate that the PDL-induced performance degradation can be mitigated. In addition, the PPC scheme, tailored to be robust against a high level of PDL, offers a suitable solution to improve the performance of the PDM-based CVQKD in terms of the secret key rate and maximal transmission distance.

scholarly journals An Improved Slice Reconciliation Protocol for Continuous-Variable Quantum Key Distribution

Entropy ◽  
2021 ◽  
Vol 23 (10) ◽  
pp. 1317
Author(s):  
Xuan Wen ◽  
Qiong Li ◽  
Haokun Mao ◽  
Xiaojun Wen ◽  
Nan Chen
Keyword(s):  
Quantum Key Distribution ◽  
Short Distance ◽  
Signal To Noise Ratio ◽  
Finite Size ◽  
Key Distribution ◽  
Continuous Variable ◽  
Polar Codes ◽  
Noisy Channel ◽  
Secret Key ◽  
Finite Size Effects

Reconciliation is an essential procedure for continuous-variable quantum key distribution (CV-QKD). As the most commonly used reconciliation protocol in short-distance CV-QKD, the slice error correction (SEC) allows a system to distill more than 1 bit from each pulse. However, the quantization efficiency is greatly affected by the noisy channel with a low signal-to-noise ratio (SNR), which usually limits the secure distance to about 30 km. In this paper, an improved SEC protocol, named Rotated-SEC (RSEC), is proposed through performing a random orthogonal rotation on the raw data before quantization, and deducing a new estimator for the quantized sequences. Moreover, the RSEC protocol is implemented with polar codes. The experimental results show that the proposed protocol can reach up to a quantization efficiency of about 99%, and maintain at around 96% even at the relatively low SNRs (0.5,1), which theoretically extends the secure distance to about 45 km. When implemented with the polar codes with a block length of 16 Mb, the RSEC achieved a reconciliation efficiency of above 95%, which outperforms all previous SEC schemes. In terms of finite-size effects, we achieved a secret key rate of 7.83×10−3 bits/pulse at a distance of 33.93 km (the corresponding SNR value is 1). These results indicate that the proposed protocol significantly improves the performance of SEC and is a competitive reconciliation scheme for the CV-QKD system.

scholarly journals Performance Analysis of Continuous-Variable Quantum Key Distribution with Multi-Core Fiber

2018 ◽  
Vol 8 (10) ◽  
pp. 1951 ◽  
Author(s):  
Fei Li ◽  
Hai Zhong ◽  
Yijun Wang ◽  
Ye Kang ◽  
Duan Huang ◽  
...  
Keyword(s):  
Performance Analysis ◽  
Quantum Key Distribution ◽  
Security Analysis ◽  
Key Distribution ◽  
Continuous Variable ◽  
Excess Noise ◽  
Secret Key ◽  
Quantum Communications ◽  
Core Fiber ◽  
Channel Wavelength

Performance analysis of continuous-variable quantum key distribution (CVQKD) has been one of the focuses of quantum communications. In this paper, we propose an approach to enhancing the secret rate of CVQKD with the multi-core fiber (MCF) system that transmits multiple spatial modes simultaneously. The excess noise contributed by the inter-core crosstalk between cores can be effectively suppressed by quantum channel wavelength management, leading to the performance improvement of the MCF-based CVQKD system. In the security analysis, we perform numerical simulations for the Gaussian-modulated coherent state CVQKD protocol, considering simultaneously the extra insert loss of fan-in/fan-out (FIFO), which is the extra optical device that should be used at the input and the output of the fiber. Simulation results show that the performance of the one-way and two-way protocols for each core are slightly degraded because of the insert loss of the FIFO, but the total secret key rate can be increased, whereas the performance of the measurement-device-independent CVQKD protocol will be degraded due to the effect of the insert loss of the FIFO. These results may provide theoretical foundation for the space-division multiplexing CVQKD system.

scholarly journals Performance Improvement of Discretely Modulated Continuous-Variable Quantum Key Distribution with Untrusted Source via Heralded Hybrid Linear Amplifier

Entropy ◽  
2020 ◽  
Vol 22 (8) ◽  
pp. 882
Author(s):  
Kunlin Zhou ◽  
Xuelin Wu ◽  
Yun Mao ◽  
Zhiya Chen ◽  
Qin Liao ◽  
...  
Keyword(s):  
Communication Networks ◽  
Quantum Key Distribution ◽  
Signal To Noise Ratio ◽  
Key Distribution ◽  
High Gain ◽  
Continuous Variable ◽  
Secret Key ◽  
Transmission Distance ◽  
Linear Amplifier ◽  
Maximum Transmission

In practical quantum communication networks, the scheme of continuous-variable quantum key distribution (CVQKD) faces a challenge that the entangled source is controlled by a malicious eavesdropper, and although it still can generate a positive key rate and security, its performance needs to be improved, especially in secret key rate and maximum transmission distance. In this paper, we proposed a method based on the four-state discrete modulation and a heralded hybrid linear amplifier to enhance the performance of CVQKD where the entangled source originates from malicious eavesdropper. The four-state CVQKD encodes information by nonorthogonal coherent states in phase space. It has better transmission distance than Gaussian modulation counterpart, especially at low signal-to-noise ratio (SNR). Moreover, the hybrid linear amplifier concatenates a deterministic linear amplifier (DLA) and a noiseless linear amplifier (NLA), which can improve the probability of amplification success and reduce the noise penalty caused by the measurement. Furthermore, the hybrid linear amplifier can raise the SNR of CVQKD and tune between two types of performance for high-gain mode and high noise-reduction mode, therefore it can extend the maximal transmission distance while the entangled source is untrusted.

scholarly journals A novel error correction protocol for continuous variable quantum key distribution

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Kadir Gümüş ◽  
Tobias A. Eriksson ◽  
Masahiro Takeoka ◽  
Mikio Fujiwara ◽  
Masahide Sasaki ◽  
...  
Keyword(s):  
Error Correction ◽  
Quantum Key Distribution ◽  
Ldpc Codes ◽  
Key Distribution ◽  
Continuous Variable ◽  
Early Termination ◽  
Parity Check ◽  
Secret Key ◽  
Ldpc Decoder ◽  
And Performance

AbstractReconciliation is a key element of continuous-variable quantum key distribution (CV-QKD) protocols, affecting both the complexity and performance of the entire system. During the reconciliation protocol, error correction is typically performed using low-density parity-check (LDPC) codes with a single decoding attempt. In this paper, we propose a modification to a conventional reconciliation protocol used in four-state protocol CV-QKD systems called the multiple decoding attempts (MDA) protocol. MDA uses multiple decoding attempts with LDPC codes, each attempt having fewer decoding iteration than the conventional protocol. Between each decoding attempt we propose to reveal information bits, which effectively lowers the code rate. MDA is shown to outperform the conventional protocol in regards to the secret key rate (SKR). A 10% decrease in frame error rate and an 8.5% increase in SKR are reported in this paper. A simple early termination for the LDPC decoder is also proposed and implemented. With early termination, MDA has decoding complexity similar to the conventional protocol while having an improved SKR.

scholarly journals Security Analysis of Discrete-Modulated Continuous-Variable Quantum Key Distribution over Seawater Channel

2019 ◽  
Vol 9 (22) ◽  
pp. 4956 ◽  
Author(s):  
Xinchao Ruan ◽  
Hang Zhang ◽  
Wei Zhao ◽  
Xiaoxue Wang ◽  
Xuan Li ◽  
...  
Keyword(s):  
Quantum Key Distribution ◽  
Secure Communication ◽  
Security Analysis ◽  
Finite Size ◽  
Key Distribution ◽  
Continuous Variable ◽  
Heterodyne Detection ◽  
Secret Key ◽  
Transmission Distance ◽  
Better Than

We investigate the optical absorption and scattering properties of four different kinds of seawater as the quantum channel. The models of discrete-modulated continuous-variable quantum key distribution (CV-QKD) in free-space seawater channel are briefly described, and the performance of the four-state protocol and the eight-state protocol in asymptotic and finite-size cases is analyzed in detail. Simulation results illustrate that the more complex is the seawater composition, the worse is the performance of the protocol. For different types of seawater channels, we can improve the performance of the protocol by selecting different optimal modulation variances and controlling the extra noise on the channel. Besides, we can find that the performance of the eight-state protocol is better than that of the four-state protocol, and there is little difference between homodyne detection and heterodyne detection. Although the secret key rate of the protocol that we propose is still relatively low and the maximum transmission distance is only a few hundred meters, the research on CV-QKD over the seawater channel is of great significance, which provides a new idea for the construction of global secure communication network.

Short-wave infrared continuous-variable quantum key distribution over satellite-to-submarine channels

2022 ◽  
Author(s):  
Qingquan Peng ◽  
Qin Liao ◽  
Hai Zhong ◽  
Junkai Hu ◽  
Ying Guo
Keyword(s):  
Quantum Key Distribution ◽  
Key Distribution ◽  
Short Wave ◽  
Continuous Variable ◽  
Sea Surface ◽  
Quantum Communications ◽  
Submarine Channels ◽  
Alternative Scheme ◽  
Transmission Distance ◽  
Short Wave Infrared

Abstract The trans-media transmission of quantum pulse is one of means of free-space transmission which can be applied in continuous-variable quantum key distribution (CVQKD) system. In traditional implementations for atmospheric channels, the 1500-to-1600-nm pulse is regarded as an ideal quantum pulse carrier. Whereas, the underwater transmission of this pulses tends to suffer from severe attenuation, which inevitably deteriorates the security of the whole CVQKD system. In this paper, we propose an alternative scheme for implementations of CVQKD over satellite-to-submarine channels. We estimate the parameters of the trans-media channels, involving atmosphere, sea surface and seawater and find that the short-wave infrared performs well in the above channels. The 450 nm pulse is used for generations of quantum signal carriers to accomplish quantum communications through atmosphere, sea surface and seawater channels. Numerical simulations show that the proposed scheme can achieve the transmission distance of 600 km. In addition, we demonstrate that non-Gaussian operations can further lengthen its maximal transmission distance, which contributes to the establishment of practical global quantum networks.

scholarly journals Improving Underwater Continuous-Variable Measurement-Device-Independent Quantum Key Distribution via Zero-Photon Catalysis

Entropy ◽  
2020 ◽  
Vol 22 (5) ◽  
pp. 571
Author(s):  
Yuang Wang ◽  
Shanhua Zou ◽  
Yun Mao ◽  
Ying Guo
Keyword(s):  
Quantum Key Distribution ◽  
Single Photon ◽  
Elevation Angle ◽  
Key Distribution ◽  
Continuous Variable ◽  
Secret Key ◽  
Underwater Communications ◽  
Measurement Device ◽  
Transmission Distance ◽  
Measurement Device Independent

Underwater quantumkey distribution (QKD) is tough but important formodern underwater communications in an insecure environment. It can guarantee secure underwater communication between submarines and enhance safety for critical network nodes. To enhance the performance of continuous-variable quantumkey distribution (CVQKD) underwater in terms ofmaximal transmission distance and secret key rate as well, we adopt measurement-device-independent (MDI) quantum key distribution with the zero-photon catalysis (ZPC) performed at the emitter of one side, which is the ZPC-based MDI-CVQKD. Numerical simulation shows that the ZPC-involved scheme, which is a Gaussian operation in essence, works better than the single photon subtraction (SPS)-involved scheme in the extreme asymmetric case. We find that the transmission of the ZPC-involved scheme is longer than that of the SPS-involved scheme. In addition, we consider the effects of temperature, salinity and solar elevation angle on the system performance in pure seawater. The maximal transmission distance decreases with the increase of temperature and the decrease of sunlight elevation angle, while it changes little over a broad range of salinity

scholarly journals SECURITY OF A NEW TWO-WAY CONTINUOUS-VARIABLE QUANTUM KEY DISTRIBUTION PROTOCOL

2012 ◽  
Vol 10 (05) ◽  
pp. 1250059 ◽  
Author(s):  
MAOZHU SUN ◽  
XIANG PENG ◽  
YUJIE SHEN ◽  
HONG GUO
Keyword(s):  
Quantum Key Distribution ◽  
Key Distribution ◽  
Continuous Variable ◽  
Excess Noise ◽  
Noisy Channel ◽  
Quantum Channels ◽  
Secret Key ◽  
Transmission Distance ◽  
The Family ◽  
The One

The original two-way continuous-variable quantum-key-distribution (CV-QKD) protocols [S. Pirandola, S. Mancini, S. Lloyd and S. L. Braunstein, Nat. Phys. 4 (2008) 726] give the security against the collective attack on the condition of the tomography of the quantum channels. We propose a family of new two-way CV-QKD protocols and prove their security against collective entangling cloner attacks without the tomography of the quantum channels. The simulation result indicates that the new protocols maintain the same advantage as the original two-way protocols whose tolerable excess noise surpasses that of the one-way CV-QKD protocol. We also show that all sub-protocols within the family have higher secret key rate and much longer transmission distance than the one-way CV-QKD protocol for the noisy channel.

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