scholarly journals Controlling excess noise in fiber-optics continuous-variable quantum key distribution

2005 ◽  
Vol 72 (5) ◽  
Author(s):  
Jérôme Lodewyck ◽  
Thierry Debuisschert ◽  
Rosa Tualle-Brouri ◽  
Philippe Grangier
Keyword(s):  
Fiber Optics ◽  
Quantum Key Distribution ◽  
Key Distribution ◽  
Continuous Variable ◽  
Excess Noise

scholarly journals Demonstration of high-speed and low-complexity continuous variable quantum key distribution system with local local oscillator

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Shengjun Ren ◽  
Shuai Yang ◽  
Adrian Wonfor ◽  
Ian White ◽  
Richard Penty
Keyword(s):  
Distribution System ◽  
Repetition Rate ◽  
Quantum Key Distribution ◽  
Optimization Technique ◽  
Key Distribution ◽  
Local Oscillator ◽  
Continuous Variable ◽  
Noise Model ◽  
System Level ◽  
Excess Noise

AbstractWe present an experimental demonstration of the feasibility of the first 20 + Mb/s Gaussian modulated coherent state continuous variable quantum key distribution system with a locally generated local oscillator at the receiver (LLO-CVQKD). To increase the signal repetition rate, and hence the potential secure key rate, we equip our system with high-performance, wideband devices and design the components to support high repetition rate operation. We have successfully trialed the signal repetition rate as high as 500 MHz. To reduce the system complexity and correct for any phase shift during transmission, reference pulses are interleaved with quantum signals at Alice. Customized monitoring software has been developed, allowing all parameters to be controlled in real-time without any physical setup modification. We introduce a system-level noise model analysis at high bandwidth and propose a new ‘combined-optimization’ technique to optimize system parameters simultaneously to high precision. We use the measured excess noise, to predict that the system is capable of realizing a record 26.9 Mb/s key generation in the asymptotic regime over a 15 km signal mode fibre. We further demonstrate the potential for an even faster implementation.

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.

scholarly journals Sub-Gbps Key Rate Four-State Continuous-Variable Quantum Key Distribution within Metropolitan Area

2021 ◽  
Author(s):  
Heng Wang ◽  
Yang Li ◽  
Yaodi Pi ◽  
Yan Pan ◽  
Yun Shao ◽  
...  
Keyword(s):  
Metropolitan Area ◽  
Quantum Key Distribution ◽  
Security Analysis ◽  
Key Distribution ◽  
Continuous Variable ◽  
High Rate ◽  
Excess Noise ◽  
Analysis Method ◽  
Secret Key ◽  
High Efficient

Abstract Continuous-variable quantum key distribution (CVQKD) has potential advantages of high secret key rate, which is very suitable for high-speed metropolitan network application. However, the reported highest secret key rates of the CVQKD systems up to now are limited in a few Mbps. Here, we address the fundamental experimental problems and demonstrate a single-carrier four-state CVQKD with sub-Gbps key rate within metropolitan area. In the demonstrated four-state CVQKD using local local oscillator, an ultra-low level of excess noise is obtained and a high efficient post-processing setup is designed for practically extracting the final secure keys. Thus, the achieved secure key rates are 190.54 Mbps and 137.76 Mbps and 52.48 Mbps using linear channel assuming security analysis method and 233.87 Mbps, 133.6 Mbps and 21.53 Mbps using semidefinite programming security analysis method over transmission distances of 5 km, 10 km and 25 km, respectively. This record-breaking result increases the previous secret key rate record by an order of magnitude, which is sufficient to achieve the one-time pad cryptographic task. Our work shows the road for future high-rate and large-scale CVQKD deployment in secure broadband metropolitan and access networks.

scholarly journals Practical Security Analysis of Reference Pulses for Continuous-Variable Quantum Key Distribution

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Wei Zhao ◽  
Ronghua Shi ◽  
Duan Huang
Keyword(s):  
Quantum Key Distribution ◽  
Beam Splitter ◽  
Security Analysis ◽  
Key Distribution ◽  
Continuous Variable ◽  
Excess Noise ◽  
Secret Key ◽  
Bayesian Algorithm ◽  
Robustness To Noise ◽  
Practical Security

AbstractBy manipulating the reference pulses amplitude, a security vulnerability is caused by self-reference continuous-variable quantum key distribution. In this paper, we formalize an attack strategy for reference pulses, showing that the proposed attack can compromise the practical security of CVQKD protocol. In this scheme, before the beam splitter attack, Eve intercepts the reference pulses emitted by Alice, using Bayesian algorithm to estimate phase shifts. Subsequently, other reference pulses are re-prepared and resubmitted to Bob. In simulations, Bayesian algorithm effectively estimates the phase drifts and has the high robustness to noise. Therefore, the eavesdropper can bias the excess noise due to the intercept-resend attack and the beam splitter attack. And Alice and Bob believe that their excess noise is below the null key threshold and can still share a secret key. Consequently, the proposed attack shows that its practical security can be compromised by transmitting the reference pulses in the continuous-variable quantum key distribution protocol.

scholarly journals Single-quadrature continuous-variable quantum key distribution

2016 ◽  
Vol 16 (13&14) ◽  
pp. 1081-1095
Author(s):  
Tobias Gehring ◽  
Christian S. Jacobsen ◽  
Ulrik L. Andersen
Keyword(s):  
Quantum Key Distribution ◽  
Coherent States ◽  
Key Distribution ◽  
Continuous Variable ◽  
Low Noise ◽  
Excess Noise ◽  
Quadrature Modulation ◽  
Amplitude Modulator

Most continuous-variable quantum key distribution schemes are based on the Gaussian modulation of coherent states followed by continuous quadrature detection using homodyne detectors. In all previous schemes, the Gaussian modulation has been carried out in conjugate quadratures thus requiring two independent modulators for their implementations. Here, we propose and experimentally test a largely simplified scheme in which the Gaussian modulation is performed in a single quadrature. The scheme is shown to be asymptotically secure against collective attacks, and considers a specific attack using asymmetric preparation and excess noise. We find that this protocol is considerably more sensitive to noise than other CVQKD schemes, as a consequence of the simplified implementation. A single-quadrature modulation approach renders the need for a costly amplitude modulator unnecessary, and thus facilitates commercialization of continuous-variable quantum key distribution, provided that the low noise requirement can be achieved.

DISCRETELY MODULATED CONTINUOUS-VARIABLE QUANTUM KEY DISTRIBUTION WITH A NONDETERMINISTIC NOISELESS AMPLIFIER

2013 ◽  
Vol 11 (04) ◽  
pp. 1350037 ◽  
Author(s):  
JIAN FANG ◽  
YUAN LU ◽  
PENG HUANG ◽  
GUANGQIANG HE ◽  
GUIHUA ZENG
Keyword(s):  
Quantum Key Distribution ◽  
Key Distribution ◽  
Continuous Variable ◽  
Excess Noise ◽  
Secret Key ◽  
Transmission Distance ◽  
Linear Amplifier ◽  
Detection Stage ◽  
Maximum Transmission ◽  
Better Than

In this paper, we first study a generalized protocol of discrete modulation for continuous-variable quantum key distribution with N coherent states in a Gaussian lossy and noisy channel and investigate its performance against collective attacks. We find that discrete modulation protocols with more than eight states do not perform better than the eight-state protocol. Then, we study the improvement of this protocol by using a nondeterministic noiseless linear amplifier (NLA) on Bob's detection stage. Results indicate that a NLA with gain g can extend the maximum transmission distance by 50 log 10g2 km and can increase the maximal tolerable excess noise. With the reconciliation efficiency β, we find the gain of NLA has a maximal value defined as g max and by adjusting the gain to about βg max one can have the best improvement on secret key rate.

scholarly journals Practical Security Bounds against Trojan Horse Attacks in Continuous-Variable Quantum Key Distribution

2020 ◽  
Vol 10 (21) ◽  
pp. 7788
Author(s):  
Yaxi Pan ◽  
Ling Zhang ◽  
Duan Huang
Keyword(s):  
Quantum Key Distribution ◽  
Information Leakage ◽  
Bright Light ◽  
Key Distribution ◽  
Continuous Variable ◽  
Trojan Horse ◽  
Excess Noise ◽  
Secret Key ◽  
Real Component ◽  
Light Pulses

As the existence of non-zero reflection coefficients in the real component of continuous-variable quantum key distribution (CV-QKD) systems, Eve can probe the system by sending the bright light pulses into Alice’s set-up. With the analysis of back-reflections, Eve only takes a few back-reflected photons to intercept information and obtain the raw key bit. In this paper, the attack problems are converted into the information leakage problems. First, we analyzed the Trojan horse attacks with different wavelengths and confirmed its side effects, such as crosstalk and anti-Stokes Raman scattering, by a numerical simulation. Then, based on the wavelength-dependent property of beam splitter, we presented a practical way to estimate the deviation of shot noise and therefore correct the excess noise by inserting different wavelength pulses under joint attacks. Finally, we specified the security bounds of the system through quantifying the excess noise bounds caused by the Trojan horse attacks and provided a theoretical reference for the secret key transmission of system. As a consequence, the transmission errors within the security bounds can be negligible and the legitimate users will not perceive the presence of Eve.

scholarly journals Enhancing of Self-Referenced Continuous-Variable Quantum Key Distribution with Virtual Photon Subtraction

Entropy ◽  
2018 ◽  
Vol 20 (8) ◽  
pp. 578 ◽  
Author(s):  
Hai Zhong ◽  
Yijun Wang ◽  
Xudong Wang ◽  
Qin Liao ◽  
Xiaodong Wu ◽  
...  
Keyword(s):  
Quantum Key Distribution ◽  
Virtual Photon ◽  
Key Distribution ◽  
Continuous Variable ◽  
Excess Noise ◽  
Electronic Noise ◽  
Reference Pulse ◽  
Transmission Distance ◽  
Amplitude Modulator ◽  
Photon Subtraction

The scheme of the self-referenced continuous-variable quantum key distribution (SR CV-QKD) has been experimentally demonstrated. However, because of the finite dynamics of Alice’s amplitude modulator, there will be an extra excess noise that is proportional to the amplitude of the reference pulse, while the maximal transmission distance of this scheme is positively correlated with the amplitude of the reference pulse. Therefore, there is a trade-off between the maximal transmission distance and the amplitude of the reference pulse. In this paper, we propose the scheme of SR CV-QKD with virtual photon subtraction, which not only has no need for the use of a high intensity reference pulse to improve the maximal transmission distance, but also has no demand of adding complex physical operations to the original self-referenced scheme. Compared to the original scheme, our simulation results show that a considerable extension of the maximal transmission distance can be obtained when using a weak reference pulse, especially for one-photon subtraction. We also find that our scheme is sensible with the detector’s electronic noise at reception. A longer maximal transmission distance can be achieved for lower electronic noise. Moreover, our scheme has a better toleration of excess noise compared to the original self-referenced scheme, which implies the advantage of using virtual photon subtraction to increase the maximal tolerable excess noise for distant users. These results suggest that our scheme can make the SR CV-QKD from the laboratory possible for practical metropolitan area application.

Noise-enhanced CVQKD with untrusted source

2017 ◽  
Vol 31 (16) ◽  
pp. 1750143 ◽  
Author(s):  
Xiaoqun Wang ◽  
Chunhui Huang
Keyword(s):  
Quantum Key Distribution ◽  
Additive Noise ◽  
Key Distribution ◽  
Continuous Variable ◽  
Excess Noise ◽  
Transmission Distance ◽  
Simulation Results ◽  
The Impact ◽  
Maximum Transmission

The performance of one-way and two-way continuous variable quantum key distribution (CVQKD) protocols can be increased by adding some noise on the reconciliation side. In this paper, we propose to add noise at the reconciliation end to improve the performance of CVQKD with untrusted source. We derive the key rate of this case and analyze the impact of the additive noise. The simulation results show that the optimal additive noise can improve the performance of the system in terms of maximum transmission distance and tolerable excess noise.

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