scholarly journals Environment-assisted bosonic quantum communications

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Stefano Pirandola ◽  
Carlo Ottaviani ◽  
Christian S. Jacobsen ◽  
Gaetana Spedalieri ◽  
Samuel L. Braunstein ◽  
...  
Keyword(s):  
Quantum Key Distribution ◽  
Quantum Communication ◽  
Continuous Variable ◽  
Markovian Model ◽  
Quantum Communications ◽  
Case Scenario ◽  
Bipartite Entanglement ◽  
Worst Case ◽  
Entanglement Distribution ◽  
First Time

AbstractWe consider a quantum relay that is used by two parties to perform several continuous-variable protocols of quantum communication, from entanglement distribution (swapping and distillation) to quantum teleportation, and quantum key distribution. The theory of these protocols is suitably extended to a non-Markovian model of decoherence characterized by correlated Gaussian noise in the bosonic environment. In the worst-case scenario where bipartite entanglement is completely lost at the relay, we show that the various protocols can be reactivated by the assistance of classical (separable) correlations in the environment. In fact, above a critical amount, these correlations are able to guarantee the distribution of a weaker form of entanglement (quadripartite), which can be localized by the relay into a stronger form (bipartite) that is exploitable by the parties. Our findings are confirmed by a proof-of-principle experiment where we show, for the first time, that memory effects in the environment can drastically enhance the performance of a quantum relay, well beyond the single-repeater bound for quantum and private communications.

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 Proposal for space-borne quantum memories for global quantum networking

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Mustafa Gündoğan ◽  
Jasminder S. Sidhu ◽  
Victoria Henderson ◽  
Luca Mazzarella ◽  
Janik Wolters ◽  
...  
Keyword(s):  
Quantum Communication ◽  
Global Scale ◽  
Space Systems ◽  
Quantum Communications ◽  
Communication Links ◽  
Probabilistic Detection ◽  
Entanglement Distribution ◽  
Near Term ◽  
Quantum Internet ◽  
Memory Characteristics

AbstractGlobal-scale quantum communication links will form the backbone of the quantum internet. However, exponential loss in optical fibres precludes any realistic application beyond few hundred kilometres. Quantum repeaters and space-based systems offer solutions to overcome this limitation. Here, we analyse the use of quantum memory (QM)-equipped satellites for quantum communication focussing on global range repeaters and memory-assisted (MA-) QKD, where QMs help increase the key rate by synchronising otherwise probabilistic detection events. We demonstrate that satellites equipped with QMs provide three orders of magnitude faster entanglement distribution rates than existing protocols based on fibre-based repeaters or space systems without QMs. We analyse how entanglement distribution performance depends on memory characteristics, determine benchmarks to assess the performance of different tasks and propose various architectures for light-matter interfaces. Our work provides a roadmap to realise unconditionally secure quantum communications over global distances with near-term technologies.

Continuous Variable Entanglement Distribution for Long-Distance Quantum Communication

2013 ◽  
Vol 30 (6) ◽  
pp. 060302 ◽  
Author(s):  
Jun-Jun Zhao ◽  
Xiao-Min Guo ◽  
Xu-Yang Wang ◽  
Ning Wang ◽  
Yong-Min Li ◽  
...  
Keyword(s):  
Quantum Communication ◽  
Continuous Variable ◽  
Long Distance ◽  
Entanglement Distribution

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 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 Performance Improvement of Atmospheric Continuous-Variable Quantum Key Distribution with Untrusted Source

Entropy ◽  
2021 ◽  
Vol 23 (6) ◽  
pp. 760
Author(s):  
Qin Liao ◽  
Gang Xiao ◽  
Shaoliang Peng
Keyword(s):  
Performance Improvement ◽  
Quantum Key Distribution ◽  
Quantum Communication ◽  
Key Distribution ◽  
Continuous Variable ◽  
Signal Source ◽  
Special Situation ◽  
Photon Subtraction ◽  
Non Gaussian ◽  
Atmospheric Channel

Atmospheric continuous-variable quantum key distribution (ACVQKD) has been proven to be secure theoretically with the assumption that the signal source is well protected by the sender so that it cannot be compromised. However, this assumption is quite unpractical in realistic quantum communication system. In this work, we investigate a practical situation in which the signal source is no longer protected by the legitimate parts, but is exposed to the untrusted atmospheric channel. We show that the performance of ACVQKD is reduced by removing the assumption, especially when putting the untrusted source at the middle of the channel. To improve the performance of the ACVQKD with the untrusted source, a non-Gaussian operation, called photon subtraction, is subsequently introduced. Numerical analysis shows that the performance of ACVQKD with an untrusted source can be improved by properly adopting the photon subtraction operation. Moreover, a special situation where the untrusted source is located in the middle of the atmospheric channel is also considered. Under direct reconciliation, we find that its performance can be significantly improved when the photon subtraction operation is manipulated by the sender.

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 Quantum communications in a moderate-to-strong turbulent space

2021 ◽  
Author(s):  
Masoud Ghalaii ◽  
Stefano Pirandola
Keyword(s):  
Free Space ◽  
Quantum Key Distribution ◽  
Continuous Variable ◽  
Optical Channel ◽  
Weak Turbulence ◽  
Free Space Optical ◽  
Quantum Communications ◽  
Long Distance ◽  
Atmospheric Extinction ◽  
Pointing Errors

Abstract Since the invention of the laser in the 60s, one of the most fundamental communication channels has been the free-space optical channel. For this type of channel, a number of effects generally need to be considered, including diffraction, refraction, atmospheric extinction, pointing errors and, most importantly, turbulence. Because of all these adverse features, the free-space channel is more difficult to study than a stable fiber-based link. For the same reasons, only recently it has been possible to establish the ultimate performances achievable in quantum communications via free-space channels. Differently from previous literature, mainly focused on the regime of weak turbulence, this work considers the free-space optical channel in the more challenging regime of moderate-to-strong turbulence. This regime may occur in long-distance free-space links on the ground, in uplink to high-altitude platform systems (HAPS) and, more interestingly, in downlink from near-horizon satellites. In such a regime we rigorously investigate ultimate limits for quantum communications and show that composable keys can be extracted using continuous variable quantum key distribution. In particular, we apply our results to downlink from satellites at large zenith angles, for which not only turbulence is strong but also refraction causes non-trivial effects in terms of trajectory elongation.

scholarly journals On Global Quantum Communication Networking

Entropy ◽  
2020 ◽  
Vol 22 (8) ◽  
pp. 831
Author(s):  
Ivan B. Djordjevic
Keyword(s):  
Optical Networks ◽  
Cyber Security ◽  
Autonomous Vehicles ◽  
Quantum Communication ◽  
Cluster State ◽  
Continuous Variable ◽  
Low Earth Orbit ◽  
Security Level ◽  
Next Generation ◽  
Quantum Communications

Research in quantum communications networks (QCNs), where multiple users desire to generate or transmit common quantum-secured information, is still in its beginning stage. To solve for the problems of both discrete variable- and continuous variable-quantum key distribution (QKD) schemes in a simultaneous manner as well as to enable the next generation of quantum communication networking, in this Special Issue paper we describe a scenario where disconnected terrestrial QCNs are coupled through low Earth orbit (LEO) satellite quantum network forming heterogeneous satellite–terrestrial QCN. The proposed heterogeneous QCN is based on the cluster state approach and can be used for numerous applications, including: (i) to teleport arbitrary quantum states between any two nodes in the QCN; (ii) to enable the next generation of cyber security systems; (iii) to enable distributed quantum computing; and (iv) to enable the next generation of quantum sensing networks. The proposed QCNs will be robust against various channel impairments over heterogeneous links. Moreover, the proposed QCNs will provide an unprecedented security level for 5G+/6G wireless networks, Internet of Things (IoT), optical networks, and autonomous vehicles, to mention a few.

Reducing Probabilistic Weather Forecasts to the Worst Case Scenario: Anchoring Effects

2008 ◽  
Author(s):  
Sonia Savelli ◽  
Susan Joslyn ◽  
Limor Nadav-Greenberg ◽  
Queena Chen
Keyword(s):  
Case Scenario ◽  
Worst Case ◽  
Weather Forecasts ◽  
Worst Case Scenario ◽  
Anchoring Effects
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