scholarly journals Coherent phase transfer for real-world twin-field quantum key distribution

2022 ◽  
Vol 13 (1) ◽  
Author(s):  
Cecilia Clivati ◽  
Alice Meda ◽  
Simone Donadello ◽  
Salvatore Virzì ◽  
Marco Genovese ◽  
...  
Keyword(s):  
Real World ◽  
Quantum Key Distribution ◽  
Phase Transfer ◽  
Key Distribution ◽  
Channel Length ◽  
Quantum Communications ◽  
Optical Length ◽  
Long Distance ◽  
Quantum Bit ◽  
Duty Cycles

AbstractQuantum mechanics allows distribution of intrinsically secure encryption keys by optical means. Twin-field quantum key distribution is one of the most promising techniques for its implementation on long-distance fiber networks, but requires stabilizing the optical length of the communication channels between parties. In proof-of-principle experiments based on spooled fibers, this was achieved by interleaving the quantum communication with periodical stabilization frames. In this approach, longer duty cycles for the key streaming come at the cost of a looser control of channel length, and a successful key-transfer using this technique in real world remains a significant challenge. Using interferometry techniques derived from frequency metrology, we develop a solution for the simultaneous key streaming and channel length control, and demonstrate it on a 206 km field-deployed fiber with 65 dB loss. Our technique reduces the quantum-bit-error-rate contributed by channel length variations to <1%, representing an effective solution for real-world quantum communications.

scholarly journals Long-Distance Free-Space Measurement-Device-Independent Quantum Key Distribution

2020 ◽  
Vol 125 (26) ◽  
Author(s):  
Yuan Cao ◽  
Yu-Huai Li ◽  
Kui-Xing Yang ◽  
Yang-Fan Jiang ◽  
Shuang-Lin Li ◽  
...  
Keyword(s):  
Free Space ◽  
Quantum Key Distribution ◽  
Key Distribution ◽  
Long Distance ◽  
Measurement Device ◽  
Space Measurement ◽  
Measurement Device Independent

scholarly journals Full daylight quantum-key-distribution at 1550 nm enabled by integrated silicon photonics

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
M. Avesani ◽  
L. Calderaro ◽  
M. Schiavon ◽  
A. Stanco ◽  
C. Agnesi ◽  
...  
Keyword(s):  
Optical Fibers ◽  
Silicon Photonics ◽  
Free Space ◽  
Quantum Key Distribution ◽  
Cost Effective ◽  
Key Distribution ◽  
Global Scale ◽  
Secret Key ◽  
Quantum Bit ◽  
Integrated Silicon Photonics

AbstractThe future envisaged global-scale quantum-communication network will comprise various nodes interconnected via optical fibers or free-space channels, depending on the link distance. The free-space segment of such a network should guarantee certain key requirements, such as daytime operation and the compatibility with the complementary telecom-based fiber infrastructure. In addition, space-to-ground links will require the capability of designing light and compact quantum devices to be placed in orbit. For these reasons, investigating available solutions matching all the above requirements is still necessary. Here we present a full prototype for daylight quantum key distribution at 1550 nm exploiting an integrated silicon-photonics chip as state encoder. We tested our prototype in the urban area of Padua (Italy) over a 145 m-long free-space link, obtaining a quantum bit error rate around 0.5% and an averaged secret key rate of 30 kbps during a whole sunny day (from 11:00 to 20:00). The developed chip represents a cost-effective solution for portable free-space transmitters and a promising resource to design quantum optical payloads for future satellite missions.

scholarly journals Long-distance quantum key distribution secure against coherent attacks

Optica ◽  
2017 ◽  
Vol 4 (1) ◽  
pp. 163 ◽  
Author(s):  
Bernd Fröhlich ◽  
Marco Lucamarini ◽  
James F. Dynes ◽  
Lucian C. Comandar ◽  
Winci W.-S. Tam ◽  
...  
Keyword(s):  
Quantum Key Distribution ◽  
Key Distribution ◽  
Long Distance

scholarly journals DECOY STATE QUANTUM KEY DISTRIBUTION

2005 ◽  
Vol 03 (supp01) ◽  
pp. 143-143 ◽  
Author(s):  
HOI-KWONG LO
Keyword(s):  
Quantum Key Distribution ◽  
Secure Communication ◽  
Key Distribution ◽  
Generation Rate ◽  
Key Generation ◽  
Long Distance ◽  
Decoy State ◽  
Bb84 Protocol ◽  
High Loss ◽  
Statistical Fluctuations

Quantum key distribution (QKD) allows two parties to communicate in absolute security based on the fundamental laws of physics. Up till now, it is widely believed that unconditionally secure QKD based on standard Bennett-Brassard (BB84) protocol is limited in both key generation rate and distance because of imperfect devices. Here, we solve these two problems directly by presenting new protocols that are feasible with only current technology. Surprisingly, our new protocols can make fiber-based QKD unconditionally secure at distances over 100km (for some experiments, such as GYS) and increase the key generation rate from O(η2) in prior art to O(η) where η is the overall transmittance. Our method is to develop the decoy state idea (first proposed by W.-Y. Hwang in "Quantum Key Distribution with High Loss: Toward Global Secure Communication", Phys. Rev. Lett. 91, 057901 (2003)) and consider simple extensions of the BB84 protocol. This part of work is published in "Decoy State Quantum Key Distribution", . We present a general theory of the decoy state protocol and propose a decoy method based on only one signal state and two decoy states. We perform optimization on the choice of intensities of the signal state and the two decoy states. Our result shows that a decoy state protocol with only two types of decoy states—a vacuum and a weak decoy state—asymptotically approaches the theoretical limit of the most general type of decoy state protocols (with an infinite number of decoy states). We also present a one-decoy-state protocol as a special case of Vacuum+Weak decoy method. Moreover, we provide estimations on the effects of statistical fluctuations and suggest that, even for long distance (larger than 100km) QKD, our two-decoy-state protocol can be implemented with only a few hours of experimental data. In conclusion, decoy state quantum key distribution is highly practical. This part of work is published in "Practical Decoy State for Quantum Key Distribution", . We also have done the first experimental demonstration of decoy state quantum key distribution, over 15km of Telecom fibers. This part of work is published in "Experimental Decoy State Quantum Key Distribution Over 15km", .

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.

Quantum cryptography

2009 ◽  
Author(s):  
Stephen Barnett
Keyword(s):  
Quantum Information ◽  
Quantum Cryptography ◽  
Quantum Key Distribution ◽  
Communication Systems ◽  
Information Technologies ◽  
Key Distribution ◽  
Julius Caesar ◽  
Secure Communications ◽  
Quantum Communications ◽  
History Of

The practical implementation of quantum information technologies requires, for the most part, highly advanced and currently experimental procedures. One exception is quantum cryptography, or quantum key distribution, which has been successfully demonstrated in many laboratories and has reached an advanced level of development. It will probably become the first commercial application of quantum information. In quantum key distribution, Alice and Bob exploit a quantum channel to create a secret shared key comprising a random string of binary digits. This key can then be used to protect a subsequent communication between them. The principal idea is that the secrecy of the key distribution is ensured by the laws of quantum physics. Proving security for practical communication systems is a challenging problem and requires techniques that are beyond the scope of this book. At a fundamental level, however, the ideas are simple and may readily be understood with the knowledge we have already acquired. Quantum cryptography is the latest idea in the long history of secure (and not so secure) communications and, if it is to develop, it will have to compete with existing technologies. For this reason we begin with a brief survey of the history and current state of the art in secure communications before turning to the possibilities offered by quantum communications. The history of cryptography is a long and fascinating one. As a consequence of the success or, more spectacularly, the failure of ciphers, wars have been fought, battles decided, kingdoms won, and heads lost. In the information age, ciphers and cryptosystems have become part of everyday life; we use them to protect our computers, to shop over the Internet, and to access our money via an ATM (automated teller machine). One of the oldest and simplest of all ciphers is the transposition or Caesarean cipher (attributed to Julius Caesar), in which the letters are shifted by a known (and secret) number of places in the alphabet. If the shift is 1, for example, then A is enciphered as B, B→C, · · ·, Y→Z, Z→A. A shift of five places leads us to make the replacements A→F, B→G, · · ·, Y→D, Z→E.

scholarly journals The Influence of Signal Polarization on Quantum Bit Error Rate for Subcarrier Wave Quantum Key Distribution Protocol

Entropy ◽  
2020 ◽  
Vol 22 (12) ◽  
pp. 1393
Author(s):  
Andrei Gaidash ◽  
Anton Kozubov ◽  
Svetlana Medvedeva ◽  
George Miroshnichenko
Keyword(s):  
Optical Fiber ◽  
Bit Error Rate ◽  
Error Rate ◽  
Quantum Key Distribution ◽  
Key Distribution ◽  
Stokes Parameters ◽  
Second Phase ◽  
Quantum Bit ◽  
Quantum Bit Error Rate ◽  
Quantum Key Distribution Protocol

In this paper, we consider the influence of a divergence of polarization of a quantum signal transmitted through an optical fiber channel on the quantum bit error rate of the subcarrier wave quantum key distribution protocol. Firstly, we investigate the dependence of the optical power of the signal on the modulation indices’ difference after the second phase modulation of the signal. Then we consider the Liouville equation with regard to relaxation in order to develop expressions of the dynamics of the Stokes parameters. As a result, we propose a model that describes quantum bit error rate for the subcarrier wave quantum key distribution depending on the characteristics of the optical fiber. Finally, we propose several methods for minimizing quantum bit error rate.

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