Security of the differential-quadrature-phase-shift quantum key distribution

Kawakami, Shun; Sasaki, Toshihiko; Koashi, Masato

doi:10.1103/physreva.94.022332

Cited by 11 publications

(30 citation statements)

References 28 publications

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“…The former simplifies the estimation of Eve's information, but requires an overly complicated QKD receiver setup [13][14][15][16] , making it impractical. The latter separates the signal from the differential phase shift protocol into blocks, each having a global phase that varies randomly, ensuring the protocol is immune against coherent attacks 17,18 . It does, however, stray from the main goal of DPR protocols to provide simpler QKD implementations, due to the phase randomization requirement that would ordinarily require extra system components.…”

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confidence: 99%

Manipulating photon coherence to enhance the security of distributed phase reference quantum key distribution

Roberts

Lucamarini

Dynes

et al. 2017

Applied Physics Letters

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Quantum key distribution (QKD) allows two users to communicate with theoretically provable secrecy by encoding information on photonic qubits. Current encoders are complex, however, which reduces their appeal for practical use and introduces potential vulnerabilities to quantum attacks. Distributed-phase-reference (DPR) systems were introduced as a simpler alternative, but have not yet been proven practically secure against all classes of attack. Here we demonstrate the first DPR QKD system with information-theoretic security. Using a novel light source, where the coherence between pulses can be controlled on a pulse-by-pulse basis, we implement a secure DPR system based on the differential quadrature phase shift protocol. The system is modulator-free, does not require active stabilization or a complex receiver, and also offers megabit per second key rates, almost three times higher than the standard Bennett-Brassard 1984 (BB84) protocol. This enhanced performance and security highlights the potential for DPR protocols to be adopted for real-world applications.Quantum key distribution (QKD) has developed strongly since the proposal of the first protocol in 1984 1-3 . The future could see widespread quantum networks similar to those in Tokyo 4 and Vienna 5 and global secure communication enabled by QKD over satellites 6 . These advances depend on the development of simple, cost-effective and high performance implementations. Innovations in both protocols and system hardware are required to achieve this.Nearly two decades after the inception of BennettBrassard 1984 (BB84) 1 , distributed phase reference (DPR) QKD was proposed, allowing for much simpler experimental implementations. The class includes the differential phase shift 7,8 and coherent-one-way 9,10 protocols. One advantage is that the transmitters needed to realize these DPR protocols can be made using off-the-shelf telecom lasers and modulators. However the benefit of their simpler implementation is outweighed by a seriously degraded performance when full security is taken into account 3,11,12 . To plug the security gap, two further DPR protocols were proposed: round-robin differential phase shift and differential quadrature phase shift (DQPS). The former simplifies the estimation of Eve's information, but requires an overly complicated QKD receiver setup 13-16 , making it impractical. The latter separates the signal from the differential phase shift protocol into blocks, each having a global phase that varies randomly, ensuring the protocol is immune against coherent attacks 17,18 . It does, however, stray from the main goal of DPR protocols to provide simpler QKD implementations, due to the phase randomization requirement that would ordinarily require extra system components. In this work we show it is possible to produce phase coherent and phase randomized pulses from a single device. This device is based on optical injection of one laser diode into another, removing the need for a phaserandomization component in DQPS by relying on the randomness pr...

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confidence: 99%

Manipulating photon coherence to enhance the security of distributed phase reference quantum key distribution

Roberts

Lucamarini

Dynes

et al. 2017

Applied Physics Letters

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“…which means that Eqs. (13) and (14) essentially hold true for the untagged rounds. Now we derive a key rate formula for the WCP BB84 protocol based on Eq.…”

Section: A the Wcp-bb84 Protocolmentioning

confidence: 84%

“…Under the assumptions for the source and measurement apparatus, the basic distributions used in the previous section, Eqs. (13) and (14), are still valid if we confine ourselves to the untagged rounds. Although the fact may be intuitively obvious for the WCP-BB84 protocol, here we give its mathematical justification since it helps when we treat a less intuitive protocol in Subsection IV C. We define a set of integers labeling the rounds in the protocol as N rep := {1, 2, ....n rep }.…”

Section: A the Wcp-bb84 Protocolmentioning

confidence: 96%

“…The first method to determine f (k X , n X , n tot ), whose utility we will emphasize throughout this paper, is based on Bernoulli sampling using the property of binomial distribution Eq. (13). This method adopts f (k X , n X ,…”

Section: (15)mentioning

confidence: 99%

“…5, we show numerical results of secure key rate per pulse l DQPS /(n rep L) as a function of overall transmittance η := η c η d to compare the DQPS protocol (L > 2) and the PE-BB84 protocol (L = 2). The solid curves represent the key rate with fixed pulse number n rep L = 10 7 , and the dashed curves represent the one for the asymptotic case, which is obtained in our previous work [13]. We assumed that Alice generates a weak coherent pulse of mean photon number µ.…”

Section: The Dqps Protocolmentioning

confidence: 99%

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Finite-key analysis for quantum key distribution with weak coherent pulses based on Bernoulli sampling

2017

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An essential step in quantum key distribution is the estimation of parameters related to the leaked amount of information, which is usually done by sampling of the communication data. When the data size is finite, the final key rate depends on how the estimation process handles statistical fluctuations. Many of the present security analyses are based on the method with simple random sampling, where hypergeometric distribution or its known bounds are used for the estimation. Here we propose a concise method based on Bernoulli sampling, which is related to binomial distribution. Our method is suitable for the BB84 protocol with weak coherent pulses, reducing the number of estimated parameters to achieve a higher key generation rate compared to the method with simple random sampling. We also applied the method to prove the security of the differentialquadrature-phase-shift (DQPS) protocol in the finite-key regime. The result indicates that, the advantage of the DQPS protocol over the phase-encoding BB84 protocol in terms of the key rate, which was previously confirmed in the asymptotic regime, persists in the finite-key regime.

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Advanced Laser Technology for Quantum Communications (Tutorial Review)

et al. 2021

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Quantum communications is the art of exchanging and manipulating information beyond the capabilities of our conventional technologies using the laws of quantum mechanics. With applications ranging from quantum computing to cryptographic systems with information-theoretic security, there is strong incentive to introduce quantum communications into many areas of our society. However, an important challenge is to develop viable technologies meeting the stringent requirements of low noise and high coherence for quantum state encoding, of high bit rate and low power for the integration with classical communication networks and of scalable and low-cost production for a practical wide-deployment. This tutorial presents recent advances in laser modulation technologies that have enabled the development of efficient and versatile light sources for quantum communications, with a particular focus on quantum key distribution (QKD). Such approaches have been successfully used to demonstrate several QKD protocols with state-of-the-art performance. The applications and experimental results are reviewed and interpreted in the light of a complete theoretical background, allowing the reader to model and simulate such sources.

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Security of the differential-quadrature-phase-shift quantum key distribution

Cited by 11 publications

References 28 publications

Manipulating photon coherence to enhance the security of distributed phase reference quantum key distribution

Manipulating photon coherence to enhance the security of distributed phase reference quantum key distribution

Finite-key analysis for quantum key distribution with weak coherent pulses based on Bernoulli sampling

Advanced Laser Technology for Quantum Communications (Tutorial Review)

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