scholarly journals Computing conditional entropies for quantum correlations

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Peter Brown ◽  
Hamza Fawzi ◽  
Omar Fawzi
Keyword(s):  
Quantum Key Distribution ◽  
Detection Efficiency ◽  
Conditional Entropy ◽  
Key Distribution ◽  
Quantum Correlations ◽  
Upper Bounds ◽  
Cryptographic Protocols ◽  
Quantum States ◽  
Security Proofs

AbstractThe rates of quantum cryptographic protocols are usually expressed in terms of a conditional entropy minimized over a certain set of quantum states. In particular, in the device-independent setting, the minimization is over all the quantum states jointly held by the adversary and the parties that are consistent with the statistics that are seen by the parties. Here, we introduce a method to approximate such entropic quantities. Applied to the setting of device-independent randomness generation and quantum key distribution, we obtain improvements on protocol rates in various settings. In particular, we find new upper bounds on the minimal global detection efficiency required to perform device-independent quantum key distribution without additional preprocessing. Furthermore, we show that our construction can be readily combined with the entropy accumulation theorem in order to establish full finite-key security proofs for these protocols.

scholarly journals High-speed device-independent quantum key distribution against collective attacks

2021 ◽  
Author(s):  
Qiang Zhang ◽  
Wen-Zhao Liu ◽  
Yu-Zhe Zhang ◽  
Yi-Zheng Zhen ◽  
Ming-Han Li ◽  
...  
Keyword(s):  
Quantum Key Distribution ◽  
High Speed ◽  
Detection Efficiency ◽  
Bell Inequality ◽  
Key Distribution ◽  
High Rate ◽  
Secret Key ◽  
Security Proofs ◽  
Secret Keys ◽  
High Detection Efficiency

Abstract The security of quantum key distribution (QKD) usually relies on that the users’s devices are well characterized according to the security models made in the security proofs. In contrast,device-independent QKD an entanglement-based protocol permits the security even without any knowledge of the underlying devices. Despite its beauty in theory, device-independent QKD is elusive to realize with current technology. This is because a faithful realization requires ahigh-quality violation of Bell inequality without the fair-sampling assumption. Particularly, in a photonic realization, a rather high detection efficiency is needed where the threshold values depend on the security proofs; this efficiency is far beyond the current reach. Here, both theoretical and experimental innovations yield the realization of device-independent QKD based on a photonic setup. On the theory side, to relax the threshold efficiency for practical deviceindependent QKD, we exploit the random post-selection combined with adding noise for preprocessing, and compute the entropy with complete nonlocal correlations. On the experiment side, we develop a high-quality polarization-entangled photonic source and achieve state-of-theart (heralded) detection efficiency of 87.49%, which outperforms previous experiments and satisfies the threshold efficiency for the first time. Together, we demonstrate device-independent QKD at a secret key rate of 466 bits/s over 20 m standard fiber in the asymptotic limit against collective attacks. Besides, we show the feasibility of generating secret keys at a fiber length of 220 meters. Importantly, our photonic implementation can generate entangled photons at a high rate and in the telecom wavelength, which is desirable for high-speed key generation over long distances. The results not only prove the feasibility of device-independent QKD with realistic devices, but also push the security of communication to an unprecedented level.

Detecting quantum correlations for quantum key distribution

2005 ◽  
Author(s):  
Marcos Curty ◽  
Otfried Guehne ◽  
Maciej Lewenstein ◽  
Norbert Luetkenhaus
Keyword(s):  
Quantum Key Distribution ◽  
Key Distribution ◽  
Quantum Correlations

Upper bounds on the performance of differential-phase-shift quantum key distribution

2009 ◽  
Vol 9 (1&2) ◽  
pp. 62-80
Author(s):  
H. Gomez-Sousa ◽  
M. Curty
Keyword(s):  
Phase Shift ◽  
Quantum Key Distribution ◽  
Key Distribution ◽  
Upper Bounds ◽  
The State ◽  
Differential Phase Shift ◽  
Differential Phase ◽  
Unambiguous Discrimination

In this paper, we investigate limitations imposed by sequential attacks on the performance of a differential-phase-shift (DPS) quantum key distribution (QKD) protocol with weak coherent pulses. Specifically, we analyze a sequential attack based on optimal unambiguous discrimination of the relative phases between consecutive signal states emitted by the source. We show that this attack can provide tighter upper bounds for the security of a DPS QKD scheme than those derived from sequential attacks where the eavesdropper aims to identify the state of each signal emitted by the source unambiguously.

scholarly journals Quantum key distribution with correlated sources

2020 ◽  
Vol 6 (37) ◽  
pp. eaaz4487 ◽  
Author(s):  
Margarida Pereira ◽  
Go Kato ◽  
Akihiro Mizutani ◽  
Marcos Curty ◽  
Kiyoshi Tamaki
Keyword(s):  
Quantum Key Distribution ◽  
Key Distribution ◽  
The Other ◽  
Correlated Sources ◽  
Information Theoretic ◽  
Security Proofs ◽  
Information Theoretic Security ◽  
Special Cases ◽  
New Framework ◽  
General Method

In theory, quantum key distribution (QKD) offers information-theoretic security. In practice, however, it does not due to the discrepancies between the assumptions used in the security proofs and the behavior of the real apparatuses. Recent years have witnessed a tremendous effort to fill the gap, but the treatment of correlations among pulses has remained a major elusive problem. Here, we close this gap by introducing a simple yet general method to prove the security of QKD with arbitrarily long-range pulse correlations. Our method is compatible with those security proofs that accommodate all the other typical device imperfections, thus paving the way toward achieving implementation security in QKD with arbitrary flawed devices. Moreover, we introduce a new framework for security proofs, which we call the reference technique. This framework includes existing security proofs as special cases, and it can be widely applied to a number of QKD protocols.

scholarly journals Detecting two-party quantum correlations in quantum-key-distribution protocols

2005 ◽  
Vol 71 (2) ◽  
Author(s):  
Marcos Curty ◽  
Otfried Gühne ◽  
Maciej Lewenstein ◽  
Norbert Lütkenhaus
Keyword(s):  
Quantum Key Distribution ◽  
Key Distribution ◽  
Quantum Correlations

scholarly journals TIGHTENING THE EAVESDROPPING ACCESSIBLE INFORMATION FOR CONTINUOUS VARIABLE QUANTUM KEY DISTRIBUTION PROTOCOLS THAT INVOLVE NONMAXIMALLY ENTANGLEMENT

2012 ◽  
Vol 26 (16) ◽  
pp. 1250109 ◽  
Author(s):  
A. BECIR ◽  
M. R. B. WAHIDDIN
Keyword(s):  
Quantum Key Distribution ◽  
Key Distribution ◽  
Continuous Variable ◽  
Upper Bounds ◽  
Entangled States ◽  
Entangled State ◽  
Protocol Implementation ◽  
Accessible Information ◽  
Heisenberg Uncertainty

In this paper, we derive tight bounds for the eavesdropping attacks on continuous variable quantum key distribution (CV-QKD) protocol that involves nonmaximally entangled states. We show that deriving bounds on the eavesdropper's accessible information based on the Heisenberg uncertainty yields upper bounds, but those bounds are not tight. For this reason, we follow different techniques to derive the desired tight bounds. The new bounds are tight for all CV-QKD protocols that involve two-mode entangled state. Our derivations are applied to direct and reverse reconciliation schemes of protocol implementation, respectively.

scholarly journals Reference-frame-independent, measurement-device-independent quantum key distribution using fewer quantum states

2020 ◽  
Vol 45 (9) ◽  
pp. 2624
Author(s):  
Donghwa Lee ◽  
Seongjin Hong ◽  
Young-Wook Cho ◽  
Hyang-Tag Lim ◽  
Sang-Wook Han ◽  
...  
Keyword(s):  
Reference Frame ◽  
Quantum Key Distribution ◽  
Key Distribution ◽  
Quantum States ◽  
Independent Measurement ◽  
Measurement Device ◽  
Measurement Device Independent
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