Beating the Fundamental Rate-Distance Limit in a Proof-of-Principle Quantum Key Distribution System

Wang, Shuang; He, De‐Yong; Yin, Zhen-Qiang; Lu, Feng-Yu; Cui, Chaohan; Chen, Wei; Zhou, Zheng; Guo, Guang‐Can; Han, Zheng‐Fu

doi:10.1103/physrevx.9.021046

Cited by 185 publications

(114 citation statements)

References 33 publications

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“…is the Shannon entropy, Figure 1. In Alice and Bob's side, The laser-modules can prepare initial phase locked weak coherent pulses with the help of the phaselocking module belongs to Charlie [16]. The phase-modulators(PM) are apply to encode key bits in code mode and randomize the phase of WCPs in decoy mode.…”

Section: Protocol Definitionmentioning

confidence: 99%

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Practical issues of twin-field quantum key distribution

Yin

Wang

et al. 2019

New J. Phys.

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Twin-field quantum key distribution(TF-QKD) protocol and its variants, such as phase-matching QKD, sending-or-not-sending QKD and no phase post-selection TF-QKD(NPP-TFQKD), are very promising for long-distance applications. However, there are still some gaps between theory and practice in these protocols. Concretely, a finite-key size analysis is still missing, and the intensity fluctuations are not taken into account. To address the finite-key size effect, we first give the key rate of NPP-TFQKD against collective attack in finite-key size region and then prove it can be against coherent attack. To deal with the intensity fluctuations, we present an analytical formula of 4-intensity decoy state NPP-TFQKD and a practical intensity fluctuation model. Finally, through detailed simulations, we show NPP-TFQKD can still keep its superiority of high key rate and long achievable distance.

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Section: Protocol Definitionmentioning

confidence: 99%

“…phase-matching QKD [10], sending-or-not-sending QKD [11] and no phase post-selection TF-QKD(NPP-TFQKD) [12][13][14], are simpler. Indeed, both the sendingor-not-sending QKD and NPP-TFQKD have been scuccessfully demonstrated [15][16][17][18].…”

Section: Introductionmentioning

confidence: 99%

Practical issues of twin-field quantum key distribution

Yin

Wang

et al. 2019

New J. Phys.

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“…Since a rigorous security proof is not provided in the original proposal, several papers have improved the protocol and provided security proof [6][7][8][9][10]. Also, recently there have been multiple reports of TF-QKD demonstrated experimentally [11][12][13][14].…”

Section: Introductionmentioning

confidence: 99%

Simple method for asymmetric twin-field quantum key distribution

Wang

2020

New J. Phys.

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Twin-field quantum key distribution (TF-QKD) can beat the linear bound of repeaterless QKD systems. After the proposal of the original protocol, multiple papers have extended the protocol to prove its security. However, these works are limited to the case where the two channels have equal amount of loss (i.e. are symmetric). In a practical network setting, it is very likely that the channels are asymmetric due to e.g. geographical locations. In this paper we extend the 'simple TF-QKD' protocol to the scenario with asymmetric channels. We show that by simply adjusting the two signal states of the two users (and not the decoy states) they can effectively compensate for channel asymmetry and consistently obtain an order of magnitude higher key rate than previous symmetric protocol. It also can provide 2-3 times higher key rate than the strategy of deliberately adding fibre to the shorter channel until channels have equal loss (and is more convenient as users only need to optimize their laser intensities and do not need to physically modify the channels). We also perform simulation for a practical case with three decoy states and finite data size, and show that our method works well and has a clear advantage over prior art methods with realistic parameters. maintain the same channel loss for all users (and users might join/leave a network at arbitrary locations). If channels are asymmetric, for prior art protocols, users would either have to suffer from much higher quantumbit-error-rate (QBER) and hence lower key rate, or would have to deliberately add fibre to the shorter channel to compensate for channel asymmetry, which is inconvenient (since it requires physically modifying the channels) and also provides sub-optimal key rate.Similar limitation to symmetric channels have been observed in MDI-QKD. In [15], we have proposed a method to overcome this limitation, by allowing Alice and Bob to adjust their intensities (and use different optimization strategies for two decoupled bases) to compensate for channel loss, without having to physically adjust the channels. The method has also been successfully experimentally verified for asymmetric .In this work, we will apply our method to TF-QKD and show that it is possible to obtain good key rate through asymmetric channels by adjusting Alice's and Bob's intensities-in fact, we will show that, Alice and Bob only need to adjust their signal intensities to obtain optimal performance. We show that the security of the protocol is not affected, and that an order of magnitude higher (than symmetric protocol) or 2-3 times higher (than adding fibre) key rate can be achieved with the new method. Furthermore, we show with numerical simulation results that our method works well for both finite-decoy and finite-data case with practical parameters, making it a convenient and powerful method to improve the performance of TF-QKD through asymmetric channels in reality.While we use the same main idea of allowing Alice and Bob to use asymmetric intensities to compensate for asymmetric channe...

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“…They devised an MDI-QKD type protocol-called twin-field QKD (TF-QKD)-in which the untrusted central node performs a single-photon interference measurement on the two incoming pulses, causing the key rate to scale with the square-root of the channel transmittance by using simple optical devices. Since the original proposal, several variants of the TF-QKD protocol were proven to be secure [18][19][20][21][22][23] and some of them were experimentally implemented [24][25][26][27].…”

Section: Introductionmentioning

confidence: 99%

Asymmetric twin-field quantum key distribution

2019

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Twin-Field (TF) quantum key distribution (QKD) is a major candidate to be the new benchmark for far-distance QKD implementations, since its secret key rate can overcome the repeaterless bound by means of a simple interferometric measurement. Many variants of the original protocol have been recently proven to be secure. Here, we focus on the TF-QKD type protocol proposed by Curty et al (2019 NPJ Quantum Inf. 5 64), which can provide a high secret key rate and whose practical feasibility has been demonstrated in various recent experiments. The security of this protocol relies on the estimation of certain detection probabilities (yields) through the decoy-state technique. Analytical bounds on the relevant yields have been recently derived assuming that both parties use the same set of decoy intensities, thus providing sub-optimal key rates in asymmetric-loss scenarios. Here we derive new analytical bounds when the parties use either two, three or four independent decoy intensity settings each. With the new bounds we optimize the protocol's performance in asymmetric-loss scenarios and show that the protocol is robust against uncorrelated intensity fluctuations affecting the parties' lasers.

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Beating the Fundamental Rate-Distance Limit in a Proof-of-Principle Quantum Key Distribution System

Cited by 185 publications

References 33 publications

Practical issues of twin-field quantum key distribution

Practical issues of twin-field quantum key distribution

Simple method for asymmetric twin-field quantum key distribution

Asymmetric twin-field quantum key distribution

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