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arXiv:2409.04204 · Journal of the Optical Society of America B

Twin-field-based multi-party quantum key agreement

Venkat Abhignan, R. Srikanth

Published Nov 20, 2024• 5 citations
arXivHTMLPDF

Abstract

Quantum key distribution (QKD) can secure cryptographic communication between two distant users, as guaranteed by the laws of quantum mechanics rather than computational assumptions. The twin-field scheme, which employs counter-propagated weak coherent light pulses, doubles the secure distance of standard QKD without using quantum repeaters. Here, we study a method to extend the twin-field key distribution protocol to a scheme for multi-party quantum key agreement. We study our protocol’s security using a minimum error discrimination analysis and derive the asymptotic key rate based on the entanglement-based source-replacement scheme. We also simulate it on the ANSYS Interconnect platform with optical components to study the protocol’s performance in certain practical situations.

DOI
10.1364/josab.541759

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Quantum key distribution (QKD) can secure cryptographic communication between two distant users, as guaranteed by the laws of quantum mechanics rather than computational assumptions. The twin-field scheme, which employs counter-propagated weak coherent light pulses, doubles the secure distance of standard QKD without using quantum repeaters. Here, we study a method to extend the twin-field key distribution protocol to a scheme for multi-party quantum key agreement. We study our protocol’s security using a minimum error discrimination analysis and derive the asymptotic key rate based on the entanglement-based source-replacement scheme. We also simulate it on the ANSYS Interconnect platform with optical components to study the protocol’s performance in certain practical situations.
Twin-field quantum key distribution (TFQKD) enables two distant parties to establish a shared secret key, by interfering weak coherent pulses (WCPs) in an intermediate measuring station. This allows TFQKD to reach greater distances than traditional QKD schemes and makes it the only scheme capable of beating the repeaterless bound on the bipartite private capacity. Here, we generalize TFQKD to the multipartite scenario. Specifically, we propose a practical conference key agreement protocol that only uses WCPs and linear optics and prove its security with a multiparty decoy-state method. Our protocol allows an arbitrary number of parties to establish a secret conference key by single-photon interference, enabling it to overcome recent bounds on the rate at which conference keys can be established in quantum networks without a repeater.
The twin-field quantum key distribution (TF-QKD) protocol is designed to beat the rate-distance limit of quantum key distributions without employing quantum repeaters; meanwhile, it can offer the measurement-device-independent secure level. In this Letter, we propose to improve the performance of TF-QKD protocols by employing modified coherent states. Based on the Wang et al. sending-or-not scheme [Phys. Rev. A98, 062323 (2018)PLRAAN1050-294710.1103/PhysRevA.98.062323], we study the key rate with the modified coherent states in finite data size and do comparisons with the one using weak coherent states. Through numerical simulations, we demonstrate that modified coherent states can substantially increase the performance of QKD more than the latter.
Twin-field quantum key distribution (TFQKD), using single-photon-type interference, offers a way to exceed the rate-distance limit without quantum repeaters. However, it still suffers from photon losses and dark counts, which impose an ultimate limit on its transmission distance. In this Letter, we propose a scheme to implement TFQKD with an entangled coherent state source in the middle to increase its range, as well as comparing its performance under coherent attacks with that of TFQKD variants. Simulations show that our protocol has a theoretical distance advantage of 400 km. Moreover, the scheme has great robustness against the misalignment error and finite-size effects. Our work is a promising step toward long-distance secure communication and is greatly compatible with future global quantum networks.
Abstract Quantum key distribution (QKD) offers a reliable solution to communication problems that require long-term data security. For its widespread use, however, the rate and reach of QKD systems must be improved. Twin-field (TF) QKD is a step forward toward this direction, with early demonstrations suggesting it can beat the current rate-versus-distance records. A recently introduced variant of TF-QKD is particularly suited for experimental implementation, and has been shown to offer a higher key rate than other variants in the asymptotic regime, where users exchange an infinite number of signals. Here, we extend the security of this protocol to the finite-key regime, showing that it can overcome the fundamental bounds on point-to-point QKD with ~1010 transmitted signals. In many practical regimes of interest, our analysis offers higher key rates than those of alternative variants. Moreover, some of the techniques we develop are applicable to the finite-key analysis of other QKD protocols.
The phase-matching quantum key distribution (PM-QKD), one of the variants of Twin-Field (TF) QKD protocol, was recently proposed to overcome the rate-distance limits of point to point protocol without quantum repeaters. In this paper, we propose a more practical PM-QKD protocol version with four-intensity decoy states and source errors, since neither the infinite decoy states nor the precise control of the light source is available in practice. We present the formulation of the secure key rate of the proposed protocol and analyze the performances of the protocol with and without source errors by numerical simulations.
Quantum Key Distribution (QKD) represents a revolutionary advancement in secure communication. It leverages principles of quantum mechanics to establish cryptographic keys between parties with theoretically unbreakable security. Among the various QKD protocols, BB84 (Bennett and Brassard, 1984) and Twin-Field QKD are prominent due to their foundational simplicity and advanced key generation efficiency, respectively. The BB84 protocol, as the first QKD protocol, uses quantum bits (qubits) in different bases to securely generate shared keys, while Twin-Field QKD enhances the key generation rate by exploiting quantum interference between distant entangled states, making it more suitable for long-distance communication. This work explores the integration of BB84 and Twin-Field QKD into a hybrid algorithm, aiming at combining the robustness of BB84 with the high key generation rate and entropy of Twin-Field QKD. The hybrid algorithm alternates between the two protocols, leveraging their individual strengths to optimize key generation performance. Simulation results indicate that the hybrid algorithm can effectively balance the robustness and simplicity of BB84 with the high efficiency and entropy of Twin-Field QKD. Specifically, the hybrid algorithm demonstrated an error rate of 8.9%, a key generation rate of 50%, and an entropy of 0.999 bits, which outperforms the compared algorithms.