scholarly journals Quantum Alice and silent Bob: Qubit-based Quantum Key Recycling with almost no classical communication

2021 ◽  
Vol 21 (1&2) ◽  
pp. 0001-0018
Author(s):  
Daan Leermakers ◽  
Boris Skoric
Keyword(s):  
Quantum Key Distribution ◽  
Key Distribution ◽  
Universal Composability ◽  
Classical Communication ◽  
Round Complexity ◽  
Security Proof ◽  
Open Question

We answer an open question about Quantum Key Recycling (QKR): Is it possible to put the message entirely in the qubits without increasing the number of qubits compared to existing QKR schemes? We show that this is indeed possible. We introduce a prepare-and-measure QKR protocol where the communication from Alice to Bob consists entirely of qubits. As usual, Bob responds with an authenticated one-bit accept/reject classical message. Compared to Quantum Key Distribution (QKD), QKR has reduced round complexity. Compared to previous qubit-based QKR protocols, our scheme has far less classical communication. We provide a security proof in the universal composability framework and find that the communication rate is asymptotically the same as for QKD with one-way postprocessing.

scholarly journals Coherent-State-Based Twin-Field Quantum Key Distribution

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Hua-Lei Yin ◽  
Zeng-Bing Chen
Keyword(s):  
Coherent State ◽  
Communication Networks ◽  
Quantum Key Distribution ◽  
Large Scale ◽  
Key Distribution ◽  
Entanglement Swapping ◽  
Secret Key ◽  
Entanglement Purification ◽  
Classical Communication ◽  
Security Proof

Abstract Large-scale quantum communication networks are still a huge challenge due to the rate-distance limit of quantum key distribution (QKD). Recently, twin-field (TF) QKD has been proposed to overcome this limit. Here, we prove that coherent-state-based TF-QKD is a time-reversed entanglement protocol, where the entanglement generation is realized with entanglement swapping operation via an entangled coherent state measurement. We propose a coherent-state-based TF-QKD with optimal secret key rate under symmetric and asymmetric channels by using coherent state and cat state coding. Furthermore, we show that our protocol can be converted to all recent coherent-state-based TF-QKD protocols by using our security proof. By using the entanglement purification with two-way classical communication, we improve the transmission distance of all coherent-state-based TF-QKD protocols.

scholarly journals Apply current exponential de Finetti theorem to realistic quantum key distribution

2014 ◽  
Vol 33 ◽  
pp. 1460370 ◽  
Author(s):  
Yi-Bo Zhao ◽  
Zhen-Qiang Yin
Keyword(s):  
Quantum Key Distribution ◽  
Key Distribution ◽  
Small Error ◽  
Heterodyne Detection ◽  
Finite Dimensional Subspace ◽  
Dimensional System ◽  
Finite Dimensional ◽  
Security Proof ◽  
De Finetti Theorem ◽  
De Finetti

In the realistic quantum key distribution (QKD), Alice and Bob respectively get a quantum state from an unknown channel, whose dimension may be unknown. However, while discussing the security, sometime we need to know exact dimension, since current exponential de Finetti theorem, crucial to the information-theoretical security proof, is deeply related with the dimension and can only be applied to finite dimensional case. Here we address this problem in detail. We show that if POVM elements corresponding to Alice and Bob's measured results can be well described in a finite dimensional subspace with sufficiently small error, then dimensions of Alice and Bob's states can be almost regarded as finite. Since the security is well defined by the smooth entropy, which is continuous with the density matrix, the small error of state actually means small change of security. Then the security of unknown-dimensional system can be solved. Finally we prove that for heterodyne detection continuous variable QKD and differential phase shift QKD, the collective attack is optimal under the infinite key size case.

scholarly journals Finite-key analysis for twin-field quantum key distribution with composable security

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Hua-Lei Yin ◽  
Zeng-Bing Chen
Keyword(s):  
Coherent State ◽  
Quantum Key Distribution ◽  
Key Distribution ◽  
Practical Implementation ◽  
Fluctuation Analysis ◽  
Statistical Fluctuation ◽  
Secret Key ◽  
Quantum Repeater ◽  
Long Distance ◽  
Security Proof

AbstractLong-distance quantum key distribution (QKD) has long time seriously relied on trusted relay or quantum repeater, which either has security threat or is far from practical implementation. Recently, a solution called twin-field (TF) QKD and its variants have been proposed to overcome this challenge. However, most security proofs are complicated, a majority of which could only ensure security against collective attacks. Until now, the full and simple security proof can only be provided with asymptotic resource assumption. Here, we provide a composable finite-key analysis for coherent-state-based TF-QKD with rigorous security proof against general attacks. Furthermore, we develop the optimal statistical fluctuation analysis method to significantly improve secret key rate in high-loss regime. The results show that coherent-state-based TF-QKD is practical and feasible, with the potential to apply over nearly one thousand kilometers.

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