Quantum key distribution (QKD) is a method that distributes a secret key to a sender and a receiver by the transmission of quantum particles (e.g., photons). Device-independent quantum key distribution (DIQKD) is a version of QKD with a stronger notion of security, in that the sender and receiver base their protocol only on the statistics of input and outputs of their devices as inspired by Bell's theorem. We study the rate at which DIQKD can be carried out for a given bipartite quantum state distributed between the sender and receiver or a quantum channel connecting them. We provide upper bounds on the achievable rate going beyond upper bounds possible for QKD. In particular, we construct states and channels where the QKD rate is significant while the DIQKD rate is negligible. This gap is illustrated for a practical case arising when using standard postprocessing techniques for entangled two-qubit states.Quantum key distribution (QKD) is a method that distributes a secret key to a sender and a receiver by the transmission of quantum particles (e.g., photons). Device-independent quantum key distribution (DIQKD) is a version of QKD with a stronger notion of security, in that the sender and receiver base their protocol only on the statistics of input and outputs of their devices as inspired by Bell's theorem. We study the rate at which DIQKD can be carried out for a given bipartite quantum state distributed between the sender and receiver or a quantum channel connecting them. We provide upper bounds on the achievable rate going beyond upper bounds possible for QKD. In particular, we construct states and channels where the QKD rate is significant while the DIQKD rate is negligible. This gap is illustrated for a practical case arising when using standard postprocessing techniques for entangled two-qubit states.

arXiv:2005.13511Physical Review LettersApr 21, 202121 citations

Quantum key distribution using a two-way quantum channel

Marco Lucamarini, Stefano Mancini

arXiv:1004.0157Theoretical Computer ScienceSep 21, 201428 citations

Key rate of quantum key distribution with hashed two-way classical communication

Shun WATANABE, 隆太郎松本, Ryutaroh Matsumoto +4 more

Jun 1, 20070 citations

Performance assessment of fiber-optic railway infrastructure QKD testbed by upper bounded deviation method

Jiri Weiss, Michal Lucki, A. Gábris +3 more

Abstract In this paper, we present an inter-city Quantum Key Distribution network testbed spanning tens of kilometers within the Central Bohemian Region. The testbed operates under harsh conditions, leveraging a robust fiber-optic infrastructure. Specifically, the quantum key distribution devices using two different key generating protocols underwent rigorous testing during winter months. The experiment assesses the performance and stability of quantum key distribution devices in a communication channel under real-world conditions. A quantum channel utilized for this experiment was established along the railway tracks provided by the Czech Railway Administration. Our findings contribute to advancing secure quantum communication networks by addressing key rate stability challenges. An upper bound for relative secret key rate deviation is introduced to support link design. Moreover, it has been experimentally verified that the measured key rate demonstrated robust stability despite its quantum nature and strong influence from outside conditions.Abstract In this paper, we present an inter-city Quantum Key Distribution network testbed spanning tens of kilometers within the Central Bohemian Region. The testbed operates under harsh conditions, leveraging a robust fiber-optic infrastructure. Specifically, the quantum key distribution devices using two different key generating protocols underwent rigorous testing during winter months. The experiment assesses the performance and stability of quantum key distribution devices in a communication channel under real-world conditions. A quantum channel utilized for this experiment was established along the railway tracks provided by the Czech Railway Administration. Our findings contribute to advancing secure quantum communication networks by addressing key rate stability challenges. An upper bound for relative secret key rate deviation is introduced to support link design. Moreover, it has been experimentally verified that the measured key rate demonstrated robust stability despite its quantum nature and strong influence from outside conditions.

Quantum Information ProcessingMay 22, 20260 citations

Side-channel-free quantum key distribution with practical devices

Cong Jiang, Zong‐Wen Yu, Hu, Xiao-Long +1 more

Based on the idea that there is no side channel in the vacuum state, the side-channel-free quantum key distribution (SCFQKD) protocol was proposed, which is immune to all attacks in the source side-channel space and all attacks in the detectors. In the original SCFQKD protocol, an important assumption is that Alice and Bob can produce the perfect vacuum pulses. But due to the finite extinction ratio of the intensity modulators, the perfect vacuum pulse is impossible in practice. In this paper, we solve this problem and make the quantum key distribution side-channel secure with real source device which does not emit perfect vacuum pulses. Our conclusion only depends on the upper bounds of the intensities of the sources. No other assumptions such as stable sources and stable side channels are needed. The numerical results show that, comparing with the results of SCFQKD protocol with perfect vacuum sources, the key rates and secure distance are only slightly decreased if the upper bound of the intensity of the imperfect vacuum source is less than $10^{-8}$ which can be achieved in experiment by two-stage intensity modulator. We also show that the two-way classical communication can be used to the data post-processing of SCFQKD protocol to improve the key rate. Specially, the active odd-parity pairing method can improve the key rates in all distances by about two times and the secure distance by about 40 km. Give that the side channel security based on imperfect vacuum, this work makes it possible to realize side channel secure QKD with real devices.Based on the idea that there is no side channel in the vacuum state, the side-channel-free quantum key distribution (SCFQKD) protocol was proposed, which is immune to all attacks in the source side-channel space and all attacks in the detectors. In the original SCFQKD protocol, an important assumption is that Alice and Bob can produce the perfect vacuum pulses. But due to the finite extinction ratio of the intensity modulators, the perfect vacuum pulse is impossible in practice. In this paper, we solve this problem and make the quantum key distribution side-channel secure with real source device which does not emit perfect vacuum pulses. Our conclusion only depends on the upper bounds of the intensities of the sources. No other assumptions such as stable sources and stable side channels are needed. The numerical results show that, comparing with the results of SCFQKD protocol with perfect vacuum sources, the key rates and secure distance are only slightly decreased if the upper bound of the intensity of the imperfect vacuum source is less than $10^{-8}$ which can be achieved in experiment by two-stage intensity modulator. We also show that the two-way classical communication can be used to the data post-processing of SCFQKD protocol to improve the key rate. Specially, the active odd-parity pairing method can improve the key rates in all distances by about two times and the secure distance by about 40 km. Give that the side channel security based on imperfect vacuum, this work makes it possible to realize side channel secure QKD with real devices.

arXiv:2205.08421May 17, 20220 citations

New protocols for quantum key distribution with explicit upper and lower bound on secret key rate

Arindam Dutta, Anirban Pathak

arXiv:2212.13089The European Physical Journal DMay 1, 20251 citation

10^{-8}

which can be achieved in experiment by two-stage intensity modulator. We also show that the two-way classical communication can be used to the data post-processing of SCFQKD protocol to improve the key rate. Specially, the active odd-parity pairing method can improve the key rates in all distances by about two times and the secure distance by about 40 km. Give that the side channel security based on imperfect vacuum, this work makes it possible to realize side channel secure QKD with real devices.