Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:1912.00768

Measurement-Protected Quantum Key Distribution

Spiros Kechrimparis, Heasin Ko, Young‐Ho Ko, Kap‐Joong Kim, Byung‐Seok Choi, Chahan M. Kropf, Chun Ju Youn, Joonwoo Bae

Published Dec 2, 2019• 1 citation
arXivHTMLPDF

Abstract

In the distribution of quantum states over a long distance, not only are quantum states corrupted by interactions with an environment but also a measurement setting should be re-aligned such that detection events can be ensured for the resulting states. In this work, we present measurement-protected quantum key distribution where a measurement is protected against the interactions quantum states experience during the transmission, without the verification of a channel. As a result, a receiver does not have to revise the measurement that has been prepared in a noiseless scenario since it would remain ever optimal. The measurement protection is achieved by applications of local unitary transformations before and after the transmission, that leads to a supermap transforming an arbitrary channel to a depolarization one. An experimental demonstration is presented with the polarization encoding on photonic qubits. It is shown that the security bounds for prepare-and-measure protocols can be improved, for instance, errors up to 20.7% can be tolerated in the Bennett-Brassard 1984 protocol.

DOI
10.48550/arxiv.1912.00768

Related papers

Measurement protection in prepare-and-measure quantum key distribution

Joonwoo Bae

In the distribution of quantum states over a long distance, not only are quantum states corrupted by interactions with an environment but also a measurement setting should be re-aligned such that detection events can be ensured for the resulting states. We here present a method of protecting a measurement in quantum key distribution against the interactions quantum states experience during the transmission, without the verification of a channel. As a result, a receiver does not have to revise the measurement that has been prepared in a noiseless scenario since it would remain ever optimal. The measurement protection is achieved by applications of local unitary transformations before and after the transmission, that leads to a supermap transforming an arbitrary channel to a depolarization one. An experimental demonstration is presented with the polarization encoding on photonic qubits. It is shown that the security bounds for prepare-and-measure protocols can be improved.

•Aug 20, 2020•0 citations

Secure Quantum Communication With the Preservation of Optimal Measurements

Heasin Ko, Spiros Kechrimparis, Young‐Ho Ko +5 more

One of the consequences in the distribution of quantum states over a long distance is that, since resulting quantum states are noisy due to the intervention of an environment, a measurement setting should be re-aligned to optimize detection events, for which additional experimental resources such as quantum tomography of a channel or resulting states is necessary. In this work, we present a protocol for protecting an optimal measurement setup without verifying a channel. A receiver does not have to revise the measurement prepared in a noiseless scenario since it would remain optimal for quantum states resulting from an unknown and noisy channel. The measurement protection protocol realizes a supermap describing transformations over quantum channels and is experimentally feasible as it only applies local unitary transformations before and after the transmission. We present experimental proof-of-principle demonstrations of the measurement protection protocol. We also apply the measurement protection to a prepare-and-measure protocol, the Bennett-Brassard 1984 (BB84) protocol, and find that preserving an optimal measurement can suppress quantum-bit error rates, allowing the protocol to tolerate an even higher noise during transmission. The BB84 protocol with the measurement protection is experimentally demonstrated with the polarization encoding on photonic qubits.

IEEE Journal on Selected Areas in Communications•May 8, 2025•3 citations

Long-distance entanglement-based quantum key distribution

G. Ribordy, Jurgen Brendel, Jean-Daniel Gautier +2 more

A detailed analysis of quantum key distribution employing entangled states is presented. We tested a system based on photon pairs entangled in energy-time optimized for long-distance transmission. It is based on a Franson-type setup for monitoring quantum correlations, and uses a protocol analogous to the Bennett-Brassard 1984 protocol. Passive-state preparation is implemented by polarization multiplexing in the interferometers. We distributed a sifted key of 0.4 Mbit at a raw rate of 134 Hz and with an error rate of 8.6% over a distance of 8.5 km. We thoroughly discuss the noise sources and practical difficulties associated with entangled-state systems. Finally, the level of security offered by this system is assessed and compared with that of faint-laser-pulse systems.

arXiv:quant-ph/0008039•Physical Review A•Dec 13, 2000•187 citations

Practical polarization-frame alignment for quantum key distribution with single-photon-level resources

Brendon L. Higgins, Jean‐Philippe Bourgoin, Thomas D. Jennewein

When quantum information is encoded in optical polarization, practical protocols must contend with the fact that preparation and measurement reference frames may be misaligned, owing to physical orientations and birefringence effects. For long-distance transmissions, a common solution involves multiplexing strong classical reference signals, providing a basis for correction. Here we numerically investigate the performance of a polarization-frame alignment protocol utilizing single-photon-level signals and measurements, in the context of quantum key distribution (QKD) over channels with detector noise and imperfect sources. To the extent possible, the same states and measurement bases are used as for the QKD protocol we intend to support. Our results show that a small fraction of resources from the overall signal---a few hundred photon detections, in total---are required for good performance, restoring the state to better than 99% of its original quality, and we illustrate the protocol's successful operation and adaptability through experimental demonstrations in which it was used in the laboratory and the field.

•Oct 9, 2018•2 citations

Noise adaptive two-way secure deterministic quantum key distribution

Abinash Kar, Ayan Patra, Aditi Sen De +1 more

We introduce noise-adaptive quantum key distribution (QKD) protocols, in which the honest parties optimize the encoding (state preparation) and decoding (measurement basis) operations according to the noise models affecting the honest subsystems induced by an eavesdropper. This extends conventional QKD schemes that employ fixed encoding and decoding strategies independent of the noise characteristics of the communication channel. We investigate three representative protocols: entanglement-based secure dense coding (SDC), the entanglement-free Lucamarini and Mancini (LM05), and a two-way prepare-and-measure Bennett Brassard (BB84) protocols. Using entropic uncertainty relations, we derive the corresponding secret key rates for both adaptive and conventional non-adaptive scenarios under collective attacks. For independent but identical noise acting on the forward and backward transmission channels, as well as for correlated and non-Markovian environments, we identify classes of channels for which adaptive schemes yield enhanced secret key rates for the considered protocols. In contrast, we also determine Pauli channels, including depolarizing and bit flip channels, for which adaptive strategies provide no benefit. We further show that these optimal sets are generally non-unique and can differ substantially from the unitaries that maximize dense-coding capacity in the absence of security constraints. Our results establish noise-adaptive encoding and decoding as a powerful framework for improving secure communication over realistic noisy quantum channels.

quant-pharXiv:2605.27902•May 28, 2026•0 citations

Side-channel-secure quantum key distribution with correlated sources

Yang-Guang Shan, Jia-Xuan Li, Zhen−Qiang Yin +5 more

Quantum key distribution (QKD) offers theoretical security guarantees for sharing secure key, but its practical systems face challenges due to the imperfections of devices. Widespread quantum state preparation imperfections, such as correlations between multiple rounds, significantly undermine the real-world security of QKD. In this paper, we propose a protocol that is immune to almost all kinds of state-preparation imperfections over multiple correlated rounds arising from both encoding and unknown non-encoding dimensions. The protocol relies only on three assumptions: the imperfect encoding produces unknown product states rather than entangled ones, a lower bound on the vacuum components is known, and the correlation has a finite range. The proposed protocol is also measurement-device-independent, ensuring high security at both the source and measurement sides. We provide the finite-key security analysis against coherent attacks and conduct numerical simulations to see the performance. The results show that for small correlation ranges, the protocol achieves excellent performance with a maximal transmission loss exceeding 60 dB (>300 km in standard fiber). Even for extreme cases, where one encoding affects up to 500 neighboring rounds, the protocol can still generate secret keys over a 10 dB-loss channel.

arXiv:2507.11243•Jul 15, 2025•0 citations
In the distribution of quantum states over a long distance, not only are quantum states corrupted by interactions with an environment but also a measurement setting should be re-aligned such that detection events can be ensured for the resulting states. In this work, we present measurement-protected quantum key distribution where a measurement is protected against the interactions quantum states experience during the transmission, without the verification of a channel. As a result, a receiver does not have to revise the measurement that has been prepared in a noiseless scenario since it would remain ever optimal. The measurement protection is achieved by applications of local unitary transformations before and after the transmission, that leads to a supermap transforming an arbitrary channel to a depolarization one. An experimental demonstration is presented with the polarization encoding on photonic qubits. It is shown that the security bounds for prepare-and-measure protocols can be improved, for instance, errors up to 20.7% can be tolerated in the Bennett-Brassard 1984 protocol.
In the distribution of quantum states over a long distance, not only are quantum states corrupted by interactions with an environment but also a measurement setting should be re-aligned such that detection events can be ensured for the resulting states. We here present a method of protecting a measurement in quantum key distribution against the interactions quantum states experience during the transmission, without the verification of a channel. As a result, a receiver does not have to revise the measurement that has been prepared in a noiseless scenario since it would remain ever optimal. The measurement protection is achieved by applications of local unitary transformations before and after the transmission, that leads to a supermap transforming an arbitrary channel to a depolarization one. An experimental demonstration is presented with the polarization encoding on photonic qubits. It is shown that the security bounds for prepare-and-measure protocols can be improved.
One of the consequences in the distribution of quantum states over a long distance is that, since resulting quantum states are noisy due to the intervention of an environment, a measurement setting should be re-aligned to optimize detection events, for which additional experimental resources such as quantum tomography of a channel or resulting states is necessary. In this work, we present a protocol for protecting an optimal measurement setup without verifying a channel. A receiver does not have to revise the measurement prepared in a noiseless scenario since it would remain optimal for quantum states resulting from an unknown and noisy channel. The measurement protection protocol realizes a supermap describing transformations over quantum channels and is experimentally feasible as it only applies local unitary transformations before and after the transmission. We present experimental proof-of-principle demonstrations of the measurement protection protocol. We also apply the measurement protection to a prepare-and-measure protocol, the Bennett-Brassard 1984 (BB84) protocol, and find that preserving an optimal measurement can suppress quantum-bit error rates, allowing the protocol to tolerate an even higher noise during transmission. The BB84 protocol with the measurement protection is experimentally demonstrated with the polarization encoding on photonic qubits.
A detailed analysis of quantum key distribution employing entangled states is presented. We tested a system based on photon pairs entangled in energy-time optimized for long-distance transmission. It is based on a Franson-type setup for monitoring quantum correlations, and uses a protocol analogous to the Bennett-Brassard 1984 protocol. Passive-state preparation is implemented by polarization multiplexing in the interferometers. We distributed a sifted key of 0.4 Mbit at a raw rate of 134 Hz and with an error rate of 8.6% over a distance of 8.5 km. We thoroughly discuss the noise sources and practical difficulties associated with entangled-state systems. Finally, the level of security offered by this system is assessed and compared with that of faint-laser-pulse systems.
When quantum information is encoded in optical polarization, practical protocols must contend with the fact that preparation and measurement reference frames may be misaligned, owing to physical orientations and birefringence effects. For long-distance transmissions, a common solution involves multiplexing strong classical reference signals, providing a basis for correction. Here we numerically investigate the performance of a polarization-frame alignment protocol utilizing single-photon-level signals and measurements, in the context of quantum key distribution (QKD) over channels with detector noise and imperfect sources. To the extent possible, the same states and measurement bases are used as for the QKD protocol we intend to support. Our results show that a small fraction of resources from the overall signal---a few hundred photon detections, in total---are required for good performance, restoring the state to better than 99% of its original quality, and we illustrate the protocol's successful operation and adaptability through experimental demonstrations in which it was used in the laboratory and the field.
We introduce noise-adaptive quantum key distribution (QKD) protocols, in which the honest parties optimize the encoding (state preparation) and decoding (measurement basis) operations according to the noise models affecting the honest subsystems induced by an eavesdropper. This extends conventional QKD schemes that employ fixed encoding and decoding strategies independent of the noise characteristics of the communication channel. We investigate three representative protocols: entanglement-based secure dense coding (SDC), the entanglement-free Lucamarini and Mancini (LM05), and a two-way prepare-and-measure Bennett Brassard (BB84) protocols. Using entropic uncertainty relations, we derive the corresponding secret key rates for both adaptive and conventional non-adaptive scenarios under collective attacks. For independent but identical noise acting on the forward and backward transmission channels, as well as for correlated and non-Markovian environments, we identify classes of channels for which adaptive schemes yield enhanced secret key rates for the considered protocols. In contrast, we also determine Pauli channels, including depolarizing and bit flip channels, for which adaptive strategies provide no benefit. We further show that these optimal sets are generally non-unique and can differ substantially from the unitaries that maximize dense-coding capacity in the absence of security constraints. Our results establish noise-adaptive encoding and decoding as a powerful framework for improving secure communication over realistic noisy quantum channels.
Quantum key distribution (QKD) offers theoretical security guarantees for sharing secure key, but its practical systems face challenges due to the imperfections of devices. Widespread quantum state preparation imperfections, such as correlations between multiple rounds, significantly undermine the real-world security of QKD. In this paper, we propose a protocol that is immune to almost all kinds of state-preparation imperfections over multiple correlated rounds arising from both encoding and unknown non-encoding dimensions. The protocol relies only on three assumptions: the imperfect encoding produces unknown product states rather than entangled ones, a lower bound on the vacuum components is known, and the correlation has a finite range. The proposed protocol is also measurement-device-independent, ensuring high security at both the source and measurement sides. We provide the finite-key security analysis against coherent attacks and conduct numerical simulations to see the performance. The results show that for small correlation ranges, the protocol achieves excellent performance with a maximal transmission loss exceeding 60 dB (>300 km in standard fiber). Even for extreme cases, where one encoding affects up to 500 neighboring rounds, the protocol can still generate secret keys over a 10 dB-loss channel.