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

IEEE Photonics Technology Letters

Quantum key distribution without a single-photon source using a strong reference

O.L. Guerreau, F.J. Malassenet, S.W. McLaughlin, Jean-Marc Mérolla

Published Jul 27, 2005• 27 citations
Publisher

Abstract

We present a single-sideband scheme that uses an enhanced BB84 protocol with a strong reference. A matrix method allows us to prove that this reference makes the system secure against the photon number splitting attack when using an imperfect laser source. The performance of a stable experimental setup with a fainted laser source is tested using an optimum average energy μ=1 photon per pulse to maximize the final key rate.

DOI
10.1109/lpt.2005.851050

Related papers

Enhanced throughput for QKD: a multiplexed approach

O.L. Guerreau, F.J. Malassenet, S.W. McLaughlin

We report a new time-domain polarization-insensitive quantum key distribution scheme using single-side pulse detection. The system includes a strong reference that makes it secure against the PNS attack while using a fainted laser as a single photon source. It is possible to multiplex this scheme with the single sideband (SSB) technique. The resulting secure bit rate is then doubled allowing secure bit rate enhancement

IEEE Journal of Selected Topics in Quantum Electronics•Jul 1, 2006•2 citations

Modelling the impact of multi-photon source on the performance of quantum key distribution cryptography

Michael Naeem, Mahmoud Reda Taha, Mohamed S. Abdelgawad +1 more

Quantum key distribution introduces a new way of key exchange through a public quantum channel between two communicating nodes. However, the first introduced BB84 protocol was theoretically verifying security based on single photon sources. At this time, it was hard to achieve such device. Therefore, it was a challenging aspect to prove the security of QKD system using coherent light sources or “multi emitting photon source”, which introduces Photon number splitting attacks. We are interested to simulate and investigate the QKD system using coherent laser sources and study the PNS attack. The idea involves that; Eve can crash a beam of light, absorbing some photons using QND measurement and transmit the others. Such attack can make Eve dominant to the situation and gain much information of the key without the fear of getting exposed to the communicating parties. Herein, this paper discusses some useful solution to detect such attack and proves the security of QKD even with weak laser sources.

Quantum Nanophotonic Materials, Devices, and Systems•Aug 20, 2020•0 citations

Unconditional security of phase-coded quantum key distribution with strong reference pulse

Masato Koashi

We discuss the unconditional security of a quantum key distribution protocol in which bit values are encoded in the phase of a weak coherent-state pulse relative to a strong reference pulse, which is essentially the one proposed by Bennett in 1992 (the B92 scheme). In the BB84 protocol with a perfect single photon source, the key rate decreases linearly with the transmission T of the channel. If we simply replace this source with a weak coherent-state pulse, the key rate drops more rapidly (as O(η2)) since the presence of multiple photons favors the eavesdropper, Eve. The B92 protocol, if modified to be encoded on the polarization of a single photon, also shows O(η2) dependence. This comes from Eve's option of sending the vacuum state, which is always registered as an inconclusive result and never causes bit errors. In the original B92 scheme with phase coding, Eve has no such option--replacing the weak pulse by the vacuum cannot avoid errors completely, thanks to the strong reference pulse. This should make the scheme stronger against the loss in the channel even coherent-state pulses from conventional lasers are used. We have obtained an unconditional security proof allowing the presence of small bit errors, and confirmed the above observation in a rigorous way. The key rate is found to drop linearly with the transmission η, and it is lower than the BB84 with a perfect single-photon source only by a constant.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•Jan 11, 2005•0 citations

Source-independent quantum key distribution without pre-sending entanglement

Rong-Zheng Liu, Hua-Lei Yin

Quantum key distribution (QKD) theoretically offers information-theoretic security. The prevailing approach is the prepare-and-measure BB84 protocol, which implements QKD using conventional laser rather than single-photon source via the decoy-state method. However, side-channel attacks targeting sources severely threaten system security. Despite extensive efforts, including fully passive scheme, this vulnerability persists even with perfect single-photon source. Here, we propose a source-independent (SI) QKD protocol that resolves all known and unknown source-side attacks without pre-sending entanglement source. Aligning with advances in quantum light sources, our protocol simultaneously doubles the transmission distance while remaining robustness against imperfection of source. Theoretical analysis shows that non-classical light source provides practical security advantages unattainable with conventional laser.

quant-pharXiv:2604.28089•Optics Letters•May 1, 2026•0 citations

A Decoy-like Protocol for Quantum Key Distribution: Enhancing the Performance with Imperfect Single Photon Sources

Chanaprom Cholsuk, Furkan Ağlarcı, Daniel K. L. Oi +2 more

Quantum key distribution (QKD) relies on single photon sources (SPSs), e.g. from solid-state systems, as flying qubits, where security strongly requires sub-Poissonian photon statistics with low second-order correlation values (\$g^{(2)}(0)\$). However, achieving such low \$g^{(2)}(0)\$ remains experimentally challenging. We therefore propose a decoy-like QKD protocol that relaxes this constraint while maintaining security. This enables the use of many SPSs with \$g^{(2)}(0) > \$0.1, routinely achieved in experiments but rarely considered viable for QKD. Monte Carlo simulations and our experiment from defects in hexagonal boron nitride show that, under linear loss, \$g^{(2)}(0)\$ remains constant, whereas photon-number-splitting (PNS) attacks introduce nonlinear effects that modify the measured \$g^{(2)}(0)\$ statistics. Exploiting this \$g^{(2)}(0)\$ variation as a diagnostic tool, our protocol detects PNS attacks analogously to decoy-state methods. Both single- and two-photon pulses consequently securely contribute to the secret key rate. Our protocol outperforms the Gottesman--Lo--Lutkenhaus--Preskill (GLLP) framework under high channel loss across various solid-state SPSs and is applicable to the satellite-based communication. Since \$g^{(2)}(0)\$ can be extracted from standard QKD experiments, no additional hardware is required. The relaxed \$g^{(2)}(0)\$ requirement simplifies the laser system for SPS generation. This establishes a practical route toward high-performance QKD without the need for ultra-pure SPSs.

arXiv:2510.09454•Oct 10, 2025•0 citations

Experimental quantum cryptography with single photons

I. I. Ryabtsev, Denis B. Tretyakov, A. V. Kolyako +3 more

Results are presented from experimental and theoretical studies of the dependence of the rate of quantum key distribution on the average number of photons in a laser pulse. The experimental data are obtained using atmospheric and fiberoptic experimental setups for a quantum key distribution based on the BB84 protocol.

Bulletin of the Russian Academy of Sciences Physics•Dec 1, 2017•3 citations
We present a single-sideband scheme that uses an enhanced BB84 protocol with a strong reference. A matrix method allows us to prove that this reference makes the system secure against the photon number splitting attack when using an imperfect laser source. The performance of a stable experimental setup with a fainted laser source is tested using an optimum average energy μ=1 photon per pulse to maximize the final key rate.
Quantum key distribution introduces a new way of key exchange through a public quantum channel between two communicating nodes. However, the first introduced BB84 protocol was theoretically verifying security based on single photon sources. At this time, it was hard to achieve such device. Therefore, it was a challenging aspect to prove the security of QKD system using coherent light sources or “multi emitting photon source”, which introduces Photon number splitting attacks. We are interested to simulate and investigate the QKD system using coherent laser sources and study the PNS attack. The idea involves that; Eve can crash a beam of light, absorbing some photons using QND measurement and transmit the others. Such attack can make Eve dominant to the situation and gain much information of the key without the fear of getting exposed to the communicating parties. Herein, this paper discusses some useful solution to detect such attack and proves the security of QKD even with weak laser sources.
We discuss the unconditional security of a quantum key distribution protocol in which bit values are encoded in the phase of a weak coherent-state pulse relative to a strong reference pulse, which is essentially the one proposed by Bennett in 1992 (the B92 scheme). In the BB84 protocol with a perfect single photon source, the key rate decreases linearly with the transmission T of the channel. If we simply replace this source with a weak coherent-state pulse, the key rate drops more rapidly (as O(η2)) since the presence of multiple photons favors the eavesdropper, Eve. The B92 protocol, if modified to be encoded on the polarization of a single photon, also shows O(η2) dependence. This comes from Eve's option of sending the vacuum state, which is always registered as an inconclusive result and never causes bit errors. In the original B92 scheme with phase coding, Eve has no such option--replacing the weak pulse by the vacuum cannot avoid errors completely, thanks to the strong reference pulse. This should make the scheme stronger against the loss in the channel even coherent-state pulses from conventional lasers are used. We have obtained an unconditional security proof allowing the presence of small bit errors, and confirmed the above observation in a rigorous way. The key rate is found to drop linearly with the transmission η, and it is lower than the BB84 with a perfect single-photon source only by a constant.
Quantum key distribution (QKD) theoretically offers information-theoretic security. The prevailing approach is the prepare-and-measure BB84 protocol, which implements QKD using conventional laser rather than single-photon source via the decoy-state method. However, side-channel attacks targeting sources severely threaten system security. Despite extensive efforts, including fully passive scheme, this vulnerability persists even with perfect single-photon source. Here, we propose a source-independent (SI) QKD protocol that resolves all known and unknown source-side attacks without pre-sending entanglement source. Aligning with advances in quantum light sources, our protocol simultaneously doubles the transmission distance while remaining robustness against imperfection of source. Theoretical analysis shows that non-classical light source provides practical security advantages unattainable with conventional laser.
Quantum key distribution (QKD) relies on single photon sources (SPSs), e.g. from solid-state systems, as flying qubits, where security strongly requires sub-Poissonian photon statistics with low second-order correlation values ($g^{(2)}(0)$). However, achieving such low $g^{(2)}(0)$ remains experimentally challenging. We therefore propose a decoy-like QKD protocol that relaxes this constraint while maintaining security. This enables the use of many SPSs with $g^{(2)}(0) > $0.1, routinely achieved in experiments but rarely considered viable for QKD. Monte Carlo simulations and our experiment from defects in hexagonal boron nitride show that, under linear loss, $g^{(2)}(0)$ remains constant, whereas photon-number-splitting (PNS) attacks introduce nonlinear effects that modify the measured $g^{(2)}(0)$ statistics. Exploiting this $g^{(2)}(0)$ variation as a diagnostic tool, our protocol detects PNS attacks analogously to decoy-state methods. Both single- and two-photon pulses consequently securely contribute to the secret key rate. Our protocol outperforms the Gottesman--Lo--Lutkenhaus--Preskill (GLLP) framework under high channel loss across various solid-state SPSs and is applicable to the satellite-based communication. Since $g^{(2)}(0)$ can be extracted from standard QKD experiments, no additional hardware is required. The relaxed $g^{(2)}(0)$ requirement simplifies the laser system for SPS generation. This establishes a practical route toward high-performance QKD without the need for ultra-pure SPSs.