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:2008.07501 · Physical Review A

Effect of source statistics on utilizing photon entanglement in quantum key distribution

Radim Hošák, Ivo Straka, Ana Predojević, Radim Filip, Miroslav Ježek

Published Apr 13, 2021• 16 citations
arXivHTMLPDF

Abstract

A workflow for evaluation of entanglement source quality is proposed. Based on quantum state density matrices obtained from theoretical models and experimental data, we make an estimate of a potential performance of a quantum entanglement source in quantum key distribution protocols. This workflow is showcased for continuously pumped spontaneous parametric down-conversion (SPDC) source, where it highlights the trade-off between entangled pair generation rate and entanglement quality caused by multiphoton nature of the generated quantum states. We employ this characterization technique to show that secure key rate of down-converted photon pairs is limited to 0.029 bits per detection window due to intrinsic multiphoton contributions. We also report that there exists one optimum gain for continuous-wave down-conversion sources. We find a bound for secure key rate extracted from SPDC sources and make a comparison with perfectly single-pair quantum states, such as those produced by quantum dots.

DOI
10.1103/physreva.103.042411

Related papers

Feasibility of entanglement-based QKD protocols with SPDC and QD sources

Mariia Gumberidze, Vladyslav C. Usenko

We theoretically analyze the feasibility of entanglement-based quantum key distribution (QKD) protocols [1], [2], considering both spontaneous parametric down-conversion (SPDC) and quantum dot (QD) sources. We account for multiphoton emission in SPDC sources and fine-structure splitting (FSS) in QD. In addition, we incorporate imperfect detection, including dark counts and limited efficiency. For SPDC sources, we confirm the presence of vacuum and multiphoton pairs renders them unsuitable for secure device-independent (DI) QKD implementations. Conversely, with QD sources, accounting for the effects of FSS results in reduced secret key rates compared to ideal conditions. Our findings are crucial for the practical implementation of entanglement-based QKD protocols using realistic sources and detectors.

International Conference on Quantum Communications, Networking, and Computing (QCNC)•Mar 31, 2025•0 citations

Feasibility of entanglement-based QKD protocols with SPDC and QD sources

Mariia Gumberidze, Vladyslav C. Usenko

We theoretically analyze the feasibility of entanglement-based quantum key distribution (QKD) protocols considering widely used spontaneous parametric down-conversion (SPDC) and novel quantum dot (QD) sources. We account for multiphoton emission in SPDC sources and fine-structure splitting (FSS) in QD. In addition, we incorporate imperfect detection, including dark counts and limited efficiency. For SPDC sources, we confirm that the presence of vacuum and multiphoton pairs renders them unsuitable for secure device-independent (DI) QKD implementations under standard detection strategies. Conversely, in the case of QD sources, accounting for the effects of FSS, results in reduced performance of protocols. Our findings are crucial for the practical implementation of entanglement-based QKD protocols using realistic sources and detectors.

arXiv:2510.20528•Oct 23, 2025•0 citations

Quantum Key Distribution with a Continuous-Wave-Pumped Spontaneous-Parametric-Down-Conversion Heralded Single-Photon Source

Xiao-Hai Zhan, Shuang Wang, Zhen-Qiu Zhong +5 more

Quantum key distribution (QKD) protocols utilize single photons for key exchanging. Heralded single-photon sources (HSPSs) with spontaneous parametric down-conversion (SPDC) is a practical and effective way of producing single photons of high fidelity, bringing extra performance especially at long distances. A pulsed laser is usually used as the pump for HSPS QKD, but it has disadvantages in operational stability and practicality compared to a cw one. On the other hand, a precise model describing the performance of HSPS with a cw pump is still missing. It is inaccurate and unsafe to apply the key rate model of the pulse-pumped HSPS QKD directly to the cw one, and it also overlooks the timing jitter and dead time of the single-photon detectors. In this paper, we study the cw case in detail, including practical imperfections of the experimental instruments. Our model shows that a cw-pumped setup can reach a much longer transmission distance (31 % longer) than the fastest pulsed HSPS QKD system at present, together with other advantages such as higher operational stability and better spectral characteristics.

Physical Review Applied•Mar 8, 2023•9 citations

Entangled photon-pair sources based on three-wave mixing in bulk crystals

Ali Anwar, Chithrabhanu Perumangatt, Fabian Steinlechner +2 more

Entangled photon pairs are a critical resource in quantum communication protocols ranging from quantum key distribution to teleportation. The current workhorse technique for producing photon pairs is via spontaneous parametric down conversion (SPDC) in bulk nonlinear crystals. The increased prominence of quantum networks has led to a growing interest in deployable high performance entangled photon-pair sources. This manuscript provides a review of the state-of-the-art bulk-optics-based SPDC sources with continuous wave pump and discusses some of the main considerations when building for deployment.

arXiv:2007.15364•Review of Scientific Instruments•Apr 1, 2021•154 citations

Spontaneous Parametric Down‐Conversion Sources for Multiphoton Experiments

Chao Zhang, Yun‐Feng Huang, Bi‐Heng Liu +2 more

Abstract Entangled photon sources are desirable and key elements for photonic quantum information processing. The spontaneous parametric down‐conversion (SPDC) process is a convenient way to produce entangled photon pairs. It has been widely used and has already made great contributions to quantum information science. SPDC sources have been thoroughly studied, and a detailed review, previously lacking, is now appropriate. In this article, different types of SPDC sources suitable for multiphoton experiments are reviewed. A comparison of their respective performances is presented, focusing on the parameters of indistinguishability, collection efficiency, and brightness, from which it is possible to see how the spatial and spectral properties of the SPDC process can be tailored, step by step, to achieve near‐perfect photon pairs. Recent progress on multiplexed heralded single‐photon sources, which effectively mitigate the nondeterministic nature of the SPDC process, is also described.

Advanced Quantum Technologies•Mar 22, 2021•126 citations

Realistic and general model for quantum key distribution with entangled-photon sources

Zhen-Qiu Zhong, Shuang Wang, Xiao-Hai Zhan +4 more

Entanglement-based quantum key distribution (EB-QKD) has several advantages over prepare-and-measure protocols, such as eliminating the need for decoy states and active modulators. At present, entanglement sources based on the spontaneous parametric down-conversion process have been widely used in EB-QKD experiments. Most of the existing models regard the photon-number distribution of pulse-pumped entanglement sources as thermal. However, doing so ignores any effects of spectral modes, which will lead to the overestimation of the secure key rate. In this paper, we analyze the correlation between the photon-number distribution and the joint spectral distribution and rewrite the quantum state of the photon pairs. Then we apply the results to EB-QKD and present a general model which can be used to calculate the secure key rate not only for any pulse-pumped systems but even for cw-pumped systems.

Physical Review A•Nov 14, 2022•16 citations
A workflow for evaluation of entanglement source quality is proposed. Based on quantum state density matrices obtained from theoretical models and experimental data, we make an estimate of a potential performance of a quantum entanglement source in quantum key distribution protocols. This workflow is showcased for continuously pumped spontaneous parametric down-conversion (SPDC) source, where it highlights the trade-off between entangled pair generation rate and entanglement quality caused by multiphoton nature of the generated quantum states. We employ this characterization technique to show that secure key rate of down-converted photon pairs is limited to 0.029 bits per detection window due to intrinsic multiphoton contributions. We also report that there exists one optimum gain for continuous-wave down-conversion sources. We find a bound for secure key rate extracted from SPDC sources and make a comparison with perfectly single-pair quantum states, such as those produced by quantum dots.
We theoretically analyze the feasibility of entanglement-based quantum key distribution (QKD) protocols [1], [2], considering both spontaneous parametric down-conversion (SPDC) and quantum dot (QD) sources. We account for multiphoton emission in SPDC sources and fine-structure splitting (FSS) in QD. In addition, we incorporate imperfect detection, including dark counts and limited efficiency. For SPDC sources, we confirm the presence of vacuum and multiphoton pairs renders them unsuitable for secure device-independent (DI) QKD implementations. Conversely, with QD sources, accounting for the effects of FSS results in reduced secret key rates compared to ideal conditions. Our findings are crucial for the practical implementation of entanglement-based QKD protocols using realistic sources and detectors.
We theoretically analyze the feasibility of entanglement-based quantum key distribution (QKD) protocols considering widely used spontaneous parametric down-conversion (SPDC) and novel quantum dot (QD) sources. We account for multiphoton emission in SPDC sources and fine-structure splitting (FSS) in QD. In addition, we incorporate imperfect detection, including dark counts and limited efficiency. For SPDC sources, we confirm that the presence of vacuum and multiphoton pairs renders them unsuitable for secure device-independent (DI) QKD implementations under standard detection strategies. Conversely, in the case of QD sources, accounting for the effects of FSS, results in reduced performance of protocols. Our findings are crucial for the practical implementation of entanglement-based QKD protocols using realistic sources and detectors.
Quantum key distribution (QKD) protocols utilize single photons for key exchanging. Heralded single-photon sources (HSPSs) with spontaneous parametric down-conversion (SPDC) is a practical and effective way of producing single photons of high fidelity, bringing extra performance especially at long distances. A pulsed laser is usually used as the pump for HSPS QKD, but it has disadvantages in operational stability and practicality compared to a cw one. On the other hand, a precise model describing the performance of HSPS with a cw pump is still missing. It is inaccurate and unsafe to apply the key rate model of the pulse-pumped HSPS QKD directly to the cw one, and it also overlooks the timing jitter and dead time of the single-photon detectors. In this paper, we study the cw case in detail, including practical imperfections of the experimental instruments. Our model shows that a cw-pumped setup can reach a much longer transmission distance (31 % longer) than the fastest pulsed HSPS QKD system at present, together with other advantages such as higher operational stability and better spectral characteristics.
Entangled photon pairs are a critical resource in quantum communication protocols ranging from quantum key distribution to teleportation. The current workhorse technique for producing photon pairs is via spontaneous parametric down conversion (SPDC) in bulk nonlinear crystals. The increased prominence of quantum networks has led to a growing interest in deployable high performance entangled photon-pair sources. This manuscript provides a review of the state-of-the-art bulk-optics-based SPDC sources with continuous wave pump and discusses some of the main considerations when building for deployment.
Abstract Entangled photon sources are desirable and key elements for photonic quantum information processing. The spontaneous parametric down‐conversion (SPDC) process is a convenient way to produce entangled photon pairs. It has been widely used and has already made great contributions to quantum information science. SPDC sources have been thoroughly studied, and a detailed review, previously lacking, is now appropriate. In this article, different types of SPDC sources suitable for multiphoton experiments are reviewed. A comparison of their respective performances is presented, focusing on the parameters of indistinguishability, collection efficiency, and brightness, from which it is possible to see how the spatial and spectral properties of the SPDC process can be tailored, step by step, to achieve near‐perfect photon pairs. Recent progress on multiplexed heralded single‐photon sources, which effectively mitigate the nondeterministic nature of the SPDC process, is also described.
Entanglement-based quantum key distribution (EB-QKD) has several advantages over prepare-and-measure protocols, such as eliminating the need for decoy states and active modulators. At present, entanglement sources based on the spontaneous parametric down-conversion process have been widely used in EB-QKD experiments. Most of the existing models regard the photon-number distribution of pulse-pumped entanglement sources as thermal. However, doing so ignores any effects of spectral modes, which will lead to the overestimation of the secure key rate. In this paper, we analyze the correlation between the photon-number distribution and the joint spectral distribution and rewrite the quantum state of the photon pairs. Then we apply the results to EB-QKD and present a general model which can be used to calculate the secure key rate not only for any pulse-pumped systems but even for cw-pumped systems.