Quantum Key Distribution (QKD) (2026) | Learning Resources, Research & Companies

Foundations & Explainers

3 entries

Plain-language overviews of what QKD is and why eavesdropping is detectable.

01What Is Quantum Key Distribution? (TechTarget)Definition and overview of QKD, how it works and its limits. 02The Principles of QKD (Quantum Flagship)European Quantum Flagship explainer on QKD principles. 03What Is Quantum Cryptography? (IBM)IBM's overview of quantum cryptography and QKD.

Courses & Learning

3 entries

Free ways to go deeper, including a BB84 simulation notebook.

04QKD Protocols – TU Delft Free CourseFree university course material on QKD protocols. 05Qiskit Textbook – Quantum Key DistributionNotebooks on quantum algorithms and protocols, including BB84. The GitHub repository was archived in January 2024, so check that the material is still current. 06IBM Quantum LearningFree courses on quantum computing and quantum information.

Research Institutes & Labs

5 entries

Where much QKD and quantum-internet research is done.

07QuTechDutch research institute working on the quantum internet and QKD. 08Institute for Quantum Computing (Waterloo)Leading Canadian institute with a quantum cryptography programme. 09Centre for Quantum Technologies (Singapore)National research centre in Singapore with quantum communication research. 10Raman Research InstituteIndian institute with work on quantum communication and free-space QKD. 11Quantum Flagship (EU)European programme funding quantum technologies including communication.

Security Analysis & Attacks

5 entries

Where real QKD implementations fall short, and what agencies say.

12Attacking QKD by Light Injection via Ventilation Openings (PLOS ONE)Side-channel attack on QKD hardware. 13QKD with Flawed and Leaky Sources (npj Quantum Information)Security analysis when QKD sources are imperfect. 14Secure QKD with Realistic Devices (Reviews of Modern Physics)Review of QKD security with imperfect devices. 15UK NCSC – Quantum Security TechnologiesUK agency's view on QKD and other quantum security technologies. 16German BSI – Quantum Technologies and PQCGerman federal agency guidance on quantum technologies and post-quantum cryptography.

Space & Free-Space Optical QKD

6 entries

Satellites and free-space links extend QKD beyond fibre limits.

17Scheduling of Space-to-Ground QKD (EPJ Quantum Technology)Scheduling satellite QKD passes to ground stations. 18QKD in Space (Aerospace Corporation)Joseph Touch and Lori Gordon on QKD in space. 19Progress in Satellite QKD (npj Quantum Information)Review of satellite-based QKD progress. 20Free-Space-Optical QKD Systems: Challenges and Trends (IntechOpen)Book chapter on free-space optical QKD. 21ESA Eagle-1ESA's planned European satellite QKD mission. 22EuroQCIEU initiative for a secure quantum communication infrastructure.

Research Papers & Journals

10 entries

Primary and survey literature on QKD protocols and networking.

23BB84: Public Key Distribution and Coin Tossing (arXiv)Original BB84 paper by Bennett and Brassard. 24Quantum Cryptography (arXiv review)Widely cited review of quantum cryptography. 25Large Scale Quantum Key Distribution: Challenges and Solutions (arXiv)Challenges in scaling QKD networks. 26QKD In-Field Implementations (EU JRC)European Commission JRC state-of-the-art review of quantum communication. 27QKD: A Networking Perspective (ACM Computing Surveys)Survey of QKD from a networking viewpoint. 28QKD with Correlated Sources (Science Advances)Security of QKD when sources are correlated. 29QKD and Its Applications (IEEE)IEEE overview of QKD and its applications. 30The Case for Quantum Key Distribution (Springer)Stebila, Mosca and Lütkenhaus on when QKD makes sense. 31Efficient High-Dimensional QKD with Hybrid Encoding (MDPI)High-dimensional QKD protocol research. 32New Approach Takes QKD Further (Optica)Optica news release on extending QKD distance.

Industry & Commercial Solutions

7 entries

Where QKD is a shipping product, and the business case.

33Toshiba QKDToshiba's QKD products and key management. 34ID QuantiqueSwiss quantum-safe security vendor with QKD systems. 35QuantumCTekChinese quantum communications company. 36QNu LabsIndian quantum-safe security company with QKD and QRNG. 37BT Quantum-Secure NetworksBT's work on quantum-secured networks in the UK. 38To QKD or Not to QKD (Forbes Tech Council)2020 opinion piece on QKD for business. 39QKD Companies directoryDirectory of QKD vendors on this site.

2 entries

Related directories on this site.

40Post-Quantum Cryptography AlgorithmsAlgorithms for post-quantum security. 41Quantum Computing PlatformsPlatforms for programming and running quantum computers.

Frequently Asked Questions

What is quantum key distribution?

QKD is a method for two parties to share a secret encryption key using quantum states of light, so that any eavesdropping disturbs the states and can be detected.

What is BB84?

BB84, proposed by Bennett and Brassard in 1984, encodes bits in photon polarisation using random bases; mismatched measurements reveal interception.

What are the limits of QKD?

It needs dedicated hardware, trusted nodes or satellites for long distances, and real devices can leak information, so several agencies recommend post-quantum cryptography first.

How far can QKD reach?

Over fibre it is limited to a few hundred kilometres without trusted nodes or repeaters, while satellites have demonstrated links over thousands of kilometres.

QKD or post-quantum cryptography?

They are complementary: PQC is software that protects most systems, while QKD may suit specific high-security links. See the PQC Providers and QKD Companies pages.