Quantum Communications in 2025 – Key Advances, Challenges, and the Road Ahead

 Quantum communication has rapidly matured into a key pillar of the emerging quantum internet, leveraging principles such as entanglement and uncertainty to deliver information-theoretic security. This report surveys major theoretical and experimental milestones—including high-rate and long-distance Quantum Key Distribution (QKD), world‑record quantum teleportation, entanglement swapping in multi‑node networks, and advances in decoherence management—and highlights critical hardware innovations like integrated photonics, chip‑scale QKD systems, and high‑efficiency single‑photon detectors. We review prominent ground‑ and satellite‑based QKD deployments in China, South Korea, Europe, and beyond, and examine the roles of industry leaders (Toshiba, ID Quantique, Quantinuum, IBM, Samsung) in commercializing quantum links and QRNG‑enabled devices. Finally, we analyze ongoing challenges in network scalability, fault tolerance, and integration with post‑quantum cryptography, and outline a hybrid, multilayered vision for a global quantum‑secure communication infrastructure.

 

 

Introduction 

Quantum communication, an emerging branch of information technology, utilizes quantum mechanics principles like entanglement and uncertainty to enable secure data transmission. Unlike classical systems, which rely on computational complexity for security, quantum communication systems guarantee security through physical laws. Over the past two decades, this field has seen remarkable growth, becoming a cornerstone of the "quantum internet." This report reviews key theoretical and experimental advancements, hardware achievements, operational and commercial projects worldwide, and the challenges and future directions for quantum networks.

Theoretical and Experimental Advancements

Recent years have witnessed significant theoretical and experimental progress in quantum communication protocols and phenomena. This section explores advancements in Quantum Key Distribution (QKD), quantum teleportation, entanglement swapping, quantum repeaters, and decoherence management.

Quantum Key Distribution (QKD)

QKD is the cornerstone of quantum communication, offering perfectly secure encryption. By transmitting single or entangled photons between two users (typically Alice and Bob), QKD generates a one-time pad key with quantum-guaranteed security. Recent advancements are notable: secure key generation rates have exceeded 100 megabits per second in labs, and key transmission over distances beyond 1,000 kilometers has been demonstrated using satellites and drones. These achievements pave the way for long-distance quantum internet applications. For instance, China’s “Micius” satellite achieved key distribution between ground stations ~1,200 kilometers apart.  In fiber optics, the “twin-field QKD” protocol set a distance record; in 2021, Toshiba researchers successfully performed QKD over 600 kilometers using dual-band phase stabilization, enabling secure communication between distant cities without trusted nodes. Additionally, advanced protocols like device-independent QKD (DI-QKD) and continuous-variable QKD have been developed to address equipment vulnerabilities and boost key rates.

Quantum Teleportation

Quantum teleportation transfers a qubit’s state between locations using entanglement and classical bit transmission, without physically moving the particle. Recent experiments have achieved record distances. In 2017, Chinese scientists teleported a photon’s state from Tibet to the Micius satellite in low Earth orbit (~1,400 kilometers), proving global-scale, ground-to-space teleportation is feasible and opening paths for ultra-secure, continent-scale communication. In ground networks, teleportation between non-adjacent nodes has been achieved. For example, in Delft, Netherlands, a three-node network used solid-state quantum memories (NV centers in diamond) to teleport qubits between non-directly connected nodes, highlighting teleportation’s role in networked quantum information transfer.

Entanglement Swapping and Quantum Repeaters

Entanglement swapping enables particles that never interacted directly to become entangled via an intermediate node, forming the basis for quantum repeaters that address signal loss in long channels. Laboratory multi-node networks have been successfully implemented. The Delft three-node network (Alice, Bob, Charlie) demonstrated entanglement swapping across two links, with Bob performing a Bell measurement to entangle Alice and Charlie despite no direct quantum link. This network also showed the potential for multi-node entanglement distribution, a key step toward a quantum internet. Quantum repeaters require advanced technologies like high-performance quantum memories. In 2021, research groups in Barcelona and China independently demonstrated entanglement with memories over tens of kilometers, published in Nature, laying the foundation for repeaters. Advances in superconductors, trapped atoms, ions, and solid-state defect centers as memory nodes keep hopes alive for extending network ranges. The Delft network serves as an early repeater prototype, linking ~1.3-kilometer segments with a quantum memory.

Decoherence Management

Decoherence and quantum losses are major obstacles for long-distance quantum communication. Photons carrying quantum information weaken in optical fibers or the atmosphere, and environmental interactions degrade their states. Without mitigation, direct entangled photon transmission in fibers is limited to ~50–100 kilometers, with a record of 248 kilometers in low-loss fibers, though detection rates are too low for practical use. To address decoherence, methods like entanglement purification—producing a higher-quality entangled pair from lower-quality ones—act as quantum error correction. Other approaches include designing quantum error-correcting codes for photons and using squeezed or cat states to reduce noise. Low-damping quantum memories aid synchronization in large networks. Quantum repeaters inherently manage decoherence by redistributing entanglement, compensating for signal loss in segments, making them critical for error management.

Hardware Developments in Quantum Communication

The success of quantum communication depends on hardware advancements for generating, transmitting, and detecting quantum states. Recent innovations in integrated photonics, entangled photon sources, single-photon detectors, and optical systems enable large-scale quantum networks.

Integrated Photonics and Entangled Photon Sources

Integrated photonics miniaturizes quantum optical components onto chips, enabling compact, stable, and cost-effective systems. In 2023, researchers developed a fully integrated quantum light source on a chip, including a laser, tunable filters, and a nonlinear loop for entangled photon generation on an In P/Si₃N₄ platform. This chip autonomously produced telecom-band entangled photon pairs with ~99% fidelity, ideal for real-world applications like satellites or data centers. Toshiba also developed a chip-based QKD system in 2021, integrating transmitter, receiver, and quantum random number generator on a 2×6 mm silicon chip, enabling mass production. Entangled photon sources using spontaneous parametric down-conversion (SPDC) in nonlinear crystals are now industry standards. In 2025, Quantum Computing Inc. launched a commercial SPDC-based source on lithium niobate (PPLN) for telecom C-band, compatible with existing fiber infrastructure. Thin-film lithium niobate (TFLN) and quantum dot-based sources are advancing toward chip integration, producing high-purity photons at cryogenic temperatures.

Quantum Detectors and Receivers

Single-photon detectors are critical for quantum systems, requiring high efficiency and precision. Superconducting nanowire single-photon detectors (SNSPDs) lead with >90% detection efficiency and <15 picosecond timing resolution at ~2 Kelvin. Their high count rates and low noise enable QKD key rates in the tens of megabits per second. Semiconductor detectors like avalanche photodiodes (APDs) are used in field applications but have lower efficiency and higher noise. Advances in near-unity efficiency detectors with minimal noise have been key to maturing QKD and quantum sensing technologies.

Optical Systems and Integration with Classical Infrastructure

Integrating quantum communication with existing telecom infrastructure is crucial. In 2020, Toshiba and BT demonstrated simultaneous QKD and 33 terabits per second classical data transmission over an 80-kilometer fiber using wavelength division multiplexing (WDM), eliminating the need for dedicated fibers. Free-space wireless systems have also advanced, with portable optical systems using small telescopes and beam stabilizers enabling QKD over tens of kilometers (e.g., between buildings) or to satellites. Ground stations for quantum communication, like those in China’s QUESS project or ESA’s Canary Islands station, incorporate automated targeting and atmospheric turbulence compensation. Consumer devices are also adopting quantum hardware; Samsung, SK Telecom, and ID Quantique integrated a 2.5×2.5 mm quantum random number generator (QRNG) chip into Galaxy Quantum smartphones, enhancing security for mobile payments and authentication.

Commercial and Operational Projects Worldwide

Quantum communication has moved beyond labs, with urban, national, and international projects emerging, alongside significant investments from tech giants.

Ground-Based and Urban QKD Networks

China leads with its Beijing-Shanghai fiber network, operational since 2017. This ~2,000-kilometer backbone connects Beijing, Jinan, Hefei, and Shanghai via 32 trusted nodes, managing loss with short fiber segments. In 2021, China integrated this with satellite links via Micius, creating a ~4,600-kilometer network extending to Europe. A quantum-encrypted video call between Beijing and Vienna (~7,600 kilometers) showcased intercontinental QKD. South Korea completed a national QKD network in 2023, connecting 48 government institutions over ~800 kilometers, using ID Quantique equipment and advanced key management. Europe’s OPENQKD project (2019–2022) tested metropolitan QKD networks in countries like Austria and the UK, while Japan’s NICT and Toshiba established secure links in Tokyo. Urban QKD networks are emerging globally, including in China, Switzerland, and Singapore.

Satellite-Based Quantum Communication

Satellites overcome fiber distance limitations. China’s Micius satellite, launched in 2016, exchanged entangled photons with ground stations, violating Bell’s inequality over 1,200 kilometers and enabling China-Austria QKD. The EU’s EuroQCI program is developing the Eagle-1 satellite for LEO by 2026, aiming for a quantum satellite constellation. North American firms like Honeywell are planning QKD satellites. China’s Dawn satellite, set for a 2027 geostationary orbit launch, will enable 24/7 global QKD coverage, connecting points like Beijing and South Africa.

Leading Companies and Commercial Applications

Major companies are driving commercialization:

• Toshiba: A pioneer in QKD, Toshiba set a 600-kilometer fiber record and commercialized chip-based QKD in 2020. It deployed metro and intercity networks in the UK, Europe, and Japan, targeting >10 Mbps rates and >500-kilometer ranges.
• ID Quantique (IDQ): This Swiss firm, founded in 2001, was the first to offer commercial QKD devices and supplies equipment for projects like South Korea’s network. IDQ’s QRNGs are used in mobile and online applications.
• Honeywell/Quantinuum: Formed in 2021, Quantinuum develops secure quantum-classical networks and satellite-based QKD for government and commercial use.
• IBM: A leader in quantum computing and post-quantum cryptography (PQC), IBM collaborates on quantum internet projects and standardizes PQC algorithms like CRYSTALS.
• Samsung: Through partnerships with SK Telecom and IDQ, Samsung integrated QRNGs into Galaxy Quantum phones and invests in QKD for 5G networks.

Current Challenges and Future Directions

Despite progress, large-scale, reliable, and secure quantum networks face challenges:

• Scalability and Quantum Repeaters: Current networks rely on trusted nodes, which are not ideal for security. Developing operational repeaters is critical to eliminate trusted intermediaries. Future efforts aim to extend direct communication distances (e.g., via twin-field QKD or satellites) and scale networks to more nodes, addressing quantum routing and memory coherence. Goals include 4–5 node networks, inter-network entanglement swapping, and 50–100-kilometer repeater distances.
• Fault Tolerance and Decoherence: Large networks face photon loss, detector noise, and memory errors. Solutions include improving device efficiency, developing error-correcting codes, and implementing entanglement purification. Self-healing networks resilient to errors are a long-term goal, potentially using machine learning for dynamic error correction.
• Integration with Post-Quantum Cryptography (PQC): As quantum computers advance, PQC algorithms resistant to quantum attacks are being standardized. QKD and PQC are seen as complementary, with QKD securing physical key distribution and PQC handling higher-level encryption. Future standards will likely combine QKD for link layers and PQC for application layers, ensuring robust security. The EU and NIST are developing guidelines for integrating QKD with classical systems.

Conclusion

By 2025, quantum communication has achieved key scientific milestones in QKD, teleportation, and entanglement swapping, with operational urban and satellite networks and commercial devices emerging. Key rates are increasing, and communication ranges are expanding. Challenges like scalability, fault tolerance, and classical integration remain, but advancements in repeaters, satellite constellations, and hybrid protocols promise a global quantum internet within the next decade. This network will revolutionize secure communication and enable new applications like quantum cloud computing and ultra-precise global timekeeping.

 

References  

1. Toshiba – Breakthrough in Long-Distance Quantum Communication (2021)
2. MDPI Entropy – Special Issue on QKD
3. Space.com – Quantum Teleportation Record
4. Toshiba – QKD Semiconductor Chip
5. ID Quantique – SNSPD Technology
6. ID Quantique – Samsung QRNG Use Case
7. ESA – Quantum Teleportation Record
8. ID Quantique – South Korea National QKD
9. EU – EuroQCI Initiative
10. Space.com – Eagle-1 Satellite Plan
11. Honeywell – Quantum Services
12. ESA – Quantum-Secure Space Network
13. Toshiba – QKD with 400Gbps Channels
14. GEANT – Toshiba Summary (PDF)
15. Toshiba – QKD and PQC Insight
16. Utimaco – QKD vs PQC
17. EIPOS – QKD vs PQC in Cybersecurity
18. Medium – Why QKD Won’t Replace PQC
19. Medium – Preparing for the Post-Quantum Era: Insights and Strategies
20. Sun, S., & Liu, B. (2024). Progress in Quantum Key Distribution. Entropy, 26(11), 922.
21. PostQuantum (2023). Entanglement Distribution Techniques in Quantum Networks.
22. PostQuantum (2023). Delft Network & Quantum Repeaters Section.
23. Quantum Computing Inc. (2025). First Commercial Entangled Photon Source Shipped.
24. ID Quantique. Technology Spotlight: SNSPDs.
25. Single Quantum. Single-Photon Detection (SNSPD system specs).
26. Mahmudlu, H., et al. (2023). Fully on-chip photonic turnkey quantum source. Nature Photonics, 17, 518–524.
27. South China Morning Post (June 26, 2025). Pan Jianwei reveals high-orbit quantum satellite "Dawn".
28. ID Quantique & SK Broadband (2023). Nation-wide QKD Network in South Korea – Case Study.
29. Space.com (Oct 15, 2022). Europe’s Eagle-1 Satellite for Quantum Encryption.
30. European Commission (2025). EuroQCI – Digital Strategy Update.
31. Toshiba Europe (Oct 21, 2021). QKD on a Semiconductor Chip.
32. Toshiba Europe (Jun 7, 2021). 600 km QKD Communication Milestone.
33. Honeywell (2023). Quantum Communications for Global Connectivity.
34. Toshiba Europe (Aug 2024). Insight Article: QKD and PQC.
35. Space.com (Jul 15, 2017). Record for Farthest Quantum Teleportation.
36. ID Quantique (2023). Samsung Galaxy Quantum Smartphone with QRNG.

Digital Signature Series: The Magic of Blind Signatures

 

Welcome to the Digital Signature Series! Each post unravels one digital signature scheme in a fun, clear way. Whether you’re new to cryptography or a security geek, this series is your guide to the tech behind secure communications. No jargon overload—just one signature at a time! Today, we’re exploring blind signatures with a twist: a post-quantum demonstration using Dilithium. This blog will stay updated with fresh content, including advancements in post-quantum cryptography (PQC). Let’s dive in!

Note: The code here is for educational purposes only. It demonstrates a simplified "blinded signing" process, not a production-ready blind signature scheme.

🔍 What’s a Blind Signature?

A blind signature lets someone sign a message without seeing what it says. It’s like getting a document notarized while keeping its contents secret. Perfect for:

• Anonymous Voting: Prove your vote is valid without revealing your choice.
• Digital Cash: Spend money anonymously while ensuring it’s legit.
• Privacy Systems: Authenticate without exposing sensitive data.

📬 Fun Analogy

Imagine:

• You write a secret message (e.g., your vote) and lock it in an envelope with a random code (blinding factor r).

• The signer stamps the envelope without opening it (signs the blinded message).

• You unlock the envelope to reveal a valid signature on your original message.

In true blind signatures, anyone can verify the signature later, and the signer can’t link it back to you. Our demo simplifies this—more on that below!

🛠️ How It Works (RSA Blind Signatures)

1. Blinding (Message Owner)

• Inputs:

  • Message m (hash first: H(m) for security).

  • Signer’s public key (e, N).

  • Random r (blinding factor, coprime to N).

• Compute blinded message:

  $$m_0=H(m)\cdot r^e\mathrm{m}\mathrm{o}\mathrm{d}N$$

  (This hides H(m) using r.)

2. Signing (Signer)

• Signer computes:

  $$s_0=m_0^d\mathrm{m}\mathrm{o}\mathrm{d}N$$

  (Uses private key d; sees only m₀, not m.)

3. Unblinding (Message Owner)

• Remove r to reveal true signature:

  $$s=s_0\cdot r^{-1}\mathrm{m}\mathrm{o}\mathrm{d}N$$

  (Now s is a standard RSA signature on H(m).)

4. Verification (Anyone)

• Check:

  $$s^e\mathrm{m}\mathrm{o}\mathrm{d}N=?H(m)\mathrm{m}\mathrm{o}\mathrm{d}N$$

 

This ensures privacy and verifiability—key traits of true blind signatures.

  

Real Example

Here’s how it plays out, using a very simple Python code (try it yourself):

Message: “This is my secret vote: Candidate A” (hashed for signing).



Blinded Message:

25897723902408099327373776355771596951454505987805654930136124529669853613571217498689712266047555878727633097755083911568054466854552878188783986656541344830523134519263213268568322177695772971330835117729396456932987581586515649824115022116802094922109371845081267710014621658369021334695128137436432538121



Blind Signature (from signer):

5404331721527606134618963912751537993817726180922751006788595610643400261256797673857856508673300186850435098081515931585908319002073523546602021280160281043681820557480739821317911636292140810422466493335397152401882199823767765417490837643254294385097067892204113527838668637097032035881736464391220513931



Unblinded Signature:

61432955544478180478345676980109024404621959943422218550091539812708838868048797277398793318100659142214413002155049337721940588986532249915418044917565614786207934212014955575354063990598631017200837783214465327211991760561018490638818742937982421995572078350543454217847437685605457067921920613509814513242



Verification: The signature is valid! Anyone can check it with the signer’s public key, and the signer never saw the vote.

 

🔮 Post-Quantum Twist: Dilithium Demo

RSA works great but is vulnerable to quantum computers. Enter Dilithium: a fast, lattice-based, NIST-standardized PQC signature scheme. Our demo adapts Dilithium for "blinded signing," but with caveats:

• What It Does: Hides the message from the signer, allows private verification.

• What It Doesn’t Do:

  • Public verifiability (needs the secret blinding factor).

  • True unlinkability (signer could link if the factor is revealed).

  • Mathematical unblinding (uses concatenation, not a proper transformation).

Why This Matters: In voting, revealing the blinding factor for verification could let the signer identify your vote, breaking privacy. True blind signatures avoid this.

 

⚠️ Dilithium’s structure poses challenges for true blind signatures, but other PQC families offer promising solutions. Explore our in-depth analysis of post-quantum cryptography for blind signatures here to learn which algorithms show the most potential. ⚠️ 

 

For production use, consider RSA or research-level lattice-based blind signatures (still evolving!). 

 

 

  

Real Example (Dilithium)

Here’s how the Dilithium-based "blinded signing" process looks, using our Python demo (try it yourself):

• Message: “This is my secret vote: Candidate A” (hashed for signing).
• Blinded Message:
  bb358387306d09453b404161ebaf39dc698771b0446f774c08d60e848039b0f5...
• Blind Signature (from signer):
  11da17115123de6622bf3d10451bd5c07c8c16977cef4fec0ea66a646c243d20...
• Unblinded Signature:
  11da17115123de6622bf3d10451bd5c07c8c16977cef4fec0ea66a646c243d20...
• Verification: The signature is valid! The message owner can verify it privately, but public verification requires the secret blinding factor, unlike RSA.

 

Note: This is a simplified demo. The long values reflect Dilithium’s lattice-based structure. For full outputs, check the GitHub repo.

 

💡 Where Are Blind Signatures Used?

Blind signatures shine in privacy-focused systems:

• Digital Cash: Early systems like eCash let users spend anonymously while banks verified transactions.
• Voting: Ensure votes are valid without exposing voter choices.
• Privacy Tech: Power zero-knowledge proofs and anonymous credentials in blockchains or secure apps.

🛡️ Why It Matters

Blind signatures let you prove authenticity without sacrificing privacy. They’re key for:

• Secure Transactions: Anonymous yet verifiable payments or votes.
• Privacy Laws: Comply with GDPR by minimizing data exposure.
• Future Security: Adaptable to post-quantum algorithms for quantum-safe privacy.

🎮 Try It Out

Play with the code yourself:

git clone https://github.com/Mehrn0ush/cryptorion.git
cd cryptorion/blind_signature

.
└── cryptorion
    ├── blind_signature
    │   ├── Dilithiumbased_blind_signature
    │   │   ├── README.md
    │   │   ├── message_owner.py
    │   │   └── signer.py
    │   ├── RSAbased_blind_signature
    │   │   ├── README.md
    │   │   ├── message_owner.py
    │   │   └── signer.py
    └── requirements.txt

This runs the full blind signature process—see the magic in action!

🚀 Coming Up

This blog is a living project, with new posts and updates on the way.

Got ideas? Comment or open an issue on GitHub!

💡 Where Are Blind Signatures Used?

• Digital Cash: Systems like eCash enabled anonymous, verifiable spending.

• Voting: Ensure vote validity without compromising privacy.

• Privacy Tech: Power zero-knowledge proofs and anonymous credentials.

🛡️ Why It Matters

Blind signatures balance authenticity and privacy—crucial for secure, anonymous transactions. Adapting them to PQC ensures future-readiness against quantum threats.

🚀 What’s Next?

 

References:

• Chaum, D. (1983). “Blind Signatures for Untraceable Payments.” 
• NIST PQC: https://csrc.nist.gov/projects/post-quantum-cryptography
• GitHub: https://github.com/Mehrn0ush/cryptorion/blind_signature
• Medium:  Understanding PQC Families Challenges for Blind Signatures