Quantum networking explained how entanglement could link future machines

[NealBinnom-Williams]

TL;DR

• A quantum network shares quantum states, especially entanglement, between distant locations rather than sending ordinary bits
• The no cloning theorem means quantum signals cannot be copied and amplified like classical ones, so long distances need quantum memories and repeaters
• In July 2026 Northwestern University reported entanglement over 24.4 km of fibre carrying live 800 Gbps internet traffic, with fidelity above 94 percent
• In August 2026 USTC reported entanglement between quantum memories over a 420 km fibre channel in Physical Review Letters, a record with important caveats
• Near term uses include linking quantum processors into larger machines, ultra precise sensor networks and secure communication research
• QKD is only one application of quantum networking, and agencies still recommend post quantum cryptography for everyday security

Why networking is the next big quantum story

Most quantum headlines focus on individual computers, measured in qubits, error rates and roadmaps. Yet many researchers believe the long term future of the field depends just as much on connecting quantum devices together. Classical computing became transformative when machines were networked, and quantum technology may follow a similar path. A quantum network would let separate processors, sensors and users share quantum states across a building, a city or eventually a continent

This thread explains what quantum networking is, why it is hard, what has been achieved so far and what it might enable. It also clears up some common confusion, especially the tendency to treat quantum networking and quantum key distribution as the same thing. They overlap, but QKD is only one narrow application. The bigger vision is often called the quantum internet

What a quantum network sends

A classical network moves bits, which are copied, amplified and routed at every hop. A quantum network instead aims to distribute qubits or, more often, entanglement between distant nodes. Entanglement is a correlation between quantum systems that has no classical equivalent. Once two nodes share entangled qubits, they can use them as a resource for tasks that classical networks cannot perform

The most famous of those tasks is quantum teleportation. Using one shared entangled pair plus an ordinary classical message, a quantum state can be transferred from one node to another without the qubit itself travelling across the link. Despite the name, nothing moves faster than light, because the classical message is still required. Teleportation is the basic tool for moving quantum information reliably across a network

Photons are the natural carriers for quantum networks. They travel through standard optical fibre or free space, interact weakly with their surroundings and can be encoded in properties such as polarisation, timing or frequency. Stationary qubits, such as trapped ions, atoms, solid state defects or superconducting circuits, act as the nodes where information is stored and processed. A working network needs efficient interfaces between flying photons and stationary qubits

The distance problem and the no cloning theorem

Optical fibre loses light gradually, and over long distances most photons simply disappear. Classical networks solve this with amplifiers and repeaters that copy and boost signals. Quantum networks cannot do that, because the no cloning theorem, proved in 1982, forbids making perfect copies of an unknown quantum state. That single rule is why quantum networking is so much harder than classical networking

The proposed solution is the quantum repeater. Instead of copying signals, repeaters create entanglement over short segments, store it in quantum memories, and then use a process called entanglement swapping to join those segments into one long entangled link. Error correction or entanglement purification cleans up imperfections along the way. In principle, a chain of repeaters could spread entanglement over thousands of kilometres

Quantum memories are the critical ingredient. They must hold a quantum state long enough for neighbouring segments to succeed, and then release it on demand. Building memories that are efficient, long lived and compatible with telecom wavelengths remains one of the central engineering challenges. Much recent progress concerns exactly this problem

Researchers often describe progress in stages. Early networks share entanglement between neighbouring nodes, later networks store it in memories, and eventually networks will correct errors on the fly. A widely cited 2018 Science paper by Stephanie Wehner, David Elkouss and Ronald Hanson set out six such stages towards a full quantum internet. That framework is a helpful way to judge where any given experiment sits

Milestones so far

Satellite experiments provided some of the earliest long distance results. In 2017, China's Micius satellite distributed entangled photon pairs to ground stations about 1,200 km apart. Satellites avoid fibre loss over most of the path, which is why they are attractive for very long links. Europe's planned Eagle-1 QKD satellite has faced delays, with reporting in June 2026 suggesting a launch no earlier than late 2027

On the ground, the Delft group at QuTech demonstrated a three node quantum network with nitrogen vacancy centres in diamond, published in Science in 2021. In 2024, a Harvard and AWS team reported entanglement between silicon vacancy memories across about 35 km of deployed fibre in the Boston area, published in Nature. These experiments showed multi node operation and memory based links in real infrastructure. They set the stage for the results of 2025 and 2026

Distributed quantum computing took a notable step in February 2025, when researchers at the University of Oxford reported in Nature that they had linked two trapped ion modules with a photonic connection and run a quantum algorithm across them using a teleported gate. The modules were only metres apart, but the principle matters enormously. It suggests large quantum computers could be built from smaller networked modules rather than one giant processor. Several companies now include photonic interconnects in their roadmaps

In July 2026, a Northwestern University team led by Prem Kumar reported in Optica Quantum that they had distributed entangled photons over a 24.4 km fibre link between Evanston and downtown Chicago while the same fibre carried commercial internet traffic, including two 800 gigabit per second channels. Entanglement fidelity stayed above 94 percent. The trick was placing the quantum signals in a quieter wavelength band away from the classical traffic, combined with picosecond timing synchronisation. Sharing existing fibre could greatly reduce the cost of future quantum networks

In August 2026, a team at the University of Science and Technology of China reported in Physical Review Letters entanglement between two atomic ensemble quantum memories across a 420 km fibre channel. The result is a record for memory to memory entanglement over fibre, building on the same group's 50 km result in 2020. Careful readers should note the caveats. Both memories sat in the same laboratory, much of the fibre was coiled on spools, and the entanglement at the longest distance was weak, so this is a channel length benchmark rather than two cities linked

What quantum networks could enable

The most exciting near term application may be modular quantum computing. Building a single processor with millions of high quality qubits is extraordinarily difficult, so linking many smaller modules could be the practical path to scale. Trapped ion, neutral atom and photonic companies all see interconnects as central to their roadmaps. In that sense, quantum networking is part of the race to fault tolerance itself

Networks of quantum sensors are another promising direction. Entangled clocks or sensors at different locations could, in principle, measure time, gravity or other quantities more precisely than independent devices. Proposals include improved timekeeping, geodesy and even very long baseline telescopes that combine light from distant observatories. These ideas are earlier stage, but they show the breadth of what entanglement distribution might offer

Secure communication is the application most people have heard of. QKD uses quantum states to establish keys with eavesdropping detection, and entanglement based protocols extend the idea. However, national security agencies including the NSA, the UK NCSC, France's ANSSI and Germany's BSI advise that QKD has significant practical limitations and recommend post quantum cryptography as the primary defence for everyday systems. Quantum networking research remains valuable even where QKD is not the right tool

Further ahead, researchers discuss blind quantum computing, where a user could run a computation on a remote quantum server without revealing the data or the algorithm. Others explore distributed quantum algorithms that need entanglement between distant parties. These are long term possibilities that depend on reliable networks existing first. They give a sense of why governments treat quantum networking as strategic

Who is investing

Quantum networking features in national strategies across the world. The UK's national quantum missions include deploying the world's most advanced quantum network at scale by 2035. The EU's EuroQCI initiative aims to build quantum communication infrastructure across member states, with terrestrial and satellite segments. The US Department of Energy has supported quantum network testbeds around national laboratories, including the Chicago area network used in the Northwestern work

Companies are active too. Telecom operators have hosted trials on their fibre, startups build memories and photonic interconnects, and large hardware companies plan networked architectures. The diversity of players means progress is coming from many directions at once. That breadth is a healthy sign for the field

Standards work has begun as well. The Internet Research Task Force hosts a Quantum Internet Research Group exploring architecture and terminology, and bodies such as ETSI and the ITU have published work on quantum key distribution networks. Agreeing on shared language early helps different research groups and vendors build compatible systems. It is the same lesson classical networking learned decades ago

Challenges still ahead

• Quantum memories with long storage times, high efficiency and telecom compatibility
• Practical repeaters that outperform direct transmission over long distances
• Efficient interfaces between photons and stationary qubits
• Standards for quantum network protocols, addressing and management
• Integration with existing fibre, timing systems and classical networks

How to read quantum networking news

As with quantum computing, headlines can blur important details. When you read about a new distance record, ask whether the endpoints sat in different places or in the same lab, whether the fibre was deployed or spooled, and whether entanglement was heralded and stored or verified after the fact. Ask whether the link involved quantum memories or only photons. These questions separate impressive engineering steps from claims that a quantum internet already exists

It also helps to separate quantum networking from QKD marketing. Some products labelled quantum networks are point to point QKD links with trusted relay nodes, which is useful in niche settings but different from entanglement based networks. Understanding that difference will make your contributions to discussions far sharper. It also protects buyers from confusing claims

Patience is worth keeping in mind too. Classical networking took decades to move from early experiments to the global internet, and quantum networks face harder physics. Each careful step, like sharing fibre with live traffic or extending memory based links, builds the foundation. Celebrating those steps without overstating them is the right balance

Closing thoughts

Quantum networking is moving from physics experiments towards engineering systems, and 2026 has brought encouraging results on real fibre and longer channels. The road to a global quantum internet is long, and nobody should expect one soon. Still, the steps being taken now could make modular quantum computers practical and open new possibilities in sensing and science. It is one of the most fascinating areas to follow on Qday.forum

If you work on networks, telecoms or photonics, your perspective would be invaluable here. Please share experiences, papers and questions below. This is exactly the kind of topic where practitioners and curious newcomers can learn a great deal from each other


Key references for citation

• Wootters and Zurek, A single quantum cannot be cloned, Nature, 1982
• Yin and colleagues, Satellite-based entanglement distribution over 1200 kilometers, Science, 2017
• Pompili and colleagues, Realization of a multinode quantum network of remote solid-state qubits, Science, 2021
• Main and colleagues, Distributed quantum computing across an optical network link, Nature, February 2025
• Northwestern University, entanglement over 24.4 km of fibre carrying commercial traffic, Optica Quantum, July 2026
• USTC, entanglement of quantum memories over a 420 km fibre channel, Physical Review Letters 137, 070801, August 2026
• UK National Quantum Strategy Missions, 2023

[ECWDreamer_99]

Great explainer. The no cloning section is the clearest I have read, and it explains why people cannot simply bolt quantum signals onto existing amplifiers. It is going straight into our onboarding notes

I work in telecoms, and the Northwestern result caught our attention immediately. Sharing fibre with live traffic changes the cost model completely. Dark fibre is expensive and scarce in many cities

Moving the quantum signal to the O-band is a neat trick. Our engineers want to know how much classical capacity that leaves usable on the same strand

If anyone has seen follow up work on that question, please share it here. Capacity planning is where trials turn into business cases