Why Quantum Distribution Is Not Just Classical Networking 2.0?

16th of July 2025

What makes distributed quantum computing fundamentally different from classical networking? It's not about faster data, but about distributing quantum correlations. This post challenges the misleading “quantum internet = internet 2.0” narrative and explores the real physics behind quantum distribution: from no-cloning and measurement collapse to error propagation, synchronization limits, and non-local state effects. As we break old assumptions and build new ones, quantum distribution reveals itself not as a network upgrade, but as a whole new computing paradigm.

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If I say “quantum internet”, you probably think of an upgrade to our current internet. Faster? Safer perhaps? More reliable? Something along the lines of “internet everywhere and for everyone all the time” might come to mind. That's the narrative echoed across LinkedIn at least ... Yet after four years in this field, I still don't see the bridge between that idea and the actual reality of quantum internet research. To me, the “quantum internet” means something very different: it's about distributing quantum correlations in a network, enabling things like collaborative sensing, atomic clock synchronization, long-distance non-local experiments, quantum cryptography, and maybe one or two more niche technologies. Could we one day see quantum networks improve or reshape what we understand as “the internet”? Perhaps. Quantum cryptography is a strong candidate. But the misnomer we've created, and keep reinforcing, is a real issue. It fuels a flood of papers proposing new architectures with little regard for the actual physics. This blog post aims to dive into what makes distributed quantum computing fundamentally different from a classical networking problem. Because after all new problems, mean new opportunities.

The Quantumness aspect

So what does the Q in DQC entail? First of all, any quantum computation can be fundamentally thought of as a large quantum state, made up of multiple qubits, correlated amongst themselves. Every time you implement a CNOT gate between two qubits, you're creating a new correlation between them. At the end of the day, all a quantum circuit does is build a big graph state aka an interconnected network (not in the networking sense) that encodes and processes a problem. A quantum network's job is to distribute this quantum state (which is itself a network) across its nodes, like a matryoshka doll. It IS NOT meant to send data across, but to send correlations across. The difference is important, we will come back to it. For now, let's focus on these correlations, also known as entanglement. Our first quantum beast. A quantum state (aka a qubit) is encoded as \( |\phi\rangle = \alpha |0\rangle + \beta |1\rangle \), with \( \alpha \) and \( \beta \) complex amplitudes such that \( |\alpha|^2 + |\beta|^2 = 1 \). When two qubits are entangled, their joint state becomes indistinguishable: \( |\phi_1\rangle |\phi_2\rangle = \frac{1}{\sqrt{2}} (|00\rangle + |11\rangle) \). One way to create this entangled state is by sending two photons with different polarizations through a beam splitter, letting them interfere, and selecting the cases where they exit in separate paths. There's also such a thing as pseudoentanglement. This occurs when states are correlated in a way that looks like entanglement, but isn't quite. Both entanglement and pseudoentanglement are considered resources for quantum communication. They are things we "burn" when we distribute quantum computations across devices.

Our second beast is the no-cloning theorem. As I said before, the name of the game here is not data transfer. And the reason is quite sound: we can't copy quantum states. The no-cloning theorem states that it is impossible to create an identical copy of an arbitrary unknown quantum state. In classical networks, data can be freely copied for redundancy or routing. Quantum networks can't do that. No fan-out. No replication. No repeaters as we know them. It's all out the window. Memories are also a problem, although incredibly speedy progress is being made. (This was actually the topic of my first patent: quantum memories for networking, a very exciting and deeply problematic challenge.) Not all is lost tho, data movement can still be helped along with classical crutches. We can forward information if we combine a quantum connection with a classical one, sidestepping the copying issue. It's a simplification, but one I found useful when I first entered the quantum communications world. This is a whole new paradigm, with a whole new set of problems and opportunities. Straightforward classical translations won't always work as the purpose of these communications is simply different: Correlations, correlations, correlations.

Our third beast is a fun one: measurement collapse. Schrödinger's cat is no longer superposed between life and death once we look into the box. It chooses its state. It collapses down to one of its two binary values. It becomes a bit. In the same spirit, when we measure qubits, they collapse into classical outcomes. They can't be copied, and they can't be re-used after being observed. This has a crazy upside: built-in cryptographic detection. You copy -> you kill -> I notice the qubit is gone -> I shut down the compromised communication. A one-tap wonder, if properly executed. Measurement collapse is also what enables the classical crutches I mentioned earlier. In the teleportation protocol, classical information obtained from measuring entangled qubits is sent to a receiving party over classical channels. They then apply a correction to their half of the entangled state and recover the original global quantum state. In this way, classical comms can help quantum comms forward information. But teleportation comes at a cost: the entanglement shared between parties is consumed (the qubits have collapsed), and we need at least two classical bits for every qubit teleported. This entanglement must be created ahead of time, distributed, and often purified (distilled). An expensive and fragile process.

Local is now Global

Because the quantum distribution game is a correlations game,not a data forwarding game, a new reality arises. The idea of locality can be violated. A change in one node can instantly affect the entire global quantum state. This is because distributed quantum systems often maintain entangled states across nodes. In classical computing, local operations affect local memory. In distributed quantum systems, even a local gate may have non-local effects. This violates classical assumptions about node independence. A single phase shift on one qubit can change interference patterns across the entire system. Fun thing to deal with when your qubits are fragile...

Due to this, error propagation becomes a serious challenge. In classical systems, faults are local, isolated, and often detectable. But in quantum systems, errors can spread through entanglement. They can even occur at the level of the entanglement generation and distribution itself. We don't just have to deal with bit flips on individual qubits, but with corrupted correlations. In this framework, classical fault isolation breaks down. An error on one node of the global state can trigger a cascade across the system. This interconnectivity, is the power and the achiles heel of quantum computing. Even simulations are non-trivial when we can't just cut up a large computation into partitions to run them independently. Unless there were clear un-connected subgraphs in the larger global graph state, cutting up a large graph without interconnecting its partitions would not be equivalent to the original graph.

Furthermore synchronization can be quite the issue if not deal with properly. Qubits are fragile things requiring precise timings and control alignements. Even nanosecond-scale timing drift can cause an entangled pair to decohere before it's useful. Distributed gates require tight control over laser pulses, clocks, and coherence windows.

The sun will come out: tomorrow

The good news is that for those of us who missed the original internet boom (we were lazy, waiting to be born and all that), we've got a new round to play. This time, the name of the game is correlations. They're fragile, unpredictable, and break down a lot of the convenient architectural assumptions we're used to. Different labs and devices still can't plug into a shared network without custom glue. The translation layers aren't set in stone yet. It's a new dawn for networking. And for one, I can't wait to see the new applications it will bring.