Long confined to laboratories, quantum technologies face a concrete obstacle when it comes to scaling up. Existing networks already carry massive volumes of data, and quantum signals, which are extremely fragile, struggle to survive in this environment. However, a recent experiment shows that quantum teleportation can operate at the very heart of current infrastructures, without requiring a dedicated network.
A unique experience at the heart of saturated optical fibers
The Northwestern University team achieved quantum state transfer over a distance of 30.2 kilometers of optical fiber, while running an Internet data stream at 400 gigabits per second. The classical signal used the same fiber as the quantum photons, a situation that reproduces the conditions of a real network rather than an isolated laboratory environment.
This device destroys a photon carrying a quantum state during a joint measurement, then recreates this state on a distant photon thanks to entanglement. The system does not physically travel information from one point to another: it only transfers the state, which is the basis of the very principle of quantum teleportation.
Until now, this operation had never been demonstrated in a fiber carrying heavy conventional traffic. The researchers thus show that a quantum network can operate without dedicated infrastructure, a point considered essential for large-scale deployment according to the study published in the journal
OPTICAL.
Quantum teleportation proves its robustness against classical signals
The main challenge comes from optical noise generated by internet transmissions. Classical data uses millions of photons of light which can mask or disrupt quantum signals, often reduced to a single photon. This phenomenon, called spontaneous Raman scattering, constitutes the dominant source of disturbances in optical fibers.
To preserve the integrity of the signal, the team placed the quantum photons in a wavelength band less exposed to noise and added very narrow spectro-temporal filters. The measurements also rely on coincidence detections which only retain events truly corresponding to quantum transmission.
The results show that the entanglement and interference required for teleportation remain stable even when the conventional signal power reaches 74 milliwatts. The average fidelity of the transfer reaches around 90%, a level well above the threshold of 66% which marks the limit of purely traditional methods, as detailed by the authors of the study cited by ScienceAlert.
Towards network convergence without new infrastructure
The experiment indicates that quantum signals can coexist at rates much higher than those tested. The researchers estimate that the power used would correspond to overall capacities of several terabits per second without significant degradation in the quality of the transfer.
This compatibility changes the perspective of the future quantum internet. Rather than building an expensive parallel network, it becomes possible to use the fibers already deployed for applications such as tamper-proof encryption, synchronization of distributed sensors or interconnection of quantum computers.
The same mechanisms could also allow more complex operations such as the exchange of entanglement between distant nodes or the operation of quantum repeaters, essential elements for extending these networks over long distances. Experience thus suggests that future hybrid architectures will be able to emerge directly within the existing infrastructure, provided that optical noise and fine management of wavelengths are controlled.
date: 2026-02-15 17:53:00