For the first time, engineers have successfully transmitted quantum signals over commercial fiber-optic lines using standard internet protocols. This experiment demonstrated that quantum networks can operate on the same infrastructure as traditional internet systems. The tests were conducted on the Verizon campus fiber-optic network.

A Breakthrough in Quantum Communications

A team from the University of Pennsylvania has developed a miniature chip called the Q-chip, which coordinates the transmission of both quantum and classical data using the same protocols as the modern internet. This paves the way for the creation of a "quantum internet" capable of linking quantum computers for collaborative information processing. For the first time on a commercial line, it was shown that the chip can not only transmit quantum signals but also automatically correct interference, combine quantum and classical data into standard internet packets, and route them using existing addressing and management systems.

How Quantum Signals Work

Quantum signals are based on the properties of "entangled" particles, which instantly affect each other when the state of one changes. Leveraging this effect allows quantum computers to pool their computational resources to solve problems that are beyond the reach of even the most powerful modern supercomputers.

The Q-chip Technology and Its Features

One of the main challenges in scaling quantum networks is that measuring quantum particles destroys their state. To address this, the Q-chip was created to coordinate the transmission of classical signals (ordinary light) and quantum particles. The classical signal is sent slightly ahead of the quantum one, allowing it to be used for routing without disturbing the quantum state.

The system works like a train: the classical "header" acts as the locomotive, while the quantum information is the cargo sealed in containers. Thanks to this approach, standard internet protocols (IP) can be used to transmit quantum data over existing infrastructure.

Overcoming Interference and Ensuring Accuracy

Transmitting quantum particles over commercial lines requires accounting for external factors such as temperature, vibrations, and seismic activity. Researchers developed an error correction method that uses the effect of interference on the classical signal to make adjustments to the quantum signal without measuring it, thus preserving the quantum state.

During testing, the system achieved a transmission accuracy above 97%, confirming the ability to overcome interference and instability typical of commercial networks. The chip is made from silicon using standard technologies, enabling mass production and scalability.

Scaling Prospects

In the current experiment, the network consisted of one server and one node connected between two buildings by a kilometer of Verizon fiber-optic cable. To expand the network, it is sufficient to produce additional chips and connect them to existing communication lines.

The main obstacle to scaling quantum networks beyond urban areas remains the inability to amplify quantum signals without destroying their entanglement. While there are already systems for transmitting "quantum keys" for ultra-secure communication over long distances, they are not suitable for linking quantum processors together.

The Significance of the Research

The work by the University of Pennsylvania marks an important step forward, showing that the chip can transmit quantum signals over commercial lines using internet packet routing, dynamic switching, and error correction compatible with existing protocols.

The experiment was conducted at the University of Pennsylvania’s School of Engineering and Applied Science with support from the Gordon and Betty Moore Foundation, the Office of Naval Research, the National Science Foundation, the Olga and Alberico Pompa endowed professorship, and a PSC-CUNY award. Researchers from the University of Pennsylvania and the City University of New York also participated in the study.