Quantum Network Runs 15 Days Interrupted Under New York Streets

Quantum networking company Qunnect has made significant progress towards a quantum internet with a prototype quantum network under the streets of Brooklyn in New York City.

Known as the GothamQ loop, the prototype network trial ran over a leased 34-kilometer-long fiber circuit for 15 continuous days.

The GothamQ loop. Credit: Qunnect

A quantum internet promises to revolutionize communication by offering ultra-secure data transfer and enabling distributed quantum computing on a global scale.

Unlike the classical internet, which relies on transmitting bits, the quantum internet uses qubits that could enable faster-than-light data correlation using the property of entanglement.

However, qubits are susceptible to environmental noise that disrupts the entangled states in fiber cable and reduces the efficiency and accuracy of signal delivery.

Qunnect said it has overcome this using polarization-entangled photons. Over the 15-day experiment, company researchers said they achieved an uptime of 99.84%.

Their study, published in the journal PRX Quantum, demonstrated a fidelity of 99% for entangled photon pairs transmitted at a rate of about 20,000 per second. At a half-million entangled photon pairs per second, the fidelity was still nearly 90%.

The Qunnect team built automated polarization compensation (APC) devices to electronically compensate for the types of noise disturbance¸ known as polarization drift, that affect polarized photons traveling in a cable.

Related:NYU, Qunnect Achieve 10-Mile Quantum Network Test

These were calibrated against classical, non-entangled photons to see how much they were affected by polarization drift and the APCs corrected the entangled pairs by the same amount.

“The robust distribution of entanglement with high rate and fidelity across deployed fibers will be critical for the development of the quantum Internet,” the researchers said in their paper.

“Here, we have presented data from a quantum test bed in New York City, GothamQ, demonstrating progress toward a fully automated practical entanglement network. This demonstration shows that robust, high-up-time, round-the-clock operation of entanglement-distribution networks is attainable for practical use cases.”