Qunnect Inc., a Brooklyn-based company, has achieved a significant milestone in quantum networking by successfully operating a prototype quantum internet for 15 days. The team utilized a 34-kilometer-long fiber circuit called the GothamQ loop to transmit polarization-entangled photons, which are essential for various quantum technologies. The researchers used infrared photons with wavelengths of 1,324 and 795 nanometers, compatible with rubidium, a common element in quantum memories and processors.
They addressed polarization drift issues by designing active compensation equipment. To generate entangled photon pairs, the team used a rubidium-enriched vapor cell. Input beams of specific wavelengths excited rubidium atoms, causing electron transitions that resulted in the emission of entangled photon pairs.
These pairs were then transmitted through the fiber in a two-qubit configuration called a Bell state.
Qunnect advances quantum network prototype
Throughout the experiment, the Qunnect team faced challenges from vibrations, bending, and environmental fluctuations affecting the fiber’s polarization.
They created Automated Polarization Compensation (APC) devices to mitigate these issues by sending non-entangled photons with known polarizations through the fiber to measure and correct polarization drift. The GothamQ loop’s success is highlighted by its long operation time and high uptime percentage, demonstrating significant progress towards a practical, automated entanglement network necessary for a future quantum internet. Mehdi Namazi, co-founder and chief science officer at Qunnect, stated, “Since we completed this work, we have already developed rack-mounted versions of all the components, allowing widespread deployment.” These components are collectively termed Qu-Val.
The study, titled “Automated Distribution of Polarization-Entangled Photons Using Deployed New York City Fibers,” by Alexander N. Craddock and team, is available in the PRX Quantum journal. This successful demonstration of stable, high-fidelity entanglement distribution through urban telecommunication infrastructure marks a significant milestone in building a functional quantum internet.
The study underscores the potential for existing fiber networks to support quantum technology, making the possibility of future quantum communication networks more realistic and imminent.
