Scientists have achieved a significant milestone by demonstrating the successful transmission of quantum information over existing commercial fibre-optic networks, paving the way for future quantum communication technologies.
Key Points
- Quantum information transmission was successfully demonstrated over commercial fibre-optic infrastructure.
- The research utilised existing fibre networks, avoiding the prohibitive cost of building new infrastructure for quantum applications.
- A commercial device entangled photon pairs, and Qunnect-developed devices stabilised their polarisation over 62 kilometres.
- The study achieved a respectable transmission rate of 1,500 entangled photons per second, maintaining entanglement for 92.8% of the time.
- This “stress test” proves that quantum networking protocols can function effectively in noisy, real-world environments.
Researchers have demonstrated that transmission of information over quantum network is possible through commercial fibre-optic infrastructure.
Quantum networks depend on a special phenomenon called quantum entanglement. Entangled objects share a unified state, meaning they cannot be described independently even if they are far apart. A measurement made on one object of an entangled pair determines the results of the measurement made on the other.
A team of researchers from the US’ National Institute of Standards and Technology (NIST), the University of Maryland and the New York-based company Qunnect tested whether quantum networks — making use of principles of quantum physics to transmit information — can run on the existing fibre-optic infrastructure that powers today’s internet.
Building entire fibre networks just for quantum applications can be prohibitively expensive, they said.
Finding a way to keep fragile entangled states alive outside the lab is among the biggest challenges of quantum networks, the team added.
Overcoming Challenges In Quantum Communication
For the study, published in the Journal of Optical Communications and Networking, the researchers used a commercial device to entangle pairs of photons — polarisation of one photon was linked to that of the other.
For example, the two polarisations could either be both parallel or at right angles to each other.
One photon from each pair was directed to an analyser in the NIST lab, which measured the photon’s polarisation. The other travelled through 62 kilometres of fibre to a second lab at the University of Maryland.
A pair of devices, developed by Qunnect, to stabilise the photons’ polarisations in real time was deployed to protect the flying photons’ quantum states. The devices sent beams of ‘reference’ light through the fibre and, at the other end, measured how their polarisation states had been transformed.
Successful Transmission And Stability
The researchers transmitted 1,500 entangled photons per second, a respectable rate though one that would need to improve for quantum networks to become practical, they said.
Over a 24-hour period, the researchers were able to distribute entangled photons 92.8 per cent of the time, needing only 7.2 per cent of the time for correcting the polarisations.
A statistical test confirmed that the photons detected at each end of the fiber had remained entangled.
Real-World Application Potential
While the study is not the first to attempt a long-distance transmission of entangled photons, it stands out for how much fibre exposed to external influences that real-world quantum networks will have to contend with.
“I would call this a stress test of quantum networking systems,” says Yicheng Shi, a physicist at NIST and the study’s lead author.
“We put this to an extreme test in an environment that’s really noisy. Amazingly, it turned out it still worked. It’s a demonstration that quantum networking protocols can work in real-world environments,” Shi said.
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