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A recent experiment in New York indicates that the quantum internet might be realized sooner than anticipated.(Image credit: Busakorn Pongparnit via Getty Images)Share this article 0Join the conversationFollow usAdd us as a preferred source on GoogleSubscribe to our newsletter
Scientists have established a network that they assert demonstrates the practical viability of a quantum internet, which is inherently resistant to hacking without detection.
In collaboration with quantum startup Qunnect and networking firm Cisco, the researchers linked three nodes across New York’s existing fiber-optic infrastructure using quantum signals in the form of photons. These packets of light utilize quantum states to convey information through entangled qubits. By distributing and exchanging entanglement among these signals, the scientists successfully formed a small-scale quantum network.
This third node functions as a central point, enabling the team to perform entanglement swapping and routing. This transforms two separate links into a compact multi-node quantum network capable of distributing entanglement between different pairs on demand, functioning more like a true network rather than a simple linear connection.
“Manhattan is a very compact place,” stated Javad Shabani, director of NYU’s Center for Quantum Information Physics and the NYU Quantum Institute. “Everything is within five or six miles, and you can find hundreds of financial institutions in a very small radius. That density — of infrastructure, institutions, and potential users — may make the city one of the first places where a quantum internet begins to take shape. Having this network right now is important. It’s a huge investment that will pay off probably in the next decade or so.”
A blueprint for future quantum networks
A quantum internet is considered “unhackable” due to device-independent quantum key distribution (DI-QKD). This technique involves encoding cryptographic keys within the quantum state of particles like photons. Since quantum states cannot be duplicated and their measurement inherently disturbs them, eavesdropping becomes exceptionally challenging and readily detectable.
While information is transmitted via photons, they are prone to loss within fiber optic cables. Furthermore, environmental interference or other disturbances, referred to as “noise,” can alter their states, thereby restricting data transmission to very limited distances.
To extend this range, the team devised a “hub-and-spoke” architecture, employing an intermediary hub for swapping and routing with two external spokes. To achieve this, they constructed basic nodes at Qunnect’s Brooklyn facility and generated pairs of entangled photons. These photons’ quantum states are interconnected, allowing them to share information across space and time. They were transmitted through 5 to 6 miles (8 to 10 kilometers) of deployed commercial fiber to a central hub located at a QTD Systems facility, a commercial data center and network hub in Lower Manhattan.
The efficacy of the quantum internet hinges on entanglement, a phenomenon where the quantum states of particles are intrinsically linked.
(Image credit: koto_feja via Getty Images)
A crucial development was “entanglement swapping,” a process enabling particles that have never interacted to become entangled. The scientists highlighted this as fundamental for constructing extended networks from shorter connections.
This process relies on measurements that effectively “transfer” entanglement from initial particle pairs to more distant ones. It leverages quantum teleportation, where multiple particles share correlated quantum states, such that measuring one instantaneously determines the properties of the others. However, rather than teleporting data between two entangled qubits, it teleports the entanglement state itself.
The swapping occurred at the QTD center, utilizing cryogenic detectors. These highly sensitive photon detectors, cooled to extremely low temperatures to reliably register single photons carrying quantum information, measured the photons and pairs that had never interacted. The outcome was entanglement spanning across the city between the original remote sources.
Addressing the internet’s Achilles’ heel
Standard data transmissions are highly vulnerable to eavesdropping. Experts suggest that the quantum internet would resolve this vulnerability, as any attempt at interception would disturb the photons, making the interference immediately detectable.
This experiment validates the functionality of metropolitan-scale quantum links utilizing live telecommunications fiber. It addresses issues such as photon weakening or loss during transmission through optical fiber cables, as well as environmental factors like extreme temperatures and vibrations that can disrupt delicate entanglement.
The hub-and-spoke design facilitates scalability by centralizing sophisticated cryogenic equipment at a single hub. This avoids the necessity for each node to possess expensive and energy-intensive cooling systems, enabling network expansion without a proportional increase in costs.
In the immediate future, this demonstration paves the way for Quantum Key Distribution (QKD), which enables the secure exchange of unhackable encryption keys to safeguard sensitive information for entities such as financial institutions, government agencies, and the healthcare sector.
Looking ahead, this represents a stride towards genuine distributed quantum computing. Such a system could interconnect multiple devices to tackle highly complex challenges, including drug discovery and climate modeling, that are beyond the capabilities of any single entity.
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Entangled networks could also be employed to enhance quantum sensing technologies, potentially leading to highly precise chronometers, GPS-independent navigation systems, and other advanced sensor arrays.
Key obstacles remain, including the exponential absorption and scattering of photons by fiber-optic cables over distance—approximately 0.2 decibels per kilometer at telecom wavelengths—which reduces entanglement success rates to near zero beyond 62 miles (100 km) without amplification. The recent experiment transmitted data over a relatively short distance of 5 to 6 miles (8 to 10 km) per segment; achieving greater distances will necessitate quantum repeaters, which currently lack the essential quantum memories for effective operation.
Nevertheless, the experiment proved significant in establishing the feasibility of quantum networks operating outside of highly controlled laboratory conditions. The researchers demonstrated that noise and signal loss can be effectively managed to maintain entanglement across a densely populated urban area like New York.
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