Entanglement at a Kilometer: Diamond Qubits Point to Secure Supply Chains

On October 14, 2015, an international team of researchers led by Ronald Hanson at Delft University of Technology in the Netherlands achieved a milestone in quantum information science that reverberated far beyond physics laboratories. In a landmark experiment, they successfully entangled nitrogen-vacancy (NV) centers in diamond separated by 1.3 kilometers. The feat not only marked the first “loophole-free” Bell test—closing the last major experimental gaps in demonstrating the reality of quantum entanglement—but also laid crucial groundwork for secure quantum communications across long distances.

For the logistics and global supply chain sectors, this achievement pointed toward a future of encrypted, tamper-proof communication channels that could one day safeguard critical trade data against espionage and cyberattacks. While still years away from practical deployment in 2015, the experiment represented a step toward integrating quantum-secure networks into the backbone of international commerce.

Closing the Loopholes in Quantum Mechanics

Quantum entanglement, famously described by Albert Einstein as “spooky action at a distance,” is a phenomenon where two particles remain correlated no matter how far apart they are. Since the 1960s, physicists have designed “Bell tests” to determine whether entanglement reflects fundamental physics or hidden local variables.

However, earlier experiments always left loopholes. The detection loophole arose when not all entangled particles were measured, leaving open the possibility that the results were biased. The locality loophole suggested that information might have passed between the detectors through classical means. Until 2015, no experiment had closed both loopholes simultaneously.

The Delft team achieved this by using diamond-based NV centers as stable qubits and entangled photons as mediators. By placing the two diamonds in labs 1.3 kilometers apart and ensuring that measurement settings were chosen and completed within time windows too short for any classical signal to travel between them, the researchers closed both the locality and detection loopholes. The result was a loophole-free Bell test—providing the most definitive experimental evidence yet that entanglement is a real and exploitable phenomenon.

The Role of Diamond Nitrogen-Vacancy Centers

The choice of NV centers in diamond was central to the experiment’s success. NV centers occur when a nitrogen atom replaces a carbon atom in the diamond lattice, leaving an adjacent vacancy. These defects can trap and manipulate single electrons, allowing them to function as highly stable qubits. NV centers are notable for their ability to maintain coherence at room temperature, unlike superconducting qubits that require near-absolute-zero conditions.

In Delft’s setup, each diamond hosted an NV center acting as a quantum memory. Entanglement was generated between photons emitted from the NV centers and transmitted through optical fibers. When photons from the separate labs interfered at a central beam splitter, entanglement was established between the two distant NV centers themselves.

This architecture demonstrated a critical capability: the reliable transmission of quantum information over practical distances. Scaling from meters to kilometers was essential if quantum communication was ever to be integrated into real-world infrastructure such as city-wide, regional, or eventually global supply chain networks.

Quantum Key Distribution and Supply Chain Security

One of the most promising applications of long-distance entanglement is quantum key distribution (QKD). QKD allows two parties to share encryption keys with absolute security. Any attempt at eavesdropping alters the quantum state and is immediately detectable.

For logistics and supply chains, this capability has enormous implications. Consider the following use cases:

• Tamper-proof cargo data: Shipping manifests, container tracking information, and customs documentation could be transmitted securely, preventing fraudulent modifications.

• Port communication security: Ports and customs agencies exchanging clearance data could eliminate risks of cyber infiltration or altered cargo instructions.

• Real-time routing protection: Logistics providers coordinating fleets and rerouting shipments based on dynamic conditions could ensure that no malicious third party interfered with instructions.

• Cross-border trade integrity: As global supply chains span multiple jurisdictions, QKD-secured communication would establish trust between trading partners with diverse cybersecurity standards.

In 2015, logistics operators were already contending with increasing cyber threats. From ransomware targeting shipping companies to data breaches at major ports, the need for stronger communication security was evident. The Delft experiment provided a scientific demonstration that the future of unbreakable encryption was not speculative but attainable.

Kilometer-Scale Entanglement as a Technical Milestone

The distance of 1.3 kilometers was not arbitrary. By proving that entanglement could survive transmission over kilometer-scale optical fibers, the researchers validated that quantum links could extend beyond laboratory benches into urban-scale infrastructure. The result suggested that city-wide quantum networks could be built using existing fiber optic cables, laying the foundation for future quantum internet systems.

This was especially relevant for logistics hubs, many of which are concentrated around cities and ports. A port authority could, in principle, establish a quantum-secure link with nearby customs offices, shipping terminals, and logistics firms spread across metropolitan regions. As technology matured, these networks could be scaled to national and international levels, connecting global trade routes with tamper-proof communication channels.

International Reaction and Industry Impact

The October 2015 result was hailed worldwide as a watershed moment. Physicists recognized it as the definitive experimental confirmation of entanglement, while industry observers began to connect the dots to practical applications. Governments in Europe, North America, and Asia cited the Delft experiment in policy documents as justification for expanding investment in quantum communication research.

For the logistics sector, this signaled that quantum-secure communication would not remain confined to theory. Companies such as Maersk, FedEx, and DHL—already grappling with cybersecurity threats—began monitoring developments in quantum key distribution. Though they did not deploy NV center-based systems immediately, the proof of concept reassured stakeholders that the long-term path to secure supply chain communication was being paved.

Technical Challenges Ahead

Despite the milestone, significant technical hurdles remained. Entanglement distribution over optical fibers is limited by photon losses, which increase with distance. Extending entanglement beyond city-scale distances would require quantum repeaters—intermediate nodes capable of storing and retransmitting entangled states without collapsing them.

NV centers, while stable, presented challenges in terms of scalability and integration with existing telecom infrastructure. Researchers explored hybrid systems, combining NV centers with other qubit platforms or leveraging satellite-based quantum communication to bypass fiber losses. Indeed, only a year later, China launched its Micius satellite, pioneering space-based entanglement distribution.

Nonetheless, the Delft experiment provided the essential proof that entanglement could be transmitted robustly and reliably across meaningful distances—an achievement that justified continued investment in solving these technical bottlenecks.

Strategic and Economic Dimensions

The logistics implications extended beyond technical feasibility. In an era of rising cybercrime and geopolitical tensions, the ability to secure communication networks became an economic and national security priority. For nations dependent on global trade, quantum-secure supply chains promised resilience against both criminal actors and state-sponsored cyberattacks.

By 2015, data breaches in logistics systems had already caused costly delays, lost cargo, and compromised customer information. The idea of embedding quantum communication into trade infrastructure suggested a future where such vulnerabilities could be mitigated. Governments recognized that leadership in quantum communication could translate into a strategic advantage for their domestic logistics and export industries.

Looking Forward from 2015

The October 2015 experiment did not immediately change how supply chains operated, but it provided a technological anchor point. It shifted the discussion from theoretical proposals to demonstrable results. For logistics professionals, the message was clear: quantum-secure communication was not science fiction but a matter of engineering and scaling.

As subsequent years brought advances in quantum networks, satellite communication, and integrated photonic technologies, the Delft experiment stood as a foundational reference point. It showed that long-distance, loophole-free entanglement was achievable and that the architecture—diamond NV centers linked by optical photons—could form the backbone of secure communication systems.

Conclusion

The Delft University experiment of October 14, 2015 was a landmark in both quantum physics and the future of global communications. By entangling diamond NV centers across 1.3 kilometers and closing all major loopholes, researchers proved that quantum communication could extend beyond the laboratory into practical distances.

For logistics and supply chain management, the significance lay in the promise of tamper-proof, encrypted communication systems that could protect the integrity of trade data and cargo routing. While widespread deployment was still years away, the experiment marked a decisive step toward integrating quantum technologies into the infrastructure of global commerce.

In a world where the security of digital communication is inseparable from the efficiency of trade, kilometer-scale entanglement in diamonds was more than a physics triumph—it was a glimpse of the logistics networks of the future: secure, resilient, and fundamentally quantum.