66: Chapter 66 Materials Make Another Contribution: The Perfect Single-Photon Source
The two fronts of the "kunpeng project" were advancing in full swing. However, whether it was the Quantum Key Distribution (QKD) system required to build the "Mozi Network" or the development of the superconducting qubits at the core of the "fuxi machine," both were stuck on a common lifeline—materials.
The core of the QKD system is the "single-photon source" capable of stably and efficiently emitting single photons. Single-photon sources prepared by traditional technologies often suffer from low efficiency, impure photon states, and poor stability, which severely restrict the practical application and long-distance deployment of QKD. Superconducting qubits, on the other hand, need to operate at extremely low temperatures, and their requirements for substrate material purity, lattice integrity, and defect density at the interface with superconducting materials are demanding to the extreme.
Just as the material experts from the two project teams were at a loss over the outrageously high technical parameters provided by "Patriot X," a report from the "Qianlong" Base Materials Laboratory, marked "Top Secret · Breakthrough," was urgently delivered to Elder Chen and the chief designers of the two projects.
The title of the report was: "Successful Preparation of Controllable Single-Photon Sources Based on New 'Nitrogen-Vacancy Center Diamond Thin Films' and Preliminary Verification in Superconducting Qubit Substrate Applications."
Elder Chen finished reading the report almost holding his breath. The report detailed a brand-new process derived from a certain "special functional crystal growth technology" provided early on by "Patriot X"—Microwave Plasma Chemical Vapor Deposition (MPCVD). This process involved the heteroepitaxial growth of high-purity, large-area single-crystal diamond thin films on specific substrates, followed by the precise introduction of Nitrogen-Vacancy (nv center) defects through ion implantation and high-temperature annealing.
These precisely manufactured nv centers could become near-perfect single-photon emitters under specific laser excitation! The test data attached to the report showed that the single-photon purity exceeded 99.9%, the emission efficiency reached over 85% of the theoretical value, and the stability was extremely high, fully meeting the requirements for the construction of the "Mozi Network" trunk lines!
Even more surprising was that this ultra-high-purity, near-zero-defect diamond thin film was itself an ideal substrate material for manufacturing superconducting qubits! Preliminary tests indicated that superconducting qubits prepared using it as a base had coherence times (a key indicator for measuring quantum state retention) several times longer than those using traditional materials!
"Materials again! It's 'Patriot X' again!" Elder Chen's fingers trembled with excitement as he immediately connected to the chief designers of the "Mozi Network" and "fuxi machine" projects. "The bottleneck has been broken! Use this new material immediately to speed up device fabrication and prototype assembly!"
The news acted like a shot of adrenaline, injected into both project teams.
Within the "Mozi Network" project team, core light-emitting devices based on the new nv center diamond thin film were quickly manufactured and integrated into the QKD transmitter. Test results showed that the communication distance and key generation rate had improved by orders of magnitude! The first experimental quantum secure communication link was successfully established in a laboratory environment, with the transmission distance exceeding three hundred kilometers and the bit error rate being so low it was negligible!
The "fuxi machine" project team was equally jubilant. After adopting the diamond thin film as a substrate, the yield and performance stability of superconducting qubits significantly increased. The project team’s confidence soared, and they began to sprint toward the goal of integrating more qubits and achieving more complex logic operations.
In the materials laboratory of the "Qianlong" Base, the team responsible for this breakthrough looked at the artificial diamond thin film shimmering with brilliant light in the precision instruments as if they were looking at the world's most precious work of art.
"We... we really made it..." a young researcher murmured. "Following the guidance of 'Patriot X' is like following a map... Performances we couldn't even imagine before have now been realized just like that!"
Materials, this most fundamental discipline, once again demonstrated its decisive power as the cornerstone of all technology. From the "Lunar Regolith Solidifier" to the "lc-1 composite material," and now to the "Nitrogen-Vacancy Center Diamond Thin Film," it seemed that "Patriot X" had already paved a broad road for the Dragon Country to lead a comprehensive technological explosion through material breakthroughs since the beginning of the layout.
Inside the Pretty Country's Cyber Command, the attackers were still fruitlessly trying to find gaps in the Dragon Country's power grid defenses. They did not know that the Dragon Country was quietly weaving an absolutely secure communication network using a technology they completely failed to understand or even detect. Even less did they know that behind this was yet another silent but lethal dimensionality reduction strike originating from materials science.
Inside the "Zhulong" safehouse, Lin Mo received reports on the material breakthrough and project progress. The system prompted that the progress of the [Quantum Communication Protocol Prototype] task had advanced significantly. He watched all this calmly, as if he had already expected it.
If the foundation is not firm, the mountains will shake. And now, the solidest cornerstone was already in place.
He said softly, "The network is about to be completed, and the machine is about to appear. It's time to bring this boring cyber farce to a complete end."