Designer diamonds could one day help build a quantum internet


Princeton University researchers are using diamonds to help create a communication network that relies on a property of subatomic particles known as their quantum state. Researchers believe such quantum information networks would be extremely secure and could also allow new quantum computers to work together to complete problems that are currently unsolvable. But scientists currently designing these networks face several challenges, including how to preserve fragile quantum information over long distances.
Now, researchers have arrived at a possible solution using synthetic diamonds.

Defects made with silicon atoms emit light more precisely, but until now haven’t been able to store qubits for longer than several nanoseconds due to their electrical interactions with nearby particles, explains Nathalie de Leon, an electrical engineer at Princeton University.
De Leon and colleagues got around this problem by forging silicon defects in a diamond infused with boron. This extra chemical ingredient shielded the delicate silicon defects from electrical interactions with nearby particles, extending the defects’ quantum memory. The boron-infused crystal nearly rivaled the long-term quantum memory of nitrogen defects, storing qubits for about a millisecond. And it gave a clean photon readout, emitting about 90 percent of its photons at the exact same frequency — compared to just 3 percent of photons spat out by nitrogen defects.

Tweaking the environment of the silicon defects was “an extremely creative way” to help keep a better grip on qubits, says Evelyn Hu, an applied physicist and electrical engineer at Harvard University not involved in the work.
This new artificial diamond could be used to construct devices called quantum repeaters for long-distance quantum communications, says David Awschalom, a physicist and quantum engineer at the University of Chicago who wasn’t involved in the work.



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