Amazon: Diamonds are a quantum network's best friend

While we're just here for De Beers

The secret to unlocking the full potential of quantum networking may be hiding at the center of a diamond, according to Amazon Web Services. This week, AWS popped the question to De Beers subsidiary Element Six in the hope of finding it.

One of the early applications of quantum networks is key distribution, which uses a pair of entangled qubits to ensure that traffic traveling over the network is secure.

"If you have entanglement between two points, it doesn't matter how you achieve that entanglement on the edges of the network. You can guarantee that there has been no interference with it," Antia Lamas-Linares, who leads the AWS Center for Quantum Networking, told The Register.

Any attempt to compromise the keys causes the quantum state to collapse, rendering them useless. Because of this, quantum networks are seen by proponents as a way to create "unhackable" networks.

While this might sound like science fiction, numerous companies – including the likes of British Telecom – have proven the viability of quantum networks. Usually this has been across short distances in limited trials. Scaling the technology to support larger networks across longer distances remains a challenge – one that Amazon hopes can be solved with diamonds.

The problem is one that optics engineers have grappled with for decades. The farther an optical signal travels, the more likely natural imperfections in the fiber will distort the signal. Traditionally, amplifiers and repeaters have been employed at regular intervals to clean up and boost the signal. This works well for conventional optics networks – but when dealing with the single photons in quantum networks, the tolerances for loss are far, far smaller.

Quantum repeaters

"We can already do some things on relatively small scales, but to really take it to a global scale – AWS is a global company – there are a few things that need to be developed," Lamas-Linares said. "One of them is this concept of a quantum repeater, which essentially does what an optical amplifier does for classical [networks]."

The key difference is that quantum repeaters can correct any loss and infidelity without disrupting the quantum state. In essence, these repeaters are like "a tiny quantum computer," she explained.

The quantum repeater catches the information encoded in the light, stores it, and then, using nearby qubits, corrects any errors. These operations are akin to parity calculations, which allow the errors to be patched without measuring the quantum state – which is kind of important if you don't want to compromise the entanglement.

And this is where Element Six and the diamonds come in. "It's been known for a while that these defects in diamonds – these color centers in diamonds – are a very promising platform for quantum memories and repeaters," Lamas-Linares said.

The defects absorb the photon containing the quantum information, and then re-emit it. "We can manipulate that absorption and re-emitting by creating structures around the defect. For example, we can … create nano structures around it that help us enhance that interaction," she explained.

More secure networks today – quantum clusters tomorrow

Harnessing diamonds to boost the range of quantum networks isn't theoretical. It's closer to commercial viability than you might think, according to AWS.

"Versions of these repeaters have been demonstrated already in academic labs," Lamas-Linares said. "Academic experiments, of course, are different than industrial applications … that's good enough for scientific results, but it's not good enough for highly available and reliable networks like we have at AWS."

While development of utility-scale quantum computers remains a long way off, quantum networks are just a handful of years away, she added. "Whether it's three, five, or seven will depend on how successful we are in getting these technology pieces all working together."

The implications of this tech are wide-reaching. As we mentioned earlier, early applications center around securing traffic as it flows across the network – but in the long term, AWS sees the potential for these networks to cluster multiple quantum computers together. If those computers ever exist in a meaningful sense. ®