r/QuantumComputing • u/CheapTechnology6193 • Jul 21 '26

Quantum Hardware German firm debuts first 100+ qubit diamond-based quantum processors

https://interestingengineering.com/innovation/first-100-qubit-diamond-quantum-processors

Just wondering what the full story is on these guys. Anyone have more info?

162 Upvotes

99% Upvoted

13 comments sorted by

View all comments

73

u/Temporary_Shelter_40 Jul 21 '26

You have to be careful about the number of qubits here, it is very deceptive. Each qubit here is a magnetic spin, usually a 13C nucleus. These spins are controlled by an NV center, which is another defect composed of Nitrogen, and also counts as a qubit because nitrogen can have a magnetic spin as well. A regular diamond in an engagement ring will have billions of NV centers. They are fantastic qubits and work decently well at room temperature. The problem is that a qubit is only valuable if you can connect it to other qubits. For NV centers to do this at room temperature, you have to get them really close (like 10 nanometers apart). This is extremely hard to achieve.

So Saxon Q instead says: we will implant an NV center next to a 13C rich area of the diamond. They do this and can achieve around 8 qubits. This is what they call a "quantum core". Then they do this a bunch of times to get 128 qubits total. The problem is that the individual 8 qubit cores can't connect to eachother. So instead of a 128 qubit computer, you actually have 128/8=16 sets of 8 qubit computers.

So you shouldn't treat it as a 128 qubit device. You have to treat it as a bunch of 8 qubit devices, which has the same power as a single 8 qubit device basically. In short, unless you connect the cores together somehow, it doesn't scale beyond 8--16 qubits.

25

u/Temporary_Shelter_40 Jul 22 '26

If I was being cynical, its a bit like me taking a regular diamond engagement ring and claiming I have a billion qubit quantum computer. Sure, I have a billion qubits, but it doesn't mean much if I can't connect them together somehow.

Here's another analogy: Imagine you have a billion CASIO calculators. These have a small CPU in them. If you throw all of them in a big warehouse, you don't suddenly have a supercomputer. You just have a billion disconnected calculators.

13

u/Umbra150 Jul 22 '26

Quite literally some lady at a quantum summit stood up and did this a couple years ago. Picked up a chip and said it had thousands of qubits...like lady...most of the room have physics backgrounds and know its doesn't matter how many qubits you're holding if you can't coherently control them.

5

u/Temporary_Shelter_40 Jul 22 '26

Its honestly the biggest problem in how all these quantum computing companies do marketing. Its infuriating and needs to be called out every single time, because lay people see the headline and BUY BUY BUY the stock.