(no title)
tomgag | 3 months ago
Regarding the coaxial cables, you seem to be an expert, so tell me if I'm wrong, but it seems to me a limitation of current designs (and in particular of superconducting qubits), I don't think there is any fundamental reason why this could not be replaced by a different tech in the future. Plus, the scaling must not need to be infinite, right? Even with current "coaxial cable tech", it "only" needs to scale up to the point of reaching one logical qubit.
JanisErdmanis|3 months ago
The QC is designed with coaxial cables running from the physical qubits outside the cryostat because the pulse measurement apparatus is most precise in large, bulky boxes. When you miniaturise it for placement next to qubits, you lose precision, which increases the error rate.
I am not even sure whether logical components work at such low temperatures, since everything becomes superconducting.
> Even with current "coaxial cable tech", it "only" needs to scale up to the point of reaching one logical qubit.
Having a logical qubit sitting in a big box is insufficient. One needs multiple logical qubits that can be interacted with and put in a superposition, for example. A chain of gates represents each logical qubit gate between each pair of physical qubits, but that's not possible to do directly at once; hence, one needs to effectively solve the 15th puzzle with the fewest steps so that the qubits don't decohere in the meantime.
wasabi991011|3 months ago
Currently finishing a course where the final project is designing a semiconductor (quantum dot) based quantum computer. Obviously not mature tech yet, but we've been stressed during the course that you can build most of the control and readout circuits to work at cryogenic temps (2-4K) using slvtfets. The theoretical limit for this quantum computing platform is, I believe, on the order of a million qubits in a single cryostat.