Could a Spherical layout of qbits enable more of them
This is not my area of expertise, However, there are some practical problems in 3D layout, because the qubits have to be connected in some way.
For example, on the D-Wave system, the qubits are implemented on a traditionally-fabricated chip, which is cooled to a very low temperature. The qubits have to be physically close to each other, and at the time of writing, the connections have been implemented on a 2D surface with multiple layers.
In theory, it’s possible to create chips with dozens of layers. However, as more layers are added, the number of possible defects tends to increase, and the yield goes down. This article describes the number of possible layers in fabricating flash memory (which is simpler than fabricating a quantum computing chip): https://www.forbes.com/sites/tomcoughlin/2017/07/27/how-many-layers-are-possible-in-3d-flash
This will be an interesting area to follow. Personally, I’m going with the theory that the new multi-layer fabrication technologies will at some point get cheaper and more reliable, and come within the reach of academic researchers. If you search for “qubit fabrication” in the literature, however, most published work is done with conventional techniques. But like I said, this is not my area of expertise and I’m hoping that someone with more information will contradict me.