# Is it possible to build a quantum processor with connections among all qubits?

Current quantum processors have constrained connectivity among qubits. For example Starmon-5 processor by Quantum Inspire has only one qubit connected to others, effectively it looks like a star. The situation is similar in case of IBM Q processors (the most obvious case is 15 qubits Melbourne processor).

I understand that connectivity among qubits is constrained by used technology. In case of semiconductor processors, probably the fact that structures are planar is the biggest obstacle. To tackle this, it would be perhaps needed to have three dimensional structures. Moreover, it seems that having full connectivity would increase a noise in NISQ processors.

My question: Is there any proposal how to build a quantum processor with full connectivity?

So if by "full connectivity" you really mean all-to-all connectivity, such that you can execute gates directly between any arbitrary pair of qubits, this requires $$n(n-1)/2$$ physical connections between qubits. It really seems that this becomes infeasible for large $$n$$ beyond, say, a few hundred. Even going to three-dimensional structures wouldn't get you too far.