Why would it expand the token budget exponentially?

Also we have nowhere near enough qubits to handle these kinds of computations. The number of bits you need to run these models is huge (GPT3 ~170bil or 10^11 parameters). Quantum computers nowadays are lucky to be around 10^3 qubits, and they decohere too quickly to be used for very long (about 10^-4 seconds). * numbers pulled from a quick Google search.

That said, new (classical computer) architectures do exist that can use longer context windows: H3 (Hungry Hungry Hippos) and RWVST or whatever it's called.