With a quantum computer and Grover's algorithm, 128-bit AES is breakable in 2^64 steps. But the quantum computer still needs to have a 128-bit quantum memory.
I’m not sure if you mean to be disagreeing here or simply adding color, but what you’re saying is the same as the parent comment. Grover’s algorithm allows symmetric key recovery for n bits in 2^(n/2) steps; as the parent commenter said, symmetric algorithm key sizes need to be doubled. A break in 2^64 steps is the same as 64-bit security, so changing the key size to 256-bit will offer 128 bits of security.