You might have misunderstood my comment (or Scott's writings?)
Classical computers are limited by what they can compute because the universe has limits. A 10,000 qubit quantum computer can factor fairly large numbers. 10,000 qubits is pretty small, one day hopefully it will fit inside a small room.
To factor those same numbers using a classical computer you'd have to make a computer the size of the entire known universe and run that computer until the heat death of the universe. Obviously this is not possible, even in principal.
Theoretically any QC computation can be simulated by a classical computer but in our limited universe you quickly run into the wall where the classical computer just becomes too big (bigger than the entire universe) and too slow (slower than the life of the universe).
Classical computers are limited by what they can compute because the universe has limits. A 10,000 qubit quantum computer can factor fairly large numbers. 10,000 qubits is pretty small, one day hopefully it will fit inside a small room.
To factor those same numbers using a classical computer you'd have to make a computer the size of the entire known universe and run that computer until the heat death of the universe. Obviously this is not possible, even in principal.
Theoretically any QC computation can be simulated by a classical computer but in our limited universe you quickly run into the wall where the classical computer just becomes too big (bigger than the entire universe) and too slow (slower than the life of the universe).