You can't simply apply a logic gate to 1 qubit at a time because qubits can become entangled with each other, so instead you apply the logic gate to the entire system at once, which is represented as a 2^n by 2^n matrix where n is the number of qubits you have in memory. This means if you were trying to simulate a machine with 250 qubits of memory, you're looking at having to construct a matrix of 2^250 by 2^250 complex numbers in order to simulate it. A matrix this large would have more elements in a single row than there are atoms in the observable universe. This is why the world record for the number of qubits simulated is only 46. Simulating 1-10 qubits is easy, but its complexity grows exponentially. Having a real quantum computer would allow you to do these operations in a single iteration. This is just a toy to help you understand quantum computers inspired by IBM's Quantum Experience. It cannot replace quantum computers. Trying to perform a quantum algorithm in a classical simulation is incredibly slow. You need a real quantum computer to get the benefits.
