Time taken on IBM Q qasm_simulator vs real backend

Question

Running the same quantum circuit (example picture below, I've tried similar circuits too), both on a simulator and real backend, I've found than the simulator is always faster (sometimes by order of 100 times). I expected real backends to be faster than the simulators (at least on relatively complex circuits), please tell me why are they slower?

PS: I tried on ibmq_london and ibmq_burlington and ibmq_qasm_simulator was always faster with the run time (given by result.time_taken()) to be 7s, 7s and 0.03s respectively

Answer 1

The circuit above is nothing but a bunch of matrix vector calculations of at most 32x32 elements. This is not hard for a classical computer to do. The quantum computer also has additional overhead, namely if your stuck in the queue, the circuit needs to be converted to waveforms, etc..