Qiskit implementation for MPS

Now, I'm implementing Matrix product state method with QasmSimulation in Qiskit. following code

The problem arise when I set number of qubits. When running it with 27qubits is very fast but, for 24, 25, 26qubits it take too much time. Why it happens?

• What times do you get for 24, 25, 26 qubits? – Yael Ben-Haim Sep 20 at 9:32
• 42sec for 23 qubits, 88sec for 24qubits, 207sec for 25qubits, 510sec for 26qubits and 0.2sec for 27 qubits. Also 0.3sec for 28qubits – 김동민 Sep 20 at 10:28
• This is indeed very mysterious. I will try to investigate this problem tomorrow. – merav-aharoni Sep 20 at 14:16
• please.. I really wonder why – 김동민 Sep 21 at 7:02

backend_opts = {'method':"matrix_product_state", 'mps_sample_measure_qubits_opt':20}