Quantum Entanglement It has been shown that entanglement is not necessary for ancilla-assisted quantum process tomography. Surprisingly, by presenting two examples of two-qutrit entangled states, it is found by Cheng-Jie Zhang and co-workers in article number 2100550 that there also exist some entangled states which are useless for ancilla-assisted quantum process tomography. Moreover, experimental verification is performed on the IBM platform ibmq_athens.