Quantum process tomography with arbitrary number of ancilla in nuclear magnetic resonance

Abstract

The purpose of quantum process tomography is to make a robust quantum computation. For the achievement of this aim, it is necessary to estimate an experimental quantum process and compare it with an ideal unitary operation quantitatively. We propose a scheme for quantum process tomography with arbitrary number of ancilla. In this scheme, $2^{2(n-m)}$ experiments are required for n qubits process tomography with m ancilla. Thus, for implementing controlled-NOT gate using two qubits and one ancilla, four experiments are required. We can gain the advantage that the optimal number of experiments and ancilla can be employed for process tomography. In addition, with entangled initial states, our experiment implemented in nuclear magnetic resonance shows an example in the quantum parallelism of entanglement.