Implementing efficient selective quantum process tomography of superconducting quantum gates on the IBM quantum processor

TL;DR

This paper introduces a modified quantum process tomography method that reduces experimental complexity and demonstrates its effectiveness on IBM quantum hardware for characterizing multi-qubit gates.

Contribution

The paper presents a reformulated SQPT approach with an efficient measurement strategy, reducing the experimental settings needed for quantum gate characterization.

Findings

Successfully implemented MSQPT on IBM QX2 processor

Efficiently characterized two- and three-qubit quantum gates

Reduced experimental complexity compared to standard SQPT

Abstract

The experimental implementation of selective quantum process tomography (SQPT) involves computing individual elements of the process matrix with the help of a special set of states called quantum 2-design states. However, the number of experimental settings required to prepare input states from quantum 2-design states to selectively and precisely compute a desired element of the process matrix is still high, and hence constructing the corresponding unitary operations in the lab is a daunting task. In order to reduce the experimental complexity, we mathematically reformulated the standard SQPT problem, which we term the modified SQPT (MSQPT) method. We designed the generalized quantum circuit to prepare the required set of input states and formulated an efficient measurement strategy aimed at minimizing the experimental cost of SQPT. We experimentally demonstrated the MSQPT protocol on the IBM QX2 cloud quantum processor and selectively characterized various two- and three-qubit quantum gates.