Experimental QND measurements of complementarity on two-qubit states with IonQ and IBM Q quantum computers

TL;DR

This paper demonstrates the experimental implementation of quantum nondemolition measurements of coherence, predictability, and concurrence on two-qubit states using IBM Q and IonQ quantum computers, comparing their performance.

Contribution

It provides the first experimental comparison of QND measurements on two-qubit states across superconducting and trapped ion quantum computers.

Findings

IonQ maintains constant state fidelity during QND measurement.

IBM Q shows fidelity drop after measurement.

IonQ outperforms IBM Q in nondemolition criteria.

Abstract

We report the experimental nondemolition measurement of coherence, predictability and concurrence on a system of two qubits. The quantum circuits proposed by De Melo et al. are implemented on IBM Q (superconducting circuit) and IonQ (trapped ion) quantum computers. Three criteria are used to compare the performance of the different machines on this task: measurement accuracy, nondemolition of the observable, and quantum state preparation. We find that the IonQ quantum computer provides constant state fidelity through the nondemolition process, outperforming IBM Q systems on which the fidelity consequently drops after the measurement. Our study compares the current performance of these two technologies at different stages of the nondemolition measurement of bipartite complementarity.