Experimental QND measurements of complementarity on two-qubit states
  with IonQ and IBM Q quantum computers
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.
Nicolas Schwaller Valeria Vento Christophe Galland