We demonstrate an inter-species entangling Rydberg gate between rubidium (Rb) and cesium (Cs) atoms with fidelity F=0.975±0.002. The two-species atom array enables in-place quantum non-demolition (QND) qubit measurements which are a key capability for quantum error correction. We demonstrate this functionality with multi-atom error syndrome measurements achieving QND measurement fidelities of FQND=0.933(12) and 0.865(17) for two- and three-qubit plaquettes, respectively.
@article{arxiv.2603.13492,
title = {Qubit syndrome measurements with a high fidelity Rb-Cs Rydberg gate},
author = {J. Miles and M. T. Lichtman and A. M. Scott and J. Scott and S. A. Norrell and M. J. Bedalov and D. A. Belknap and D. C. Cole and S. Y. Eubanks and M. Gillette and P. Gokhale and J. Goldwin and M. Iliev and R. A. Jones and K. W. Kuper and D. Mason and P. T. Mitchell and J. D. Murphree and N. A. Neff-Mallon and T. W. Noel and A. G. Radnaev and I. V. Vinogradov and M. Saffman},
journal= {arXiv preprint arXiv:2603.13492},
year = {2026}
}