Multi-qubit gates and 'Schrödinger cat' states in an optical clock

We acknowledge earlier contributions to the experiment from M. A. Norcia and N. Schine as well as fruitful discussions with R. Kaubruegger and P. Zoller. The authors also wish to thank S. Lannig and A. M. Rey for careful readings of the manuscript and helpful comments. In addition, we thankfully acknowledge helpful technical discussions and contributions to the clock laser system from A. Aeppli, M. N. Frankel, J. Hur, D. Kedar, S. Lannig, B. Lewis, M. Miklos, W. R. Milner, Y. M. Tso, W. Warfield, Z. Hu, Z. Yao. This material is based upon work supported by the Army Research Office (W911NF-19-1-0149, W911NF-19-1-0223), the Air Force Office for Scientific Research (FA9550-19-1-0275), the National Science Foundation QLCI (OMA-2016244), the U.S. Department of Energy, Office of Science, the National Quantum Information Science Research Centers, Quantum Systems Accelerator, and the National Institute of Standards and Technology. This research also received funding from the European Union’s Horizon 2020 program under the Marie Sklodowska-Curie project 955479 (MOQS), the Horizon Europe program HORIZON-CL4-2021- DIGITALEMERGING-01-30 via the project 101070144 (EuRyQa) and from the French National Research Agency under the Investments of the Future Program project ANR-21-ESRE-0032 (aQCess). We also acknowledge funding from Lockheed Martin. A.C. acknowledges support from the NSF Graduate Research Fellowship Program (Grant No. DGE2040434); W.J.E. acknowledges support from the NDSEG Fellowship; N.D.O. acknowledges support from the Alexander von Humboldt Foundation.

A.C., W.J.E., T.L.Y., A.W.Y., N.D.O. and A.M.K. contributed to the experimental setup, performed the measurements and analyzed the data. S.J. and G.P. conceptualized the multi-qubit gate design. L.Y. and K.K. contributed to the clock laser system under supervision from J.Y. A.M.K. supervised the work. All authors contributed to the manuscript.