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Quantum simulation of conical intersections using trapped ions


Conical intersections often control the reaction products of photochemical processes and occur when two electronic potential energy surfaces intersect. Theory predicts that the conical intersection will result in a geometric phase for a wavepacket on the ground potential energy surface, and although conical intersections have been observed experimentally, the geometric phase has not been directly observed in a molecular system. Here we use a trapped atomic ion system to perform a quantum simulation of a conical intersection. The ion’s internal state serves as the electronic state, and the motion of the atomic nuclei is encoded into the motion of the ions. The simulated electronic potential is constructed by applying state-dependent optical forces to the ion. We experimentally observe a clear manifestation of the geometric phase using adiabatic state preparation followed by motional state measurement. Our experiment shows the advantage of combining spin and motion degrees for quantum simulation of chemical reactions.

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Fig. 1: Overview of the simulated conical intersection and the effects on the wavefunction.
Fig. 2: Experimental data before the Fourier transform.
Fig. 3: Experimental data after the Fourier transform.

Data availability

Source data are provided with this paper.


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We thank C. Valahu, V. Olaya-Agudelo, T. Rei Tan, I. Kassal, M. Biercuk and E. Novakoski for insightful discussions. This work was supported by the Office of the Director of National Intelligence, Intelligence Advanced Research Projects Activity through ARO contract W911NF-16-1-0082 (Z.J., Y.W., C.F., J.K. and K.R.B.), the National Science Foundation STAQ Project Phy-1818914 (J.W., J.K. and K.R.B.) and the U.S. Department of Energy, Office of Advanced Scientific Computing Research QSCOUT programme (K.R.B.), DOE basic energy sciences award no. DE-0019449 (Y.W., C.F., J.K. and K.R.B.), ARO MURI grant no. W911NF-18-1-0218 (K.R.B) and NSF Quantum Leap Challenge Institute for Robust Quantum Simulation grant no. OMA-2120757 (K.R.B.).

Author information

Authors and Affiliations



J.W. performed classical simulations, designed and ran the experiment, and wrote the paper. Z.J. performed classical simulations and designed the experiment. Y.W. and C.F. built and maintained the experimental setup. J.K. supervised the experimental setup. K.R.B. developed the original project idea and supervised the research.

Corresponding author

Correspondence to Kenneth R. Brown.

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Competing interests

K.R.B. is a scientific advisor for IonQ, Inc. and has a personal financial interest in the company. The remaining authors declare no competing interests.

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Nature Chemistry thanks Tsveta Miteva and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary information

Supplementary Information

Supplementary Notes 1–4 and Figs. 1 and 2.

Source data

Source Data Fig. 2

Population of second ion in excited state, 100 trials each.

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Whitlow, J., Jia, Z., Wang, Y. et al. Quantum simulation of conical intersections using trapped ions. Nat. Chem. 15, 1509–1514 (2023).

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