The quantum mechanical treatment of both electrons and nuclei is critical for a wide range of materials, biological, and atmospheric processes, specifically those that involve the transfer of light nuclei like hydrogen. Yet, the detailed treatment of such problems is confounded by the exponential scaling in studying quantum nuclear effects, such as hydrogen tunneling, coupled with the steep algebraic scaling of electronic structure methods. Calculating the observable properties of such chemical systems is, therefore, often classically intractable, and is widely viewed as a promising application of quantum information processing. While promising quantum algorithms have been proposed to address systems with strongly correlated electrons, these techniques are completely inapplicable to the study of quantum nuclei in proton and hydrogen transfer reactions, ubiquitous in the aforementioned complex processes. Here, we present the experimental implementation for a protocol developed to study the quantum dynamics and vibrational analysis of nuclei in molecular clusters, on near-term quantum hardware.<br/>We use Sandia National lab’s Quantum Scientific Computing Open User Testbed (QSCOUT) ion-trap quantum computer to simulate the quantum dynamics of a shared proton within a short-strong hydrogen-bonded system. For a range of initial wave packet states, we experimentally drive the ion-trap system to emulate the quantum wave packet of the shared proton as it evolves along the potential energy surface generated by the nuclear frameworks and electronic structure. Following the experimental creation of the shared-proton wave packet, we then extract measurement observables such as its time-dependent spatial projection and its characteristic vibrational frequencies to spectroscopic accuracy of 3.3 cm−1 wavenumbers. Our approach demonstrates a new paradigm for studying the quantum chemical dynamics and vibrational spectra of molecules, and when combined with existing algorithms for electronic structure, opens the possibility to describe the complete behavior of complex molecular systems with unprecedented accuracy.

Simulating the quantum chemical dynamics and vibrational spectra of hydrogen-bonded systems on ion-trap quantum devices

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