Quantum Computation of Hydrogen Bond Dynamics and Vibrational Spectra

Calculating observable properties of quantum chemical systems is a promising application of quantum computers. While most quantum algorithms and experimental demonstrations to date have focused on calculations of electronic structure in molecules, we have recently developed a protocol to study nuclear dynamics processes as well. In this talk, I will describe experiments which use the QSCOUT and IonQ trapped-ion quantum computers to emulate the quantum dynamics and vibrational properties of hydrogen-bonded systems. In our approach, we first treat the proton dynamics as a reduced-dimensional problem on a discretized lattice, then map its Hamiltonian to a sequence of quantum gate operations. Next, we implement these quantum gates on an ion-trap quantum computer to simulate how the proton wavepacket evolves due to the surrounding nuclear framework and electronic potential. Finally, we extract the characteristic vibrational frequencies for the proton motion using the experimentally-simulated dynamics. Our approach offers a new paradigm for simulating quantum dynamics and for computing accurate expectations values, opening the potential to study a range of chemical systems which are otherwise intractable.